Q43:

43. Evaluate K_p for the reaction : H₂ + I₂ $\rightleftharpoons$ 2HI, If 2 moles each of H₂ and I₂ are taken initially. The equilibrium moles of HI are 2. 
(1) 2.5        (2) 4        (3) 0.25          (4) 1.0

Dear Student

The reaction is -
                                          ​H₂    ​ +       ​I₂       ​$\leftrightarrow$        ​2HI

So,
Moles at t = 0                    2                 2                      0
Moles at equilibrium       (2 -x)          (2 - x)                2x

Thus, 
K_p = $\frac{(n_{HI}{)}^2}{\left(n_{H_2}\right) x \left(n_{I_2}\right)}$
Here, we have taken 2x = 2 and x = 1
K_p    = $\frac{(2{)}^2}{\left(1\right) x \left(1\right)} = 4$
So, the correct option is (2).

Regards