[dannysmith]

Hi everyone,

I have a question on combined Gas Laws (Charles+Boyle).  I have attempted this but no luck so far.

A balloon is filled with helium to a volume of 4.0 L when the pressure is 1.0 atm and the temperature is 27 C. It escapes and rises until the pressure is .25 atm and the temp is -23 C.  What is the new volume?

I started with Charles law because for Boyle the temperature must be constant.

Volume = Constant x Temp

4.0 L = constant x 300 K
4.0 L = 1/75 x 300 K

Next I plugged the constant in to new temp after gas escapes

?L= 1/75 x 250 K
?L= 3.3

Unfortunately I must be doing something wrong, because the answer key says the answer is 6.7 .

If anyone could help me, I would be so grateful!

[Borek]

Write combined gas law formula.