🔥 Thermochemistry — Intermediate#

Scope — Quantitative treatment of heat, enthalpy changes, calorimetry, and Hess’s law.

Key concepts#

• Enthalpy (H) — heat content of a system at constant pressure.
• Calorimetry — experimental measurement of heat transfer.
• Hess’s law — total enthalpy change is path independent.

Seed Q&A triads#

• Q: What does a positive ΔH indicate?
  A: The process is endothermic; the system absorbs heat.

• Q: How does a calorimeter measure heat change?
  A: By relating temperature change of a known mass and heat capacity to the heat exchanged.

• Q: Why does Hess’s law work?
  A: Enthalpy is a state function, so its change depends only on initial and final states, not the reaction pathway.

Short exercises#

• Calculate ΔH for a reaction using given calorimetry data.
• Use Hess’s law to determine ΔH for a target reaction from known steps.