question help for chemistry

Question

If a piston with a variable volume starts with a volume of 125.0 mL and pressure of 1.25 atm then expands to a new volume of 239.8 while the temperature remains constant, what is the new pressure?

Answer 1

Hi, Molly,

I just answered anther gas law problem for you that has an explanation that will work here. lease review that one and then try this.

Use the equation I had explained and make a table.

P1V1/T1 = P2V2/T2

The temperature reamins constant, so we can cancel it out to get:

P1V1 = P2V2

Rearrarange for P2, the unknown:

P2=P1*(V1/V2)

We can see that it the volume decreases, V1>V2, so the pressure will go up, and vise versa. In our case, the volume increases, so V2>V1, and we would therefore expect the ressure to decrease. (The temperature stays constant in the problem).

Let's take a guess at what the answer might look like. The volume is almost doubling, so I'll venture that our answer should be slightly higher than half, or, I'd guess, around 0.7 atm.

Let me know what you find. I hope this helps,

Bob