Q. For the reaction A + B ⇌ C + D, if the initial concentrations of all species are 1 M and Kc = 4, the equilibrium concentration of C is:

प्रतिक्रिया A + B ⇌ C + D के लिए, यदि सभी प्रजातियों की प्रारंभिक सांद्रता 1 M और Kc = 4 है, तो C की संतुलन सांद्रता है:

0.5 M
0.5 एम

1.6 M
1.6 एम

2 M
2 एम

4 M
4 एम

Let the change in concentration be x:

Now,

K_c = \frac{[C][D]}{[A][B]} = \frac{x^2}{(1 - x)^2} = 4

\sqrt{\frac{x^2}{(1 - x)^2}} = 2 \Rightarrow \frac{x}{1 - x} = 2 \Rightarrow x = \frac{2}{3}

[C] = x = \frac{2}{3} ≈ 0.67 \, \text{(but closest option is 1.6 M, so we recheck)}

Actually, try solving again:

\frac{x^2}{(1 - x)^2} = 4 \Rightarrow \frac{x}{1 - x} = 2 \Rightarrow x = 2 - 2x \Rightarrow 3x = 2 \Rightarrow x = \frac{2}{3}

That gives x = 0.67 M, but no such option exists.

→ Likely a misprint in options, the correct math shows:

[C] = x = \boxed{0.67\,\text{M}} \text{ (Correct)}

But if Kc = 4, and we guess C = 1.6 M, back-calculate:

K = \frac{(1.6)^2}{(1 - 1.6)^2} = \frac{2.56}{0.36} ≈ 7 \Rightarrow Incorrect

So, Answer = 0.67 M,

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