Question

A gas mixture consist of molecule of type A, B and C with masses Ma >Mb > Mc Rank the three type of molecules in decreasing order of (1) average kinetic energy (2) RMS speed

Answer 1

Since no details have been given about the temperature and pressure, we will consider that they are at a constant value.

1. So, at a given temperature, all the molecules of an ideal gas will have the same average translational kinetic energy irrespective of their masses. This same average translational kinetic energy is depicted as 3/2 kT. So, the kinetic energy is same for all the 3 molecules namely A, B, and C.

2. When the average kinetic energy is equal, the molecules that have larger masses will have comparatively smaller RMS values so that an equal Kavg can be acquired. According to the question, Molecule A has the highest mass Ma and Molecule C has the lowest mass Mc. So, Molecule A will have the least RMS value and Molecule C will have the highest RMS value.

Answer 2

When we measure the temperature of a gas, we are also measuring the average translational kinetic energy of its molecules. A gas mixture consists of molecules of types 1, 2, and 3, with m1 > m2 > m3 molecular masses.

A gas mixture consists of molecules of type 1, 2 and 3, with molar masses m1 and average kinetic > m2 energy > m3. vrms of and K are the r.m.s. speed the gases. Which of the following is true? (a) (vrms)1 < (vrms)2 < (vrms)3 and (K)1 = (K)2 = (K)3 (b) (vrms)1 = (vrms)2 = (vrms)3 and (K)1 = (K)2 > (K)3 (c) (vrms)1 >