Question

Nitric acid is composed of HNO3 molecules. A sample weighing 4.50 g contains 4.30 X 10^22 HNO3 molecules. How many nitrogen atoms are in this sample? How many oxygen atoms are in 61.0 g of nitric acid?

Answer 1

1 molecules of $HNO_3$ contains 1 molecules of nitrogen atoms.

So, $4.3\times 10^{22}$ molecules of $HNO_3$ contains $4.3\times 10^{22}$ molecules of nitrogen atoms.

Now, 61 g of $HNO_3$ contains :

$=\dfrac{61}{4.5}\times 10^{22}\\\\=1.356\times 10^{23}\ molecules$

Now , 1 molecule of nitric acid contains 3 molecules of oxygen.

So, number of oxygen molecules in 61 g nitric acid is :

$n = 3\times 1.356\times 10^{23}\ molecules\\\\n =4.068\times 10^{23}\ molecules$

Hence, this is the required solution.