Practical Skills

Question 1

methods of collecting gas

Answer 1

1. collection over water: only suitable for gases that are insoluble in water, inverted measuring cylinder over a basin of water
2. using a gas syringe
3. displacement of air: the direction of the delivery tube will be determined by the density of gas being collected

Question 2

methods of heating

Answer 2

1. using a bunsen burner: useful for heating, a reaction, which has no flammable reactants or products
2. Using a water bath.
3. Using a heating mantle.
   - Both two and three would be used when reactants or products are flammable heating mantels also allow the temperature to be controlled.

Question 3

separating techniques

Answer 3

1. Filtration: used to separate insoluble solid from a liquid.
2. Evaporation colon used to separate soluble solid from a liquid.
3. Distillation: used to separate a mixture of liquids, which have two different boiling points.

Question 4

what is a standard solution

Answer 4

a solution with an accurately known concentration

Question 5

how to fill a burette

Answer 5

1. ensure the top of the burette is below eye level
2. thé burette should first be rinsed with the solution being used and make sure the valve is closed
3. slowly fill the burette using a filter funnel and hold the funnel to prevent bubbles
4. full the burette past the mark as you need to run some out to ensure the bottom of the burette is filled
5. carefully open the valve to allow the burette to drain slightly and bring down to 0 mark. Ensure the bottom on the meniscus is on the top of the mark
6. adjust the butter so it’s sitting securely on the bench over a conical flask

Question 6

how to carry out a volumetric titration

Answer 6

1. pipette an accurate volume of solution A into a conical flask
2. add a few drops of indicator solution (if required) and place the conical flask on a white surface
3. not the initial burette reading from the bottom of the meniscus
4. add solution B from tree burette whilst gently swirling the solution in the conical flask
5. when the colour starts to disappear more slowly add solution B at a slower pace one drop at a time until the solution changes colour
6. record the final burette reading
7. wash out the conical flask
8. repeat until you get concordant results, not including your rough titre

Question 7

what is chromatography

Answer 7

the process which exploits the differences in size and polarity of different molecules in a mixture

Question 8

what results are ignored in experiments

Answer 8

rouge results (results that are vastly different to others) are ignored as well as rough titres
rouge results should also be excluded from the line of best fit on scatter graphs