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2.C – Conserving Matter

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Page 1: 2.C – Conserving Matter. Objectives State and apply the Law of Conservation of Matter. Learn how to balance chemical equations. Explain the mole concept

2.C – Conserving Matter

Page 2: 2.C – Conserving Matter. Objectives State and apply the Law of Conservation of Matter. Learn how to balance chemical equations. Explain the mole concept

Objectives

State and apply the Law of Conservation of Matter.

Learn how to balance chemical equations. Explain the mole concept. Calculate molar mass of a compound. Calculate percent composition of elements. Distinguish between renewable and

nonrenewable resources.

Page 3: 2.C – Conserving Matter. Objectives State and apply the Law of Conservation of Matter. Learn how to balance chemical equations. Explain the mole concept

C.1: Keeping Track of Atoms

Complete the reading guide handout

Page 4: 2.C – Conserving Matter. Objectives State and apply the Law of Conservation of Matter. Learn how to balance chemical equations. Explain the mole concept

In some chemical reactions, matter seems to be created. When a nail rusts.

In other reactions, matter seems to disappear. When paper burns and apparently vanishes

However, neither creation or destruction of matter occurs.

Matter may undergo physical or chemical changes.

C.1: Keeping Track of Atoms

Page 5: 2.C – Conserving Matter. Objectives State and apply the Law of Conservation of Matter. Learn how to balance chemical equations. Explain the mole concept

C.1: Keeping Track of Atoms

In a car engine gasoline is burned. What happens to the molecules of gasoline?

Gasoline is made up of carbon and hydrogen atoms (C and H atoms)

When gasoline burns these atoms react with oxygen atoms in air to form carbon dioxide (CO2), carbon monoxide (CO) and water (H2O).

The original atoms of gasoline are not destroyed but become rearranged.

Page 6: 2.C – Conserving Matter. Objectives State and apply the Law of Conservation of Matter. Learn how to balance chemical equations. Explain the mole concept

Basic chemical equation:

CxHx + O2 CO2 + CO + H2O

Molecules can be converted or decompose by chemical reactions; but the atoms remain.

reactants products

Page 7: 2.C – Conserving Matter. Objectives State and apply the Law of Conservation of Matter. Learn how to balance chemical equations. Explain the mole concept

C.1: Keeping Track of Atoms

Law of Conservation of Matter: Matter is neither created nor destroyed.

Since chemical reactions cannot create or destroy atoms, chemical equations representing the reactions must always be BALANCED.

This means that the number of atoms of each element is the same on the reactant and product sides of a chemical equation.

Page 8: 2.C – Conserving Matter. Objectives State and apply the Law of Conservation of Matter. Learn how to balance chemical equations. Explain the mole concept

Example:

The burning of coal is a reaction where carbon reacts with oxygen to produce carbon dioxide. The number of carbon and oxygen atoms is the same on both sides of the equation.

C + O2

CO2

Page 9: 2.C – Conserving Matter. Objectives State and apply the Law of Conservation of Matter. Learn how to balance chemical equations. Explain the mole concept

Atomic Perspective:

C O2 CO2

1 Carbon atom 1 oxygen molecule 1 carbon dioxide molecule

1. What are the reactants in this chemical equation?

2. What are the products in this chemical equation?

3. Are there the same number of atoms on both sides of the equation?

a. Were any atoms destroyed or created?

b. Was the Law of Conservation of Matter maintained?

Page 10: 2.C – Conserving Matter. Objectives State and apply the Law of Conservation of Matter. Learn how to balance chemical equations. Explain the mole concept

Atomic Perspective:

Cu (s) + O2 (g) CuO (s)

From the burning of copper lab:

Is this reaction balanced?

Does it obey the Law of Conservation of Matter?

Page 11: 2.C – Conserving Matter. Objectives State and apply the Law of Conservation of Matter. Learn how to balance chemical equations. Explain the mole concept

2 Cu (s) + O2 (g) 2 CuO (s)

COEFFICIENTS - indicates the number of units of each substance involved.

1. Does the oxygen molecule have a coefficient?

2. What do the subscripts represent?

3. Can subscripts be removed from chemical equations?

The above reaction reads: 2 copper atoms react with 1 oxygen to produce 2 molecules of copper oxide.

Page 12: 2.C – Conserving Matter. Objectives State and apply the Law of Conservation of Matter. Learn how to balance chemical equations. Explain the mole concept

C.2: Accounting for Atoms

To obey the Law of Conservation of Matter atoms can not be created or destroyed.

All atoms must be accounted for on both sides of the reaction arrow.

