Inorganic Chemistry - Acids, Bases and Salt Preperations (Paper 2)

Question 1

how would you prepare a pure, dry sample of a soluble salt, starting from an acid and alkali?

Answer 1

• pipette 25cm3 of alkali into a conical flask
• do not add an indicator to prevent contamination
• using the titration values, titrate the known volume acid into a conical flask
• transfer to an evaporating basin & heat the solution
• allow the solution to cool so that hydrated crystals form
• remove the crystals by filtration and wash with distilled water
• dry by leaving it in a warm place

Question 2

how would you prepare a pure, dry sample of an insoluble salt, starting from two soluble reactants?

Answer 2

• mix the two salt solutions in a beaker
• stir with a glass rod
• filter using filter paper and funnel
• wash with distilled water
• dry by leaving it in a warm place

Question 3

how would you prepare a sample of pure, dry lead(II) sulfate?

Answer 3

• start with lead (II) nitrate solution and sodium sulfate solution
• mix similar volumes of lead nitrate solution and sodium sulfate solution in a beaker, precise volumes do not matter
• a white precipitate of lead (II) sulfate will form.
• filter the creation mixture
• wash the residue left on the filter paper with distilled water several times to remove impurities
• dry in a warm oven