Question

Kc = 9 for the reaction, A + B C + D, If A and B are taken in equal amounts, then amount of C in equilibrium is :

• A. 1
• B. 0.25
• C. 0.75
• D. None of these

Answer 1

Answer: (C)

0.75

Answer 2

A + BC + D

Initial 1 1 0 0

At equili. (1 – x) (1 – x) x x

$\therefore$ $K_{c} = \frac{\lbrack C\rbrack\lbrack D\rbrack}{\lbrack A\rbrack\lbrack B\rbrack} = 9$

$\therefore$ $\frac{x.x}{(1 - x)^{2}} = 9$

or x2 = 9 + 9x2 – 18 x

or 8x2 – 18x + 9 = 0

$\therefore$ x = $\frac{3}{2}$ or $\frac{3}{4}$

Hence, among the given options, the option (3) i.e., 0.75 is correct.