Answer :
The molar mass of the unknown gas is 18.2 g/mol. Hence, the correct option is (a).
Given data: The sample of helium diffuses 4.57 times faster than an unknown gas diffuses.
Let's assume that the molar mass of the unknown gas is M2 g/mol.
Therefore, the molar mass of helium will be M1 = 4g/mol.
Using Graham's law of diffusion, we have;
rate of effusion of gas 1:rate of effusion of gas 2=Molar mass of gas 2/Molar mass of gas 1
Let's substitute the values we have:1:4.57 = M2 / 4
We have 1 as the rate of effusion of Helium since it was assumed to be 4g/mol which is the value given for the rate of effusion of the unknown gas. Now we can solve for M2:M2 = 4.57 × 4= 18.28
Therefore, the molar mass of the unknown gas is 18.28 g/mol
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