Question

Nickel and carbon monoxide react to form nickel carbonyl like this:

Ni(s) + 4CO(g) ⇔ Ni(CO)4(g)

A 7.8 L vessel contains a mixture of nickel, carbon monoxide, and nickel carbonyl with the composition tabulated below. What is the value of the equilibrium constant, Kc?

compound amount

Ni 50.1

CO 1.9

Ni(CO)4 .307

A. 0.16

B. 4.0 × 10^4

C. 2.4 × 10^-2

D. 4.7 × 10^-4

E. 3.7 × 10^5

Answer 1

Number of moles of CO = 1.9/28 = 0.0678 moles

Since the volume of vessel is 7.8L

Hence molarity of CO = number of moles/Volume of solution(L) = 0.00869 M

Molar mass of Ni(CO)4 = 170.73 gm/mol

moles of Ni(CO)4 = 0.307/170.73 = 0.00179 moles

Molarity of Ni(CO)4 = 0.0179/7.8 = 2.3053 * 10^(-4)

Kc = [Ni(CO)4]/[CO]^4 (conc of Ni doesn't matter since it is present in the solid phase)

=> 2.3053 * 10^(-4)/(0.00869)^4

=> 4.0424 * 10^(4)

Hence the correct answer is Option B