## 8.13- negative signs?

$w=-P\Delta V$
and
$w=-\int_{V_{1}}^{V_{2}}PdV=-nRTln\frac{V_{2}}{V_{1}}$

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Remi Lathrop 1G
Posts: 51
Joined: Fri Sep 29, 2017 7:07 am

### 8.13- negative signs?

Question 13 from chapter 8 problems reads:
In a combustion cylinder, the total internal energy change produced from the burning of a fuel is -2373kJ. The cooling system that surrounds the cylinder absorbs 947 kJ as heat. How much work can be done by the fuel in the cylinder?

I understand that ∆U = q + w, but the answer key showed the heat (q) as a negative number, can someone explain why the heat being absorbed is negative in this case?

Thu Uyen Tran 1B
Posts: 31
Joined: Fri Sep 29, 2017 7:05 am

### Re: 8.13- negative signs?

Since 947 kJ is being absorbed as heat by the surroundings, there must be a release of heat by the system itself. Therefore, this would result in a negative q.

Adrian Lim 1G
Posts: 88
Joined: Fri Sep 29, 2017 7:03 am

### Re: 8.13- negative signs?

Also, the problem says that the surroundings is a cooling system, which means that the surroundings will absorb the heat from the system. Thus, because the system is losing heat, the q in relation to the system would be negative.

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