Question

3: Consider molecules of hydrogen (tiny ones) and oxygen (bigger ones) in a gas mixture. If they have the same average kinetic energy (they will at the same temperature), which molecules have the greatest average speed

Answer 1

Answer: Hydrogen molecules will have greatest average speed.

Explanation:

The formula for average speed is  :

$\mu_{av}={\sqrt{\frac{8RT}{\pi\times M}}}$

R = gas constant  

T = temperature  

M = Molecular Mass

Now putting all the values:

$\frac{\nu_{H_2}}{\nu_{O_2}}=\sqrt{\frac{8RT}{\pi\times M_{H_2}}}/{\sqrt{\frac{8RT}{\pi\times M_{O_2}}}$

$\frac{\nu_{H_2}}{\nu_{O_2}}=\sqrt{\frac{16}{2}}$

$\frac{\nu_{av}_{H_2}}{\nu_{av}_{O_2}}=8$

Thus average speed of hydrogen is 8 times the average speed of oxygen. Thus hydrogen molecules will have greatest average speed