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प्रश्न
Solve problem:
Calculate the number of moles of magnesium oxide, MgO in
- 80 g, and
- 10 g of the compound.
(Average atomic masses of Mg = 24 and O = 16)
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उत्तर
Given: i. Mass of MgO = 80 g
ii. Mass of MgO = 10 g
To find: Number of moles of MgO
Formulae: Number of moles (n) = `"Mass of a substance"/"Molar mass of a substance"`
Calculation: i. Molecular mass of MgO = (1 × Average atomic mass of Mg) + (1 × Average atomic mass of O)
= (1 × 24 u) + (1 × 16 u)
= 40 u
∴ Molar mass of MgO = 40 g mol−1
Mass of MgO = 80 g
Number of moles (n) = `"Mass of a substance"/"Molar mass of a substance"`
= `(80 "g")/(40 "g mol"^-1)`
= 2 mol
ii. Mass of MgO = 10 g, Molar mass of MgO = 40 g mol–1
Number of moles (n) = `"Mass of a substance"/"Molar mass of a substance"`
= `(10 "g")/(40 "g mol"^-1)`
= 0.25 mol
- The number of moles in 80 g of magnesium oxide, MgO = 2 mol
- The number of moles in 10 g of magnesium oxide, MgO = 0.25 mol
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