# Problem: Olympic cyclists fill their tires with helium to make them lighter. Assume that the volume of the tire is 860 mL , that it is filled to a total pressure of 125 psi , and that the temperature is 25 oC. Also, assume an average molar mass for air of 28.8 g/mol.What is the mass difference between the two?

###### FREE Expert Solution

Calculate the moles of that can occupy the tire:

$\mathbf{PV}\mathbf{=}\mathbf{nRT}\phantom{\rule{0ex}{0ex}}\frac{\mathbf{PV}}{\mathbf{RT}}\mathbf{=}\frac{\mathbf{n}\overline{)\mathbf{RT}}}{\overline{)\mathbf{RT}}}\phantom{\rule{0ex}{0ex}}\overline{)\mathbf{n}\mathbf{=}\frac{\mathbf{PV}}{\mathbf{RT}}}$

T = 25°C +273.15 = 298.15 K

V = 0.860 L

P = 8.6058 atm

n = 0.299 mol ≈ 0.30 mol

Calculate the mass of helium (He) and air:

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###### Problem Details

Olympic cyclists fill their tires with helium to make them lighter. Assume that the volume of the tire is 860 mL , that it is filled to a total pressure of 125 psi , and that the temperature is 25 oC. Also, assume an average molar mass for air of 28.8 g/mol.

What is the mass difference between the two?