Thermodynamics
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Question : 5
Total: 10
In changing the state of a gas adiabatically from an equilibrium state A to another equilibrium state B, an amount of work equal to 22.3 J is done on the system. If the gas is taken from state A to B via a process in which the net heat absorbed by the system is 9.35 cal, how much is the net work done by the system in the latter case? (Take 1 cal = 4.19 J)
Solution:
In first case, the state of the gas changes adiabatically from A to B.
Therefore,Δ Q = 0 , D W = – 22.3 J
IfΔ U
Δ Q = Δ U + Δ W
⇒ 0 = Δ U + Δ W
Δ U = − Δ W = − ( − 22.3 J )
= 22.3 J
In the second case, when the state A is taken to state B, the heat absorbed by the system
Δ Q = 9.35 cal
= 9.35 × 4.2 J = 39.27 J
= 39.3 J , Δ W = ?
Applying first law of thermodynamics
Δ Q = Δ U + Δ W
Δ W = Δ U − Δ Q
= 39.3 − 22.3 = 17.0 J
Therefore,
If
In the second case, when the state A is taken to state B, the heat absorbed by the system
Applying first law of thermodynamics
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