a) An ideal gas initially at 120 K undergoes an isobaric expansion at 6 kPa. If
ID: 1294816 • Letter: A
Question
a)
An ideal gas initially at 120 K undergoes an isobaric expansion at 6 kPa. If the volume increases from 1.3 m3 to 1.4 m3 and 5.9 kJ of thermal energy is transferred to the gas, ?nd the change in its internal energy.
Answer in units of kJ
b)
Find the ?nal temperature of the gas.
Answer in units of K
c)
A gas is compressed at a constant pressure of 0.805 atm from 8.3 L to 5.65 L. In the process, 382 J of energy leaves the gas by heat. What is the work done on the gas?
Answer in units of J
d)
What is the change in its internal energy?
Answer in units of J
Explanation / Answer
#a)
dW = P*(V2 - V1)
dQ = du + dW
dU = dQ - dW
dU = 5900 - (6000*(1.4-1.3)) = 5300 J = 5.3 kJ
#b)
T2/T1 = V2/V1
T2 = (120*1.4)/1.3
T2 = 129.23 K
#c)
dW = P*(V2 - V1) = 0.805*1.013e5*(5.65-8.3)*1e-3 = -216.09 J
#d)
dQ = du + dW
dU = dQ - dW
dU = -382 + 216.09 = -165.91 J
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