Question

The order of increasing relative molecular mass of the following gases is, hydrogen, oxygen, carbondioxide, sulphurdioxide, chlorine. Given 8 gram of each gas at STP, which will contain the least number of molecules and which the most?

Answer 1

Molecular masses of given molecule:-

$H_2<O_2<C{O}_2<S{O}_2<C{l}_2$

$2<32<44.01<64<71$

Number of moles=$\frac{Weight}{Molecularmass}$ [All gases are $8$ gram]

(i) For $H_2$:- Number of moles=$\frac{8}{2}=4$

Number of molecules= Number of moles $\times$ Avogadro number

$=4\times 6.022\times {10}^{23}$

Number of molecules=$24.088\times {10}^{23}$

(ii) For $O_2$:- Number of moles=$\frac{8}{32}=0.25$

Number of molecules=$0.25\times 6.022\times {10}^{23}$

$=1.505\times {10}^{23}$

(iii) For $C{l}_2$:- Number of moles=$\frac{8}{71}=0.11$

$\therefore$ Number of molecules=$0.11\times 6.022\times {10}^{23}$

$=0.6624\times {10}^{23}$

It can be seen that Hydrogen gas has most number of molecules and chlorine gas least number of molecules.