C3 quantitative chemistry

What is relative formula mass (Mr)?

Relative atomic masses of all atoms in the molecular formula added together

How do you calculate % mass of an element in a compound?

Ar × number of atoms of that element ÷ Mr of the compound × 100

What is tha Avogadro constant?

6.02 × 10²³

What is the mole?

The unit used to measure the amount of chemical we have. One mole of a substance is an amount of thet substance that contains an Avogadro number of particles

How to find out the number of moles?

Mass in g ÷ Mr

What is the law of conservation of mass?

Atoms cannot be created or destroyed. The mass of products is the same as the mass of reactants

How to use moles to balance the equation?

1. Calculate the Mr values for each substance in the equation

2. Calculate the moles of each substance using moles=mass/Mr

3. Simplify the ratio

4. Use the ration to balance the equation

What is a limiting reactant?

The reactant that is used up in a reaction. Any other reactants are in excess. The reactant is limiting as it limits the amount of product.

How can you calculate the mass of a product formed in a reaction by using the mass of the limiting reactant?

1. Write down tha balanced equation

2. Work out Mr of tge reactant and product you want

3. Find out how many moles there are of the substance you know the mass of

4. Use the balanced equation to work out how many moles there’ll be of the other substance

5. Use the number of moles to calculate the mass

What is concentration?

The amount of substance per unit volume of solution

How can you measure concentration?

mass of solute (g) ÷ volume of solvent (dm³)

How many cm³ are in 1 dm³

1000