The mole is the SI unit for the amount of substance. One mole of any substance contains 6 × 10²³ particles (Avogadro’s number). These particles can be atoms, molecules, ions, or electrons.
1. Number of Particles
One mole of substance contains 6 x 1023 particles.
This value is called Avogadro’s number.
Number of particles in 1 mol of substance = 6 x 1023
Number of particles in 2 mol of substance = 2 x 6 x 1023
Number of particles in y mol of substance = y x (6 x 1023)
Hence,
Formula: Number of particles = number of moles x (6 x 1023)
2. Volume of Gas at r.t.p.
One mole of any gas occupies 24 dm³ (24 000 cm³) at room temperature and pressure (r.t.p.). This is called the molar volume.
At r.t.p,
Volume occupied by 1 mol of gas = 24 dm3
Volume occupied by 2 mol of gas = (2 x 24) dm3
Volume occupied by y mol of gas = (y x 24) dm3
Hence,
Formula: Volume of gas (dm³) = Number of moles × 24 dm3
3. Mass of Substance
Molar mass is the mass of one mole of a substance (unit: g/mol). It is obtained from the Periodic Table.
For example, copper metal
Mass of 1 mol of copper metal = 64 g (64 gmol-1)
Note: 64 gmol-1 is the molar mass of copper metal. This value is obtained from The Periodic Table
Mass of 2 mol of copper metal = (2 x 64) g
Mass of y mol of copper metal = (y x 64) g
Hence, Formula: Mass (g) = Number of moles × Molar mass
4. Concentration of Aqueous Solution
Concentration tells us how much solute is dissolved in a given volume of solution. It can be expressed in g/dm³ or mol/dm³ (molar concentration).
When concentration is expressed in moldm-3, it is called the molar concentration.
Concentration of aqueous solution in gdm-3 can be calculated by multiplying concentration in moldm-3 with the molar mass of the solute
Formula: Concentration (g/dm³) = Concentration (mol/dm³) × Molar mass
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