Question 6 - 2021 (24 Feb Shift 1)

The stepwise formation of $[\text{Cu}(\text{NH}_3)_4]^{2+}$ is given below:

$\text{Cu}^{2+} + \text{NH}_3 \xrightleftharpoons{K_1} [\text{Cu}(\text{NH}_3)]^{2+}$

$[\text{Cu}(\text{NH}_3)]^{2+} + \text{NH}_3 \xrightleftharpoons{K_2} [\text{Cu}(\text{NH}_3)_2]^{2+}$

$[\text{Cu}(\text{NH}_3)_2]^{2+} + \text{NH}_3 \xrightleftharpoons{K_3} [\text{Cu}(\text{NH}_3)_3]^{2+}$

$[\text{Cu}(\text{NH}_3)_3]^{2+} + \text{NH}_3 \xrightleftharpoons{K_4} [\text{Cu}(\text{NH}_3)_4]^{2+}$

The value of stability constants $K_1$, $K_2$, $K_3$ and $K_4$ are $10^4$, $1.58 \times 10^3$, $5 \times 10^2$ and $10^2$ respectively. The overall equilibrium constant for dissociation of $[\text{Cu}(\text{NH}_3)_4]^{2+}$ is $x \times 10^{-12}$. The value of $x$ is ____. (Rounded off to the nearest integer)