Question

At certain temperature ($T$) for the gas phase reaction
$2H_{2}O\left(g\right)+2{Cl}_2\left(g\right)\rightleftharpoons 4HCl\left(g\right)+O_2\left(g\right);K_P=12\times {10}^{8}atm$
If ${Cl}_2$, $HCl$ and $O_2$ are mixed in such a manner that the partial pressure of each is $2atm$ and the mixture is brough into contact with excess of liquid water. What would be approximate partial pressure of ${Cl}_2$ when equilibrium is attained at temperature ($T$)?
[Given:Vapour pressure of water is $380mm$ $Hg$ at temperature ($T$)]

• A. $3.6\times {10}^{-5}atm$
• B. ${10}^{-4}atm$
• C. $3.6\times {10}^{-3}atm$
• D. $0.01$atm

Answer 1

The correct option is A $3.6\times {10}^{-5}atm$

$2H_{2}O+2C{l}_2\rightleftharpoons 4HCl+O_2$

$K_P=\frac{\left[HCl{]}^4\right[O_2]}{\left[H_{2}O{]}^2\right[C{l}_2{]}^2}$

Given, partial pressure is $2atm$ for $C{l}_2,HCl,O_2.$

$\Rightarrow 12\times {10}^8=\frac{\left(2{)}^4\right(2)}{\left(2{)}^2\right[Cl{]}^2}$

Hence, $P_{C{l}_2}$ is $3.6\times {10}^{-5}atm$