Part A: Calculate the change in internal energy of the following system: A ballo

Question

Part A:

Calculate the change in internal energy of the following system: A balloon is cooled by removing 0.652 kJ of heat. It shrinks on cooling, and the atmosphere does 388 J of work on the balloon. Express your answer to three significant figures and include the appropriate units.

Part B:

Calculate the change in internal energy of the following system: A 100.0-g bar of gold is heated from 25C to 50C during which it absorbs 322 J of heat. Assume the volume of the gold bar remains constant. Express your answer to three significant figures and include the appropriate units.

Explanation / Answer

A)

we know that

dU = Q - W

given

heat is removed from the system

so

Q = -0.652 x 1000

Q = -652 J

now

388 J of work is done on the balloon

So

W = -388 J

so

dU = -652 - (-388)

dU = -264

so

the change in internal energy is -264 J

that is

internal energy is decreased by -264 J

B)

given

volume is constant

so

work done (W) = 0

now

given

322 J of heat is absorbed

so

Q = + 322

now

dU = Q - W

dU = 322

so

the change in internal energy is + 322 J

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