Thermodynamics

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Question : 2
Total: 10
What amount of heat must be supplied to 2.0×102 kg of nitrogen (at room temperature) to raise its temperature by 45°C at constant pressure? (Molecular mass of N2=28;R=8.3Jmol1K1.)
Solution:  
Mass of nitrogen gas, m=2×102kg=20 g
Molecular mass of nitrogen gas =28 g
Rise in temperature, ΔT=45°C
Heat supplied = ?
Number of moles n=
m
M
=
20
28
=
5
7

For nitrogen (N2) which is a diatomic gas, molar specific heat at constant pressure
Cp=
7
2
R
where R=8.3Jmol1K1
Therefore, heat supplied to the gas
ΔQ=nCpΔT
=
5
7
×
7
2
×R
×45

=
5
7
×
7
2
×8.3
×45

=933.8 J934 J
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