Question

A vessel at 1000 K contains carbon dioxide with a pressure of 0.5 atm. Some of the carbon dioxide is converted to carbon monoxide on addition of graphite.
$C{O}_2+C\rightleftharpoons 2CO$
Calculate the value of $K_p$ if total pressure at equilibrium is 0.8 atm.

• A. 2.5 atm
• B. 1.1 atm
• C. 0.5 atm
• D. 1.8 atm

Answer 1

The correct option is D 1.8 atm

The reaction is, $C{O}_2+C\rightleftharpoons 2CO$

Initial pressure of $C{O}_2=0.5atm$
Initial pressure of $CO=0atm$
$\text{Final pressure of}C{O}_2=(0.5-x)atm$
Final pressure of $CO=2xatm$
$\text{Total pressure at equilibrium = Partial pressures of}C{O}_{2}andCO$
$\text{Total pressure at equilibrium}=(0.5-x)+2x=0.8atm\left(\text{given}\right)$
$x=0.3$
$\therefore K_p=\frac{P_{CO}^2}{P_{C{O}_2}}=\frac{(0.6{)}^2}{0.2}=1.8atm$