alleryStart learning →What is the standard enthalpy of combustion of a substance?
AThe heat needed to melt one mole of it
BThe heat change when one mole of it burns
CThe heat change when one gram of it burns
DThe heat given out when one mole dissolves
Answer & Solution
Correct answer: B. The heat change when one mole of it burns
1. Standard enthalpy of combustion is defined for exactly 1 mole of the substance.
2. That mole combines vigorously with oxygen under standard state conditions.
3. For ethanol the value is minus 1366.8 kJ per mole.
4. The basis is one mole, not one gram, so per-gram figures must be worked out separately.
_Source: OpenStax Chemistry (CC BY 4.0), Ch 5 "Thermochemistry", section 5.3 Enthalpy_
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