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Chemistry question involving delta U?
I'm getting desperate, my chemistry midterm is tomorrow and I can't even figure out the simplest questions! This is one of the questions I'm having trouble with.
When 2.00 kJ of energy is transferred as heat to nitrogen in a cylinder fitted with a piston at an external pressure of 2.00 atm, the nitrogen gas expands from 2.00 to 5.00L against this constant perssure. What is delta U (internal energy) for the process?
The answer is +1.39 kJ but I keep getting 1.78 kJ. If anyone could explain how to do the question, that would be very much appreciated.
1 Answer
- Anonymous8 years agoFavorite Answer
First: convert atm to kPa, so p = 202.6kPa
Second: realize that it's constant pressure so q = ΔH = 2.00kJ
Third: Use;
ΔU = q - w
ΔU = 2.00kJ - pΔV
ΔU = 2000J - (202.6kPa) * (3.00L) (Convert to Joules)
ΔU = 1 392.2J
ΔU = 1.3922kJ (Convert back to kJ)
ΔU = 1.39kJ (Round for Sig Figs)
Hope this helps! :)
Source(s): I'm probably taking the same midterm with you tomorrow... seeing as how I just did this exact question two hours ago. You go to UofG?