The mole

What is the mole?

Amount of substance is measured using a unit called the mole (mol for short) and given the symbol n. One mole is roughly 6.02 x 1023 particles (the Avogadro constant). It doesn't matter what the particles are. They can be atoms, molecules, electrons, ions, penguins - anything.

Avagadros Constant

You can use the Avogadro constant to convert between number of particles and number of moles. Just remember this formula:

Number of particles = Number of moles x Avogadro's constant

Examples:

Calculations with moles

1 mole of any substance has a mass that's the same as its relative molecular mass (M) in grams.

Example

What is the mass of 1 mole of water?

M, of H,O = (1.0 x 2) + 16.0 = 18.0, so 1 mole of water has a mass of 18.0 g.

This means that you can work out how many moles of a substance you

Here's the formula you need:

have from the mass of the substance and its relative molecular mass (M).

Number of moles = mass of substance

———————————-

Mr

Moles and concentration

The concentration of a solution is how many moles are dissolved per 1 dm³ of solution. The units are mol dm³

Here's the formula to find the number of moles.

Number of moles = Concentration × Volume (in cm³)

1000

Or: Number of moles = Concentration x Volume (in dm³)