Question

Two flasks $A$ and $B$ have equal volumes. Flask $A$ contains hydrogen at $600\text{K}$ while flask $B$ contains same mass of $C{H}_4$ at $300\text{K}$. Then choose the correct options.

• A. In flask $A$ the molecules move faster than $B$
• B. In flask $B$ the molecules move faster than $A$
• C. Flask $A$ contains greater number of molecules than $B$
• D. Flask $B$ contains more molecules than $A$

Answer 1

Answer: (A), (C)

Flask $A$ contains greater number of molecules than $B$

The average velocity for the gas molecules is given by $=\sqrt{\frac{8RT}{\pi M}}$.So, the molecules which have more $\frac{T}{M}$ will have greater average velocity and will move faster .
For $H_2$ in flask A, $\frac{T}{M}$$=$ $\frac{600}{2}$
For flask B, $\frac{T}{M}$$=$ $\frac{300}{16}$
$\therefore$ $H_2$ moves faster.

We know, $n$$=$$\frac{m}{M}$.For $H_2$.

As masses of two gas are same, then we have $n$$\propto$$\frac{1}{M}$.For $H_2$, there are more number of moles , hence greater number of molecules as compared to the one in flask B ( containing$C{H}_4$ ).