Page 13: 2.C – Conserving Matter. Objectives State and apply the Law of Conservation of Matter. Learn how to balance chemical equations. Explain the mole concept

Homework: Complete C1 Supplement worksheet

Due:

Accounting for Atoms

Page 14: 2.C – Conserving Matter. Objectives State and apply the Law of Conservation of Matter. Learn how to balance chemical equations. Explain the mole concept

C.2: Accounting for Atoms

Classwork: Page 155-157 Questions 1-5, parts A, C and D only

Page 15: 2.C – Conserving Matter. Objectives State and apply the Law of Conservation of Matter. Learn how to balance chemical equations. Explain the mole concept

C.3: Balancing Chemical Equations

Page 16: 2.C – Conserving Matter. Objectives State and apply the Law of Conservation of Matter. Learn how to balance chemical equations. Explain the mole concept

Balancing Equations

Page 17: 2.C – Conserving Matter. Objectives State and apply the Law of Conservation of Matter. Learn how to balance chemical equations. Explain the mole concept

Balancing EquationsLaw of Conservation of Atoms:

The number of atoms of each type of element must be the same on each side of the equation.

Page 18: 2.C – Conserving Matter. Objectives State and apply the Law of Conservation of Matter. Learn how to balance chemical equations. Explain the mole concept

Balancing Equations

Balancing hints:Balance the metals first.Balance the non metals next.Save the oxygen and hydrogen

atoms until the end.

Page 19: 2.C – Conserving Matter. Objectives State and apply the Law of Conservation of Matter. Learn how to balance chemical equations. Explain the mole concept

How do we Balance Equations?

H2 + O2 H2O

Below is the chemical equation for the reaction of hydrogen gas with oxygen gas to produce water.

Is this reaction balanced?

Page 20: 2.C – Conserving Matter. Objectives State and apply the Law of Conservation of Matter. Learn how to balance chemical equations. Explain the mole concept

Balancing Equations

Hydrogen and oxygen are diatomic elements. Their subscripts cannot be changed. The subscripts on water cannot be changed.

Hydrogen + oxygen water

H2 + O2 H2O

Page 21: 2.C – Conserving Matter. Objectives State and apply the Law of Conservation of Matter. Learn how to balance chemical equations. Explain the mole concept

Balancing Equation

Count the atoms on each side.Reactant side: 2 atoms H and 2 atoms OProduct side: 2 atoms H and 1 atom O

H2 + O2 H2O

Page 22: 2.C – Conserving Matter. Objectives State and apply the Law of Conservation of Matter. Learn how to balance chemical equations. Explain the mole concept

Balancing Equations

H2 + O2 H2O

If the subscripts cannot be altered, how can the atoms be made equal?

Adjust the number of molecules by changing the coefficients.

Page 23: 2.C – Conserving Matter. Objectives State and apply the Law of Conservation of Matter. Learn how to balance chemical equations. Explain the mole concept

Balancing Equations

Balance one atom at a time: Let’s start with balancing oxygen!

Reactants: 2 atoms of H and 2 atoms of O Products: 4 atoms of H and 2 atoms of O H is no longer balanced!

H2 + O2 2H2O

Page 24: 2.C – Conserving Matter. Objectives State and apply the Law of Conservation of Matter. Learn how to balance chemical equations. Explain the mole concept

Balancing Equations

Now try to balance the hydrogens by placing a 2 in front of the reactant H2

Reactant side: 4 atoms of H and 2 atoms of O Product side: 4 atoms of H and 2 atoms of O It’s Balanced!

2H2 + O2 2H2O

Page 25: 2.C – Conserving Matter. Objectives State and apply the Law of Conservation of Matter. Learn how to balance chemical equations. Explain the mole concept

How do we Balance Equations?

2 H2 + O2 2 H2O

Subscripts

Coefficients

# of atoms in a compound

Number of compounds in the reaction

Subscripts can not be changed.

Coefficients balance atoms in an equation

Page 26: 2.C – Conserving Matter. Objectives State and apply the Law of Conservation of Matter. Learn how to balance chemical equations. Explain the mole concept

Make a table of elements

_____ __________

How to Balance By Inspection:

1

Reactants Products

H

O

C

CH4 + O2 H2 O CO2+_____

Page 27: 2.C – Conserving Matter. Objectives State and apply the Law of Conservation of Matter. Learn how to balance chemical equations. Explain the mole concept

2 Count the number of each element or ion on the reactants and products side.

_____ __________

How to Balance By Inspection:

Reactants Products

H

O

4

2 3

2

C 1 1

CH4 + O2 H2 O CO2+_____

Don’t forget to add all the atoms of the same element together—even if it appears in more than one compound!

