counting the number of molecules by freezing point...
TRANSCRIPT
Pre-lab 1
Counting the Number of Molecules by Freezing Point Depression
One of the most important and tricky measurements to make in a molecular science is to count how many
molecules are present in a sample. Last semester you counted the number of acid molecules by titration. A
powerful technique for counting molecules (or rather moles of molecules) is from the colligative properties
of solutions. This is a property that changes linearly with the addition of a solute. This week in lab we will
use the colligative property of freezing point depression to measure the amount of solute added to solvent.
This topic is covered in section 12.6 of the Chang text.
A student is given 1.30 g of an unknown compound and asked to determine the molar mass of the
compound by freezing point depression. To make this measurement the student determines the freezing
point of pure cyclohexene to be 6.65 °C.
The student then dissolves the 1.30 g of the unknown compound in 22.93 grams of cyclohexane. The
student then observes a new freezing point for the cyclohexane solution of 3.41 °C.
1. How much has the freezing point been lowered (∆T) by the addition of the unkown solute? Table
12.2 in the textbook gives the freezing point depression constant (Kf) for cyclohexane. Record
this value in the space below with the proper units.
∆T = __________________ °C Kf = _____________________
2. From her freezing point data, determine the molality (m) of the unknown solute in the cyclohexane
solution. If you have not covered this in lecture, examine equation 12.7 on page 506.
m = _________________________
3. Molality reports how many moles of the unknown would be present in a 1000 g of the
cyclohexane solution. The student making these measurements was only using 22.93 g of
cyclcohexane. Calculate the number of moles of unknown compound in the experimental
cyclcohexane solution.
Moles of unknown in 22.93 g cyclohexane = _______________________
4. From the mass of unknown compound and the moles of the unknown compound found from the
change in freezing point, determine the molar mass of the unknown compound.
Unknown molar mass = _____________________________ g/mol
Pre-lab 2
Counting the Number of Molecules by Freezing Point Depression
One of the most important and tricky measurements to make in a molecular science is to count how many
molecules are present in a sample. Last semester you counted the number of acid molecules by titration. A
powerful technique for counting molecules (or rather moles of molecules) is from the colligative properties
of solutions. This is a property that changes linearly with the addition of a solute. This week in lab we will
use the colligative property of freezing point depression to measure the amount of solute added to solvent.
This topic is covered in section 12.6 of the Chang text.
A student is given 3.00 g of an unknown compound and asked to determine the molar mass of the
compound by freezing point depression. To make this measurement the student determines the freezing
point of pure cyclohexene to be 6.56 °C.
The student then dissolves the 3.00 g of the unknown compound in 22.18 grams of cyclohexane. The
student then observes a new freezing point for the cyclohexane solution of -0.19 °C.
1. How much has the freezing point been lowered (∆T) by the addition of the unkown solute? Table
12.2 in the textbook gives the freezing point depression constant (Kf) for cyclohexane. Record
this value in the space below with the proper units.
∆T = __________________ °C Kf = _____________________
2. From her freezing point data, determine the molality (m) of the unknown solute in the cyclohexane
solution. If you have not covered this in lecture, examine equation 12.7 on page 506.
m = _________________________
3. Molality reports how many moles of the unknown would be present in a 1000 g of the
cyclohexane solution. The student making these measurements was only using 22.18 g of
cyclcohexane. Calculate the number of moles of unknown compound in the experimental
cyclcohexane solution.
Moles of unknown in 22.18 g cyclohexane = _______________________
4. From the mass of unknown compound and the moles of the unknown compound found from the
change in freezing point, determine the molar mass of the unknown compound.
Unknown molar mass = _____________________________ g/mol
Pre-lab 3
Counting the Number of Molecules by Freezing Point Depression
One of the most important and tricky measurements to make in a molecular science is to count how many
molecules are present in a sample. Last semester you counted the number of acid molecules by titration. A
powerful technique for counting molecules (or rather moles of molecules) is from the colligative properties
of solutions. This is a property that changes linearly with the addition of a solute. This week in lab we will
use the colligative property of freezing point depression to measure the amount of solute added to solvent.
This topic is covered in section 12.6 of the Chang text.
A student is given 2.02 g of an unknown compound and asked to determine the molar mass of the
compound by freezing point depression. To make this measurement the student determines the freezing
point of pure cyclohexene to be 6.6 °C.
The student then dissolves the 2.02 g of the unknown compound in 22.10 grams of cyclohexane. The
student then observes a new freezing point for the cyclohexane solution of 2.53 °C.
1. How much has the freezing point been lowered (∆T) by the addition of the unkown solute? Table
12.2 in the textbook gives the freezing point depression constant (Kf) for cyclohexane. Record
this value in the space below with the proper units.
∆T = __________________ °C Kf = _____________________
2. From her freezing point data, determine the molality (m) of the unknown solute in the cyclohexane
solution. If you have not covered this in lecture, examine equation 12.7 on page 506.
m = _________________________
3. Molality reports how many moles of the unknown would be present in a 1000 g of the
cyclohexane solution. The student making these measurements was only using 22.10 g of
cyclcohexane. Calculate the number of moles of unknown compound in the experimental
cyclcohexane solution.
Moles of unknown in 22.10 g cyclohexane = _______________________
4. From the mass of unknown compound and the moles of the unknown compound found from the
change in freezing point, determine the molar mass of the unknown compound.
Unknown molar mass = _____________________________ g/mol
Pre-lab 4
Counting the Number of Molecules by Freezing Point Depression
One of the most important and tricky measurements to make in a molecular science is to count how many
molecules are present in a sample. Last semester you counted the number of acid molecules by titration. A
powerful technique for counting molecules (or rather moles of molecules) is from the colligative properties
of solutions. This is a property that changes linearly with the addition of a solute. This week in lab we will
use the colligative property of freezing point depression to measure the amount of solute added to solvent.
This topic is covered in section 12.6 of the Chang text.
A student is given 2.67 g of an unknown compound and asked to determine the molar mass of the
compound by freezing point depression. To make this measurement the student determines the freezing
point of pure cyclohexene to be 6.65 °C.
