Question

The number of molecules present in 200 g of N₂O₅ is

• A. 1.11 X 10²⁴
• B. 1.01 X 10²⁶
• C. 1.43 X 10²⁴

Answer 1

The correct option is A 1.11 X 10²⁴

Given mass of $N_2{O}_5$ = 200 g
Avogadro's number = $6.022\times {10}^{23}$

Gram molecular mass of $N_2{O}_5$ = (2$\times$ gram atomic mass of nitrogen) + (5$\times$ gram atomic mass of oxygen)
= 2 $\times$ 14 + 5 $\times$ 16 = 108 g

$No.ofmoles=\frac{Givenmass}{Grammolecularmass}$

Number of moles in 200 g of $N_2{O}_5$ = 200/108 = 1.85 moles.

Number of molecules present in 1 mole of $N_2{O}_5$ = $6.022\times {10}^{23}$

So, the number of molecules present in 1.85 moles = 1.85 $\times$ 6.022 $\times {10}^{23}$ = 1.11 $\times {10}^{24}$.