Chemical Forums
Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: zerothedestroyer on June 04, 2010, 10:21:47 AM
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3. Thermo-Firstlaw a (Points: 1)
Gas in a piston-cylinder apparatus is heated with 1.500 kcal while simultaneously increasing its volume from 0.500 L to 1.500 L at a constant pressure of 1.000 atm. What is the total energy change for this process? Pay attention to units.
1. +1.524 kcal
2. 0 (the work and heat contributions cancel out)
3. +1.476 kcal
4. -1.476 kcal
5. -1.524 kcal
Step 1. I know that I have to find work done on system and work done to system. Is that where I start off?
It is asking What is the total energy change for this process? So that's like
ΔU = Q - W,
where ΔU is the change in internal energy, Q is the heat added to the system, and W is the work done by the system. of course, when work is done to the system (like your problem), W is negative, so that -W is positive, resulting in an increase in internal energy (like your problem):
How would I convert 0.500 L to 1.500 L at a constant pressure of 1.000 atm to Kcal and then use the Delta U=Q-W equation to solve the change?
Please let me know.
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You need an equation for work done by an expanding gas. This will allow you to calculate the work done.
Also, here are some conversions that may help
1 L-atm = 101.325J
1cal = 4.184J