Question

A rigid container contain 1 kg N, gas at 400 K if linal terneprature is 800 K then find change in entropy (J K-1) [Given : C, = 29.099 joule) (1) 512.86 (2) 1025.736 (3) 256.43 (4) 170.9​

Answer 1

The change in entropy is 1440.83 joules

An entropy of a system is determined by the molecular energy distribution of the system.

An entropy of a system tends to obtain the maximum energy of the system.

It is often confused with heat and energy.

Also entropy is a state function.

It can be determined only by initial and final states only.

To calculate the change in entropy of a system,

We use

Del S= integration of dQ/dt

Or, Del S= n* integration of (Cp/T)*dr

Or, Del S= n* Cp ln T2/T1

Here given, Cp = 29.099 joule

The weight of Nitrogen gas is 1 kg.

Hence no. Of moles = 1000/14 = 71.42 moles

Hence,

Del S= 71.42* 29.099* ln 800/400

Or, Del S= 1440.83 J

Hence the change in entropy is 1440.83 joules

Answer 2

Answer:

Option-1 change in entropy=nCv lnT2/T1 +nR lnV2/V1, since container is rigid so V2=V1 ,lnV2/V1=0 so now n=1000/28=250/7 and gas is diatomic so Cv=5R/2 and T2=8ook and T1=400k on putting value in formula we get 1st option as answer