MHTCET 20 Apr 2026 Shift 2 Paper

Concept:The number of molecules is calculated by first converting the given mass into moles, then multiplying the moles by Avogadro's number.Explanation:The molar mass of ammonia, $\mathrm{NH}_3$, is:$$14 + 3(1) = 17 \ \mathrm{g\,mol}^{-1}$$The given mass of ammonia is $2.125 \ \mathrm{g}$.The number of moles is:$$\mathrm{Moles} = \frac{\text{Given mass}}{\text{Molar mass}} = \frac{2.125}{17} = 0.125 \ \mathrm{mol}$$One mole of any substance contains $6.022 \times 10^{23}$ molecules.Thus, the number of molecules in $0.125 \ \mathrm{mol}$ is:$$0.125 \times 6.022 \times 10^{23} = 7.527 \times 10^{22}$$This value matches option D.Answer:The number of molecules in $2.125 \ \mathrm{g}$ of ammonia is $7.527 \times 10^{22}$.Therefore, the correct option is D.