Required Practical Methods Flashcards
RP1: making up a volumetric solution for a titration
- Weigh the weighing boat containing the solid
- Transfer solid to a beaker and reweigh the weighing boat
- Record the difference in mass
- Add distilled water and stir with a glass rod until all the solid has dissolved
- Transfer to a volumetric flask with washings
- Make up to the 250cm3 mark with distilled water
- Invert flask
RP1: carrying out a simple acid bass titration
- Rinse equipment - burette with acid, pipette with alkali, conical flask with distilled water.
- 25 cm³ of alkaline into conical flask
- Touch surface of alkaline with pipette
- Add acid solution from burette and make sure the jet space is filled with acid
- Add a few drops of indicator use a white tile underneath the flask.
- Add acid to alkaline whilst swirling the mixture and add acid drop wise at endpoint
- note burette reading before and after adding acid
- Repeat titration until at least two concordant results.
RP2: measuring the entropy change for a reaction (calorimetry)
- Put polystyrene cup in a glass speaker for insulation
- measure out desired volumes of solutions with volumetric pipettes and transfer to cup
- clamp thermometer into place and measure the initial temperatures of the solutions every 2 to 3 minutes
- at minute 3 transfer second reagent to cup
- record temperature every minute after for several minutes
RP3: how the rate of a reaction changes with temperature
1- use a disappearing cross
2- put acid into container with a cross
3- add second reactant and start timing
4. Repeat at different temperatures
5. Record time for cross to disappear
6. Other variables kept constant
7. 1/t is rate
8. Plot rate against T
RP7: measuring the rate of reaction by an initial rate method
- Put each of the chemicals in separate burettes
- in each experiment measure out required volumes of potassium iodide, sodium thiosulfate, starch and water into a small chronicle flask from the burettes
- measure the hydrogen peroxide into a test tube
- pour it into the conical flask and immediately start timer. stir the mixture
- time until the first hint of blue/black colour appears
- Repeat with different concentrations of potassium iodide at the same temperature
RP7: measuring the rate of reaction by continuous monitoring method
- Add 50 cm³ of 1 mole HCl to a conical flask
- set up the gas syringe
- Add a strip of magnesium ribbon to the conical flask. place the bung into the top of the flask and start the timer
- record the volume of hydrogen gas collected every 15 seconds for 3 minutes
- Alter the concentration of HCl and repeat steps 1-4
RP10: preparation of a pure organic solid and testing its purity (eg aspirin)
1) dissolve sample in a minimum volume of hot solvent
2) hot filter solution through filter paper quickly
3) cool the filtered solution by putting beaker in ice
4) vacuum filter with a buchner flask and funnel to separate out crystals
5) wash the crystals with the distilled water
6) dry the crystals with paper
RP5: distillation of a product from a reaction
- mixture heated in a suitable flask
- With still head containing a thermometer
- Water cooled condenser connected to the still head and suitable cooled collecting vessel
- Collect sample at the boiling point of ethanal
- Cooled collection vessel necessary to reduce evaporation of ethanal
RP12: Thin layer chromatography (TLC)
1) Wearing gloves draw a pencil line 1 cm above the bottom of a TLC plate
2) use a capillary tube to add a tiny drop of each solution
3) add solvent to a beaker with a lid no more than 1 cm depth
4) place the plate into the beaker making sure that the level of the solvent is below the pencil line
5) mark with a pencil where the solvent finishes don’t allow it to travel to the top of the plate
6) allow it to dry in the fume cupboard
7) place a plate under a UV lamp to see the spots and calculate the RF values
