a tank of ideal gas is sealed off at 20 degrees C and 1.00 atm pressure. What will be the pressure (in kPa and mmHg) in the tank if the gas temperature is decreased to -35degrees C ?

the book answer is
82kPa = 6.2 x10^2 mmHg

can you help me figure out how the book got this answer.

I've tried to plug the numbers into the gas formulas and have not had any luck.

1 answer

At constant V and number of moles, P is proportional to absolute T.

P2/P1 = T2/T1 = 238/293 = 0.8123

P2 = 760 mm Hg * 0.8123 = 617 mm Hg
rRound it off to 620.

You have to know that 7600 mm Hg = 1 atmosphere, and how to convert degrees C to K