AP Chemistry / Unit 6: Thermochemistry
6.6 Introduction to Enthalpy of Reaction
Notes
$\Delta H$ is the heat change at constant pressure.
- It scales with the amount: doubling the equation doubles $\Delta H$.
- Reversing a reaction flips the sign of $\Delta H$.
Practice
$A\to B$, $\Delta H=-50$ kJ. For $B\to A$:
Reverse flips the sign.
$2A\to2B$ has $\Delta H=$ (using $A\to B$, $-50$ kJ):
Double the amount.
Burning 1 mol of fuel releases 800 kJ. Burning 0.5 mol releases:
Half as much.
Ready for more? Take the Unit 6 test.