The student then dissolves the 2.67 g of the unknown compound in 21.51 grams of cyclohexane. The
student then observes a new freezing point for the cyclohexane solution of 0.45 °C.
1. How much has the freezing point been lowered (∆T) by the addition of the unkown solute? Table
12.2 in the textbook gives the freezing point depression constant (Kf) for cyclohexane. Record
this value in the space below with the proper units.
∆T = __________________ °C Kf = _____________________
2. From her freezing point data, determine the molality (m) of the unknown solute in the cyclohexane
solution. If you have not covered this in lecture, examine equation 12.7 on page 506.
m = _________________________
3. Molality reports how many moles of the unknown would be present in a 1000 g of the
cyclohexane solution. The student making these measurements was only using 21.51 g of
cyclcohexane. Calculate the number of moles of unknown compound in the experimental
cyclcohexane solution.
Moles of unknown in 21.51 g cyclohexane = _______________________
4. From the mass of unknown compound and the moles of the unknown compound found from the
change in freezing point, determine the molar mass of the unknown compound.
Unknown molar mass = _____________________________ g/mol
Pre-lab 5
Counting the Number of Molecules by Freezing Point Depression
One of the most important and tricky measurements to make in a molecular science is to count how many
molecules are present in a sample. Last semester you counted the number of acid molecules by titration. A
powerful technique for counting molecules (or rather moles of molecules) is from the colligative properties
of solutions. This is a property that changes linearly with the addition of a solute. This week in lab we will
use the colligative property of freezing point depression to measure the amount of solute added to solvent.
This topic is covered in section 12.6 of the Chang text.
A student is given 2.00 g of an unknown compound and asked to determine the molar mass of the
compound by freezing point depression. To make this measurement the student determines the freezing
point of pure cyclohexene to be 6.64 °C.
The student then dissolves the 2.00 g of the unknown compound in 24.08 grams of cyclohexane. The
student then observes a new freezing point for the cyclohexane solution of -9.97 °C.
1. How much has the freezing point been lowered (∆T) by the addition of the unkown solute? Table
12.2 in the textbook gives the freezing point depression constant (Kf) for cyclohexane. Record
this value in the space below with the proper units.
∆T = __________________ °C Kf = _____________________
2. From her freezing point data, determine the molality (m) of the unknown solute in the cyclohexane
solution. If you have not covered this in lecture, examine equation 12.7 on page 506.
m = _________________________
3. Molality reports how many moles of the unknown would be present in a 1000 g of the
cyclohexane solution. The student making these measurements was only using 24.08 g of
cyclcohexane. Calculate the number of moles of unknown compound in the experimental
cyclcohexane solution.
Moles of unknown in 24.08 g cyclohexane = _______________________
4. From the mass of unknown compound and the moles of the unknown compound found from the
change in freezing point, determine the molar mass of the unknown compound.
Unknown molar mass = _____________________________ g/mol
Pre-lab 6
Counting the Number of Molecules by Freezing Point Depression
One of the most important and tricky measurements to make in a molecular science is to count how many
molecules are present in a sample. Last semester you counted the number of acid molecules by titration. A
powerful technique for counting molecules (or rather moles of molecules) is from the colligative properties
of solutions. This is a property that changes linearly with the addition of a solute. This week in lab we will
use the colligative property of freezing point depression to measure the amount of solute added to solvent.
This topic is covered in section 12.6 of the Chang text.
A student is given 1.65 g of an unknown compound and asked to determine the molar mass of the
compound by freezing point depression. To make this measurement the student determines the freezing
point of pure cyclohexene to be 6.6 °C.
The student then dissolves the 1.65 g of the unknown compound in 15.43 grams of cyclohexane. The
student then observes a new freezing point for the cyclohexane solution of -7.63 °C.
1. How much has the freezing point been lowered (∆T) by the addition of the unkown solute? Table
12.2 in the textbook gives the freezing point depression constant (Kf) for cyclohexane. Record
this value in the space below with the proper units.
∆T = __________________ °C Kf = _____________________
2. From her freezing point data, determine the molality (m) of the unknown solute in the cyclohexane
solution. If you have not covered this in lecture, examine equation 12.7 on page 506.
m = _________________________
3. Molality reports how many moles of the unknown would be present in a 1000 g of the
cyclohexane solution. The student making these measurements was only using 15.43 g of
cyclcohexane. Calculate the number of moles of unknown compound in the experimental
cyclcohexane solution.
Moles of unknown in 15.43 g cyclohexane = _______________________
4. From the mass of unknown compound and the moles of the unknown compound found from the
change in freezing point, determine the molar mass of the unknown compound.
Unknown molar mass = _____________________________ g/mol
Pre-lab 7
Counting the Number of Molecules by Freezing Point Depression
One of the most important and tricky measurements to make in a molecular science is to count how many
molecules are present in a sample. Last semester you counted the number of acid molecules by titration. A
powerful technique for counting molecules (or rather moles of molecules) is from the colligative properties
of solutions. This is a property that changes linearly with the addition of a solute. This week in lab we will
use the colligative property of freezing point depression to measure the amount of solute added to solvent.
This topic is covered in section 12.6 of the Chang text.
A student is given 1.97 g of an unknown compound and asked to determine the molar mass of the
compound by freezing point depression. To make this measurement the student determines the freezing
point of pure cyclohexene to be 6.69 °C.
The student then dissolves the 1.97 g of the unknown compound in 24.03 grams of cyclohexane. The
student then observes a new freezing point for the cyclohexane solution of 1.22 °C.
1. How much has the freezing point been lowered (∆T) by the addition of the unkown solute? Table
12.2 in the textbook gives the freezing point depression constant (Kf) for cyclohexane. Record
this value in the space below with the proper units.
