AQA A Level Chemistry Required
Practical 10 Questions and Answers
What do you need to consider when choosing a solvent ? - answerIt will dissolve both
compound + impurities at high temps
It will not dissolve compound at low temp (so it will crystallise)
Why is the minimum volume of solvent used ? - answerTo make a saturated solution
To increase the yield of the compound (enable crystallisation on cooling)
Why do you hot filter the solution ? - answerRemove insoluble impurities
Prevent crystals reforming
Why do you need to cool the beaker solution in ice ? - answerCrystals reform (ice
increases yield)
Soluble impurities in solution
Why use suction filtration ? - answerThe water pump decreases the pressure and
speeds up filtration
If asked to draw the suction filtration what should you draw ? - answerBuchner suction
funnel
One armed flask
Why do you wash the crystals with distilled water? - answerTo remove soluble
impurities
Why might the yield be lower ? - answerCrystals lost filtering and washing
Product remains into solution after crystallisation
side reactions
Practical 10 Questions and Answers
What do you need to consider when choosing a solvent ? - answerIt will dissolve both
compound + impurities at high temps
It will not dissolve compound at low temp (so it will crystallise)
Why is the minimum volume of solvent used ? - answerTo make a saturated solution
To increase the yield of the compound (enable crystallisation on cooling)
Why do you hot filter the solution ? - answerRemove insoluble impurities
Prevent crystals reforming
Why do you need to cool the beaker solution in ice ? - answerCrystals reform (ice
increases yield)
Soluble impurities in solution
Why use suction filtration ? - answerThe water pump decreases the pressure and
speeds up filtration
If asked to draw the suction filtration what should you draw ? - answerBuchner suction
funnel
One armed flask
Why do you wash the crystals with distilled water? - answerTo remove soluble
impurities
Why might the yield be lower ? - answerCrystals lost filtering and washing
Product remains into solution after crystallisation
side reactions
