Internal energy and expanding gas

AI Thread Summary
The discussion focuses on calculating the change in internal energy (ΔU) of an expanding gas that absorbs 17x10^5 joules of heat while doing 8x10^5 joules of work. The correct formula for ΔU is ΔU = Q - W, leading to ΔU being 9x10^5 joules. For the change in volume at constant pressure, the equation PΔV = Q - ΔU is mentioned, but it's noted that this second equation is unnecessary since work is provided directly. Overall, the calculations and formulas discussed are valid for determining the internal energy and volume change of the gas.
tomahawk1985
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17x10^5 joules are absorbed by an expanding gas that does 8x10^5 joules of work. (a) Find ΔU; (b) Assuming it expands at constant pressure, what's the change in volume?

Am I correct to use this:

ΔU = Q - W

Then after finding ΔU,

PΔV = Q - ΔU

Or does this make no sense?
 
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Both equations are OK. Except the second one is not really required, since you are given W directly.
 

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