Heat and Thermodynamics 4 Question 13

15. A15g mass of nitrogen gas is enclosed in a vessel at a temperature 27C. Amount of heat transferred to the gas, so that rms velocity of molecules is doubled is about

(Take, R=8.3J/K - mol)

(2019 Main, 9 Jan II)

(a) 10kJ

(b) 0.9kJ

(c) 14kJ

(d) 6kJ

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Solution:

  1. We know that from kinetic theory of gases,

Vrms=3RTM or VrmsT

where, R is gas constant, T is temperature and M is molecular mass of a gas.

Here, to double the vrms, temperature must be

4 times of the initial temperature.

New temperature,

T2=4×T1 As, T1=27C=300KT2=4×300=1200K

As, gas is kept inside a closed vessel.

Q=nCVdT=1528×5R2(1200300)[ As, n=mM=1528 for nitrogen ]=1528×52×8.3×900

[Given, R=8.3J/Kmole ]

 or Q=10004.4J10kJ



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