If a balloon will rise off the ground when it contains 0.0211 mol of helium in a volume of 0.460 L, how many moles of helium are needed to make the balloon rise when its volume is 0.867 .

Question

Assume that temperature and pressure stay constant.

Answer 1

PV = nRT

rearrange to get

PV/nT = R

PV/nT = P₂V₂/n₂T₂

Pressure and temp. are equal so they can be removed

V/n = V₂/T₂

0.460 L/ 0.0211 mol = 0.867 L / n

rearrange and solve for n