Energetics: Practice Questions

Which of the following chemical equations correctly represents the standard enthalpy of formation of liquid methanol, \(CH_3OH(l)\)?

Using the standard enthalpy of formation data provided, calculate the standard enthalpy change for the following reaction:
\(2NH_3(g) + 3Cl_2(g) \rightarrow N_2(g) + 6HCl(g)\)
\(\Delta_f H^{\ominus}[NH_3(g)] = -46 \text{ kJ mol}^{-1}\)
\(\Delta_f H^{\ominus}[HCl(g)] = -92 \text{ kJ mol}^{-1}\)

Using the mean bond enthalpy data provided, calculate the enthalpy change, \(\Delta H\), for the following gaseous reaction:
\(H_2(g) + Cl_2(g) \rightarrow 2HCl(g)\)
Mean bond enthalpies (\(\text{kJ mol}^{-1}\)): \(H-H = 436\), \(Cl-Cl = 242\), \(H-Cl = 431\).

In a calorimetry experiment, \(50.0 \text{ cm}^3\) of \(1.00 \text{ mol dm}^{-3} \text{ NaOH}\) is reacted with \(50.0 \text{ cm}^3\) of \(1.00 \text{ mol dm}^{-3} \text{ HCl}\). The temperature of the resulting solution increases by \(6.5 \text{ K}\). Calculate the heat energy change, \(q\), for this reaction.
(Assume the density of the solution is \(1.00 \text{ g cm}^{-3}\) and its specific heat capacity is \(4.18 \text{ J g}^{-1} \text{ K}^{-1}\))

State what is meant by the standard enthalpy of combustion (\(\Delta_c H^\theta\)).

A student used a simple calorimeter to determine the enthalpy of combustion of propan-1-ol (\(M_r = 60.0\)). Burning 1.25 g of the alcohol increased the temperature of 250 g of water by 22.5 K.
(a) Calculate the heat energy, \(q\), in kJ, absorbed by the water. (Specific heat capacity of water \(c = 4.18 \text{ J g}^{-1} \text{ K}^{-1}\)).
(b) Calculate the molar enthalpy of combustion of propan-1-ol in \(\text{kJ mol}^{-1}\).