Question

Find the change in entropy of helium when it is heated from 300k to 1000k

Answer 1

change in entropy is given by, $\Delta S=\int\limits^{T_f}_{T_i}\frac{nC_p}{T}\,dT$

= $nC_p\int\limits^{T_f}_{T_i}{\frac{1}{T}}\,dT$

= $nC_pln\left[\frac{T_f}{T_i}\right]$

where, Cp is molar specific heat at constant pressure. for helium (monatomic) Cp = 5R/2 J/mol.K , n is no of mole of gas. here no of mole of helium, n = 1

final temperature, Tf = 1000K

and initial temperature, Ti = 300K

so, ∆S = 1 × 5R/2 × ln(1000/300)

= 5R/2ln(10/3) J/K

hence, change in entropy is 5R/2ln(10/3) J/K

Answer 2

Answer:

helium when it is heated from 300 K to 1000 K at constant

pressure. (mass of amount of helium=1 kg)