Thermochemistry Summary
System
Part of the universe chosen for study
Surroundings
Everything outside the system that can interact with it
Heat (q)
Energy transferred due to temperature difference
Work (w)
Energy transferred by force acting through distance
Internal Energy (U)
Total energy of a system
Enthalpy (H)
Internal energy plus pressure-volume work (H = U + PV)
q = mc∆T
Heat capacity equation
w = -P∆V
Pressure-volume work
∆U = q + w
First law of thermodynamics
∆H = qp
Enthalpy change at constant pressure
  • Exothermic reactions release heat to surroundings (q < 0)
  • Endothermic reactions absorb heat from surroundings (q > 0)
  • State functions are path independent (like U and H)
  • Heat and work are path dependent