Page 28: 2.C – Conserving Matter. Objectives State and apply the Law of Conservation of Matter. Learn how to balance chemical equations. Explain the mole concept

3Each time you add a coefficient, update your table with the new quantities of each atom.

Add coefficients to balance the numbers

_____ __________2

How to Balance By Inspection:

Reactants Products

H

O

4

2 3

2

C 1 1

2

4

44

CH4 + O2 _____ H2 O CO2+

Page 29: 2.C – Conserving Matter. Objectives State and apply the Law of Conservation of Matter. Learn how to balance chemical equations. Explain the mole concept

4

Filling each coefficient location lets you and the grader know that you finished the problem rather than you left some blank because you weren’t done!

Place a “1” in any empty coefficient location

_____ __________2

How to Balance By Inspection:

Reactants Products

H

O

4

2 3

2

C 1 1

2

4

44

1 1CH4 + O2 _____ H2 O CO2+

Page 30: 2.C – Conserving Matter. Objectives State and apply the Law of Conservation of Matter. Learn how to balance chemical equations. Explain the mole concept

What do Coefficients Really Mean?

CH4 + 2 O2 CO2 + 2 H2O

Total:1 C4 H4 O

Total:1 C4 H4 O

The equation is balanced.

H

C

H

HH

O O

O O

CO O HO

H

HO

H

H

CC

H

HH

O O

O O

CCO O HO

H

HO

H

Page 31: 2.C – Conserving Matter. Objectives State and apply the Law of Conservation of Matter. Learn how to balance chemical equations. Explain the mole concept

Balancing Equations

Count atoms.Reactants: 2 atoms N and 2 atoms HProducts: 1 atom N and 3 atoms of H

N2 + H2 NH3

Nitrogen + hydrogen ammonia

Page 32: 2.C – Conserving Matter. Objectives State and apply the Law of Conservation of Matter. Learn how to balance chemical equations. Explain the mole concept

Balancing EquationsNothing is balanced.Balance the nitrogen first by placing a

coefficient of 2 in front of the NH3.

N2 + H2 2NH3

Page 33: 2.C – Conserving Matter. Objectives State and apply the Law of Conservation of Matter. Learn how to balance chemical equations. Explain the mole concept

Balancing Equations Hydrogen is not balanced. Place a 3 in front of H2.

Reactant side: 2 atoms N, 6 atoms H Product side: 2 atoms N, 6 atoms H It’s balanced!

N2 + 3H2 2NH3

Page 34: 2.C – Conserving Matter. Objectives State and apply the Law of Conservation of Matter. Learn how to balance chemical equations. Explain the mole concept

Balancing Equations

Count Atoms: Reactants: Cu – 1, H – 2, S – 1, O – 4 Products: Cu – 1, H – 2, S - 2, O - 7

Cu + H2SO4 CuSO4 + H2O + SO2

Page 35: 2.C – Conserving Matter. Objectives State and apply the Law of Conservation of Matter. Learn how to balance chemical equations. Explain the mole concept

Balancing EquationsSulfur is not balanced.Place a two in front of sulfuric acid.Count Atoms: Reactants: Cu – 1, H – 4, S – 1, O – 8 Products: Cu – 1, H – 2, S - 2, O - 7

Cu + 2H2SO4 CuSO4 + H2O + SO2

Page 36: 2.C – Conserving Matter. Objectives State and apply the Law of Conservation of Matter. Learn how to balance chemical equations. Explain the mole concept

Balancing EquationsHydrogen needs to be balanced so

place a 2 in front of the H2O. Count the number of atoms.

Cu + 2H2SO4 CuSO4 + 2H2O + SO2

Page 37: 2.C – Conserving Matter. Objectives State and apply the Law of Conservation of Matter. Learn how to balance chemical equations. Explain the mole concept

Balancing Equations

Reactants: Cu – 1, H – 4, S – 2, O – 8 Products: Cu – 1, H – 4, S – 2, O – 8

It’s balanced!

Cu + 2H2SO4 CuSO4 + 2H2O + SO2

Page 38: 2.C – Conserving Matter. Objectives State and apply the Law of Conservation of Matter. Learn how to balance chemical equations. Explain the mole concept

Balancing Equations

Count atoms.Reactants: Ca – 3 atoms, P – 2 atoms,

O – 12 atoms, H – 2 atoms, S – 1 atom

Ca3(PO4)2 + H2SO4 CaSO4 + H3PO4

Page 39: 2.C – Conserving Matter. Objectives State and apply the Law of Conservation of Matter. Learn how to balance chemical equations. Explain the mole concept

Balancing Equations

Side note on Ca3(PO4)2

The subscript after the phosphate indicates two phosphate groups.

