Mole

Key Stage 4

Meaning

A mole is an SI Unit used to show 6.02x10²³ particles of a chemical.

About Moles

Moles are based on the number of Carbon atoms in exactly 0.012kg (12g) of Carbon.

Moles are used to give a conversion between the number of atoms in a substance and useful quantities for chemical reactions. It would not be useful to talk about 1,000,000,000 atoms in a chemical reaction because that would be such a small amount of the chemical (0.0000000000000017g).

The relative atomic mass of an element is the mass of 1 mole or the mass of 6.02x10²³ atoms. So 1g of Hydrogen is 1 mole and contains 6.02x10²³ atoms. 235g of Uranium-235 is 1 mole and contains 6.02x10²³ atoms.

Calculating Moles

Number of Moles of an Element = (Mass of Element)/(Relative Atomic Mass of Element)

Number of Moles = \({\frac{M}{A_r}}\)

Where:

M = The mass of element being used.

A_r = The Relative Atomic Mass of the Element

Number of Moles of a Compound = (Mass of compound)/(Relative Formula Mass of compound)

Number of Moles = \({\frac{M}{M_r}}\)

Where:

M = The mass of compound being used.

M_r = The Relative Formula Mass of the compound