Question

Which of the following gases contains the largest number of molecules?

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

Answer 1

The correct option is A

40 g of hydrogen

We know that,

$\mathrm{moles}=\frac{\mathrm{weight}}{\mathrm{Molecular}\mathrm{weight}}$

and number of molecules $=\mathrm{moles}\times {\mathrm{N}}_{\mathrm{A}}$

Explanation for the correct option

(A) 40 g of hydrogen

$\mathrm{mole}=\frac{40}{1}$

mole = 40

and number of molecules$=40\times {\mathrm{N}}_{\mathrm{A}}$

Explanation for the incorrect options

(B) 4 moles of ${\mathbf{SO}}_{\mathbf{2}}$

Number of molecules $=4\times {\mathrm{N}}_{\mathrm{A}}$

(C) 35.5g of ${\mathbf{Cl}}_{\mathbf{2}}$

$\mathrm{mole}=\frac{35.5}{71}$

number of molecules $=\mathrm{mole}\times {\mathrm{N}}_{\mathrm{A}}$

$=\frac{1}{2}\times {\mathrm{N}}_{\mathrm{A}}$

(D) 40 g of ${\mathbf{O}}_{\mathbf{2}}$

$\mathrm{mole}=\frac{\mathrm{weight}}{\mathrm{Molecular}\mathrm{weight}}$

$=\frac{40}{32}$

$=\frac{5}{4}$

number of molecules $=\mathrm{mole}\times {\mathrm{N}}_{\mathrm{A}}$

$=\frac{5}{4}\times {\mathrm{N}}_{\mathrm{A}}$

Then we see that 40g of hydrogen contains the largest number of molecules.

So, the correct option is (A)