∆T = __________________ °C Kf = _____________________
2. From her freezing point data, determine the molality (m) of the unknown solute in the cyclohexane
solution. If you have not covered this in lecture, examine equation 12.7 on page 506.
m = _________________________
3. Molality reports how many moles of the unknown would be present in a 1000 g of the
cyclohexane solution. The student making these measurements was only using 24.03 g of
cyclcohexane. Calculate the number of moles of unknown compound in the experimental
cyclcohexane solution.
Moles of unknown in 24.03 g cyclohexane = _______________________
4. From the mass of unknown compound and the moles of the unknown compound found from the
change in freezing point, determine the molar mass of the unknown compound.
Unknown molar mass = _____________________________ g/mol
Pre-lab 8
Counting the Number of Molecules by Freezing Point Depression
One of the most important and tricky measurements to make in a molecular science is to count how many
molecules are present in a sample. Last semester you counted the number of acid molecules by titration. A
powerful technique for counting molecules (or rather moles of molecules) is from the colligative properties
of solutions. This is a property that changes linearly with the addition of a solute. This week in lab we will
use the colligative property of freezing point depression to measure the amount of solute added to solvent.
This topic is covered in section 12.6 of the Chang text.
A student is given 2.43 g of an unknown compound and asked to determine the molar mass of the
compound by freezing point depression. To make this measurement the student determines the freezing
point of pure cyclohexene to be 6.64 °C.
The student then dissolves the 2.43 g of the unknown compound in 19.98 grams of cyclohexane. The
student then observes a new freezing point for the cyclohexane solution of -3.09 °C.
1. How much has the freezing point been lowered (∆T) by the addition of the unkown solute? Table
12.2 in the textbook gives the freezing point depression constant (Kf) for cyclohexane. Record
this value in the space below with the proper units.
∆T = __________________ °C Kf = _____________________
2. From her freezing point data, determine the molality (m) of the unknown solute in the cyclohexane
solution. If you have not covered this in lecture, examine equation 12.7 on page 506.
m = _________________________
3. Molality reports how many moles of the unknown would be present in a 1000 g of the
cyclohexane solution. The student making these measurements was only using 19.98 g of
cyclcohexane. Calculate the number of moles of unknown compound in the experimental
cyclcohexane solution.
Moles of unknown in 19.98 g cyclohexane = _______________________
4. From the mass of unknown compound and the moles of the unknown compound found from the
change in freezing point, determine the molar mass of the unknown compound.
Unknown molar mass = _____________________________ g/mol
Pre-lab 9
Counting the Number of Molecules by Freezing Point Depression
One of the most important and tricky measurements to make in a molecular science is to count how many
molecules are present in a sample. Last semester you counted the number of acid molecules by titration. A
powerful technique for counting molecules (or rather moles of molecules) is from the colligative properties
of solutions. This is a property that changes linearly with the addition of a solute. This week in lab we will
use the colligative property of freezing point depression to measure the amount of solute added to solvent.
This topic is covered in section 12.6 of the Chang text.
A student is given 1.23 g of an unknown compound and asked to determine the molar mass of the
compound by freezing point depression. To make this measurement the student determines the freezing
point of pure cyclohexene to be 6.61 °C.
The student then dissolves the 1.23 g of the unknown compound in 16.43 grams of cyclohexane. The
student then observes a new freezing point for the cyclohexane solution of 2.86 °C.
1. How much has the freezing point been lowered (∆T) by the addition of the unkown solute? Table
12.2 in the textbook gives the freezing point depression constant (Kf) for cyclohexane. Record
this value in the space below with the proper units.
∆T = __________________ °C Kf = _____________________
2. From her freezing point data, determine the molality (m) of the unknown solute in the cyclohexane
solution. If you have not covered this in lecture, examine equation 12.7 on page 506.
m = _________________________
3. Molality reports how many moles of the unknown would be present in a 1000 g of the
cyclohexane solution. The student making these measurements was only using 16.43 g of
cyclcohexane. Calculate the number of moles of unknown compound in the experimental
cyclcohexane solution.
Moles of unknown in 16.43 g cyclohexane = _______________________
4. From the mass of unknown compound and the moles of the unknown compound found from the
change in freezing point, determine the molar mass of the unknown compound.
Unknown molar mass = _____________________________ g/mol
Pre-lab 10
Counting the Number of Molecules by Freezing Point Depression
One of the most important and tricky measurements to make in a molecular science is to count how many
molecules are present in a sample. Last semester you counted the number of acid molecules by titration. A
powerful technique for counting molecules (or rather moles of molecules) is from the colligative properties
of solutions. This is a property that changes linearly with the addition of a solute. This week in lab we will
use the colligative property of freezing point depression to measure the amount of solute added to solvent.
This topic is covered in section 12.6 of the Chang text.
A student is given 1.02 g of an unknown compound and asked to determine the molar mass of the
compound by freezing point depression. To make this measurement the student determines the freezing
point of pure cyclohexene to be 6.57 °C.
The student then dissolves the 1.02 g of the unknown compound in 18.19 grams of cyclohexane. The
student then observes a new freezing point for the cyclohexane solution of 3.76 °C.
1. How much has the freezing point been lowered (∆T) by the addition of the unkown solute? Table
12.2 in the textbook gives the freezing point depression constant (Kf) for cyclohexane. Record
this value in the space below with the proper units.
∆T = __________________ °C Kf = _____________________
2. From her freezing point data, determine the molality (m) of the unknown solute in the cyclohexane
solution. If you have not covered this in lecture, examine equation 12.7 on page 506.
m = _________________________
3. Molality reports how many moles of the unknown would be present in a 1000 g of the
cyclohexane solution. The student making these measurements was only using 18.19 g of
cyclcohexane. Calculate the number of moles of unknown compound in the experimental
cyclcohexane solution.
Moles of unknown in 18.19 g cyclohexane = _______________________
4. From the mass of unknown compound and the moles of the unknown compound found from the
change in freezing point, determine the molar mass of the unknown compound.
