Question

2g
of oxygen contains number of atoms equal to that in [BHU 1992]
A) 0.5g
of hydrogen B) 4g
of sulphur C) 7g
of nitrogen D) 2.3g
of sodium

Answer 1

Hey !!

Equal number of moles contain  equal number of atoms

2g of oxygen = $\frac{2}{16}$ mole = 0.125 mole

Similarly, 4 g of sulphur = $\frac{4}{32} = \frac{2}{16}$ mole

      = 0.125 mole

0.5 g of hydrogen = $\frac{0.5}{1}$ = 0.5 mole

7.0 g nitrogen = $\frac{7}{14}$ = 0.5 mole

2.3 g sodium = $\frac{23}{23}$ = 0.1 mole

Therefore atoms in 2 g oxygen = atoms in 4.0 g sulphur.

Option (B) 4 g

Good luck !!

Answer 2

Given: 2g oxygen.

To find: We have to find the option which has an equal number of atoms to 2g oxygen.

Solution:

The atomic weight of oxygen is 16g.

Thus 16g oxygen has $6.022×10^{23}$ number of atoms.

2g oxygen have $6.022×10^{23}×\dfrac{2}{16}\\=0.75×10^{23}$ number of atoms.

Now considering the following options we get-

(A)

1g hydrogen has $6.022×10^{23}$ number of atoms.

0.5g hydrogen have $6.022×10^{23}×\dfrac{0.5}{1}\\=3.011×10^{23}$ number of atoms.

(B)

32g sulfur has $6.022×10^{23}$ number of atoms.

4g sulfur have $6.022×10^{23}×\dfrac{4}{32}\\=0.75×10^{23}$ number of atoms.

(C)

14g nitrogen has $6.022×10^{23}$ number of atoms.

7g N has $6.022×10^{23}×\dfrac{7}{14}\\=3.011×10^{23}$ number of atoms.

(D)

23g sodium has $6.022×10^{23}$ number of atoms.

2.3g Na has $6.022×10^{23}×\dfrac{2.3}{23}\\=0.60×10^{23}$ number of atoms.

Thus 4g sulfur contains a number of atoms equal to that in 2g oxygen.

The correct option is B.