(b) $A + B \rightleftharpoons C + D$ $a\ \ \ \ \ a\ \ \ \ \ \ 2a\ \ \ 2a$ at equilibrium $\therefore\ \ K_{c} = \frac{\lbrack C\rbrack\lbrack D\rbrack}{\lbrack A\rbrack\lbrack B\rbrack}$ $= \frac{2a \times 2a}{a \times a} = 4$
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.