Substance X combusts with an enthalpy change of per mole and has a molar mass of
CHEMISTRY · Single correct · A Level · Chemistry · Energetics · Energetics
Problem
Substance X combusts with an enthalpy change of −7.30×102kJ per mole and has a molar mass of 58.0g mol−1. Pellet A has twice the mass of pellet B, and both pellets are burned completely under identical conditions. Which statement correctly predicts the comparative heat release?
(a) Pellet A releases less heat because the negative sign on ΔH means the reaction absorbs energy.
(b) Pellet A releases twice as much heat because doubling the mass doubles the number of moles that react.
(c) Pellet A releases the same amount of heat because the enthalpy change per mole is constant.
(d) Pellet A releases half as much heat because larger pellets burn less efficiently, reducing heat per mole.