Textbook Question
Calculate the solubility of silver chloride in a solution that is 0.100 M in NH3.
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18. Aqueous Equilibrium
Complex Ions: Formation Constant
Multiple Choice
What concentration of Cu2+ is needed to have a concentration of Cu(CN)4^2- equal to 2.0 x 10^-5 M in a solution with a [CN^-] of 9.3 x 10^-4 M? Kf of Cu(CN)4^2- = 1.0 x 10^25
A
2.2 x 10^-30 M
B
3.1 x 10^-15 M
C
4.5 x 10^-25 M
D
1.0 x 10^-20 M
Verified step by step guidance1
Understand the problem: We need to find the concentration of Cu2+ ions required to achieve a specific concentration of the complex ion Cu(CN)4^2- in the presence of a given concentration of CN- ions. The formation constant (Kf) for the complex is provided.
Write the equilibrium expression for the formation of the complex ion Cu(CN)4^2-. The reaction is: Cu2+ + 4CN- ⇌ Cu(CN)4^2-. The equilibrium constant expression (Kf) is:
Substitute the known values into the equilibrium expression. We know is 2.0 x 10^-5 M and is 9.3 x 10^-4 M. Plug these into the equation:
Rearrange the equation to solve for the concentration of Cu2+. This involves isolating on one side of the equation:
Calculate the concentration of Cu2+ using the rearranged equation. This involves substituting the values for Kf, the concentration of Cu(CN)4^2-, and the concentration of CN- into the equation and performing the arithmetic operations to find the concentration of Cu2+.
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