Which one of the following equation shows standard enthalpy of combustion?
Correct answer: A. CH4(g) + 2O2(g) → CO2(g) + 2H2O(g)
- A. CH4(g) + 2O2(g) → CO2(g) + 2H2O(g)
- B. 2CH4(g) + 4O2(g) → 2CO2(g) + 4H2O(g)
- C. CH4(s) + 2O2(g) → CO2(g) + 2H2O(g)
- D. CH4(l) + 2O2(g) → CO2(g) + 2H2O(g)
Explanation
The standard enthalpy of combustion is defined for the combustion of one mole of a substance in its standard state. Equation A correctly shows the combustion of one mole of methane gas to form products in their standard states (water as a liquid at 25°C).
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About Enthalpy
Enthalpy is the heat content of a system measured at constant pressure, and its change indicates whether a reaction or physical process is endothermic or exothermic. The topic covers state functions, enthalpy diagrams, standard enthalpy of formation, combustion and neutralisation, and the relationship between ΔH and internal energy change.
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If ∆H is the enthalpy change and ∆U is the change in internal energy accompanying a gaseous reaction, then:
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