Question

$4.5 \,moles$ each of hydrogen and iodine were heated in a sealed ten litre vessel. At equilibrium 3 moles of HI were found. The equilibrium constant for ${H_{2(g)} +I_{2(g)}}$ is

• A. $1$
• B. $10$
• C. $5$
• D. $0.33$

Answer 1

Answer: (A)

$1$

Answer 2

$2\, moles$ of $HI$ are formed from $1\, mole$ of $H_2$ and $I_2$. $\begin{matrix}\therefore&H_{2}&+&I_{2}&?&2HI\\\ Initial\, moles&4.5&&4.5&&0\\\ At \,equilibrium&4.5-1.5&&4.5-1.5&&3\\\ &=3&&=3&&\end{matrix}$ $K=\frac{\left[Hi\right]^{2}}{\left[H_{2}\right]\left[I_{2}\right]}=\frac{\left(3\right)^{2}}{3\times3}=1$