Monthly Archives: April 2017

AQA Paper 3

People have kept asking for a guide on the practicals. As I have explained before I am not producing one. It is worth remembering paper 3 is only partially practical based. There will be multiple choice questions and short answer questions on all parts of the syllabus. There are no short cuts. You need to know everything practical or non practical. It is not going to be an easy paper.

You will need to know the 12 required practicals but you will also get questions on other practicals which may be unfamiliar.

Practical questions could be about:

  • write the method for a common practical
  • draw diagrams of common apparatus
  • create a method for an unusual experiment
  • suggest improvements to a given method
  • state why a step in a method is done
  • draw graphs, take gradients and make conclusions from given results
  • see if results confirm a given hypothesis
  • give expected observations for a reaction
  • write chemical equations that match observations given
  • describing  causes of common errors
  • explain how errors could be minimised
  • explain what effect errors might have on the result

The 12 required practicals for AQA are given below with the relevant revision guides where I have mentioned them.  For some I have included brief methods where I think they are needed but not all. You should refer to your practical work for the full methods or the AQA practical handbook.

1 Make up a volumetric solution and carry out a simple acid–base titration – see 1.2 Calculations and  see 1.25 titrations for lots of questions on errors and method

2 Measurement of an enthalpy change see 1.4 Energetics

Consider – neutralisation reactions, solution plus solid and combustion reactions

3 Investigation of how the rate of a reaction changes with temperature see 1.5 Kinetics

Usually sodium thiosulphate and acid –the result from this experiment can be used to work out activation energy see 1.9 Rate Equations

4 Carry out simple test-tube reactions to identify:

 

5 Distillation of a product from a reaction   see 3.5 Alcohols and 3.14 Synthetic routes

 

 6 Tests for alcohol, aldehyde, alkene and carboxylic acid  see 3.6 Analysis and 3.14 Synthetic routes

7 Measuring the rate of reaction:  see 1.9 Rate Equations or  4. Reaction Kinetics

  •  by an initial rate method – generally ‘clock reactions’ or timing how long it takes for a cross  to disappear
  • by a continuous monitoring method- generally following with a gas syringe, but could be titration of samples or colorimeter

8 Measuring the EMF of an electrochemical cell   see 1.11 Redox Equilibria

9 Investigate how pH changes when a weak acid reacts with a strong base and when a strong acid reacts with a weak base   see 1.12 Acid Base Equilibria

10 Preparation of: 

11 Carry out simple test-tube reactions to identify transition metal ions in aqueous solution see 2.5 Transition Metals  and 2.6. Reactions of Inorganic Compounds in Aqueous Solution

12 Separation of species by thin-layer chromatography see  3.16 Chromatography and 3.13 Amino Acids, Proteins and DNA

Other important experiments commonly asked about in the past that could still well come up:

Simple measuring mass and gas volume experiments such a heating a hydrated salt or measuring the Mr of a volatile liquid see 1.2 Calculations

Colorimeters see 2.5 Transition Metals

Redox titrations and EDTA titrations see 2.5 Transition Metals

Autocatalysis reaction see 2.5 Transition Metals

Measuring an equilibrium constant for an esterification reaction 1.6 Equilibria

Comparing rates of hydrolysis of halogenoalkanes see 3.3 Halogenoalkanes

Any test tube reaction from inorganic or organic part of syllabus

Don’t forget

Calculating uncertainties and safety see 1.2 Calculations