Enthalpy — Prelims Questions

For the reaction $2SO_2(g) + O_2(g) \rightarrow 2SO_3(g)$, if $\Delta H = -198\,\text{kJ}$ at $298\,\text{K}$, what is the value of $\Delta U$ for the reaction at the same temperature? (Given $R = 8.314\,\text{J mol}^{-1}\text{K}^{-1}$)

Which of the following statements about enthalpy is INCORRECT?

Given the following standard enthalpies of formation:\n$\Delta H_f^\circ (C_2H_4(g)) = +52.3\,\text{kJ mol}^{-1}$\n$\Delta H_f^\circ (CO_2(g)) = -393.5\,\text{kJ mol}^{-1}$\n$\Delta H_f^\circ (H_2O(l)) = -285.8\,\text{kJ mol}^{-1}$\nCalculate the standard enthalpy of combustion ($\Delta H_c^\circ$) for ethene ($C_2H_4(g)$).

Which of the following processes is associated with a positive $\Delta H$?

The enthalpy of vaporization of water at $100\,\text{°C}$ is $40.66\,\text{kJ mol}^{-1}$. Calculate the internal energy change ($\Delta U$) when one mole of water is vaporized at $100\,\text{°C}$ and $1\,\text{atm}$ pressure. (Assume ideal gas behavior for steam, $R = 8.314\,\text{J mol}^{-1}\text{K}^{-1}$)

Given the following reactions:\n1. $C(s) + O_2(g) \rightarrow CO_2(g)$, $\Delta H_1 = -393.5\,\text{kJ}$\n2. $H_2(g) + \frac{1}{2}O_2(g) \rightarrow H_2O(l)$, $\Delta H_2 = -285.8\,\text{kJ}$\n3. $C_2H_6(g) + \frac{7}{2}O_2(g) \rightarrow 2CO_2(g) + 3H_2O(l)$, $\Delta H_3 = -1560.0\,\text{kJ}$\nCalculate the standard enthalpy of formation of ethane ($C_2H_6(g)$).

Which of the following conditions would lead to $\Delta H = \Delta U$ for a chemical reaction?