Question

Using the graph below, determine the gas that has the lowest molecular mass at STP A) A B) B C) C D) D E) All of the gases have the same density at STP. Of the following gases, ______ will have the greatest rate of effusion at a given temperature. A) NH_3 B) Ar C) CH_4 D) HBr E) HCl

Answer 1

The Boltzmann equation of gas molecules is 14) dn_e/n = 4 pi [m/2 pi k T]^3/2 M c^2/e^2k T C^2 dc where, dn_c/n is the relative numbers of particles and Cisthe velocity Therefore, relative numbers of particles is proportional with square of velocity and molar mas, M in the exponential term is inversely proportional with relative numbers of particles Therefore, more the velocity, less is the molar mass Therefore, the gas with lowest molar mass is D Correct answer: A) D 15) Gases with lower molecular weight have greater rates of effusions Among the given gases, CH_4 has lowest molecular weight Hence, the correct answer is C) CH_4