The pH of a solution can be calculated using the formula:

pH = -log[H+]

Given that the solution is NH4CN, we need to find the concentration of H+ ions.

NH4CN is a weak acid, and it dissociates in water to form NH4+ and CN- ions. The CN- ion will react with water to form HCN and OH- ions. Therefore, the concentration of H+ ions will be determined by the dissociation of HCN.

HCN is a weak acid, and it dissociates in water to form H+ and CN- ions. The dissociation constant (Ka) for HCN is given as 9.2 x 10^(-10).

The equation for the dissociation of HCN is:

HCN ⇌ H+ + CN-

Let x be the concentration of H+ ions (which is equal to the concentration of HCN).

The concentration of CN- ions will also be x.

Using the dissociation constant expression, we can write:

Ka = [H+][CN-] / [HCN]

Substituting the values, we get:

9.2 x 10^(-10) = x * x / x

Simplifying, we find:

9.2 x 10^(-10) = x

Taking the square root of both sides, we get:

x = √(9.2 x 10^(-10))

x ≈ 3.03 x 10^(-5)

Therefore, the concentration of H+ ions (and HCN) in the solution is approximately 3.03 x 10^(-5) M.

To calculate the pH, we can use the formula:

pH = -log[H+]

pH = -log(3.03 x 10^(-5))

pH ≈ 4.52

Therefore, the pH of the aqueous solution of NH4CN (or HCN) is approximately 4.52.