This means two P and eight O atoms.

Page 40: 2.C – Conserving Matter. Objectives State and apply the Law of Conservation of Matter. Learn how to balance chemical equations. Explain the mole concept

Balancing Equations

Ca3(PO4)2 + H2SO4 CaSO4 + H3PO4

Count atoms in the product.Ca atoms – 1, S atom – 1, O atoms – 8;

H atoms – 3, P atom – 1,

Page 41: 2.C – Conserving Matter. Objectives State and apply the Law of Conservation of Matter. Learn how to balance chemical equations. Explain the mole concept

Balancing Equations

Balance the metal first by placing a coefficient of 3 in front of CaSO4.

Ca3(PO4)2 + H2SO4 3CaSO4 + H3PO4

Page 42: 2.C – Conserving Matter. Objectives State and apply the Law of Conservation of Matter. Learn how to balance chemical equations. Explain the mole concept

Balancing Equations

Now balance the S atoms followed by the P atoms.

Ca3(PO4)2 + 3H2SO4 3CaSO4 + H3PO4

Page 43: 2.C – Conserving Matter. Objectives State and apply the Law of Conservation of Matter. Learn how to balance chemical equations. Explain the mole concept

Balancing EquationsA coefficient of 2 placed in front of

H3PO4 which balances both hydrogen and phosphate.

Ca3(PO4)2 + 3H2SO4 3CaSO4 + 2H3PO4

Page 44: 2.C – Conserving Matter. Objectives State and apply the Law of Conservation of Matter. Learn how to balance chemical equations. Explain the mole concept

Balancing Equations

This method of balancing equations is trial and error.

Practice.

Page 45: 2.C – Conserving Matter. Objectives State and apply the Law of Conservation of Matter. Learn how to balance chemical equations. Explain the mole concept

Let’s Practice #1

Example:Balance the

following equation

__ HCl + __ Ca(OH)2 __ CaCl2 + __ H2O

Page 46: 2.C – Conserving Matter. Objectives State and apply the Law of Conservation of Matter. Learn how to balance chemical equations. Explain the mole concept

Let’s Practice #2

Example:Balance the

following equation

__ H2 + __ O2 __ H2O

Page 47: 2.C – Conserving Matter. Objectives State and apply the Law of Conservation of Matter. Learn how to balance chemical equations. Explain the mole concept

Let’s Practice #3

Example:Balance the

following equation

__ Fe + __ O2 ___ Fe2O3

Page 48: 2.C – Conserving Matter. Objectives State and apply the Law of Conservation of Matter. Learn how to balance chemical equations. Explain the mole concept

C.4: Balancing Equations

Classwork: Complete questions 1-6 on page 160-

161

Due:

Page 49: 2.C – Conserving Matter. Objectives State and apply the Law of Conservation of Matter. Learn how to balance chemical equations. Explain the mole concept

Balancing Equations

Homework: Complete C3 Supplement worksheet

Due:

Page 50: 2.C – Conserving Matter. Objectives State and apply the Law of Conservation of Matter. Learn how to balance chemical equations. Explain the mole concept

Balancing Equations

Additional Worksheets

Page 51: 2.C – Conserving Matter. Objectives State and apply the Law of Conservation of Matter. Learn how to balance chemical equations. Explain the mole concept

C.5 The Mole Concept

Definition:

Mole – Unit for counting for chemists.

Counting atoms is impractical because atoms areso small and are not visible to the naked eye.

You can not weigh individual atoms on laboratory balance.

Page 52: 2.C – Conserving Matter. Objectives State and apply the Law of Conservation of Matter. Learn how to balance chemical equations. Explain the mole concept

Relating Mass to Numbers of Atoms

Introduction of three very important concepts:

1)The mole

2)Avogadro’s number

3)Molar mass

Page 53: 2.C – Conserving Matter. Objectives State and apply the Law of Conservation of Matter. Learn how to balance chemical equations. Explain the mole concept

What is a counting unit?

