Question

Assertion: 1 g $O_2$ and 1 g $O_3$ have equal number of atoms.
Reason: Mass of 1-mole atom is equal to its gram-atomic mass.

• A. If both (A) and (R) are correct and (R) is the correct explanation of (A).
• B. If both (A) and (R) are correct but (R) is not the correct explanation of (A).
• C. If (A) is correct but (R) is wrong.
• D. If (A) is wrong but (R) is correct.
• E. If both (A) and (R) are wrong.

Answer 1

The correct option is A If both (A) and (R) are correct and (R) is the correct explanation of (A).

1 mol of $O_2$ $\to 2$ atoms of $O$ and 1 mole of $O_3\to 3$ atoms of $O$.

Therefore no. of atoms in 1g $O_2$ = $\frac{1}{32}\times 2\times 6.02\times {10}^{23}$ =$\frac{6.02\times {10}^{23}}{16}$

Similarly , no. of atoms in 1g $O_3$ = $\frac{1}{48}\times 3\times 6.02\times {10}^{23}$ = $\frac{6.02\times {10}^{23}}{16}$

They have same no. of atoms

Mass of 1 mole is its gram- atomic mass.

Hence, option $A$ is correct.