Oxidation and combustion of organic compounds are exothermic reactions. The heat of reaction due to — Organic Chemistry Chemistry Question
Carbon dioxide I
Oxidation and combustion of organic compounds are exothermic reactions. The heat of reaction due to the combustion of fossil fuels such as oil, coal and natural gas has been utilized as main sources of energy.
Calculate the heat of reaction, ∆H°, due to the complete combustion of 1 mol of methane at 298 K in the atmosphere, using the following data of the standard enthalpy of formation of methane, carbon dioxide and water.
Methane: –74.82 kJ mol-1
Carbon dioxide: –393.5 kJ mol-1
Water: –285.8 kJ mol-1
Model Answer
Methane ： C + 2 H2 → CH4 ∆H°f = –74.82 kJ mol–1
Carbon dioxide ： C + O2 → CO2 ∆H°f = –393.5 kJ mol–1
Water ： H2 + ½ O2 → H2O ∆H°f = –285.8 kJ mol–1
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CH4 + 2 O2 → CO2 + 2 H2O ∆H°f = –890.28 kJ mol–1
In a laboratory, we can generate carbon dioxide from calcium carbonate and hydrochloric acid. Calculate the volume, V (unite, cm3), of generated carbon dioxide from 10.0 g of calcium carbonate and 50.0 cm3 of 1.00 mol dm–3 aqueous hydrochloric acid at 298 K and 1013 hPa, assuming that the reaction proceeds completely and the generated carbon dioxide acts as an ideal gas.
Model Answer
n(CaCO3) = 10.0 g / 100.1 g mol–1 = 0.100 mol
n(HCl) = 1.00 mol dm–3 × 0.0500 dm3 = 0.0500 mol
CaCO3 + 2 HCl → CaCl2 + H2O + CO2
The amount of generated carbon dioxide = 0.0250 mol
Calculation by use of an equation for ideal gas:
V(CO2) = (0.0250 mol × 8.31 J K–1 mol–1 × 298 K) / (1013 × 100 Pa) = 6.11 × 10–4 m3 = 611 cm3