Unknown molar mass = _____________________________ g/mol
Pre-lab 11
Counting the Number of Molecules by Freezing Point Depression
One of the most important and tricky measurements to make in a molecular science is to count how many
molecules are present in a sample. Last semester you counted the number of acid molecules by titration. A
powerful technique for counting molecules (or rather moles of molecules) is from the colligative properties
of solutions. This is a property that changes linearly with the addition of a solute. This week in lab we will
use the colligative property of freezing point depression to measure the amount of solute added to solvent.
This topic is covered in section 12.6 of the Chang text.
A student is given 1.95 g of an unknown compound and asked to determine the molar mass of the
compound by freezing point depression. To make this measurement the student determines the freezing
point of pure cyclohexene to be 6.58 °C.
The student then dissolves the 1.95 g of the unknown compound in 19.23 grams of cyclohexane. The
student then observes a new freezing point for the cyclohexane solution of 2.07 °C.
1. How much has the freezing point been lowered (∆T) by the addition of the unkown solute? Table
12.2 in the textbook gives the freezing point depression constant (Kf) for cyclohexane. Record
this value in the space below with the proper units.
∆T = __________________ °C Kf = _____________________
2. From her freezing point data, determine the molality (m) of the unknown solute in the cyclohexane
solution. If you have not covered this in lecture, examine equation 12.7 on page 506.
m = _________________________
3. Molality reports how many moles of the unknown would be present in a 1000 g of the
cyclohexane solution. The student making these measurements was only using 19.23 g of
cyclcohexane. Calculate the number of moles of unknown compound in the experimental
cyclcohexane solution.
Moles of unknown in 19.23 g cyclohexane = _______________________
4. From the mass of unknown compound and the moles of the unknown compound found from the
change in freezing point, determine the molar mass of the unknown compound.
Unknown molar mass = _____________________________ g/mol
Pre-lab 12
Counting the Number of Molecules by Freezing Point Depression
One of the most important and tricky measurements to make in a molecular science is to count how many
molecules are present in a sample. Last semester you counted the number of acid molecules by titration. A
powerful technique for counting molecules (or rather moles of molecules) is from the colligative properties
of solutions. This is a property that changes linearly with the addition of a solute. This week in lab we will
use the colligative property of freezing point depression to measure the amount of solute added to solvent.
This topic is covered in section 12.6 of the Chang text.
A student is given 2.97 g of an unknown compound and asked to determine the molar mass of the
compound by freezing point depression. To make this measurement the student determines the freezing
point of pure cyclohexene to be 6.53 °C.
The student then dissolves the 2.97 g of the unknown compound in 17.58 grams of cyclohexane. The
student then observes a new freezing point for the cyclohexane solution of -0.97 °C.
1. How much has the freezing point been lowered (∆T) by the addition of the unkown solute? Table
12.2 in the textbook gives the freezing point depression constant (Kf) for cyclohexane. Record
this value in the space below with the proper units.
∆T = __________________ °C Kf = _____________________
2. From her freezing point data, determine the molality (m) of the unknown solute in the cyclohexane
solution. If you have not covered this in lecture, examine equation 12.7 on page 506.
m = _________________________
3. Molality reports how many moles of the unknown would be present in a 1000 g of the
cyclohexane solution. The student making these measurements was only using 17.58 g of
cyclcohexane. Calculate the number of moles of unknown compound in the experimental
cyclcohexane solution.
Moles of unknown in 17.58 g cyclohexane = _______________________
4. From the mass of unknown compound and the moles of the unknown compound found from the
change in freezing point, determine the molar mass of the unknown compound.
Unknown molar mass = _____________________________ g/mol
Pre-lab 13
Counting the Number of Molecules by Freezing Point Depression
One of the most important and tricky measurements to make in a molecular science is to count how many
molecules are present in a sample. Last semester you counted the number of acid molecules by titration. A
powerful technique for counting molecules (or rather moles of molecules) is from the colligative properties
of solutions. This is a property that changes linearly with the addition of a solute. This week in lab we will
use the colligative property of freezing point depression to measure the amount of solute added to solvent.
This topic is covered in section 12.6 of the Chang text.
A student is given 1.01 g of an unknown compound and asked to determine the molar mass of the
compound by freezing point depression. To make this measurement the student determines the freezing
point of pure cyclohexene to be 6.68 °C.
The student then dissolves the 1.01 g of the unknown compound in 18.60 grams of cyclohexane. The
student then observes a new freezing point for the cyclohexane solution of 1.26 °C.
1. How much has the freezing point been lowered (∆T) by the addition of the unkown solute? Table
12.2 in the textbook gives the freezing point depression constant (Kf) for cyclohexane. Record
this value in the space below with the proper units.
∆T = __________________ °C Kf = _____________________
2. From her freezing point data, determine the molality (m) of the unknown solute in the cyclohexane
solution. If you have not covered this in lecture, examine equation 12.7 on page 506.
m = _________________________
3. Molality reports how many moles of the unknown would be present in a 1000 g of the
cyclohexane solution. The student making these measurements was only using 18.60 g of
cyclcohexane. Calculate the number of moles of unknown compound in the experimental
cyclcohexane solution.
Moles of unknown in 18.60 g cyclohexane = _______________________
4. From the mass of unknown compound and the moles of the unknown compound found from the
change in freezing point, determine the molar mass of the unknown compound.
Unknown molar mass = _____________________________ g/mol
Pre-lab 14
Counting the Number of Molecules by Freezing Point Depression
One of the most important and tricky measurements to make in a molecular science is to count how many
molecules are present in a sample. Last semester you counted the number of acid molecules by titration. A
powerful technique for counting molecules (or rather moles of molecules) is from the colligative properties
of solutions. This is a property that changes linearly with the addition of a solute. This week in lab we will
use the colligative property of freezing point depression to measure the amount of solute added to solvent.
This topic is covered in section 12.6 of the Chang text.
A student is given 1.49 g of an unknown compound and asked to determine the molar mass of the
compound by freezing point depression. To make this measurement the student determines the freezing
point of pure cyclohexene to be 6.63 °C.
The student then dissolves the 1.49 g of the unknown compound in 22.11 grams of cyclohexane. The
student then observes a new freezing point for the cyclohexane solution of -2.35 °C.
