Question

The molar mass of carbon dioxide is 44 g. The number of molecules present in 176 g of carbon dioxide is

• A. $5.60\times {10}^{23}$
• B. $2.41\times {10}^{24}$
• C. $1.19\times {10}^{24}$
• D. $3.19\times {10}^{23}$

Answer 1

The correct option is B $2.41\times {10}^{24}$

Given, mass of carbon dioxide = 156 g
Also, molar mass of ${\text{CO}}_2$ = 44 g
Avogadro number = $6.022\times {10}^{23}$

Number of molecules of carbon dioxide
= $\text{Number of moles}\times \text{Avogadro number}$ ...(i)

Number of moles of carbon dioxide
= $\frac{\text{Given mass in gm}}{\text{Molar mass in gm}}$ ....(ii)

Inserting equation (ii) in equation (i) we get

Number of molecules of carbon dioxide
= $\frac{\text{Given mass in gm}}{\text{Molar mass in gm}}\times \text{Avogadro number}$ ...(iii)

Inserting values of mass, avogadro number and molar mass in equation (iii) we get

Number of molecules of carbon dioxide
= $\frac{156}{44}\times 6.022\times {10}^{23}$

$\therefore$ Number of molecules of carbon dioxide
= $4\times 6.022\times {10}^{23}$
= $2.41\times {10}^{24}$