# 11 calibration graphfall06

8/4/2019 # 11 Calibration Graphfall06

1/19

A Calibration Graph

Experiment 11


2/19

Introduction

Purpose: To build a calibration graph and

use it to determine concentration.

Calibration graph Used to determine

concentration of an unknown solution bymeasuring the absorption of a solution with

a known concentration.

the solution we will be using today isCuSO4

.5H20


3/19

Absorption

Absorption is directly proportional toconcentration.

Absorption Light is passed through a

solution, at a particular wavelength. The instrument used to measure

absorption is a spectrophotometer. The

device measures the intensity of lightafter it has been projected through a

sample.


4/19

Review

Solute Vs. Solvent

Molarity Concentration

M = moles/L of Solution moles= grams/mw

1L = 1000ml


5/19

Review # 2

What would be the concentration if we

placed that .60 mol of NaCl into 1L of

water? M=mol/L = .60moles/1L thus .6M NaCl

Note: does not always have to be 1 L

# moles in 35 grams of NaCl ?

NaClmoles60.NaCl58g

NaCl1mole

1

NaCl35g


6/19

Obtain and crush a small amount of CuSO4.5H20

Measure accurately 0.04grams of CuSO4.5H20

Obtain, clean, and label 4 small beakers A-D

Obtain 1 small graduated cylinder

In beaker A add your CuSO4 and 20 ml of Di. water

Under the hood add 8 drops of NH4OH

Mix Carefully

Making our calibration graph


7/19

In B add 10 ml of cylinder A + 10ml of Di

water plus 8 drops of NH4OH In Cylinder C add 10 ml of cylinder B +

10 ml of water plus 8 drops of NH4OH

In Cylinder D add 10 ml of cylinder C + 10ml of water plus 8 drops of NH4OH

Each cylinder is the concentration of the

previous cylinder. Each cylinder will be a lighter shade of blue.


8/19

Set wavelength to 610nm and follow the

directions on the spec 20.

Transfer a portion of your sample to test

tube one for each cylinder.

Determine the absorbance for each sample.

How to determine absorbance


9/19

My Trial

I Used 0.040g of CuSO4.5H20

so grams / 20 mL = 0.040g

and grams /20 mL X10+2 = 4.0

my second sample is of the CuSO4 from sample #1

thus 0.020 g

my third sample of the CuSO4 from sample # 2 thus1.00X10- 2 g


10/19

Chart on pg 152

G/20 mL. Is asking for how many

grams you used. For my trial 0.040g

G/20 mL.X 10 +2 = 4.0g


11/19

Chart on pg 152 Continued

= 8.0 X10 -3 moles CuSO4/ 1L

For M convert to G/20 mL M/L

249.60g

0.04g CuSO4.5H2O

20 mL 1L

1000mL 1mol CuSO4.5H 2O

= M

M X 103 = 8.0


12/19

1. Type in Data X data first

2. Highlight data

3. Click on Chart Wizard

4. Use X-Y scatter5. Pick type of graph you want to use

6. Click next

7. Add Title and Units for X and Y

8. Add trend line if required.9. Add your name date and section to

the worksheet.

How To make a Graph using Excel


13/19

Independent Vs. Dependent Variables

Independent variable We can change this variable.

Graphed on X axis.

Dependent variable - We cannot change this variable.We measure the dependent variable as the independent

changes. Graphed on Y axis. Title of graph should be Independent Vs. Dependent


14/19

How to place equation of line on graph

1. Right click on line

2. Click on add trend line

3. Click on linear

4. Click on options5. Click on Display equation on chart


15/19

Graph #1

Molarity Vs. Absorbance

y = 0.0325x + 0.0505

0

0.2

0.4

0.6

0 5 10 15

Molarity (mol/L)X10+2

Absorba

nce

Lou Tisone

116-30


16/19

Graph #2

g/20ml Vs. Absorbance

y = 0.0649x + 0.0516

0

0.2

0.4

0.6

0 2 4 6 8

g/20ml X10+2

Absorbance

Lou Tisone

116-30


17/19

If given absorbance (y-axis)

and need concentration solve

for (x)

y=mx +b

xm

b-y

bmxy


18/19

To Determine M X 10 +3 (from graph)

My absorbance = .448

Y= 0.0325X + 0.0505

Put abs in for Y and solve for X

12.20MX

0.0325

0.0505.448

This is M X 10 +3

To determine M simply x10-3 1.22X10-2 M

The equation of graph # 1


19/19

Due Next Week

Calculate mol and M for each sample. Complete chart on page 152 and questions

1a-d

Question # 2 Two computerized graphs are required

(1) Absorbance Vs. Grams/20mL X10+2

(2) Absorbance Vs. Molarity X10+3

Place equation of line on graph

# 11 calibration graphfall06

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