Closed gas system

Question

A closed gas system initially has volume and temperature of 6420mL and 66.00 oC with the pressure unknown. If the same closed system has values of 1220torr, 9610mL and 207.0 oC, what was the initial pressure in atm? 

Answer 1

Combined gas law: P1V1/T1 = P2V2/T2

P1 = initial pressure = ?

V1 = initial volume = 6420 ml

T1 = initial temperatuer in K = 66ºC + 273 = 339K

P2 = final pressure = 1220 torr

V2 = final volume = 9610 ml

T2 = final temperature in K = 207ºC + 273 = 480K

Solving for P1, we have...

P1 = P2V2T1 / V1T2 = (1220)(9610)(339) / (6420)(480)

P1 = 1290 torr

Converting this to atm, we have...

1290 torr x 1 atm / 760 torr = 1.70 atm final pressure (3 sig. figs.)