AS Practicals Flashcards
Apparatus error for each piece of equipment =
100 x (margin of error/quantity measured)
Experimental error =
100 x (real answer - experiment answer)/real answer
Experimental results are accurate if….
experimental error is smaller than apparatus error
What type of flask do you use in creating a stock solution for titrations?
Volumetric flask
What type of pipette do you use in creating a stock solution for titrations?
A clean teat pipette
Concordant results are within a margin of…?
0.10
How do you clean a weighing bottle?
Wash and put in the oven/the lid on the drying rack
In titrations, results should be recorded to…?
The nearest 0.05cm3
Why do we use anti-bumping granules when refluxing an alcohol?
They prevent large bubbles being formed, which would make the reaction mixture jump vigorously. Instead, many smaller bubbles are formed
How do you separate the product from the reaction mixture when you have liquids?
Distillation
How do you separate the product from the reaction mixture when you have solids?
Filtration
Filtration uses what kind of flask?
Buchner flask
Equipment required for distillation of liquids? (x5)
Thermometer; distillation flask; condenser; heat supply; conical flask.
How are solids purified?
Re-crystallisation
How does re-crystallisation work?
Solids are dissolved in the MINIMUM amount of a hot solvent to create a solution saturated with that product. This is allowed to cool slowly and the product crystallises out of the solution, whilst impurities remain dissolved.
Re-crystallisation must be done slowly to ensure…?
That only the desired pure product crystallises out (if it’s cooled too quickly, impurities will crystallise out also.
How is the purity of a liquid tested?
Distillation (testing bpt).
How is the purity of a solid tested?
A small sample of the product is placed in a capillary tube and strapped to a thermometer. You then add oil to a boiling tube and increase the temp. until the product melts - stir the oil with a rod.
% yield =
moles product formed/theoretical moles of product x 100
What do you observe with the addition of sodium hydrogencarbonate to ethanoic acid?
Colourless solution -> fizzing and colourless solution
Calorimetry: q=
q=mcΔT