You’re already familiar with one counting unit…a “dozen”

“Dozen” 12

A dozen doughnuts 12 doughnuts

A dozen books

A dozen cars

A dozen people

12 books

12 cars

12 people

A dozen = 12

Page 54: 2.C – Conserving Matter. Objectives State and apply the Law of Conservation of Matter. Learn how to balance chemical equations. Explain the mole concept

A Mole of ParticlesA Mole of Particles Contains 6.02 x 1023 particles

Avogadro’s Number

1 mole C = 6.02 x 1023 C atoms

1 mole H2O = 6.02 x 1023 H2O molecules

1 mole NaCl= 6.02 x 1023 NaCl “molecules”

Page 55: 2.C – Conserving Matter. Objectives State and apply the Law of Conservation of Matter. Learn how to balance chemical equations. Explain the mole concept

How big is a mole? Enough soft drink cans to cover the

surface of the earth to a depth of over 200 miles.

If you had Avogadro's number of unpopped popcorn kernels, and spread them across the United States of America, the country would be covered in popcorn to a depth of over 9 miles.

If we were able to count atoms at the rate of 10 million per second, it would take about 2 billion years to count the atoms in one mole.

One mole of paper clips would wrap around the earth 400 trillion times!

Page 56: 2.C – Conserving Matter. Objectives State and apply the Law of Conservation of Matter. Learn how to balance chemical equations. Explain the mole concept

What does a “mole” count in?

A mole = 6.02 1023 (called Avogadro’s number)

“mole” 6.02 1023

1 mole of doughnuts 6.02 1023 doughnuts

1 mole of atoms

1 mole of molecules

6.02 1023 atoms

6.02 1023 molecules

6.02 1023 = 602,000,000,000,000,000,000,000

Page 57: 2.C – Conserving Matter. Objectives State and apply the Law of Conservation of Matter. Learn how to balance chemical equations. Explain the mole concept

1. Mole of a substance = grams of substance/MW of substance

2. The mole enables chemists to move from the microscopic world of atoms and molecules to the real world of grams and kilograms.

Page 58: 2.C – Conserving Matter. Objectives State and apply the Law of Conservation of Matter. Learn how to balance chemical equations. Explain the mole concept

Molar Mass

Page 59: 2.C – Conserving Matter. Objectives State and apply the Law of Conservation of Matter. Learn how to balance chemical equations. Explain the mole concept

Definition

Molar Mass – The mass for one mole of an atom or molecule.

Other terms commonly used for the same meaning:

Molecular WeightAtomic Weight (used for atoms)

Page 60: 2.C – Conserving Matter. Objectives State and apply the Law of Conservation of Matter. Learn how to balance chemical equations. Explain the mole concept

Mass for 1 mole of atomsThe average atomic mass = grams for 1 mole

Element Mass

1 mole of carbon atoms 12.01 g

1 mole of oxygen atoms

1 mole of hydrogen atoms

16.00 g

1.01 g

Unit for molar mass: g/mole or g/mol

Average atomic mass is found on the periodic table

Page 61: 2.C – Conserving Matter. Objectives State and apply the Law of Conservation of Matter. Learn how to balance chemical equations. Explain the mole concept

One mole of carbon (12 grams) and one mole of copper (63.5 grams)

Page 62: 2.C – Conserving Matter. Objectives State and apply the Law of Conservation of Matter. Learn how to balance chemical equations. Explain the mole concept

Molar Mass

Examples:

Molar mass of lithium (Li) = 6.94 g/mol

Molar mass of helium (He) = 4.00 g/mol

Molar mass of mercury (Hg) = 200.6 g/mol

Page 63: 2.C – Conserving Matter. Objectives State and apply the Law of Conservation of Matter. Learn how to balance chemical equations. Explain the mole concept

A molar mass of an element contains one mole of atoms.

4.00 g helium = 1mole = 6.02 x 1023 atoms.

6.94 g lithium = 1mole = 6.02 x 1023 atoms.

200.6 g mercury = 1mole = 6.02 x 1023 atoms.

Molar Mass

Page 64: 2.C – Conserving Matter. Objectives State and apply the Law of Conservation of Matter. Learn how to balance chemical equations. Explain the mole concept

Molar mass for molecules

The molar mass for a molecule = the sum of the molar masses of all the atoms

Page 65: 2.C – Conserving Matter. Objectives State and apply the Law of Conservation of Matter. Learn how to balance chemical equations. Explain the mole concept

Calculating a Molecule’s Mass

Count the number of each type of atom

Find the molar mass of each atom on the periodic table

Multiple the # of atoms molar mass for each atom

Find the sum of all the masses

1

2

3

4

To find the molar mass of a molecule:

Page 66: 2.C – Conserving Matter. Objectives State and apply the Law of Conservation of Matter. Learn how to balance chemical equations. Explain the mole concept

Example: Molar Mass

Example:Find the

molar mass for

CaBr2

Page 67: 2.C – Conserving Matter. Objectives State and apply the Law of Conservation of Matter. Learn how to balance chemical equations. Explain the mole concept

