The stepwise formation of \(\left[ Cu \left( NH _3\right)_4\right]^{2+}\) is given below: \(\begin{aligned} & Cu ^{2…

The stepwise formation of \(\left[ Cu \left( NH _3\right)_4\right]^{2+}\) is given below:
\(\begin{aligned} & Cu ^{2+}+ NH _3 \stackrel{ k _1}{\rightleftharpoons}\left[ Cu \left( NH _3\right)\right]^{2+} \\ & {\left[ Cu \left( NH _3\right)\right]^{2+}+ NH _3 \stackrel{ k _2}{\rightleftharpoons}\left[ Cu \left( NH _3\right)_2\right]^{2+}} \\ & {\left[ Cu \left( NH _3\right)_2\right]^{2+}+ NH _3 \stackrel{ k _3}{\rightleftharpoons}\left[ Cu \left( NH _3\right)_3\right]^{2+}} \\ & {\left[ Cu \left( NH _3\right)_3\right]^{2+}+ NH _3 \stackrel{ k _4}{\rightleftharpoons}\left[ Cu \left( NH _3\right)_4\right]^{2+}}\end{aligned}\)

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 constants for dissociation of \(\left[ Cu \left( NH _3\right)_4\right]^{2+}\) is \(x \times 10^{-12}\). The value of \(x\) is ---------------------(Rounded off to the nearest integer)

[JEE Main 2021, 24 Feb (Shift 1)]