The viscosity 7 of a gas depends on the mass, the effective diameter and the mean speed of the molecules. Use dimensional analysis to find n as a function of these variables. Hence estimate the diameter of the methane (CH.) molecule given that n has values of 2.0 x 10-8 kg m-'s=' for helium and 1.1 x 10-$ kg m-'s-' for methane at room temperature, and that the diameter of the helium atom is 2.1 x 10-10 m. [Relative atomic masses for C and He are 12 and 4 respectively.]

The viscosity 7 of a gas depends on the mass, the effective diameter and the mean speed of the molecules. Use dimensional analysis to find n as a function of these variables. Hence estimate the diameter of the methane (CH.) molecule given that n has values of 2.0 x 10-8 kg m-'s=' for helium and 1.1 x 10-$ kg m-'s-' for methane at room temperature, and that the diameter of the helium atom is 2.1 x 10-10 m. [Relative atomic masses for C and He are 12 and 4 respectively.]