## q(sys)= -q(surr)

$\Delta S = \frac{q_{rev}}{T}$

jophan3F
Posts: 5
Joined: Fri Sep 26, 2014 2:02 pm

### q(sys)= -q(surr)

In what situations or types of problems are you supposed to use the formula q(sys)= -q(surr)

martha-1I
Posts: 76
Joined: Fri Sep 26, 2014 2:02 pm

### Re: q(sys)= -q(surr)

q=-q is mostly used for thermal equilibrium problems. An example would be if you were to put a certain amount of warm water into a certain amount of cold water. In this case, you would use the equation to solve for the final temperature since the masses and the initial temperatures of the samples of water would be given.
You would also use this equation for bomb calorimeter problems since heat is not released so thermal equilibrium must be reached at a certain point. An example of this one would be a warm metal placed in cold water inside a bomb calorimeter.

Justin Le 2I
Posts: 142
Joined: Fri Sep 26, 2014 2:02 pm

### Re: q(sys)= -q(surr)

Another way to think of the equation is heat lost by system = heat gained by surroundings and vice versa. This logically makes sense provided that there is no heat being lost.

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