Solution:

To determine the apparent Kf for complex formation, we need to use the equilibrium concentration of Co2+ and N2H4 in the solution. From the given information, we know that the equilibrium concentration of [Co2+] is 6 × 10–3 M. Now we need to calculate the concentration of N2H4 in the solution.

Calculating the Concentration of N2H4:

Let x be the concentration of N2H4 in the solution. Since Co(NO3)2 and N2H4 react in a 1:2 molar ratio, the concentration of N2H4 will be twice the concentration of Co2+.

Therefore, [N2H4] = 2 * [Co2+] = 2 * 6 × 10–3 M = 1.2 × 10–2 M.

Writing the Complex Formation Reaction:

The complex formation reaction between Co2+ and N2H4 can be written as:

Co2+ + 2N2H4 ⇌ Co(N2H4)2

Writing the Equilibrium Expression:

The equilibrium expression for the complex formation reaction can be written as:

Kf = [Co(N2H4)2] / [Co2+]^1 * [N2H4]^2

Substituting the Known Values:

We know from the question that the concentration of [Co(N2H4)2] is 0.0100 M and the concentration of [Co2+] is 6 × 10–3 M. We also calculated the concentration of N2H4 to be 1.2 × 10–2 M.

Substituting these values into the equilibrium expression, we get:

Kf = (0.0100 M) / (6 × 10–3 M)^1 * (1.2 × 10–2 M)^2

Simplifying this expression, we get:

Kf = (0.0100 M) / (6 × 10–3 M) * (1.44 × 10–4 M^2)

Kf = 2.40 × 10^3 M^–1

Therefore, the apparent Kf for complex formation is 2.40 × 10^3 M^–1.

Explanation:

In this solution, Co2+ reacts with N2H4 to form the complex Co(N2H4)2. The equilibrium concentration of [Co2+] in the solution is given as 6 × 10–3 M. By assuming that the only complex formed is Co(N2H4)2, we can calculate the concentration of N2H4 in the solution. Using the equilibrium expression for complex formation, we can then substitute the known values to calculate the apparent Kf. The calculation shows that the apparent Kf for complex formation is 2.40 × 10^3 M^–1. This value indicates the strength of the complex formation between Co2+ and N2H4, with a higher Kf value indicating a stronger complex formation.