Question

For the reactions,
$A\rightleftharpoons B,K_c=1;B\rightleftharpoons C,K_c=3;C\rightleftharpoons D,K_c=5$. $K_c$ for reaction $A\rightleftharpoons D$ is:

• A. $15$
• B. $5$
• C. $3$
• D. $1$

Answer 1

Answer: (A)

$15$

For the reactions,
$A\rightleftharpoons B,K_c=\frac{\left[B\right]}{\left[A\right]}=1;B\rightleftharpoons C,K_c=\frac{\left[C\right]}{\left[B\right]}=3;C\rightleftharpoons D,K_c=\frac{\left[D\right]}{\left[C\right]}=5$ $K_c$ for reaction $A\rightleftharpoons D$ is $K_c=\frac{\left[D\right]}{\left[A\right]}=15$
Note
$K_c=\frac{\left[D\right]}{\left[A\right]}=\frac{\left[B\right]}{\left[A\right]}\times \frac{\left[C\right]}{\left[B\right]}\times \frac{\left[D\right]}{\left[C\right]}=1\times 3\times 5=15$