1. Limiting and Excess Reagents

2. First Objective Your first objective of this lab begins before lab.
You should come to lab with the balanced chemical equation, table finished (pg.125), and #4.
Make sure that you check your values with me, either via or before lab.

3. Assigned Data to Collect
Each lab group will determine a different section of the lab data.
The data will then be shared after it is collected.
Group A: (1mL/6mL)
Group B: (2mL/5mL)
Group C: (3mL/4mL)
Group D: (4mL/3mL)
Group E: (5mL/2mL)
Group F: (6mL/1mL)

4. Experiment
Each lab group should follow these directions with the assigned volumes.
Collect 6 small test tubes and tongs
Label 1,1a,1b,2,2a,2b
A and 2 should be pyrex (heated later) and wipe clean of fingerprints and don’t touch again
Weigh 1 and 2

5. Test tubes 1 and 2
Add assigned volumes of Cu(NO3)2 and KI in test tubes 1 and 2
Record any observations
Use kimwipe to hold top of test tube and also to tap bottom on test tube to mix chemicals
Set in test tube rack for 5 minutes to fully react
Centrifuge the test tubes to collect solid for 5 minutes

6. Test tubes 1 and 2
Remove test tubes with kimwipe, gently to insure that the precipitant is not disturbed
Supernatant should be clear brown-green and solid gray precip. At bottom of test tubes
Put in test tube rack
Gently draw off supernatant with disposable pipet (read directions is lab book!! #6 pg120)

7. Test tubes 1 and 2  1a,1b,2a,2b
Place half of the supernatant from test tube 1 into test tube 1a, and the other half into test tube 1b
Place half of the supernatant from test tube 2 into test tube 2a, and the other half into test tube 2b
Set to side for further testing later

8. Test tubes 1 and 2
Wash precip. by adding ~3mL methanol (MeOH) to test tube 1 and 2.
Add the same to both test tube
Use kimwip to gently shake tubes so precip starts to cloud the solution.
Place back in centrifuge for 5 minutes
Supernatant should be clear again

9. Test tubes 1 and 2 Remove supernatant without disturbing precip
Supernatant this time will not be tested
Can use same pipet
Discard supernatant into waste container
Place test tubes 1 and 2 in 100mL beaker
Write name on beaker
Place in oven for at least 20 mins to dry
Test tubes must cool before weighing

10. Test tubes 1a,1b,2a,2b While waiting for test tubes 1 and 2 to dry
Add 1mL Cu(NO3)2 solution to test tubes 1a and 2a
Record any observations
Add 1mL KI solution to test tubes 1b and 2b

11. Test tubes 1 and 2
After test tubes have been in oven at least 20 mins, remove and place in desiccator to cool for at least 10 minutes
Desiccator keeps precip from absorbing moisture
Weigh each test tube once cool
Calculate mass precip in each tube
Give to instructor to post for whole class
Make sure you have all the data (from all lab groups) before leaving class

12. % error vs % yield % error = [(actual-theoretical)/theoretical)]*100
% yield = (actual/theoretical) *100