Mole Concept

Concentration formulae(g/dm^3 and mol/dm^3)

Mass formulae

Gases

Formulae - No. of moles

Mass of one mole of element or compound: Ar or Mr

Mass of an element in a compound

1) No. of moles × Ar or Mr

(No. of atoms of the element in the formula × Ar of the element / Mr of the compound) × Mass of sample

*Comparing the mole ratio - Finding the limiting and excess reagents / Finding no. of moles

2) Mass / Ar or Mr

1) No. of particles / Avogadro's constant

1 mole = 6 × 10^23 particles

*Avogadro's law: Equal volumes of all gases at the same temperature and pressure contain the same no. of particles

Volume of 1 mole of any gas = 24dm^3 (molar volume)

1) No. of moles × Molar volume

Other formulae

Deriving the empirical formula

1) Divide each mass by Ar or percentage to obtain no. of moles -> 2) Divide each no. of moles by the smallest number from step 1-> 3) Obtain the empirical formula

Deriving the molecular formula

n(empirical formula) = molecular formula

Empirical Formula - Simplest whole number ratio
Molecular Formula - Exact no. of atoms in a molecule

n = Mr of the compound / Mr of the empirical formula of the same compound

1) Mass of solute / Volume of solution (dm^3)

2) Concentration (mol/dm^3) × Mr of solute

1) No. of moles of solute / Volume of solution (dm^3)

4) Molarity (mol/dm^3) × Volume of solution (dm^3)

3) Volume of gas / 24dm^3 (Gas)

Percentage

Yield

Purity

Percentage of an element in a compound

(Actual yield / Theoretical yield) × 100%

(Actual amount of pure substance / Theoretical amount of substance) × 100%

*Theoretical amount of substance = Mass of impure sample (Given)

Units

1) Mass = grams

2) Mole = Mol

3) Volume = dm^3

4) Mass concentration = g/dm^3

5) Mole concentration = mol/dm^3