Question

.2kg of Mg3N2=__no of molecules​

Answer 1

Answer- The above question is from the chapter 'Some Basic Concepts of Chemistry'.

Concept Used: 1) Number of moles = $\frac{Given \: mass}{Molar \: mass}$

2) No. of molecules = Number of moles × Avogadro's Number

(Let Avogadro's Number be 6.02 × 10²³.)

Given question: 0.2 kg of Mg₃N₂ has _______ number of molecules.

(Atomic masses of Mg = 24 u and N = 14 u.)

Answer: Molar mass of Mg₃N₂ = 3 [Mg] + 2 [N] = 3 [24] + 2 [14] = 100 g

Given mass of Mg₃N₂ = 0.2 kg = 200 g

Number of moles = $\frac{Given \: mass}{Molar \: mass}$

                              = $\frac{200}{1000}$

                              = $\frac{1}{5}$

No. of molecules = Number of moles × Avogadro's Number

                            = $\frac{1}{5}$ × 6.02 × 10²³

                             = 1.204 × 10²³ molecules

∴ 0.2 kg of Mg₃N₂ has 1.204 × 10²³ number of molecules.