Further Practical Techniques (OCR A-Level Chemistry A): Flashcards
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Practise the cards
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Purpose of filtration under reduced pressure
Purpose of filtration under reduced pressure
Separate solid from liquid faster & partially dry product on filter
Key feature of Büchner flask
Key feature of Büchner flask
Thick-walled conical flask with side arm
Why wet filter paper before adding sample?
Why wet filter paper before adding sample?
Creates better seal, prevents solid passing through gaps at edges
Principle of recrystallisation
Principle of recrystallisation
Dissolve in minimum hot solvent, cool slowly for pure crystals
Why use minimum solvent volume in recrystallisation?
Why use minimum solvent volume in recrystallisation?
To maximize yield - less product stays dissolved in cold solvent
Melting point range of pure organic substance
Melting point range of pure organic substance
Sharp, narrow range of
Two effects of impurities on melting point
Two effects of impurities on melting point
Wider temperature range & lower melting point than pure substance
Definition of melting range
Definition of melting range
Difference between temp when melting starts & when complete
Why heat slowly when approaching melting point?
Why heat slowly when approaching melting point?
To obtain accurate measurement of when melting begins and ends
How to heat flammable solvents during recrystallisation?
How to heat flammable solvents during recrystallisation?
Use water bath, never direct flame