Question

A balloon holding 4.00 moles of neon (Ne) gas absorbs 955 J of thermal energy while doing 132 J of work expanding to a larger volume.

(a) Find the change in the balloon's internal energy (in J). _________ J

(b) Calculate the change in temperature of the gas (in K). __________ K

Answer 1

1.

From 1st law of thermodynamics:

dU = dQ + W

W = Work-done on the gas = -132 J (Negative since it expands the volume of gas)

dQ = thermal energy absorbed = 955 J

So,

dU = change in Balloon's internal energy = ?

dU = 955 - 132

dU = 823 J

Part B.

Change in internal energy is also given by:

dU = n*Cv*dT

n = number of moles of Ne gas = 4.00 moles

Cv, for monoatomic gas = 3R/2

dT = change in temperature = ?

dT = dU/(n*Cv)

dT = 823/(4.00*3*8.314/2)

dT = 16.5 K

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