1. How much has the freezing point been lowered (∆T) by the addition of the unkown solute? Table
12.2 in the textbook gives the freezing point depression constant (Kf) for cyclohexane. Record
this value in the space below with the proper units.
∆T = __________________ °C Kf = _____________________
2. From her freezing point data, determine the molality (m) of the unknown solute in the cyclohexane
solution. If you have not covered this in lecture, examine equation 12.7 on page 506.
m = _________________________
3. Molality reports how many moles of the unknown would be present in a 1000 g of the
cyclohexane solution. The student making these measurements was only using 22.11 g of
cyclcohexane. Calculate the number of moles of unknown compound in the experimental
cyclcohexane solution.
Moles of unknown in 22.11 g cyclohexane = _______________________
4. From the mass of unknown compound and the moles of the unknown compound found from the
change in freezing point, determine the molar mass of the unknown compound.
Unknown molar mass = _____________________________ g/mol
Pre-lab 15
Counting the Number of Molecules by Freezing Point Depression
One of the most important and tricky measurements to make in a molecular science is to count how many
molecules are present in a sample. Last semester you counted the number of acid molecules by titration. A
powerful technique for counting molecules (or rather moles of molecules) is from the colligative properties
of solutions. This is a property that changes linearly with the addition of a solute. This week in lab we will
use the colligative property of freezing point depression to measure the amount of solute added to solvent.
This topic is covered in section 12.6 of the Chang text.
A student is given 2.28 g of an unknown compound and asked to determine the molar mass of the
compound by freezing point depression. To make this measurement the student determines the freezing
point of pure cyclohexene to be 6.53 °C.
The student then dissolves the 2.28 g of the unknown compound in 15.16 grams of cyclohexane. The
student then observes a new freezing point for the cyclohexane solution of -23.60 °C.
1. How much has the freezing point been lowered (∆T) by the addition of the unkown solute? Table
12.2 in the textbook gives the freezing point depression constant (Kf) for cyclohexane. Record
this value in the space below with the proper units.
∆T = __________________ °C Kf = _____________________
2. From her freezing point data, determine the molality (m) of the unknown solute in the cyclohexane
solution. If you have not covered this in lecture, examine equation 12.7 on page 506.
m = _________________________
3. Molality reports how many moles of the unknown would be present in a 1000 g of the
cyclohexane solution. The student making these measurements was only using 15.16 g of
cyclcohexane. Calculate the number of moles of unknown compound in the experimental
cyclcohexane solution.
Moles of unknown in 15.16 g cyclohexane = _______________________
4. From the mass of unknown compound and the moles of the unknown compound found from the
change in freezing point, determine the molar mass of the unknown compound.
Unknown molar mass = _____________________________ g/mol
Pre-lab 16
Counting the Number of Molecules by Freezing Point Depression
One of the most important and tricky measurements to make in a molecular science is to count how many
molecules are present in a sample. Last semester you counted the number of acid molecules by titration. A
powerful technique for counting molecules (or rather moles of molecules) is from the colligative properties
of solutions. This is a property that changes linearly with the addition of a solute. This week in lab we will
use the colligative property of freezing point depression to measure the amount of solute added to solvent.
This topic is covered in section 12.6 of the Chang text.
A student is given 1.09 g of an unknown compound and asked to determine the molar mass of the
compound by freezing point depression. To make this measurement the student determines the freezing
point of pure cyclohexene to be 6.66 °C.
The student then dissolves the 1.09 g of the unknown compound in 20.17 grams of cyclohexane. The
student then observes a new freezing point for the cyclohexane solution of 3.05 °C.
1. How much has the freezing point been lowered (∆T) by the addition of the unkown solute? Table
12.2 in the textbook gives the freezing point depression constant (Kf) for cyclohexane. Record
this value in the space below with the proper units.
∆T = __________________ °C Kf = _____________________
2. From her freezing point data, determine the molality (m) of the unknown solute in the cyclohexane
solution. If you have not covered this in lecture, examine equation 12.7 on page 506.
m = _________________________
3. Molality reports how many moles of the unknown would be present in a 1000 g of the
cyclohexane solution. The student making these measurements was only using 20.17 g of
cyclcohexane. Calculate the number of moles of unknown compound in the experimental
cyclcohexane solution.
Moles of unknown in 20.17 g cyclohexane = _______________________
4. From the mass of unknown compound and the moles of the unknown compound found from the
change in freezing point, determine the molar mass of the unknown compound.
Unknown molar mass = _____________________________ g/mol
Pre-lab 17
Counting the Number of Molecules by Freezing Point Depression
One of the most important and tricky measurements to make in a molecular science is to count how many
molecules are present in a sample. Last semester you counted the number of acid molecules by titration. A
powerful technique for counting molecules (or rather moles of molecules) is from the colligative properties
of solutions. This is a property that changes linearly with the addition of a solute. This week in lab we will
use the colligative property of freezing point depression to measure the amount of solute added to solvent.
This topic is covered in section 12.6 of the Chang text.
A student is given 2.76 g of an unknown compound and asked to determine the molar mass of the
compound by freezing point depression. To make this measurement the student determines the freezing
point of pure cyclohexene to be 6.66 °C.
The student then dissolves the 2.76 g of the unknown compound in 17.77 grams of cyclohexane. The
student then observes a new freezing point for the cyclohexane solution of -24.39 °C.
1. How much has the freezing point been lowered (∆T) by the addition of the unkown solute? Table
12.2 in the textbook gives the freezing point depression constant (Kf) for cyclohexane. Record
this value in the space below with the proper units.
∆T = __________________ °C Kf = _____________________
2. From her freezing point data, determine the molality (m) of the unknown solute in the cyclohexane
solution. If you have not covered this in lecture, examine equation 12.7 on page 506.
m = _________________________
3. Molality reports how many moles of the unknown would be present in a 1000 g of the
cyclohexane solution. The student making these measurements was only using 17.77 g of
cyclcohexane. Calculate the number of moles of unknown compound in the experimental
cyclcohexane solution.
