I need help with these mastering chemistry problems... If you could explain how

Question

I need help with these mastering chemistry problems... If you could explain how you got the answers that would be very helpful because I'm trying to learn how to do this myself and I'm struggling trying to figure it out. Thanks!

1. Calculate the change in internal energy of the following system: a balloon is cooled by removing 0.651 kJ of heat. It shrinks on cooling, and the atmosphere does 384J work on the balloon. (Answer in kJ)

2. Calculate the change in internal energy in the following system: a 100.0 g of gold is heated from 25 C to 50 C during which it absorbs 322 J of heat. Assume the volume of the gold bar remains constant. (Answer in J)

Explanation / Answer

1)

according to the fist law of themodynamics

Q+W=delU

651 = delU-384

change in internal energy(delU)=651+384

=1035J=1.035 kJ..............answer

2)

again we use the same formula

change in internal energy del U=Q+W

but,W=P(V2-V1)

since volume is constant W=0

there fore

change in internal energy del U=Q

del U=heat absorbs

del U=322 J..............................answer

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