Unit 3 - Stoichiometry

The number and type of different atoms in a molecule e.g. CO2

Simplest whole number ratio for different atoms e.g. H2O2 = OH

Number of electrons gained or lost

• Group I = 1 • Group II = 2 • Group III = 3 • Group IV = 4 • Group V = 3 • Group VI = 2 • Group VII = 1 • group VIII = 0

• Ions are charged to get full outer shells • Compounds final charge must be neutral e.g. k+ + F- = KF

Chemical names of all reactants and products

Names of substances are replaced by element symbols

Ions that have more than one element, e.g. SO4, covalently bonded but unequal protons and electrons

• Hydroxide/OH = 1- • Carbonate/CO3 = 2- • Chlorate/ClO4 = 1- • Nitrate/NO3 = 1- • Sulfate/SO4 = 2-

In a reaction the mass of the reactants will equal the mass of the products - mass is conserved

• Solid = (s) • Liquid = (l) • Gas = (g) • Aqueous = (aq)

Brackets around ion with amount e.g. Al(NO3)3

NH4 = 1+

NH3

Every atom’s mass is relative to 1/12th of carbon - 12

Ar

The mass of all atoms in a compound or molecule - can be used for ionic compounds

Mr

1 mole of a substance has 6.02 x 10^23 atoms in it

1 mole of a substance is weighs its Ar or Mr in grams e.g. 1 mole of H20 = 18g

• Mass = Moles x Mr • Moles = Mass ÷ Mr • Mr = Mass ÷ Moles

Under same temperature and pressure conditions, equal volumes of different gasses contain an equal number of molecules

1 mole of a gas = 24dm^3 = 24000cm^3 = 0.024m^3

25˚C and 1 atmospheric pressure