A system delivers 1275 J of heat while the surroundings perform 855 J of work on it. Calculate internal energy (delta E) in J.
2006-11-29 06:28:16 · 2 answers · asked by Anonymous in Science & Mathematics ➔ Chemistry
If you are doing this in terms of the system,
since the system is losing energy (delivers heat) then the amount of energy is "-1275 J". The surrounding add heat (perform work on) to the system, so the amount of energy is "+855". The internal energy of the system is the sum of the energy loss and the work done to the system, so -1275 J + 855 J = -420 J.
If you are doing this problem in terms of the surroundings, the all the signs are reversed and you should end up with +420 J.
2006-11-29 06:40:03 · answer #1 · answered by Mr. Payne 3 · 2⤊ 3⤋
Q = ΔE + w so ΔE = Q - w.
Now Q (heat) is negative because the system delivers heat to the surroundings and w (work) is positive because the system performs work. So:
ΔE = -1275 + 855 = -420 J.
2006-11-29 06:46:12 · answer #2 · answered by Dimos F 4 · 5⤊ 0⤋