Question

Calculate the number of atoms present in 7.1 g of chlorine

• A. $0.2{\mathrm{N}}_{\mathrm{A}}$
• B. $0.3{\mathrm{N}}_{\mathrm{A}}$
• C. $0.4{\mathrm{N}}_{\mathrm{A}}$
• D. $0.5{\mathrm{N}}_{\mathrm{A}}$

Answer 1

The correct option is A

$0.2{\mathrm{N}}_{\mathrm{A}}$

Explanation of the correct answer:

The correct answer is option A:

From the given,

$$\begin{gathered} Mass\mathit{}of\mathit{}{\mathrm{Cl}}_2,\mathrm{W}=7.1\mathrm{g} \\ Molar\mathit{}mass\mathit{}of\mathit{}{\mathrm{Cl}}_2,\mathrm{M}=71\mathrm{g}/\mathrm{mol} \\ Number\mathit{}of\mathit{}moles\mathit{,}\mathit{}x=\frac{W}{M}=\frac{7.1\mathrm{g}}{70\mathrm{g}/\mathrm{mol}}=0.1\mathrm{mol} \\ \therefore Number\mathit{}of\mathit{}{\mathrm{Cl}}_{2}atom, \\ \mathrm{N}=2\times \mathrm{n}\times {\mathrm{N}}_{\mathrm{A}} \\ =2\times 0.1\times {\mathrm{N}}_{\mathrm{A}} \\ =0.2{\mathrm{N}}_{\mathrm{A}} \end{gathered}$$

Hence, option A is correct.