Question

For the reaction $CaCO _{3}(s) \rightleftharpoons CaO ( s )+ CO _{2}( g ) K _{ p }=$ 1.16 atm at $800^{\circ} C$. If $20 \,g$ of $CaCO _{3}$ were kept in a 10 litre container & heated upto $800^{\circ} C$, what $\%$ age by weight of $CaCO _{3}$ would remain unreacted at equilibrium-

• A. $35 \%$
• B. $6.8 \%$
• C. $10.2 \%$
• D. None of those

Answer 1

Answer: (B)

$\underset{(s)}{CaCO_{3}} \rightleftharpoons \underset{(s)}{CaO}+CO_{2}$

$K_{p}=p_{c o_{2}}=1.16\,atm$

Apply, $P V=nRT$

$\frac{1.16 \times 10}{0.0821 \times 1073}=0.132$ moles

Initial moles of $CaCO _{3}=\frac{20}{100}=0.2$

Mole of $CaCO _{3}$ reacted $=0.132$

Mole of $CaCO$ unreacted $=0.2-0.132=0.068$

So, weight of $CaCO_{3}$ unreacted $=0.068 \times 100=6.8$

$\%$ age of $CaCO _{3}$ unreacted by weight $=\frac{6.8}{20} \times 100=35 \%$