Example: Molar Mass

Count the number of each type of atom1

Ca

Br

1

2

Example:Find the

molar mass for

CaBr2

Page 68: 2.C – Conserving Matter. Objectives State and apply the Law of Conservation of Matter. Learn how to balance chemical equations. Explain the mole concept

Example: Molar Mass

Find the molar mass of each atom on the periodic table2

Ca

Br

1

2

40.08 g/mole

79.91 g/mole

Example:Find the

molar mass for

CaBr2

Page 69: 2.C – Conserving Matter. Objectives State and apply the Law of Conservation of Matter. Learn how to balance chemical equations. Explain the mole concept

Example: Molar Mass

Multiple the # of atoms molar mass for each atom3

Ca

Br

1

2

40.08 g/mole

79.91 g/mole

Example:Find the

molar mass for

CaBr2

= 40.08 g/mole

= 159.82 g/mole

Page 70: 2.C – Conserving Matter. Objectives State and apply the Law of Conservation of Matter. Learn how to balance chemical equations. Explain the mole concept

Example: Molar Mass

Find the sum of all the masses4

Ca

Br

1

2

40.08 g/mole

79.91 g/mole

= 40.08 g/mole

= 159.82 g/mole+

199.90 g/mole

1 mole of CaBr2 molecules would have a mass of 199.90 g

Example:Find the

molar mass for

CaBr2

Page 71: 2.C – Conserving Matter. Objectives State and apply the Law of Conservation of Matter. Learn how to balance chemical equations. Explain the mole concept

Molar Mass

A molar mass of a compound is the sum of the molar masses of the elements.

Example: Water, H2O:

2 H = 2 x 1 g/mole = 2 g/mole1 O = 1 x 16 g/mole = 16 g/mole

molar mass of H20 =18 g/mol

Page 72: 2.C – Conserving Matter. Objectives State and apply the Law of Conservation of Matter. Learn how to balance chemical equations. Explain the mole concept

Molar Mass

A molar mass of a compound is the sum of the molar masses of the elements.

Example: methane, CH4:

4 H = 4 x 1 g = 4 g/mole1 C = 1 x 12g = 12 g/mole

molar mass of CH4 =16 g/mol

Page 73: 2.C – Conserving Matter. Objectives State and apply the Law of Conservation of Matter. Learn how to balance chemical equations. Explain the mole concept

Example: Molar Mass & Parenthesis

Be sure to distribute the subscript outside the parenthesis to each element inside the parenthesis.

Example:Find the

molar mass for Sr(NO3)2

Page 74: 2.C – Conserving Matter. Objectives State and apply the Law of Conservation of Matter. Learn how to balance chemical equations. Explain the mole concept

Let’s Practice #1

Example:Find the

molar mass for CH2Cl2

Page 75: 2.C – Conserving Matter. Objectives State and apply the Law of Conservation of Matter. Learn how to balance chemical equations. Explain the mole concept

Let’s Practice #2

Example:Find the

molar mass for Al(OH)3

Page 76: 2.C – Conserving Matter. Objectives State and apply the Law of Conservation of Matter. Learn how to balance chemical equations. Explain the mole concept

Classwork: C.6: Molar Masses

Page 163; questions1-9

Page 77: 2.C – Conserving Matter. Objectives State and apply the Law of Conservation of Matter. Learn how to balance chemical equations. Explain the mole concept

Homework: C.5 SupplementWorksheet

Due:

Page 78: 2.C – Conserving Matter. Objectives State and apply the Law of Conservation of Matter. Learn how to balance chemical equations. Explain the mole concept

C.8: Molar Relationships

Page 79: 2.C – Conserving Matter. Objectives State and apply the Law of Conservation of Matter. Learn how to balance chemical equations. Explain the mole concept

Molar mass for molecules

The molar mass for a molecule = the sum of the molar masses of all the atoms in the molecule.

Example:

1 mole of H2O = 18 grams

1 mole of H2O weighs 18 grams.

Page 80: 2.C – Conserving Matter. Objectives State and apply the Law of Conservation of Matter. Learn how to balance chemical equations. Explain the mole concept

What happens when you do not have 18 grams of water?

How do you calculate the number of moles of water?

Page 81: 2.C – Conserving Matter. Objectives State and apply the Law of Conservation of Matter. Learn how to balance chemical equations. Explain the mole concept

Conversion Factors

Conversion factor – a way that can be used to convert from one unit to the other.

