Amount of substance and molar mass
Answers are for parents and teachers.
1
Find the number of atoms in 54 g of aluminium (M = 27 g/mol).
1.2·10²⁴
2
Find the mass of 5 mol of nitrogen N₂ (M = 28 g/mol). Answer in grams.
140
3
A gas molecule has a mass of 4.7·10⁻²⁶ kg. Estimate the gas’s molar mass (N_A = 6·10²³ mol⁻¹). Which gas could it be?
M = m₀N_A ≈ 0.028 kg/mol = 28 g/mol; for example nitrogen N₂.
4
How many molecules are in 3.6·10⁻⁵ m³ of water (ρ = 1000 kg/m³, M = 18 g/mol)?
1.2·10²⁴
5
Why do 1 mol of water and 1 mol of iron have different masses but the same number of particles?
The number of particles is N_A in both, but the mass of a single particle (molar mass) differs.