Question

The number of molecules present in 2.8 g of
nitrogen is
(A) 6.023 x 1020 (B) 6.023 x 1022
(C) 6.023 x 1021 (D) 6.023 x 1023​

Answer 1

Mass of Nitrogen given = 2.8 grams

Mass of 1 atom of Nitrogen = 14 units

Molar mass of Nitrogen =2*14 = 28 Grams

$\rule{200}{2}$

Number of moles of any element is equal to :-

$moles=\dfrac{mass\:given}{molar\:mass}$

Thus,

Moles of Nitrogen given will be :-

$moles=\dfrac{2.8}{28}\\ \\ \\moles=0.1$

$\rule{200}{2}$

Now :-

$1 mole=N_A\:Molecules$

where:-

$N_A=6.023*10^{23}$

$\rule{200}{2}$

So,

Total molecules present in given sample of nitrogen will be :-

$=0.1*N_A\\ \\ \\=0.1N_A\:Molecules$

where

$N_A=AVOGADRO's\:NUMBER$

Thus:-

$=0.1*6.023*10^{23}\\ \\ \\=\dfrac{1}{10}*6.023*10^{23}\\ \\ \\=6.023*10^{22}$

$\rule{200}{2}$

Correct Option = Option(B)

Answer 2

Answer:

( B ). 6.023 * 10^22 molecules

Option ( B ) is correct.

Explanation :

Refer the attached picture.