Physics Heat transfer question (will award BEST ANSWER)?
SOMEONE ASKED π
Physics Heat transfer question (will award BEST ANSWER)?
HERE THE ANSWERS π
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A
Process A is a constant volume process. The heat transferred in such a process equals the change in internal energy of the gas.
Q = βU
Assuming ideal gas behavior the change in internal energy of the nitrogen gas is given by:
βU = nβCvββT
The molar heat capacity at constant volume for an diatomic ideal gas like nitrogen is
Cv = (5/2)βR
Hence,
Q =β(5/2)βnβRββT
From ideal gas law
nβRβT = pβV
follows for an constant volume process:
nβRββT = β(pβV) = Vββp
Hence,
Q =β(5/2)βVββp = (5/2)βVβ(p_f – p_i)
= (5/2) β 2000cmΒ³ β (1atm – 3atm)
= (5/2) β 2000mΒ³Γ10β»βΆmΒ³ β (- 2 β 1.01325Γ10β΅ Pa)
= -1013.25 J
B
Process B is a constant pressure process. The heat transferred in such a process equals the change in enthalpy of the gas.
Q = βH
Assuming ideal gas behavior the change in enthalpy of the nitrogen gas is given by:
βH = nβCpββT
The molar heat capacity at constant pressure for an diatomic ideal gas like nitrogen is
Cv = (7/2)βR
Hence,
Q =β(5/2)βnβRββT
From ideal gas law
nβRβT = pβV
follows for an constant pressure process:
nβRββT = β(pβV) = pββV
Hence,
Q =β(7/2)βpββV = (5/2)βpβ(V_f – V_i)
= (7/2) β 2atm β (3000cmΒ³ – 1000cmΒ³)
= (7/2) β 2β1.01325Γ10β΅ Pa β 2000mΒ³Γ10β»βΆmΒ³
= 1418.55 J
