8. Quantities in Chemical Reactions

Thermochemical Equations

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Methanol, CH3OH, is used as race car fuel. How many kilojoules are released by burning 50.0 g of methanol?
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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?
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The vaporization of Br2 from the liquid to the gas state requires 7.4 kcal/mol (31.0 kJ/mol). How many kilojoules are needed to evaporate 82 g of Br2?
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Converting liquid water to solid ice releases 1.44 kcal/mol (6.02 kJ/mol). How many kilocalories are released by freezing 32 g of H2O?
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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) How many kilocalories are required to produce 10.0 g of aluminum? How many kilojoules?
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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)?
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For the evaporation of water, H2O(l) → H2O(g), AT 100°C, ∆H = +9.72 kcal/mol (+40.7 kJ/mol). How many kilojoules are released when 10.0 g of H2O(g) is condensed?
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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?
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For the production of ammonia from its elements, ∆H = -22 kcal/mol(-19 kJ/mol). How much energy (in kilocalories and kilojoules) is involved in the production of 0.700 mol of NH3?
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Glucose, also known as 'blood sugar' when measured in blood, has the formula C6H12O6. What is the minimum amount of energy (in kJ) a plant must absorb to produce 15.0 g of glucose?
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