During an effusion experiment, oxygen gas passed through a tiny hole 2.5 times faster than the same number of moles of another gas under the same conditions. what is the molar mass of the unknown gas? (note: the molar mass of oxygen gas is 32.0 g/mol.) 2.0 × 102 g

Mass oxygen = 32.0 g/mol
Mass of unknown gas = ???

Rate of effusion unknown gas  = x
Rate of effusion (O2) = 2.5 x

r1/r2 = sqrt(m2)/sqrt(m1)
2.5x/x = sqrt(unknown mass)/sqrt(oxygen mass)
2.5/1 = sqrt(unknown mass)/sqrt(32)
2.5 * sqrt(32) = sqrt(unknown) Square both sides.
6.25*32 = unknown mass

200 = mass of unknown gas.<<<=== answer