The heat of combustion of carbon to $CO_2$ is $-393.5 \text{ kJ/mol}$. The heat released upon formation of $35.2 \text{ g}$ of $CO_2$ from carbon and oxygen gas is

For the reaction $CO_{(g)} + \frac{1}{2}O_{2_{(g)}} \rightarrow CO_{2_{(g)}}$ at $17^o C$ and constant volume,the heat of reaction is $-67.71 \, K \, cal$. What is the heat of reaction at constant pressure at $17^o C$ in $K \, cal$?

The heat change for the following reaction at $298 \ K$ and at constant pressure is $+ 7.3 \ kcal$. $A_2B_{(s)} \to 2A_{(s)} + 1/2 \ B_{2(g)}$,$\Delta H = + 7.3 \ kcal$. The heat change at constant volume would be

Calculate $\Delta H^{\circ}$ for the reaction, $Na_2O_{(s)} + SO_{3(g)} \longrightarrow Na_2SO_{4(s)}$, given the following reactions:
$(A) \ Na_{(s)} + H_2O_{(l)} \longrightarrow NaOH_{(s)} + \frac{1}{2}H_{2(g)} \quad \Delta H^{\circ} = -146 \ kJ$
$(B) \ Na_2SO_{4(s)} + H_2O_{(l)} \longrightarrow 2NaOH_{(s)} + SO_{3(g)} \quad \Delta H^{\circ} = +418 \ kJ$
$(C) \ 2Na_2O_{(s)} + 2H_{2(g)} \longrightarrow 4Na_{(s)} + 2H_2O_{(l)} \quad \Delta H^{\circ} = +259 \ kJ$

$C_{(s)} + 2 H_{2(g)} \rightarrow CH_{4(g)}$; $\Delta H = -74.8 \ kJ \ mol^{-1}$
Which of the following diagrams gives an accurate representation of the above reaction?
[$R \rightarrow$ reactants; $P \rightarrow$ products]

An ideal gas expanded irreversibly against $10 \ bar$ pressure from $20 \ L$ to $30 \ L$. Calculate $Q$ if the process is isoenthalpic. $(1 \ L \ bar = 100 \ J)$