Moles of unknown in 17.77 g cyclohexane = _______________________
4. From the mass of unknown compound and the moles of the unknown compound found from the
change in freezing point, determine the molar mass of the unknown compound.
Unknown molar mass = _____________________________ g/mol
Pre-lab 18
Counting the Number of Molecules by Freezing Point Depression
One of the most important and tricky measurements to make in a molecular science is to count how many
molecules are present in a sample. Last semester you counted the number of acid molecules by titration. A
powerful technique for counting molecules (or rather moles of molecules) is from the colligative properties
of solutions. This is a property that changes linearly with the addition of a solute. This week in lab we will
use the colligative property of freezing point depression to measure the amount of solute added to solvent.
This topic is covered in section 12.6 of the Chang text.
A student is given 2.22 g of an unknown compound and asked to determine the molar mass of the
compound by freezing point depression. To make this measurement the student determines the freezing
point of pure cyclohexene to be 6.64 °C.
The student then dissolves the 2.22 g of the unknown compound in 18.78 grams of cyclohexane. The
student then observes a new freezing point for the cyclohexane solution of 0.72 °C.
1. How much has the freezing point been lowered (∆T) by the addition of the unkown solute? Table
12.2 in the textbook gives the freezing point depression constant (Kf) for cyclohexane. Record
this value in the space below with the proper units.
∆T = __________________ °C Kf = _____________________
2. From her freezing point data, determine the molality (m) of the unknown solute in the cyclohexane
solution. If you have not covered this in lecture, examine equation 12.7 on page 506.
m = _________________________
3. Molality reports how many moles of the unknown would be present in a 1000 g of the
cyclohexane solution. The student making these measurements was only using 18.78 g of
cyclcohexane. Calculate the number of moles of unknown compound in the experimental
cyclcohexane solution.
Moles of unknown in 18.78 g cyclohexane = _______________________
4. From the mass of unknown compound and the moles of the unknown compound found from the
change in freezing point, determine the molar mass of the unknown compound.
Unknown molar mass = _____________________________ g/mol
Pre-lab 19
Counting the Number of Molecules by Freezing Point Depression
One of the most important and tricky measurements to make in a molecular science is to count how many
molecules are present in a sample. Last semester you counted the number of acid molecules by titration. A
powerful technique for counting molecules (or rather moles of molecules) is from the colligative properties
of solutions. This is a property that changes linearly with the addition of a solute. This week in lab we will
use the colligative property of freezing point depression to measure the amount of solute added to solvent.
This topic is covered in section 12.6 of the Chang text.
A student is given 2.94 g of an unknown compound and asked to determine the molar mass of the
compound by freezing point depression. To make this measurement the student determines the freezing
point of pure cyclohexene to be 6.65 °C.
The student then dissolves the 2.94 g of the unknown compound in 21.04 grams of cyclohexane. The
student then observes a new freezing point for the cyclohexane solution of 0.45 °C.
1. How much has the freezing point been lowered (∆T) by the addition of the unkown solute? Table
12.2 in the textbook gives the freezing point depression constant (Kf) for cyclohexane. Record
this value in the space below with the proper units.
∆T = __________________ °C Kf = _____________________
2. From her freezing point data, determine the molality (m) of the unknown solute in the cyclohexane
solution. If you have not covered this in lecture, examine equation 12.7 on page 506.
m = _________________________
3. Molality reports how many moles of the unknown would be present in a 1000 g of the
cyclohexane solution. The student making these measurements was only using 21.04 g of
cyclcohexane. Calculate the number of moles of unknown compound in the experimental
cyclcohexane solution.
Moles of unknown in 21.04 g cyclohexane = _______________________
4. From the mass of unknown compound and the moles of the unknown compound found from the
change in freezing point, determine the molar mass of the unknown compound.
Unknown molar mass = _____________________________ g/mol
Pre-lab 20
Counting the Number of Molecules by Freezing Point Depression
One of the most important and tricky measurements to make in a molecular science is to count how many
molecules are present in a sample. Last semester you counted the number of acid molecules by titration. A
powerful technique for counting molecules (or rather moles of molecules) is from the colligative properties
of solutions. This is a property that changes linearly with the addition of a solute. This week in lab we will
use the colligative property of freezing point depression to measure the amount of solute added to solvent.
This topic is covered in section 12.6 of the Chang text.
A student is given 2.32 g of an unknown compound and asked to determine the molar mass of the
compound by freezing point depression. To make this measurement the student determines the freezing
point of pure cyclohexene to be 6.58 °C.
The student then dissolves the 2.32 g of the unknown compound in 18.14 grams of cyclohexane. The
student then observes a new freezing point for the cyclohexane solution of 0.18 °C.
1. How much has the freezing point been lowered (∆T) by the addition of the unkown solute? Table
12.2 in the textbook gives the freezing point depression constant (Kf) for cyclohexane. Record
this value in the space below with the proper units.
∆T = __________________ °C Kf = _____________________
2. From her freezing point data, determine the molality (m) of the unknown solute in the cyclohexane
solution. If you have not covered this in lecture, examine equation 12.7 on page 506.
m = _________________________
3. Molality reports how many moles of the unknown would be present in a 1000 g of the
cyclohexane solution. The student making these measurements was only using 18.14 g of
cyclcohexane. Calculate the number of moles of unknown compound in the experimental
cyclcohexane solution.
Moles of unknown in 18.14 g cyclohexane = _______________________
4. From the mass of unknown compound and the moles of the unknown compound found from the
change in freezing point, determine the molar mass of the unknown compound.
Unknown molar mass = _____________________________ g/mol
Pre-lab 21
Counting the Number of Molecules by Freezing Point Depression
One of the most important and tricky measurements to make in a molecular science is to count how many
molecules are present in a sample. Last semester you counted the number of acid molecules by titration. A
powerful technique for counting molecules (or rather moles of molecules) is from the colligative properties
of solutions. This is a property that changes linearly with the addition of a solute. This week in lab we will
use the colligative property of freezing point depression to measure the amount of solute added to solvent.
