Chemical quantities

All substances are made up of atoms.

The periodic table lists all the chemical elements, with eight main groups each containing elements with similar chemical properties.

Elements only contain one type of atom. 

Compounds contain more than one type of atom.

No new atoms are ever created or destroyed in a chemical reaction

- the total mass of reactants = the total mass of products

There is the same number of each type of atom on each side of a balanced symbol equation.

You can include state symbols to give extra information in balanced symbol equations. 

The masses of atoms are compared by measuring them relative to atoms of Carbon-12. 

You can work out the relative formula mass of a compound by adding up the relative atomic masses of the elements in it, in the ratio shown by its formula.

- One mole of any substance is its relative formula mass, in grams.

- Amount of substance (mol) = mass of sample (g) / molar mass (g/mol).

A mole of a substance always contains the same amount of atoms, molecules or ions. It is a huge number and this value is called the Avogrado constant.

- Avogrado constant is 6.02 x 10 to the 23rd per mole.

Balanced symbol equations tell you the number of moles of substances involved in a chemical reaction. 

You can use balanced symbol equations to calculate the masses of reactants and products in a chemical reaction.

You can deduce balanced symbol equations from the masses of substances involved in a chemical reaction.

The reactant that gets used up first in a reaction is called the limiting reactant. This is the reactant that is not in excess.

Therefore the amounts of product formed in a chemical reaction are determined by the limiting factor.

- Concentration (g/dm3) = Mass of solute (g) / Volume of solution (dm3). 

To calculate the mass of solute in a certain volume of solution of known concentration:

- Calculate the mass of the solute there is in 1 dm3 of the solution.

- Calculate the mass of the solute there is in 1 cm3 of the solution.

- Calculate the mass of solute there is in the given volume of the solution. 

A more concentrated solution has more solute in the same volume of solution than a less concentrated solution.