Practicals- Please Do Well Flashcards
Preparing standard solution
- weigh solid
- dissolve solid in a beaker using distilled water
- transfer to volumetric flask
- rinse flask
- fill up to 250cm^3
- invert several times
Explain the effect of the flask is filled with water above the graduation line
Titre would be less as solution is more dilute
Explain what would happen if you did not invert the flask
Solution used in the 1st titre would be more dilute than solution used later
1st titre would need less solution
Carrying out a titration
- add measured volume of one solution using a pipette into a conical flask
- add other solution to burette, record reading
- add indicator to flask
- add solution from burette
- with swirling
- stop at end point
- repeat
Preparing a liquid product
• use of a separating funnel to remove an organic layer from an aqueous layer
• drying with an anhydrous salt (e.g. MgSO4, CaCl 2)
• redistillation
Filtration under reduced pressure apparatus
- buchner flask
- buchner funnel
- pressure tubing
- filter paper
- vaccum
Filtration under reduced pressure
- ensure good seal of flask and funnel by adding pressure to it
- place filter paper and wet it
- filter the sample
- rise beaker
Why is it important to heat the sample slowly when carrying out a melting point determination
- Sample melts over a range of temp
- heating too quickly will result i the thermometer recording a higher temp than actual range
What effect would not cooling the mixture after recrystallisation have on the final yield?
- some of the solid will still be dissolved in the solvent and so not all the solid will have crystallised
- yield would be lower because of the solid is still dissolved in the solvent
What does Rf stand for?
Retention factor
How to calculate Rf
Distance moved by the compound/ distance moved by the solvent front
What does TLC indicate?
How many compounds are in a mixture
Identify carboxylic acid
Add aqueous sodium carbonate
Effervescence
