Question

16 g of carbon dioxide ($C{O}_2$) when passed through limewater turns it milky. The number of molecules of carbon dioxide present in 16 g are _________.

• A. $2.18\times {10}^{23}$
• B. $9.022\times {10}^{23}$
• C. $3.24\times {10}^{23}$
• D. $8.069\times {10}^{23}$

Answer 1

The correct option is A $2.18\times {10}^{23}$

Given mass of carbon dioxide (${\text{CO}}_2$) = 16 g

Gram molecular mass of ${\text{CO}}_2$:

Atomic mass of carbon + Atomic mass of oxygen $\times$ 2
= 12 + (16 $\times 2$)
= 44 g

Number of moles in the given mass of ${\text{CO}}_2$, n = $\frac{Givenmassingrams}{Grammolecularmass}$

= $\frac{16}{44}$= 0.363 mol

We know that,
1 mole of a substance contains =$6.022\times {10}^{23}$ molecules
Thus, 0.363 mol ${\text{CO}}_2$ contains $0.363\times 6.02\times {10}^{23}$ = $2.18\times {10}^{23}$ molecules.