How Far? The Extent of Chemical Change · Paper 1 — Free Chemistry HL Practice Questions

For the esterification reaction $\text{CH}_3\text{COOH}(\text{l}) + \text{C}_2\text{H}_5\text{OH}(\text{l}) \rightleftharpoons \text{CH}_3\text{COOC}_2\text{H}_5(\text{l}) + \text{H}_2\text{O}(\text{l})$, a student mixes $2.0\ \text{mol}$ of ethanoic acid with $2.0\ \text{mol}$ of ethanol in a $1.0\ \text{dm}^3$ flask. At equilibrium, $1.2\ \text{mol}$ of ethyl ethanoate is present. What is the value of $K_c$?

A student investigates the equilibrium $\text{PCl}_5(\text{g}) \rightleftharpoons \text{PCl}_3(\text{g}) + \text{Cl}_2(\text{g})$. She places $0.20\ \text{mol}$ of $\text{PCl}_5$ in a $1.0\ \text{dm}^3$ container and allows the system to reach equilibrium, at which point $0.12\ \text{mol}$ of $\text{PCl}_5$ remains. What is the value of $K_c$?

A 1.00 dm³ flask initially contains 0.100 mol of $\text{PCl}_5(\text{g})$ only. The system reaches equilibrium according to $\text{PCl}_5(\text{g}) \rightleftharpoons \text{PCl}_3(\text{g}) + \text{Cl}_2(\text{g})$, at which point $[\text{Cl}_2] = 0.040 \text{ mol dm}^{-3}$. What is the value of $K_c$?

In the Haber process, $\text{N}_2(g) + 3\text{H}_2(g) \rightleftharpoons 2\text{NH}_3(g)$, a student places $0.20\ \text{mol}$ of $\text{N}_2$ and $0.60\ \text{mol}$ of $\text{H}_2$ in a $1.0\ \text{dm}^3$ container at $400\ \text{°C}$. At equilibrium, $[\text{NH}_3] = 0.20\ \text{mol dm}^{-3}$. What is the equilibrium concentration of $\text{H}_2$?