Question

Which statement holds true when the molar mass of hydrogen is 2.0 grams and that of helium is 4.0 grams? Hydrogen effuses 1.4 times faster than helium. Hydrogen effuses 0.71 times faster than helium. Helium effuses 1.4 times faster than hydrogen. Helium effuses 0.71 times faster than hydrogen. The rate of effusion of both gases is the same.

Answer 1

Answer:
             Hydrogen effuses 1.4 times faster than Helium.

Explanation:
                   According to Graham's Law of Effusion, "the rate of effusion of a gas is inversely proportional to the square root of its density or molar mass".

Mathematically,
                                       Rₐ / Rₓ  =  $\sqrt{Mx/Ma}$    ----- (1)
Where;
            Rₐ  =  Rate of effusion of H₂

            Rₓ  =  Rate of effusion of He

            Mₐ  =  Molar Mass of H₂  =  2 g.mol⁻¹

            Mₓ  =  Molar Mass of He  =  4 g.mol⁻¹

Putting values in equation 1,

                                       Rₐ / Rₓ  =  $\sqrt{4/2}$

                                       Rₐ / Rₓ  =  $\sqrt{2}$

                                       Rₐ / Rₓ  =  1.41

Result:
          Hence, H₂ effuses 1.41 times faster than He.