Question

At a given temperature, 'Kinetic theory of gas' predicts that:

• A. all the molecules have the same average speed
• B. all the molecules have the same average K.E.
• C. lighter molecules have higher average K.E.
• D. lighter molecules have lower average K.E.

Answer 1

Answer: (B)

all the molecules have the same average K.E.

The mean kinetic energy of a molecule in a gas is given by: $\epsilon =\frac{3}{2}kT$, where k=Boltzmann constant and T=absolute Temperature.

So, at a given temperature, all the molecules have same amount of average kinetic energy.

But average speed is given by:

$c_a=\frac{n_1{c}_1+n_2{c}_2+n_3{c}_3+--------}{n_1+n_2+n_3+------}=\overline{c}$

So, $c_a\ne c_1$, or $c_a\ne c_2$, or -----.