GCSE Chemistry C5

HideShow resource information
  • Created by: Maddie
  • Created on: 14-06-11 21:44

C5a&c - Moles and empirical formulae & Quantitive

No. of Moles = Mass(g) / Molar Mass(g) (relative formular mass) 

Mass = No. of Moles X Molar Mass

Molar Mass = Mass / No. of Moles

Empirical formulae (e.g. C6H1206 = CH2O)

Concentration = Moles / Volume (dm^3)

Moles = concentration X Volume

Volume = moles / concentration 

cm^3 / 1000 = dm^3

g/dm / Molar mass = mol/dm^3

1 of 7

C5b - Electrolysis

Electrolysis is the decomposition of the liquid eletolyte, by passing a current through it. Moving ions transfer charge in the eletrolyte whilst electrons transfer charge in the wire.

+ions (Cation) accept electrons at the cathode and are discharged, they then move through the eletolyte and transfer charge. The now -ions (anion) are now attracted to the Anode where they give up the electrons before becoming discharged in to the eletrolyte again. 

  • Anode - + electrode
  • Anion - - Ions (onions, crying, sad, negative)
  • Cathode - -electrode
  • Cation - +ions (pussytive)

H+ and OH- are always present in aq. solutions. 

Mass gained at Cathode = Mass lost at Anode


ANode Oxidation Is Loss Reduction Is Gain Cathode

2 of 7

C5b - Electrolysis Continued...

Metal ions (& hydrogen) are positive

non-Metal ions are negative

Q=IT          (Charge = Current X Time)

Amount deposited on Cathode (removed from Anode) increases proportionaly with both time and current.

3 of 7

C5d - Titrations

Titration allows you to measure the amount of a substance present in a solution

Titration curve: Equivalence point = neutralisation point = 25cm^3, Acid to Alkali


 Titre = volume needed to neutralise 

4 of 7

C5e - Gas volumes

Measured using

  • Gas syringe
  • Upturned burette filled with water
  • Upturned measuring cylinder filled with water

Reactions stop when one of the reactants is used up. The reactant used up first is called the limiting reactant, the other/s is called the excess

A mole of gas at room temperature and pressure has a volume of 24dm^3

Volume (dm^3) = number of moles X 24

5 of 7

C5f - Equilibria

Equilibria = reversible reactions – forward and backward reactions are equal Equilibrium = reversible reactions proceeds at the same rate in a closed system Reactants ............ concentration is greater then reactants       - Equilibrium - Right Concentration is greater then product ............ products           - Equilibrium - Left Add more product or remove reactant - reaction shifted to the left Remove product or add more reactant - reaction shifted to the right Increasing pressure moves equilibrium to the side with the least no. of moles of gas

6 of 7

C5g - Strong and weak acids

Acids ionise in water to produce hydrogen ions (H+). 

Strong acids

  • higher electrical conductivity (more H+ available to carry charge)
  • Produces gas rapidly when reacting with magnesium or calcium carbonate (higher concentration of H+ causes more collisions between acid and ^)
  • Lower pH (the higher the H+ the lower the pH
  • Higher concentration of hydrogen ions
  • Ionises completely in water to form ions and no molecules are present

Weak acids - (opposite to strong)

  • Ionises slightly in water and produces an equilibrium mix containing acid molecules and ions
7 of 7


alex colton

very good i like the little things to help you remember

Similar Chemistry resources:

See all Chemistry resources »See all resources »