Question

The reaction, $A\left(g\right)+B\left(g\right)\rightleftharpoons C\left(g\right)+D\left(g\right)$ is studied in a one litre vessel at ${250}^{\circ }$C. The initial concentration of $A$ was $3n$ and that of $B$ was $n$. When equilibrium is attained, equilibrium concentration of $C$ was found to the equal to the equilibrium concentration of $B$. What is the concentration of $D$ at equilibrium?

• A. $n/2$
• B. $(3n-1/2)$
• C. $(n-n/3)$
• D. $n$

Answer 1

Answer: (A)

$n/2$

$A\left(g\right)+B\left(g\right)\rightleftharpoons C\left(g\right)+D\left(g\right)$

$Concentration$	$A$	$B$	$C$	$D$
$Att=0$	$3n$	$n$	$0$	$0$
$Att=t$	$3n(1-x)$	$n(1-x)$	$nx$	$nx$

At equilibrium $\left[B\right]=\left[C\right]$

$n(1-x)=nx$

$x=0.5$

$\left[D\right]=nx=0.5n$