# Mole

## Key Stage 4

### Meaning

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

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.

### Equation

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.

Ar = 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.

Mr = The Relative Formula Mass of the compound

### Calculating Moles

#### Calculating Moles from Masses

The Periodic Table is needed to for mole calculations in order to find the Relative Atomic Masses of the elements.

 Calculate the number of moles in 36g of Carbon Calculate the number of moles in 2g of Oxygen atoms Calculate the number of moles in 47g of Uranium-235 Relative Atomic Mass of Carbon = 12g No. Moles = $${\frac{m}{A_r}}$$ No. Moles = $${\frac{36}{12}}$$ No. Moles = 3mol Relative Atomic Mass of Oxygen = 16g No. Moles = $${\frac{m}{A_r}}$$ No. Moles = $${\frac{2}{16}}$$ No. Moles = 0.125mol Relative Atomic Mass of Uranium-235 = 235g No. Moles = $${\frac{m}{A_r}}$$ No. Moles = $${\frac{47}{235}}$$ No. Moles = 0.2mol
 Calculate the number of moles in 32g of Methane Calculate the number of moles in 22g of Carbon Dioxide Calculate the number of moles in 115g of Ethanol Chemical Formula of Methane = CH4 Relative Atomic Mass of Carbon = 12g Relative Formula Mass of CH4 = 12 + 1 x 4 Relative Formula Mass of CH4 = 16 No. Moles = $${\frac{m}{M_r}}$$ No. Moles = $${\frac{32}{16}}$$ No. Moles = 2mol Relative Atomic Mass of Carbon = 12g Relative Atomic Mass of Oxygen = 16g Relative Formula Mass of CH4 = 12 + 16 x 2 Relative Formula Mass of CH4 = 44g No. Moles = $${\frac{m}{M_r}}$$ No. Moles = $${\frac{22}{44}}$$ No. Moles = 0.5mol Chemical Formula of Ethanol = C2H5OH Relative Atomic Mass of Carbon = 12g Relative Atomic Mass of Oxygen = 16g Relative Formula Mass of CH4 = 12x2 + 1x6 + 16 Relative Formula Mass of CH4 = 46g No. Moles = $${\frac{m}{M_r}}$$ No. Moles = $${\frac{115}{46}}$$ No. Moles = 2.5mol