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Chromate and dichromate ions form an equilibrium according to the following equation - HSC - SSCE Chemistry - Question 18 - 2010 - Paper 1
Question 18
Chromate and dichromate ions form an equilibrium according to the following equation. $$ 2CrO_4^{2-}(aq) + 2H^+(aq) \rightleftharpoons Cr_2O_7^{2-}(aq) + H_2O(l) $$... show full transcript
Worked Solution & Example Answer:Chromate and dichromate ions form an equilibrium according to the following equation - HSC - SSCE Chemistry - Question 18 - 2010 - Paper 1
Step 1
Which solution would increase the concentration of the chromate ion (CrO_4^{2-})?
Answer
To determine which solution would increase the concentration of chromate ions, we must consider the Le Chatelier's principle. According to this principle, if a stress is applied to an equilibrium system, the system will adjust in a direction that counteracts that stress.
In this case, adding a solution that provides hydroxide ions (OH^-) would shift the equilibrium to the left, favoring the formation of the chromate ions from dichromate ions.
Sodium acetate (option C) is a solution that contains acetate ions, which can act as a weak base. Therefore, when added to the solution, sodium acetate will increase the concentration of OH^-, leading to a shift in the equilibrium towards the formation of CrO_4^{2-} ions.
Thus, the correct choice is (C) Sodium acetate.