PAPER 2 req practicals

Question 1

Measure enthalpy change when making a solution

Answer 1

Measure 50cm3 of water using burette
Transfer to polystyrene cup with lid
Measure 4g of CuSO4 using accurate 2dp balance
Use thermometer to take temp of water for 4 mins to establish inital temp
Pour copper sulfate into water at min 5
Reweigh weighing boat to estalish mass transferred
Replace lid and stir
Continue recording temp and minute intervals up to 15 minutes
Plot temp against time
Extrapolate back to point of addition and determine deltaT
q=mcat
deltaH = q/n
mol = mass/mr

Question 2

Thin layer chromatography
Mixture of amino acids separate using TLC

Answer 2

Wear gloves to prevent contamination of plate
Draw a pencil line parallel to bottom of plate
Use a capillary tube to add small spot of amino acid mixture to line
Allow plate to completely dry
Add 1cm of developing solvent to tank
Place TLC plate in tank ensuring solvent does not reach pencil line
Replace lid of tank to prevent solvent evaporating
Remove plate when solvent is 1cm from top
Mark position reached with pencil line
Dry plate in fume cupboard
Visualise plate under UV light and mark location of spots
Calculate Rf value or each spot
Compare Rf to data book to identify amino acid

Question 3

Purifying a sample of aspirin

Answer 3

Filter/decant to remove from reaction mixture
Dissolve rude aspirin in a minimum volume of hot solvent
Filter hot through fluted filter paper
Slowly cool until aspirin recrystallises
Filter using Buchner funnel
Wash with cold solvent
Dry