Practical Skills Flashcards
What is the process of weighing a solid?
Zero the balance. Weigh the solid + the weighing bottle. Record. Empty out the solid. Reweigh the weighing bottle. Calculate the difference.
Uncertainty of ±0.1
What is the process of measuring a liquid in a pipette?
Ensure it is clean. Use a pipette filler to draw enough solution to reach the bottom of the meniscus. Run the solution into suitable glassware.
What is the process of measuring a liquid in a burette.
Rinse out burette. Ensure burette tap is closed. Clamp burette in place. Pour solution into burette using a funnel.
Uncertainty of ±0.05
What are the two methods of measuring volumes of gas?
Gas syringe.
Inverted measuring cylinder.
Describe heating under reflux.
Add reactants into a pear shaped flask. Add anti-bumping granules. Attach a condenser, water flows in at the bottom and out at the top. Heat gently, any vapours should condense back into the liquid.
Describe purification using a separating funnel.
Organic product and an immiscible liquid. Layers can be separated by a separating funnel. Denser layer is at the bottom. Dispose of the other liquid. Run the organic product into a conical flask. If acidic impurities are present, add sodium hydroxide carbonate solution. If alkaline impurities are present, add a dilute acid. Dry crude product with anhydrous sodium sulfate. Separate by distillation.
Describe distillation.
Pear shaped flask and anti-bumping granules. Heat gently. Collect in a beaker.
Describe Thin Layer Chromatography.
Spot test mixture and reference samples on a pencil line 1cm from the base of chromatography paper or a silica plate. Pencil does not run into the solvent. Suspend plate in solvent, covering with a watchglass. Allow time for the solvent to run. Mark where it reaches, View under a UV lamp. Compare with references.
Describe recrystallisation.
Select a solvent for desired substance. Dissolve mixture in a minimum amount of hot solvent. Filter to remove impurities. Retain the filtrate. Leave filtrate to cool. Collect crystals through vacuum filtration. Dry crystals.
Describe vacuum filtration.
Connect a conical flask to the vacuum pump. Dampen filter paper and place in the Buchner funnel. Switch vacuum pump on. Pour mixture to be filtered.
Disconnect filter before turning the pump off.
What is the process of determining melting points?
Seal glass melting point tube in a flame. Allow a small amount of solid to fall into the tube. Fix tube into the apparatus. Heat surrounding liquid gently. Record temperature. Compare to published value.
What is the process of a standard solution?
Calculate required solute. Weigh to the nearest 0.01g. Pour 100cm3 of deionised water into a beaker, adding the solute. Reweigh. Stir the mixture to ensure it has dissolved. Transfer to a 250cm3 volumetric flask. Rinse beaker. Fill up to the meniscus with distilled water. Insert stopped and invert the flask.
What is the process of a standard solution dilution.
Rinse a beaker with solution and half fill. Rinse a 25.0cm3 volumetric pipette with solution. Fill to the meniscus of the pipette. Run solution into a 250cm3 volumetric flask. Add deionised water up to the meniscus. Insert stopper and invert volumetric flask.
Describe an iodine-thiosulfate titration.
Rinse a 25cm3 volumetric pipette with potassium iodate and the burette with sodium thiosulfate. Use a pipette fill to fill the volumetric pipette up to the bottom of the meniscus. Transfer the potassium iodate to a conical flask. Add 20cm3 of dilute sulfuric acid into a measuring cylinder with 10cm3 of potassium iodate. Add these to a conical flask. Ensure the burette tap is closed before filling it up to the zero mark with sodium thiosulfate. Run the sodium thiosulfate into the conical flask. Add starch indicator when the solution appears pale yellow. This will turn the solution black. Add sodium thiosulfate drop by drop. The end of the titration is marked by the solution turning colourless.
Describe colorimetry.
Select a complementary colour filter. Make up a range of standard solutions. Zero the colorimeter using water. Measure absorbances. Compare absorbances. Plot calibration curve.
