Question

Find the number of oxygen atoms in 126 g of $HN{O}_3$.

• A. 36.132*10²³
• B. 9.033×10²³
• C. 120.44*10²³
• D. 16.132*10²³

Answer 1

The correct option is A

36.132*10²³

Given, $\frac{mass}{molarmass}$ = number of moles.
Molar mass of $HN{O}_3$ = 63 g
Moles of $HN{O}_3$ = $\frac{126}{63}$ = 2 moles.
In 1 molecule of $HN{O}_3$, we have 3 atoms of oxygen.
In 1 mole, we have 3 moles of oxygen atoms. In 2 mole, we will have 6 moles of oxygen atoms.
Number of atoms = $6\times 6.022\times {10}^{23}$
$\Rightarrow 36.132\times {10}^{23}$ atoms.