If a sample of 0.29 moles of Ar occupies 3.8 L under certain conditions, what volume will 0.66 moles occupy under the same conditions?

In order to determine the change in volume, we may use the equation of state for an ideal gas:

PV = nRT

Here, the pressure and temperature of the gas is not changing, therefore, we may simplify the expression to:

Volume is proportional to moles

V / n = constant

V₁/n₁ = V₂/n₂

V₂ = 3.8 * 0.66 / 0.29

V₂ = 8.65 L

0.66 moles of Ar will occupy 8.65 liters of volume.