A gas is confined to a cylinder fitted with a piston and an internal heater/cool

Question

A gas is confined to a cylinder fitted with a piston and an internal heater/cooler. Suppose that coolant is circulated throughout the cooler so that 50 kJ of heat is removed from the gas sample. The external pressure on the container remained constant at 1.0 atm. Be specific as possible with your answers. What can you say about the value of q for the system? Justify. What can you say about the value for w for the system? Justify. Was work done on the system, by the system, no work was done or cannot be determined? Justify. What can you say about the value for the change in internal energy for the gas sample? Justify. What can you say about the value for the change in enthalpy of the system? Justify.

Explanation / Answer

Q removed = -50 kJ

P = constant

a)

the vlaue of Q; heat, is NEGATIVe, since we re removing heat energy from the system, that is, we are cooling the system

b)

There is a small amount of work done in the system, since it will decrease in T ( due to the heat); therefore it will lose volume, that is change in volume at constant P; means Work

c)

the atmosphere "pushed" the drop of gvolume of the cylinder, therefore, the work was done TO the gas

d)

Value of U must be dropping, since heat was remoeved, therefore, expect final internal energy to be less than the original

e)

enthalpy is essneitally:

H = U + PV

since U is being decreased, and Volume also decreases, enthalpy must be decreasing

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