Experimental Techniques and Chemical Analysis

Worked examples (12)extended set

• 1Naming apparatus and choosing the right one
• 2Solvent, solute, residue and filtrate in purifying rock salt
• 3Multiple choice: best apparatus for each measurement
• 4Reading a thermometer and a measuring cylinder
• 5Using a solubility curve: crystals on cooling
• 6Planning: the solubility of a salt at 40 °C
• 7Comparing gas-collection methods
• 8Repeats, anomalous results and a source of error
• 9Making dilutions and controlling variables
• 10Improving a temperature-change experiment
• 11Planning a fair comparison of two dissolving salts
• 12Choosing between mass loss and gas volume

Model answers (6)

• ✓Model answer — Paper 6 short-answer style
• ✓Model answer — Paper 6 structured style
• ✓Model answer — Paper 6 structured style
• ✓Model answer — Paper 6 (Extended) structured style
• ✓Model answer — Paper 6 (Alternative to Practical) style
• ✓Model answer — Paper 6 (Alternative to Practical) style

Worked examples (12)extended set

• 1Describing a titration: apparatus, indicator and end-point
• 2Multiple choice: thymolphthalein colours in a titration
• 3Reading burettes and choosing concordant titres
• 4Methyl orange end-point and good titration technique
• 5Concentration of ethanoic acid in vinegar
• 6Sodium carbonate and hydrochloric acid: a 1 : 2 ratio
• 7Multiple choice: volume of acid for calcium hydroxide
• 8Making a pure salt by titration
• 9How errors in technique change the titre
• 10Comparing the concentrations of two alkalis
• 11Water of crystallisation in washing soda by titration
• 12Percentage purity of potassium hydroxide

Model answers (6)

• ✓Model answer — Paper 6 short-answer style
• ✓Model answer — Paper 6 structured style
• ✓Model answer — Paper 4 structured style
• ✓Model answer — Paper 6 (Alternative to Practical) style
• ✓Model answer — Paper 4 (Extended) calculation style
• ✓Model answer — Paper 4 (Extended) calculation style

Worked examples (12)extended set

• 1Spot the mistakes in a chromatography set-up
• 2Which colourings share a dye? Reading a chromatogram
• 3Calculating Rf values from a measured chromatogram
• 4Rf value when the baseline is above the paper's edge (multiple choice)
• 5When is a locating agent needed? (multiple choice)
• 6Describing chromatography of colourless sugars
• 7Four substances but only three spots (multiple choice)
• 8What is in the painkiller, and is the new batch pure?
• 9Identifying the dyes in a sweet from Rf values
• 10Evaluating a student's chromatography method
• 11One elongated spot: are dyes X and Y both present?
• 12Using a second solvent to identify substance K

Model answers (6)

• ✓Model answer — Paper 4 short-answer style
• ✓Model answer — Paper 6 (Alternative to Practical) style
• ✓Model answer — Paper 4 (Extended) structured style
• ✓Model answer — Paper 6 (Alternative to Practical) style
• ✓Model answer — Paper 4 (Extended) structured style
• ✓Model answer — Paper 4 (Extended) structured style

Worked examples (12)extended set

• 1Filtration: naming the residue and the filtrate
• 2Obtaining crystals from a solution (multiple choice)
• 3Simple distillation: condenser, water flow and thermometer
• 4Effect of a dissolved impurity on melting and boiling points (multiple choice)
• 5Cooling curves: which sample is pure?
• 6Proving that distilled water is pure (multiple choice)
• 7Fractional distillation with a water bath
• 8Separating three solids using water and a second solvent
• 9Reading a distillation temperature graph
• 10Planning: a pure, dry insoluble salt from two soluble solids
• 11Finding the solubility of potassium chloride at 40 °C
• 12Heated to dryness: evaluating a crystallisation

Model answers (6)

• ✓Model answer — Paper 4 short-answer style
• ✓Model answer — Paper 4 short-answer style
• ✓Model answer — Paper 4 structured style
• ✓Model answer — Paper 4 structured style
• ✓Model answer — Paper 4 (Extended) structured style
• ✓Model answer — Paper 4 (Extended) structured / planning style

Worked examples (12)extended set

• 1Name the gas and give its test
• 2Flame colour and halide precipitate (multiple choice)
• 3Which cation? Sodium hydroxide and ammonia in excess (multiple choice)
• 4Carrying out a flame test
• 5Identifying salt R from a table of results
• 6Predicting every observation for zinc bromide
• 7Ammonium or nitrate? Testing a fertiliser
• 8Ionic equations for the precipitation tests
• 9Sulfite or sulfate? Using acidified manganate(VII)
• 10One reagent to tell zinc from aluminium (multiple choice)
• 11Copper(II) ions and ammonia: the precipitate-mass graph
• 12Flow chart: identifying the ions in solid Z

Model answers (6)

• ✓Model answer — Paper 4 short-answer style
• ✓Model answer — Paper 4 short-answer style
• ✓Model answer — Paper 4 structured style
• ✓Model answer — Paper 4 (Extended) structured style
• ✓Model answer — Paper 4 (Extended) structured style
• ✓Model answer — Paper 4 (Extended) structured style