Key Equations

q = c \times m \times Δ T = c \times m \times (T_{final} - T_{initial})

Δ U = q + w

Δ H_{reaction}^{°} = \sum n \times Δ H_{f}^{°} (products) - \sum n \times Δ H_{f}^{°} (reactants)

Bond energy for a diatomic molecule:

XY (g) ⟶ X (g) + Y (g) D_{X–Y} = Δ H °

Enthalpy change: ΔH = ƩD_{bonds broken} – ƩD_{bonds formed}

Lattice energy for a solid MX:

MX (s) ⟶ M^{n +} (g) + X^{n −} (g) Δ H_{lattice}

Lattice energy for an ionic crystal:

Δ H_{lattice} = \frac{C (Z^{+}) (Z^{−})}{R_{o}}