Question

Which of the following contain the largest number of molecules?

• A. 40 g of ${\mathrm{H}}_{2_{}}$
• B. 4 moles of ${\mathrm{SO}}_2$
• C. 35.5 g of ${\mathrm{Cl}}_2$
• D. 40 g of ${\mathrm{O}}_2$

Answer 1

The correct option is A

40 g of ${\mathrm{H}}_{2_{}}$

Explanation for the correct option :

(A) 1 mole of ${\mathrm{H}}_2$= molecular mass of ${\mathrm{H}}_2$= 2g

Also, 1 mole of ${\mathrm{H}}_2$= $6.023\times {10}^{23}$ molecules of ${\mathrm{H}}_2$

2g of ${\mathrm{H}}_2$=$6.023\times {10}^{23}$ molecules of ${\mathrm{H}}_2$

40 g of ${\mathrm{H}}_2$= $\frac{6.023\times {10}^{23}}{2}\times 40$

$=1.204\times {10}^{25}$

Explanation for the incorrect option :

(B) 1 mole of ${\mathrm{SO}}_2$= $6.023\times {10}^{23}$ molecules of ${\mathrm{SO}}_2$

4 moles of ${\mathrm{SO}}_2$= $$\begin{gathered} 4\times 6.023\times {10}^{23} \\ =2.409\times {10}^{24} \end{gathered}$$molecules of ${\mathrm{SO}}_2$

(C) 1 mole of ${\mathrm{Cl}}_2$= molecular mass of ${\mathrm{Cl}}_2$= $35.5\times 2=70$g

70 g of ${\mathrm{Cl}}_2$ = $6.023\times {10}^{23}$ molecules of ${\mathrm{Cl}}_2$

35.5 g of ${\mathrm{Cl}}_2$ = $3.023\times {10}^{23}$ molecules of ${\mathrm{Cl}}_2$

(D) 1 mole of ${\mathrm{O}}_2$= molecular mass of ${\mathrm{O}}_2$= 32g

Also, 1 mole of ${\mathrm{O}}_2$ = $6.023\times {10}^{23}$ molecules of ${\mathrm{O}}_2$

32g of ${\mathrm{O}}_2$ = $6.023\times {10}^{23}$ molecules of ${\mathrm{O}}_2$

40g of ${\mathrm{O}}_2$ = $\frac{6.023\times {10}^{23}}{32}\times 40$

40g of ${\mathrm{O}}_2$ = $7.528\times {10}^{23}$ molecules of ${\mathrm{O}}_2$

Thus, option A is correct i.e. 40 g of ${\mathrm{H}}_{2_{}}$contains the largest number of molecules.