alleryStart learning →What does Hess's law state?
AThe enthalpy change of a process equals the sum of its steps
BThe enthalpy change of a process depends on the path taken
CThe enthalpy change of a process equals its heat capacity
DThe enthalpy change of a process is always negative in sign
Answer & Solution
Correct answer: A. The enthalpy change of a process equals the sum of its steps
1. A reaction may be written as a sum of stepwise processes.
2. Hess's law says the total enthalpy change equals the sum of the step values.
3. This works because enthalpy is a state function.
4. Enthalpy changes depend only on where a process starts and ends, not on the route.
_Source: OpenStax Chemistry (CC BY 4.0), Ch 5 "Thermochemistry", section 5.3 Enthalpy_
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