01052 moles of an unknown blue ideal gas is in a container a

0.1052 moles of an unknown blue ideal gas is in a container as shown to the right. The initial temperature of the gas is 293.15 K and the pressure is 5.400 times 105Pa. Heat is added to the system, causing the gas to expand until the volume has tripled (the initial volume is 4.750 times 10-4m3). The pressure stays constant, as does the number of moles of gas. What is the new temperature of the system? During the process in part (a), the internal energy of the system increases by 769.2 J. How much heat was added to the system during this process? A locking pin is stuck into the piston so that it can no longer move (and therefore the volume stays the same). Heat is then removed from the system. What happens to the internal energy of the system? (circle correct answer) What happens to the pressure? (circle correct answer)

Solution

a)   V1 = 4.75e-4

V2 = 3*v1

P1 = 5.4e5 Pa

at constant pressure the temperature is propotional to volume ( charles law)

T2 / T1 = V2/V1

T2 = 3*T1 = 3*293.15 = 879.45 K

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b) wokdone at constant pressure = W = P*dV = P*(V2-V1)

P*(3v1 - v1) = P*2*V1= 5.4e5*2*4.75e-4 = 513 J

from first law of thermodynamics dQ = dU + dW

dQ = 769.2+513 = 1282.2 J

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iii) decreases

iii)decreases