Consider the following reaction: 
2 C₆H₆ (l) + 15 O₂ (g) → 12 CO₂ (g) + 6 H₂­O (g)  ∆Hº = – 6278 kJ
What volume of benzene (C₆H₆, d = 0.880 g/mL, molar mass = 78.11 g/mol) is necessary to evolve 5.19 x 10⁹ kJ of heat? 

For the evaporation of water, H₂O(l) → H₂O(g), at 100°C, ∆H = +9.72 kcal/mol (+40.7 kJ/mol).

b. How many kilojoules are released when 10.0 g of H₂O(g) is condensed?

Methanol, CH₃OH, is used as race car fuel.

c. How many kilojoules are released by burning 50.0 g of methanol?

Nitromethane (CH₃NO₂), sometimes used as a fuel for drag racing, burns according to the following reaction:

4 CH₃NO₂ (l) + 7 O₂ (g) → 4 CO₂ (g) + 6 H₂O (g) + 4 NO₂ (g)   ∆Hº = – 2441.6 kJ

How much heat is released by burning 125.0 g of nitromethane (MW:61.044 g/mol)?

The creation of liquid methanol is accomplished by the hydrogenation of carbon monoxide: 

CO (g) + 2 H₂ (g) → CH₃OH (l)       ∆Hº = – 128.1 kJ

How much heat (in kJ) is released when 125.0 g CO reacts with 2.32 x 10² g H₂?

The following equation shows the conversion of aluminum oxide (from the ore bauxite) to aluminum:

2 Al₂O₃(s) → 4 Al(s) + 3 O₂(g) ∆H = +801 kcal/mol (+3350 kJ/mol)

c. How many kilocalories are required to produce 10.0 g of aluminum? How many kilojoules?

The vaporization of Br₂ from the liquid to the gas state requires 7.4 kcal/mol (31.0 kJ/mol).

c. How many kilojoules are needed to evaporate 82 g of Br₂?