Ideal Gas Law Chemistry

Question

A gas sample of 5 moles, has a volume of 95 L. How many moles of the same gas should I add to obtain a volume of 133 L at the same temperature and pressure.

Answer 1

Using the formula n= PV/RT

5 = 95P/RT or 1 = 19P/RT

since the pressure and temperature is the same the equation we are trying to solve is

n = 133P/RT

133/19 = 7 so n = 7 moles.

Answer 2

the underlying formula that you want to use here is

V1/n1 = V2/n2

for this question we're trying to solve for n2

n2 = V2 * n1 / V1

n2 = 133L x 5 moles / 95 L

n2 = 665/95 = 7 moles

that is the number of moles in the final sample, meaning that

Moles added = 7 moles - 5 moles = 2 moles

so to obtain a volume of 133 L from an initial volume of 95 L you would need to add 2 moles of the gas