# Equilibrium Temperature.

1. Jun 15, 2008

### Altairs

I am not a novice at thermodynamics but still the following question made me think over my status more than twice.

I have to find the equilibrium temperature when a 50 Kg block of copper at 80C is placed in a container which as 120L of water at 25C.

I made simple equations of heat lost = heat gained. Used Specific Heat for water = 4.18 and for copper 0.285 (and 0.391) and used mcdelT. But the answer I get is below 25C. Where as it should be between 25 and 80.

2. Jun 15, 2008

### tiny-tim

Hi Altairs!

You know you should show us your working … otherwise how can we see where you went wrong?

3. Jun 16, 2008

### Altairs

Oh I forgot the PF SOP

Heat Lost (by copper) = Heat Gained (by water)

$$50 * 0.385 (T_{e} - 80) = 0.12 * 1000 *4.18 (T_{e} - 25)$$

4. Jun 16, 2008

### tiny-tim

no wonder they both got colder!

It would be less confusing if you said "total heat change = 0, therefore:"

$$50 * 0.385 (T_{e} - 80)\,+\,0.12 * 1000 *4.18 (T_{e} - 25)\,=\,0$$

5. Jun 18, 2008

Ooh ! Thanks