Question

(a) An ideal gas occupies a volume of 1.0 cm3 at 20°C and atmospheric pressure. Determine the number of molecules of gas in the container.
i got that right to be 2.5e19 molecules
(b) If the pressure of the 1.0 cm3 volume is reduced to 1.0 10-11 Pa (an extremely good vacuum) while the temperature remains constant, how many moles of gas remain in the container?
im not sure how to do this part. and i keep getting it wrong. can you please help me?

Answer 1

Atmospheric pressure is 1.015*10^5 Pa

A decrease in pressure to 10^-11 Pa is a factor of 10^16 reduction.

At the same temperature, the number of moles and molecules present in the fixed volume must decrease by a factor of 10^16.

The number of moles in part A is the number of molecules divided by Avogadro's number.