Question

How many molecules are present in 252g of HNO_{3 .}

(Molecular Mass of HNO₃ =63).

• A. 6.022 x ${10}^{23}$
• B. 2.41 x ${10}^{24}$
• C. 1.505 x ${10}^{23}$
• D. 4

Answer 1

The correct option is B

2.41 x ${10}^{24}$

Number of molecules of any substance is given by:

Number of molecules = Number of moles x Avogadro Constant

Since, Number of Moles = $\frac{Mass}{Molecularmass}$ = $\frac{252}{63}$ = 4.

Therefore, number of molecules present in 252g $HN{O}_3$ = $\frac{252}{63}$ x 6.022 x ${10}^{23}$

= 4 x 6.022 x ${10}^{23}$

= 2.41 x ${10}^{24}$