Temperature Dependance of the Heat of Reaction

ΔH = v3h3 + v4h4 - v1h1 + v2h2

(3.56)

h = h0 + ∫Cp dt

(3.57)

Therefore,

ΔH = v3h03 + v4h04 - v1h01 + v2h02 + ∫(v3Cp3 + v4Cp4 - v1Cp1 + v2Cp2)dT

(3.58)

Denoting                     ΔH = v₃h₀₃ + v₄h₀₄ - v₁h₀₁ + v₂h₀₂

ΔH = ΔH0 + ∫(v3C3 + v4C4 - v1C1 + v2C2)dT

(3.59)

If C_p is known as a function of temperature and if at any temperature ΔH is  known, then at any other temperature, ΔH can be determined for a certain chemical reaction from the above relation.
Some chemical reactions may be expressed as the result of two or more reactions. If ΔH₀ is known for each of the separate reactions, then ΔH₀ of the resultant reaction may be calculated.

For example,

TEMPERATURE DEPENDENCE OF THE  EQUILIBRIUM  CONSTANT

ln K = -(v3Φ3 + v4Φ4 - v1Φ1 - v2Φ2)

(3.60)

where

(3.61)

On substitution

(3.62)

If

ΔH0 = v3h03 + v4h04 - v1h01 + v2h02 ΔS0 = v3s03 + v4s04 - v1s01 + v2s02

(3.63)

Then,

(3.64)

This equation is sometimes called as the Nernst’s equation.