This topic is covered in section 12.6 of the Chang text.
A student is given 2.23 g of an unknown compound and asked to determine the molar mass of the
compound by freezing point depression. To make this measurement the student determines the freezing
point of pure cyclohexene to be 6.7 °C.
The student then dissolves the 2.23 g of the unknown compound in 17.68 grams of cyclohexane. The
student then observes a new freezing point for the cyclohexane solution of -0.52 °C.
1. How much has the freezing point been lowered (∆T) by the addition of the unkown solute? Table
12.2 in the textbook gives the freezing point depression constant (Kf) for cyclohexane. Record
this value in the space below with the proper units.
∆T = __________________ °C Kf = _____________________
2. From her freezing point data, determine the molality (m) of the unknown solute in the cyclohexane
solution. If you have not covered this in lecture, examine equation 12.7 on page 506.
m = _________________________
3. Molality reports how many moles of the unknown would be present in a 1000 g of the
cyclohexane solution. The student making these measurements was only using 17.68 g of
cyclcohexane. Calculate the number of moles of unknown compound in the experimental
cyclcohexane solution.
Moles of unknown in 17.68 g cyclohexane = _______________________
4. From the mass of unknown compound and the moles of the unknown compound found from the
change in freezing point, determine the molar mass of the unknown compound.
Unknown molar mass = _____________________________ g/mol
Pre-lab 22
Counting the Number of Molecules by Freezing Point Depression
One of the most important and tricky measurements to make in a molecular science is to count how many
molecules are present in a sample. Last semester you counted the number of acid molecules by titration. A
powerful technique for counting molecules (or rather moles of molecules) is from the colligative properties
of solutions. This is a property that changes linearly with the addition of a solute. This week in lab we will
use the colligative property of freezing point depression to measure the amount of solute added to solvent.
This topic is covered in section 12.6 of the Chang text.
A student is given 2.46 g of an unknown compound and asked to determine the molar mass of the
compound by freezing point depression. To make this measurement the student determines the freezing
point of pure cyclohexene to be 6.67 °C.
The student then dissolves the 2.46 g of the unknown compound in 21.32 grams of cyclohexane. The
student then observes a new freezing point for the cyclohexane solution of 0.90 °C.
1. How much has the freezing point been lowered (∆T) by the addition of the unkown solute? Table
12.2 in the textbook gives the freezing point depression constant (Kf) for cyclohexane. Record
this value in the space below with the proper units.
∆T = __________________ °C Kf = _____________________
2. From her freezing point data, determine the molality (m) of the unknown solute in the cyclohexane
solution. If you have not covered this in lecture, examine equation 12.7 on page 506.
m = _________________________
3. Molality reports how many moles of the unknown would be present in a 1000 g of the
cyclohexane solution. The student making these measurements was only using 21.32 g of
cyclcohexane. Calculate the number of moles of unknown compound in the experimental
cyclcohexane solution.
Moles of unknown in 21.32 g cyclohexane = _______________________
4. From the mass of unknown compound and the moles of the unknown compound found from the
change in freezing point, determine the molar mass of the unknown compound.
Unknown molar mass = _____________________________ g/mol
Pre-lab 23
Counting the Number of Molecules by Freezing Point Depression
One of the most important and tricky measurements to make in a molecular science is to count how many
molecules are present in a sample. Last semester you counted the number of acid molecules by titration. A
powerful technique for counting molecules (or rather moles of molecules) is from the colligative properties
of solutions. This is a property that changes linearly with the addition of a solute. This week in lab we will
use the colligative property of freezing point depression to measure the amount of solute added to solvent.
This topic is covered in section 12.6 of the Chang text.
A student is given 1.67 g of an unknown compound and asked to determine the molar mass of the
compound by freezing point depression. To make this measurement the student determines the freezing
point of pure cyclohexene to be 6.57 °C.
The student then dissolves the 1.67 g of the unknown compound in 25.05 grams of cyclohexane. The
student then observes a new freezing point for the cyclohexane solution of 2.12 °C.
1. How much has the freezing point been lowered (∆T) by the addition of the unkown solute? Table
12.2 in the textbook gives the freezing point depression constant (Kf) for cyclohexane. Record
this value in the space below with the proper units.
∆T = __________________ °C Kf = _____________________
2. From her freezing point data, determine the molality (m) of the unknown solute in the cyclohexane
solution. If you have not covered this in lecture, examine equation 12.7 on page 506.
m = _________________________
3. Molality reports how many moles of the unknown would be present in a 1000 g of the
cyclohexane solution. The student making these measurements was only using 25.05 g of
cyclcohexane. Calculate the number of moles of unknown compound in the experimental
cyclcohexane solution.
Moles of unknown in 25.05 g cyclohexane = _______________________
4. From the mass of unknown compound and the moles of the unknown compound found from the
change in freezing point, determine the molar mass of the unknown compound.
Unknown molar mass = _____________________________ g/mol
Pre-lab 24
Counting the Number of Molecules by Freezing Point Depression
One of the most important and tricky measurements to make in a molecular science is to count how many
molecules are present in a sample. Last semester you counted the number of acid molecules by titration. A
powerful technique for counting molecules (or rather moles of molecules) is from the colligative properties
of solutions. This is a property that changes linearly with the addition of a solute. This week in lab we will
use the colligative property of freezing point depression to measure the amount of solute added to solvent.
This topic is covered in section 12.6 of the Chang text.
A student is given 2.74 g of an unknown compound and asked to determine the molar mass of the
compound by freezing point depression. To make this measurement the student determines the freezing
point of pure cyclohexene to be 6.53 °C.
The student then dissolves the 2.74 g of the unknown compound in 15.61 grams of cyclohexane. The
student then observes a new freezing point for the cyclohexane solution of -3.50 °C.
1. How much has the freezing point been lowered (∆T) by the addition of the unkown solute? Table
12.2 in the textbook gives the freezing point depression constant (Kf) for cyclohexane. Record
this value in the space below with the proper units.
