Question

Show that change in enthalpy is equal equal to the heat at constant pressure.

Answer 1

Dear student ,
From the first law of Thermodynamics : q_p = $∆$ E + P $∆$ V .....(i) ( when pressure remains constant )
Now from the concept of enthalpy , H = total energy content = E + PV
Let a system changes as follows , Initial ....................Final
H₁ , E₁ , V₁ H₂ , E₂ , V₂ ( P remains constant )
Noe the change in enthalpy ; $∆$ H = H₂ - H₁
= ( E₂+ PV₂) - ( E₁ + PV₁)
= ( E₂- E₁ ) + P ( V₂-V₁)
= $∆$ E + P$∆$ V
From eq. (i) ; $∆$ H = q_p
Regards