Example: the conversion between quarters and dollars:

4 quarters 1 dollar 1 dollar or 4 quarters

Page 82: 2.C – Conserving Matter. Objectives State and apply the Law of Conservation of Matter. Learn how to balance chemical equations. Explain the mole concept

Conversion Factors

Page 83: 2.C – Conserving Matter. Objectives State and apply the Law of Conservation of Matter. Learn how to balance chemical equations. Explain the mole concept

Lets return to the term dozen.

12 roses = 1 dozen roses (conversion factor)6 roses = ½ dozen

Calculations:

6 roses____ = 0.5 dozen12 roses/dozen

Conversion Factors

Page 84: 2.C – Conserving Matter. Objectives State and apply the Law of Conservation of Matter. Learn how to balance chemical equations. Explain the mole concept

Molar masses can be used as a conversion factor in chemical calculations.

Molar masses allow the chemist to convert from grams to moles of a compound and from moles to grams of a compound.

Grams Molesmolar mass

Page 85: 2.C – Conserving Matter. Objectives State and apply the Law of Conservation of Matter. Learn how to balance chemical equations. Explain the mole concept

Gram/Mole Conversions

Page 86: 2.C – Conserving Matter. Objectives State and apply the Law of Conservation of Matter. Learn how to balance chemical equations. Explain the mole concept

Example: Moles to Grams

Example:How many grams are

in 1.25 moles of water?

Page 87: 2.C – Conserving Matter. Objectives State and apply the Law of Conservation of Matter. Learn how to balance chemical equations. Explain the mole concept

Example: Moles to Grams

1.25 mol H2O = _______ g H2Omol H2O

g H2O18.02

1

22.53

When converting between grams and moles, the molar mass is needed

1 mole H2O molecules = 18.02 g

HO

21

1.01 g/mole16.00 g/mole

= 2.02 g/mole= 16.00 g/mole+

18.02 g/mole

Example:How many grams are

in 1.25 moles of water?

Page 88: 2.C – Conserving Matter. Objectives State and apply the Law of Conservation of Matter. Learn how to balance chemical equations. Explain the mole concept

Problem

How many grams are in 2.25 moles of iron, Fe?

Page 89: 2.C – Conserving Matter. Objectives State and apply the Law of Conservation of Matter. Learn how to balance chemical equations. Explain the mole concept

Problem

How many grams are in 2.25 moles of iron, Fe?

Answer: 126 grams Fe

Page 90: 2.C – Conserving Matter. Objectives State and apply the Law of Conservation of Matter. Learn how to balance chemical equations. Explain the mole concept

Problem

How many grams are in 0.375 moles of

potassium, K?

Page 91: 2.C – Conserving Matter. Objectives State and apply the Law of Conservation of Matter. Learn how to balance chemical equations. Explain the mole concept

Problem

How many grams are in 0.375 moles of

potassium, K?

Answer: 14.7 grams

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Problem

How many grams are in 20 moles of methane, CH4?

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Problem

How many grams are in 20 moles of methane, CH4?

Answer: 320 grams

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Grams to Moles

If you are given a quantity in grams you can determine how moles you have by using the molar mass.

molar massGrams Moles

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Let’s Practice

Example:How many moles are in 25.5 g NaCl?

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Let’s Practice

25.5 g NaCl = _______ mole NaClg NaCl

mole NaCl1

58.44

0.44

1 mole NaCl molecules = 58.44 g

NaCl

11

22.99 g/mole35.45 g/mole

= 22.99 g/mole= 35.45 g/mole+

58.44 g/mole

Example:How many moles are in 25.5 g NaCl?

Page 97: 2.C – Conserving Matter. Objectives State and apply the Law of Conservation of Matter. Learn how to balance chemical equations. Explain the mole concept

Example: Grams to Moles

A chemist produced 11.9 g of aluminum, Al. How many moles of aluminum were produced?

mass of Al in grams amount of Al in moles

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Problem

How many moles of calcium, Ca, are in 5.00 grams of calcium?

Page 99: 2.C – Conserving Matter. Objectives State and apply the Law of Conservation of Matter. Learn how to balance chemical equations. Explain the mole concept

Problem

How many moles of calcium, Ca, are in 5.00 grams of calcium?

Answer: 0.125 moles

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Problem

How many moles of sodium chloride, NaCl, are in 75 grams of NaCl?

Page 101: 2.C – Conserving Matter. Objectives State and apply the Law of Conservation of Matter. Learn how to balance chemical equations. Explain the mole concept

Problem

How many moles of sodium chloride, NaCl, are in 75 grams of NaCl?

