Question

A chemist prepares a sample of hydrogen bromide and finds that it occupies 296 mL at 68°C and 475 Torr. What volume would it occupy at 0°C at the same pressure?

Answer in units of mL.

Answer 1

Here, we want to get the final volume

From the general gas equation, we have it that:

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

From the question, we have it that:

P1 is the initial pressure which is 475 torr

V1 is the initial volume which is 296 mL

T1 is the initial temperature which we have to convert to absolute value by adding 273.15 K (
`68 + 273.15 = 341.15 \ \text{K}`)

P2 is the final pressure that is the same as the initial which is 475 torr

V2 is the final volume that we want to calculate

T2 is the final temperature which is 273.15 K (0 degrees Celsius is 273.15 K)

Substituting the values, we have:

`(475*296)/(341.15)=(475* V_2)/(273.15)`

`V_2=\cfrac{475*296*273.15}{341.15*475} =\boxed{\bold{237 \ mL}}`

We could have solved this by using Charles' law that relates temperature to volume (volume is directly proportional to temperature)