Chemistry Practicals Flashcards
Heating under reflux
Boiling a mixture
condensing the vapour to return it to the flask
Vacuum filtration diagram
funnel with filter paper above a perforated plate
fitting into a flask or tube with a side arm
removal of air from the flask through the side arm
Recrystallisation
Dissolve crystals in minimum of hot solvent
Cool solution to produce crystals
Filter off crystals and wash with cold solvent
Pure crystal is more soluble in hot solvent than in cold solvent
Percentage yield
Done in moles
Actual mole*100/predicted moles
Experiment to compare thermal stabilities of group 2 hydroxides
Crush any lumps of XCaCO3 with a pestle and mortar
Add Calcium hydroxide to distilled water and filter
Glass boiling tube containing solid is fitted with a bung carrying a delivery tube which dips into a solution of CaOh in a test tube
Tube is heated and is about horizontal
Measure time for cloudiness to first appear
Measure time taken to obscure a cross on paper
Equal mass of xCO3 and YCO3
Same volume and concentration of CaOH
Enthalpy Change of combustion
Enthalpy change to react one mole of fuel with oxygen
ALWAYS NEGATIVE
Black deposit on beakers after burning
Carbon formed due to incomplete combustion of fuel
How to use a solution of known strength and a colorimeter to find the concentration of an unknown solution
Dilute solution using burettes and pipettes
To include range of (x-y)%
Mix each dilution thoroughly to ensure standard solution
Zero colorimeter using water
Use appropriate filter
Measures absorbance of diluted solutions ensuring each sample is in a clean cuvette
Plot absorbance against dilution and draw a line of best fit
Should go through 0,0
Phenolphthalein
Colourless in acid
Pink in alkali