Answer: 1.28 moles

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C.8: Molar Relationships

Classwork: C.8 Problems

Page 166 questions 1-3 (hold on 4)

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Homework: C.7-1 SupplementWorksheet

Due:

Page 104: 2.C – Conserving Matter. Objectives State and apply the Law of Conservation of Matter. Learn how to balance chemical equations. Explain the mole concept

C.7:Equations and Molar Relationships

How are chemical equations and molar masses related?

2 CuO + C 2 Cu + CO2

2 moles 1 mole 2 moles 1mole

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C.7:Equations and Molar Relationships

2 CuO + C 2 Cu + CO2

2 moles 1 mole 2 moles 1mole

159.1 g + 12.01 g 127.1 g + 44 g

171.1 g total 171.1 g total

Same total mass on the reactant and product side

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C.7:Equations and Molar Relationships

StoichiometryPowerPoint

Page 107: 2.C – Conserving Matter. Objectives State and apply the Law of Conservation of Matter. Learn how to balance chemical equations. Explain the mole concept

Example: Grams to Molecules

Example:How many molecules

are in 25.5 g NaCl?

Skip

Page 108: 2.C – Conserving Matter. Objectives State and apply the Law of Conservation of Matter. Learn how to balance chemical equations. Explain the mole concept

25.5 g NaCl

Example: Grams to Molecules

= _________ molecules NaCl

g NaCl

mol NaCl1

58.44

2.63 1023

1 mol = 6.021023 molecules

1 moles NaCl molecules = 58.44 g

NaCl

11

22.99 g/mole35.45 g/mole

= 22.99 g/mole= 35.45 g/mole+

58.44 g/mole

mol NaCl

molecules NaCl6.021023

1

Example:How many molecules

are in 25.5 g NaCl?

Page 109: 2.C – Conserving Matter. Objectives State and apply the Law of Conservation of Matter. Learn how to balance chemical equations. Explain the mole concept

Let’s Practice #4

Example:How many grams is a sample of 2.75 × 1024

molecules of SrCl2?

Skip

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Homework: C.7-2 SupplementWorksheet

Due:

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C.9: Percent Composition

Percent Composition - The percent mass of each element found in a mixture

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Sample problem 1: A post-1982 penny with a mass of 2.50 g is composed of 2.44 g of zinc and 0.06 g copper. What is the percent composition of each element?

Mixtures

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Zinc: 2.44 g zinc x 100% = 97.5% 2.50 g total

Copper: 0.06 g Cu x 100% = 2.5% 2.50 g total

Total percent must equal 100%

The percent composition of the penny can be found by dividing the mass of each element by the total mass of the penny and multiplying by 100%.

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Sample problem 2: The formula for the copper containing mineral chalcocite is Cu2S.

1) What percentage of copper (Cu) is in this mineral?

2) What percentage of sulfur (S) is in this mineral?

Relating molar mass and percent composition

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% Cu = mass of Cu x 100% mass of Cu2S

% Cu: 127.1 g Cu x 100% = 79.9% 159.2 g Cu2S

The formula for chalcocite indicates one mole of Cu2S contains two molecules of Cu (127.1 g) and one mole of S (32 g). The molar mass of Cu2S = 159.2 g.

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% S = mass of S x 100% mass of Cu2S

% Cu: 32 g Cu x 100% = 20.1% 159.2 g Cu2S

The formula for chalcocite indicates one mole of Cu2S contains two molecules of Cu (127.1 g) and one mole of S (32 g). The molar mass of Cu2S = 159.2 g.

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C.10: Percent Composition

Classwork: page 168, problems 2 and 4

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C.10: Percent Composition

Homework: C.10: Worksheetpercent composition

Due:

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C.11:

Lab: Retrieving Copper

Read over the lab procedure

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C.12: Conservation

Renewable resources: resources that can be replenished.

Examples include fresh water, air, fertile soil, plants and animals.

As long as natural cycles are not disturbed too much, supplies of renewable resources can be maintained indefinitely.

Page 121: 2.C – Conserving Matter. Objectives State and apply the Law of Conservation of Matter. Learn how to balance chemical equations. Explain the mole concept

Nonrenewable resources: resources that can not be readily replenished.

Examples include metals, natural gas, coal and petroleum.

The length of time to replenish these resources are very large.

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End of Unit

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Replacing: replace a resource by finding a substitute, preferably from renewable resources.

Reusing: refurbish or repair an item to use again. Examples include car parts and printer cartridges.

Recycle: reprocess to use again. Examples include aluminum cans, newspaper and glass bottles.

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C.12: Conservation

C12: Complete worksheet.

These terms will appear again on a test or final exam!