# Homework Help: Charles, Gay-Lussac and of course Boyle

1. Oct 4, 2008

### susan__t

I'm having a little bit of an issue trying to find an equation to use when the initial and final temperature, pressure and volume are all variable

I know $$\frac{V1}{T1}$$ =$$\frac{V2}{T2}$$

and $$\frac{P1}{T1}$$ =$$\frac{P2}{T2}$$

and P1V1=P2V2

But I want to combine them so that I can get the V2 when the Pressure and Temperature 1 and 2 both vary.

2. Oct 4, 2008

### susan__t

maybe P1V1/T1 = P2V2/T2 ? Sorry I used to know this but i can't seem to remember

3. Oct 4, 2008

### GCT

If I understood your question accurately ... yes , assuming that the moles are constant.

4. Oct 5, 2008

### Desh627

The combined gas law states that when moles are constant, P1V1T2=P2V2T1 (basically what has been said above, but getting rid of those fractions).