Here is a short description of the mole concept and some related important definitions.

Definitions and Examples

1. Mole

When the molar mass (atomic mass, ionic mass, molecular mass, formula unit mass) of particles (atoms, ions, molecules, formula units) of any substance is expressed in grams, it is called mole OR

A mole is the amount of substance that contains as many particles (atoms, ions, or molecules) as there are atoms in exactly 12 grams of carbon-12. This number is equal to Avogadro’s number (6.022 × 10²³ particles).

Examples:

1. One mole of water molecules (H₂O) contains 6.022 × 10²³ molecules.
2. One mole of sodium atoms (Na) contains 6.022 × 10²³ atoms.

2. Gram Atom

A gram atom refers to the mass of one mole of an element, expressed in grams, and is numerically equal to the atomic mass of the element.

Examples:

1. One gram atom of oxygen (O) weighs 16 g.
2. One gram atom of magnesium (Mg) weighs 24.31 g.

3. Gram Ion

A gram ion is the mass of one mole of ions, expressed in grams, equal to the ionic mass of the ion.

Examples:

1. One gram ion of sodium ions (Na⁺) weighs 23 g.
2. One gram ion of chloride ions (Cl⁻) weighs 35.45 g.

4. Gram Molecule

A gram molecule is the mass of one mole of molecules of a substance, expressed in grams, and is numerically equal to the molecular mass of the substance.

Examples:

1. One gram molecule of carbon dioxide (CO₂) weighs 44 g.
2. One gram molecule of ammonia (NH₃) weighs 17 g.

5. Gram Formula Unit

A gram formula unit is the mass of one mole of formula units of a compound, expressed in grams, based on its empirical formula.

Examples:

1. One gram formula unit of sodium chloride (NaCl) weighs 58.44 g.
2. One gram formula unit of potassium nitrate (KNO₃) weighs 101.1 g.

6. Atomic Mass

The atomic mass of an element is the weighted average mass of its isotopes, measured in atomic mass units (amu).

Examples:

1. The atomic mass of hydrogen (H) is 1.008 amu.
2. The atomic mass of carbon (C) is 12.01 amu.

7. Molecular Mass

The molecular mass is the sum of the atomic masses of all atoms in a molecule, measured in atomic mass units (amu).

Examples:

1. The molecular mass of water (H₂O) is 18.02 amu.
2. The molecular mass of methane (CH₄) is 16.04 amu.

8. Ionic Mass

Ionic mass refers to the mass of an ion, typically expressed in atomic mass units (amu). It is the same as the atomic mass for monatomic ions.

Examples:

1. The ionic mass of sodium ion (Na⁺) is 23 amu.
2. The ionic mass of sulfate ion (SO₄²⁻) is 96.06 amu.

9. Gram Formula Mass

The gram formula mass is the mass of one mole of a compound, calculated by summing the atomic masses of the elements in its formula, expressed in grams.

Examples:

1. The gram formula mass of sodium sulfate (Na₂SO₄) is 142.04 g.
2. The gram formula mass of calcium carbonate (CaCO₃) is 100.09 g.

10. Avogadro’s Number

Avogadro’s number is the number of entities (atoms, ions, or molecules) in one mole of a substance, equal to 6.022 × 10²³.

Examples:

1. One mole of helium atoms contains 6.022 × 10²³ atoms.
2. One mole of glucose molecules (C₆H₁₂O₆) contains 6.022 × 10²³ molecules.

11. Molar Volume

The molar volume is the volume occupied by one mole of a gas at standard temperature and pressure (STP: 0°C and 1 atm), equal to 22.4 L or 22.414 dm³

Examples:

1. One mole of oxygen gas (O₂) occupies 22.4 L at STP.
2. One mole of nitrogen gas (N₂) occupies 22.4 L at STP.

Watch full mole concept on YouTube.

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