Practice Test 4

Use Hess’s law to determine $\Delta H$ for the target reaction:

Target: $\mathrm{CaCO_3(s) \rightarrow CaO(s) + CO_2(g)}$

Given:

1. $\mathrm{Ca(s) + C(s) + \tfrac{3}{2}O_2(g) \rightarrow CaCO_3(s)}$ $\Delta H = -1207\ \text{kJ}$

2. $\mathrm{Ca(s) + \tfrac{1}{2}O_2(g) \rightarrow CaO(s)}$ $\Delta H = -635\ \text{kJ}$

3. $\mathrm{C(s) + O_2(g) \rightarrow CO_2(g)}$ $\Delta H = -394\ \text{kJ}$

Use Hess’s law to determine $\Delta H$ for the target reaction:

Target: $\mathrm{H_2S(g) + \tfrac{3}{2}O_2(g) \rightarrow SO_2(g) + H_2O(l)}$

Given:

1. $\mathrm{H_2(g) + \tfrac{1}{2}O_2(g) \rightarrow H_2O(l)}$ $\Delta H = -286\ \text{kJ}$

2. $\mathrm{H_2(g) + S(s) \rightarrow H_2S(g)}$ $\Delta H = -21\ \text{kJ}$

3. $\mathrm{S(s) + O_2(g) \rightarrow SO_2(g)}$ $\Delta H = -297\ \text{kJ}$