∆T = __________________ °C Kf = _____________________
2. From her freezing point data, determine the molality (m) of the unknown solute in the cyclohexane
solution. If you have not covered this in lecture, examine equation 12.7 on page 506.
m = _________________________
3. Molality reports how many moles of the unknown would be present in a 1000 g of the
cyclohexane solution. The student making these measurements was only using 15.61 g of
cyclcohexane. Calculate the number of moles of unknown compound in the experimental
cyclcohexane solution.
Moles of unknown in 15.61 g cyclohexane = _______________________
4. From the mass of unknown compound and the moles of the unknown compound found from the
change in freezing point, determine the molar mass of the unknown compound.
Unknown molar mass = _____________________________ g/mol
Pre-lab 25
Counting the Number of Molecules by Freezing Point Depression
One of the most important and tricky measurements to make in a molecular science is to count how many
molecules are present in a sample. Last semester you counted the number of acid molecules by titration. A
powerful technique for counting molecules (or rather moles of molecules) is from the colligative properties
of solutions. This is a property that changes linearly with the addition of a solute. This week in lab we will
use the colligative property of freezing point depression to measure the amount of solute added to solvent.
This topic is covered in section 12.6 of the Chang text.
A student is given 2.52 g of an unknown compound and asked to determine the molar mass of the
compound by freezing point depression. To make this measurement the student determines the freezing
point of pure cyclohexene to be 6.51 °C.
The student then dissolves the 2.52 g of the unknown compound in 17.61 grams of cyclohexane. The
student then observes a new freezing point for the cyclohexane solution of 0.15 °C.
1. How much has the freezing point been lowered (∆T) by the addition of the unkown solute? Table
12.2 in the textbook gives the freezing point depression constant (Kf) for cyclohexane. Record
this value in the space below with the proper units.
∆T = __________________ °C Kf = _____________________
2. From her freezing point data, determine the molality (m) of the unknown solute in the cyclohexane
solution. If you have not covered this in lecture, examine equation 12.7 on page 506.
m = _________________________
3. Molality reports how many moles of the unknown would be present in a 1000 g of the
cyclohexane solution. The student making these measurements was only using 17.61 g of
cyclcohexane. Calculate the number of moles of unknown compound in the experimental
cyclcohexane solution.
Moles of unknown in 17.61 g cyclohexane = _______________________
4. From the mass of unknown compound and the moles of the unknown compound found from the
change in freezing point, determine the molar mass of the unknown compound.
Unknown molar mass = _____________________________ g/mol
Pre-lab 26
Counting the Number of Molecules by Freezing Point Depression
One of the most important and tricky measurements to make in a molecular science is to count how many
molecules are present in a sample. Last semester you counted the number of acid molecules by titration. A
powerful technique for counting molecules (or rather moles of molecules) is from the colligative properties
of solutions. This is a property that changes linearly with the addition of a solute. This week in lab we will
use the colligative property of freezing point depression to measure the amount of solute added to solvent.
This topic is covered in section 12.6 of the Chang text.
A student is given 1.80 g of an unknown compound and asked to determine the molar mass of the
compound by freezing point depression. To make this measurement the student determines the freezing
point of pure cyclohexene to be 6.53 °C.
The student then dissolves the 1.80 g of the unknown compound in 15.61 grams of cyclohexane. The
student then observes a new freezing point for the cyclohexane solution of -16.49 °C.
1. How much has the freezing point been lowered (∆T) by the addition of the unkown solute? Table
12.2 in the textbook gives the freezing point depression constant (Kf) for cyclohexane. Record
this value in the space below with the proper units.
∆T = __________________ °C Kf = _____________________
2. From her freezing point data, determine the molality (m) of the unknown solute in the cyclohexane
solution. If you have not covered this in lecture, examine equation 12.7 on page 506.
m = _________________________
3. Molality reports how many moles of the unknown would be present in a 1000 g of the
cyclohexane solution. The student making these measurements was only using 15.61 g of
cyclcohexane. Calculate the number of moles of unknown compound in the experimental
cyclcohexane solution.
Moles of unknown in 15.61 g cyclohexane = _______________________
4. From the mass of unknown compound and the moles of the unknown compound found from the
change in freezing point, determine the molar mass of the unknown compound.
Unknown molar mass = _____________________________ g/mol
Pre-lab 27
Counting the Number of Molecules by Freezing Point Depression
One of the most important and tricky measurements to make in a molecular science is to count how many
molecules are present in a sample. Last semester you counted the number of acid molecules by titration. A
powerful technique for counting molecules (or rather moles of molecules) is from the colligative properties
of solutions. This is a property that changes linearly with the addition of a solute. This week in lab we will
use the colligative property of freezing point depression to measure the amount of solute added to solvent.
This topic is covered in section 12.6 of the Chang text.
A student is given 1.55 g of an unknown compound and asked to determine the molar mass of the
compound by freezing point depression. To make this measurement the student determines the freezing
point of pure cyclohexene to be 6.68 °C.
The student then dissolves the 1.55 g of the unknown compound in 17.61 grams of cyclohexane. The
student then observes a new freezing point for the cyclohexane solution of 2.27 °C.
1. How much has the freezing point been lowered (∆T) by the addition of the unkown solute? Table
12.2 in the textbook gives the freezing point depression constant (Kf) for cyclohexane. Record
this value in the space below with the proper units.
∆T = __________________ °C Kf = _____________________
2. From her freezing point data, determine the molality (m) of the unknown solute in the cyclohexane
solution. If you have not covered this in lecture, examine equation 12.7 on page 506.
m = _________________________
3. Molality reports how many moles of the unknown would be present in a 1000 g of the
cyclohexane solution. The student making these measurements was only using 17.61 g of
cyclcohexane. Calculate the number of moles of unknown compound in the experimental
cyclcohexane solution.
Moles of unknown in 17.61 g cyclohexane = _______________________
4. From the mass of unknown compound and the moles of the unknown compound found from the
change in freezing point, determine the molar mass of the unknown compound.
Unknown molar mass = _____________________________ g/mol