Cobalt ion exists as (Co(H_2O)]^2+in aqueous solutions. The following equilibriu
ID: 1063918 • Letter: C
Question
Cobalt ion exists as (Co(H_2O)]^2+in aqueous solutions. The following equilibrium reaction represents the two types of complexes of cobalt with two different colors. [CoCl_4]^2- (aq, blue) + 6 H_2O(I) irreversible [Co(H_2O)_6]^2+ (aq, pink) + 4 Cl^- (aq) what change in color do you expect when you add 10 drops of 12 M HCl to an aqueous solution of cobalt salt? Explain your answer in terms of LeChatlier principle. To the above mixture, if you add distilled water drop-wise what change you expect? Explain your answer in terms of LeChatlier principle. The above solution is divided equally into three test tubes A, B, C, . Test tube "A" is placed in an ice bath kept at 0 degree C, test tube "B" is kept at room temperature (25 degree C) and test tube "C" is placed in a boiling hot water bath maintained at 100 degree C. The following are the colors of the solutions observed in each case. Solution "A" remained pink, solution "B" became dark pink and solution "C" turned blue. What do you conclude about the effect of temperature change on the position of equilibrium between cobalt complex ions (use the equation given above). Is the forward equilibrium reaction an exothermic or endothermic process? Explain.Explanation / Answer
The equilibrium is
CoCl4-2 (aq,blue) + 6 H2 O ------->[ Co(H2O)6 ]+2 (aq, pink) + 4 Cl-
a) When HCl is added, we adding the product /common ion into the equilibrium . Thus according to Le-chatlier, the equilibrium rponds ina way to reduce the effect, that is back ward reaction is favored.
The color of solution turns blue.
b) when distilled water is added dropwise , the reactant concentration is increeased , and hence the equilibrium shifts right side, that is the forward reaction is favored according to Le - Chatlier principle.. Slowly the pink colr increases.
c) A - kept at 0 C- pink color remained
B - kept at room temperature - dark pink
C - kept at 100C - blue in color
As the temperature is raised to 100 C , the back ward reaction is very much favored. Hence we can say backward reaction is endothermic.
Thus the forward reaction is exothermic.
Thus aat room temperature it has more of pink colour and at 0C also the pink color remained.
Hence the forward reaction is exothermic and backward reaction is endothermic.