Question

A sample of helium at a pressure of 745 torr and in a volume of 2.58 L was heated from 24.0 to 75.0 degree C. The volume of the container expended to 2.81 L. What was the final pressure (in torr) of the helium?

Answer 1

The final pressure will be 801 torr.

You will need to use the combined gas law to solve this problem. The equation is:

`(P_1V_1)/(T_1) = (P_2V_2)/(T_2)`

Known/Given:
`P_1 = 745 "torr"`
`V_1 = 2.58 L`
`T_1 = 24.0"^(o)C + 273.15 = 297.2 K` (temp must be in Kelvins)
`V_2 = 2.81 L`
`T_2 = 75.0"^(o)C + 273.15 = 348.2 K`

Unknown:
`P_2`

Solution: Rearrange the combined gas law equation to isolate and solve for `P_2`.

`P_2 = (P_1V_1T_2)/(T_1V_2) = (745 "torr"*2.58 cancel (L)*348.2 cancel (K))/(297.2 cancel (K)*2.81 cancel (L)) = 801 "torr"`