Chemistry Lab

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  • Topic: Chemistry, Chromate, Chromates
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  • Published : January 4, 2013
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Investigating Chemical Equilibrium
(Experiment 19 A)

Purpose:
1.to recognize the macroscopic properties of five chemical systems at equilibrium 2.to observe shifts in equilibrium concentrations as stresses are applied to the systems 3.to observe a shift in equilibrium concentrations associated with changes in temperature 4.to explain the observations obtained by applying Le Chatelier’s principle Materials Required:

See page 209 Heath Chemistry Laboratory Experiments

Procedure:
See pages 209-211 Heath Chemistry Laboratory Experiments

Data and Observations:

Table 1 Equilibrium Involving Thymol Blue
REAGENT ADDEDSTRESS
(ION ADDED)COLOR
OBSERVATIONDIRECTION OF
EQUILIBRIUM SHIFT
HCl (Step 3)
HCl (Step 4)
NaOH (Step 5)
NaOH (Step 6)

Table 2 Equilibrium Involving Thiocyanatoiron (III) Ion
REAGENT ADDEDSTRESS
(ION ADDED)OBERSERVATIONDIRECRTION OF
EQUILIBRIUM SHIFT
KCl (test tube B)
Fe(NO3)3 (test tube C)
KSCN (test tube D)
NaOH (test tube E)

Table 3 Equilibrium Involving Cobalt (II) Complexes
STRESSOBSERVATIONDIRECTION OF EQUILIBRIUM SHIFT
Step 3
Step 4
Step 5

Table 4 Equilibrium Involving Chromate and Dichromate Ions Steps
2
and
30.1 M K2CrO40.1 M K2Cr2O7
Initial Color
1 M NaOH added
1 M HCl added
Step 40.1 M K2CrO40.1 M K2Cr2O7
Initial Color
1 M HCl added
1 M NaOH added
Steps
5 and
6INITIAL COLOR+ 1 M NaOH+ 0.1 M Ba(NO3)2+ 1 M HCl
0.1 M K2CrO4

Steps
7 and 8INITIAL COLOR+ 1 M HCl+ 0.1 M Ba(NO3)2+ 1 M NaOH
0.1 M K2Cr2O7

Step 90.1 M K2CrO40.1 M K2Cr2O7
Add 0.1 M Ba(NO3)2

Table 5 Equilibrium Involving Copper (II) Complexes
0.1 M CuSO4+ 3 DROPS NH3+ MORE NH31 M HCl ADDED
Appearances
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