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E-9
[Fe
3+
] that reacted with the OH
-
(aq)
. This shift will result in a decrease in the concentration of
[Fe(NCS)]
2+
(aq)
causing the colour intensity of the solution to lighten.
5.
An acidic solution, containing approximately equal concentrations of [CoCl
4
]²
-
(aq)
and
[Co(H2O)
6
]
2+
(aq)
in equilibrium was studied (equation (11)). This solution changed from violet to pink
when cooled. Use Le Châtelier's Principle to determine if this reaction is endothermic or exothermic.
6.
Calculate the initial concentrations of copper(II) nitrate and sodium hydroxide, if 2.0 mL of
0.50 M Cu(NO3)2 was combined in a test tube with 5.0 mL of 6.0 M NaOH.
Answer: Cu(NO3)2 is 0.14 M and NaOH is 4.3 M
REAGENTS
0.050 M and 0.10 M Fe(NO3)3 (iron(III) nitrate)
0.020 M KNCS (potassium thiocyanate)
6.0 M NaOH (sodium hydroxide)
0.20 M Na2C2O
4
(sodium oxalate)
0.20 M NaF (sodium fluoride)
0.10 M K
4
[Fe(CN)
6
] (potassium hexacyanoferrate(II))
1.0 M NH3 (ammonia)
0.10 M AgNO3 (silver nitrate)
1.0 M Pb(NO3)2 (lead(II) nitrate)
1.0 M NaCl (sodium chloride)
0.50 M Na2CrO
4
(sodium chromate)
1.0 M Na2S (sodium sulfide)
12.4 M HCl (hydrochloric acid)
1.0 M HCl (hydrochloric acid)
[CoCl
4
]²
-
/ [Co(H2O)
6
]
2+
equilibrium solution
ice
EXPERIMENTAL PROCEDURE
NOTE:
Some of the chemicals used in this experiment are very toxic. Therefore these solutions must NOT be
poured down the drain. Label a large beaker TOXIC WASTE and keep it at your workstation so that all
toxic waste can be poured into it as you work through the experiment. At the end of the laboratory
session, pour the content of this beaker into the designated TOXIC WASTE container in the fumehood.
Part I. The Iron(III) Thiocyanate Equilibrium
Using automatic dispensers, combine 1.0 mL of 0.050 M Fe(NO3)3 and 1.0 mL of 0.020 M KNCS in a 50 mL
graduated cylinder and dilute the solution by adding deionized water to the 20.0 mL mark. Pour the diluted
solution into a 50 mL beaker and mix the solution well. Transfer 2.0 mL of this solution into each of 9
different 13 x 100 mm test tubes.
Hint:
Measure 2.0 mL in a clean 10 mL graduated cylinder and transfer to test tube #1. Fill the remaining
8 test tubes to the same level
-
To test tube 1, add 5 drops of deionized H2O. This test tube provides a reference colour for
comparison with the other solutions. Record the colour of this solution on your Observations Sheet.
