Question

A balloon containing 0.56 mol of helium has a volume of 10.0 L. What volume will the balloon occupy if helium is lost and only 0.21 mol remain?

Answer 1

According to the ideal gas law
pV₁ = n₁RT - at the beginning

pV₂ = n₂RT - after part of helium is lost

p (pressure), T(temperature), R (universal gas constant) - don't change
V₁, V₂ - volumes
n₁, n₂ - moles

(pV₁/pV₂) = (n₁RT)/(n₂RT)

V₁/V₂ = n1/n2

After helium is lost the volume is

V₂ = (V₁n₂)/n1

V₂ = (10.0 x 0.21)/ 0.56 = 3.75 L

Answer: V₂ = 3.75 L