(a) According to a postulate of kinetic theory of gases, collision between the molecules as well as with the wall of container is perfectly elastic in nature.
(b) If a gas molecule of man ' $m$ ' moving with speed ' $u$ ' collide to the wall of container, the change in momentum is $\Delta p=-2 \mathrm{mu}$. Therefore, heavier molecule will transfer more momentum to the wall as there will be greater change in momentum of the colliding gas malecule. However this was not postulated in kinetic theory of Gases.
(c) According to Maxwell-Boltzmann distribution of molecular speed, very few molecules have either very high or very low speeds. Most of the molecules moves in a specific, intermediate speed range.
(d) According to kinetic theory of gases, a gas molecule moves in straight line unless it collide with another molecular or to the wall of container and change in momentum is observed only after collision.