Another Chem question I need help with! Please show your work!

Question

A sample of helium gas has a volume of 620mL at a temperature of 500 K. If we decrease the temperature to 100 K while keeping the pressure constant, what will the new volume be?

Answer 1

At constant pressure, we are dealing with Charles' Law:

V1/T1 = V2/T2

V1 = 620 ml

T1 = 500K

V2 = ?

T2 = 100K

620 ml / 500K = V2 / 100K

V2 = (620 ml)(100K) / 500K

V2 = 124 ml

Answer 2

pV = nRT

p is constant, n (moles of gas) is constant, R is constant

so V/T = nR/p which is constant

V/T =k (constant)

First situation

V = 0.62 l, T = 500, so k = (0.62 / 500)

V = kT, second situation T=100, so V = (0.62 / 500) x 100 = 0.124 l