Question

You're provided with a bottle labled [CoCl₂^.6H₂O] = 0.066 M in 4.60 M HCl. You heat a small volume of the solution in a hot water bath to 50 ^∘C. If you determine that [CoCl₄^2-] = 0.037 M at 50 ^∘C at equilibrium, what must be the equilibrium concentration of [Cl^-] at 50 ^∘C?

Express your response in units of M to three digits after the decimal.

Answer 1

equilibrium concentration of Cl^- = 4.526 M

Explanation

initial concentration CoCl₂ = 0.066 M

initial concentration Cl^- = 4.60 M

equilibrium concentration CoCl₄^2- = 0.037 M

ICE table	CoCl2	2 Cl-	$\rightleftharpoons$	CoCl42-
Initial conc.	0.066 M	4.60 M		0
Change	-x	-2x		+x
Equilibrium conc.	0.066 M - x	4.60 M - 2x		+x

equilibrium concentration CoCl₄^2- = 0.037 M (given) = x (from table)

Hence, x = 0.037 M

equilibrium concentration Cl^- = 4.60 M - 2x

equilibrium concentration Cl^- = 4.60 M - 2 * (0.037 M)

equilibrium concentration Cl^- = 4.60 M - 0.074 M

equilibrium concentration Cl^- = 4.526 M