I have a few questions involving equilibrium and Le Chatelier\'s Principle. a. W

Question

I have a few questions involving equilibrium and Le Chatelier's Principle.

a. What is the net ionic equation of CoCl4^2- + 6H2O (l) ? Co(H2O)6^2+ (aq) + 4Cl^- (aq) that describes the observed precipitation reaction after both HCl (aq) and AgNO3 (aq) have been added?

b. What are the spectator ions and the acid and base in Ni^2+ (aq) + 6NH3 (aq) ? Ni(NH3)6^2+ (aq) after HCl (aq) and Ni(NO3)2 (aq) has been added?

c. What is the net ionic equation of Mg(OH)2 ? Mg^2+ + 2OH^- after NaOH (aq) and MgCl2 (aq) have been added?

Explanation / Answer

(a)

When the solution is heated to boiling, it turns from pink to blue. This blue solution shifts back to pink as the AgNO3 is added. When HCl is added to a pink solution, it turns blue.

Co(H2O)62+(aq) + 4 Cl-(aq) <=> CoCl42-(aq) + 6 H2O(g)

The Co(H2O)62+ complex is pink, and the CoCl42- complex is blue.

This reaction is endothermic as written, so adding heat causes the equilibrium constant to shift to the right. This, correspondingly, makes the solution blue.

When the AgNO3 is added, Cl- is removed from solution. This shifts the equation back to the left, and the solution turns pink again.

When HCl is added, there is more Cl- in solution, so the equilibrium is shifted to the right, and the solution turns blue.

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