practicals

Question 1

measure the molar volume of gas

Answer 1

1. measure a volume of ethnic acid and transfer to a conical flask
2. attach conical flask to gas syringe
3. measure the mass of a weighing bottle with a mass of calcium carbonate
4. add calcium carbonate to the conical flask- releasing bung quickly so no gas escapes
5. measure the final total volume of gas
6. reweigh the empty weighing bottle from step 3
7. repeat experiment several more times, increasing the mass of calcium carbonate

Question 2

making up a volumetric solution

Answer 2

1. weigh the weighing boat with required mass of solid
2. transfer to beaker
3. reweigh the empty weighing boat
4. record the difference in mass
5. add 100cm3 of water to dissolve the solid and use a glass rod to stir
6. pour solution into volumetric flask
7. rinse beaker and funnel and add washings from the beaker and glass rod to the volumetric flask
8. make up the mark with distilled water
9. invert the volumetric flask several times

Question 3

carry out simple acid base titration

Answer 3

1. rinse equipment
2. pipette alkali into conical flask
3. add acid to the burette
4. make sure the jet space is also filled with acid
5. add few drops of indicator
6. add acid to alkali whilst swirling and add drop wise when nearing the end point
7. note burette reading before and after titration
8. repeat titration until at least 2 concordant results are obtained

Question 4

oxidation of alcohol

Answer 4

partial:
1. place a volume of dilute sulphuric acid in a flask and add a mass of potassium dichromate and some anti bumping granules
2. shake the contents and then add alcohol in drops
3. set up distillation
full:
1. add a volume of water to bioling tube and add sodium dichromate and dissolve it
2. add alcohol to round bottom flask and add antibumping granules
3. put a condenser on the flask for reflux and add sulphuric acid down the condenser and add sodium dichromate, the mixture should boil without any external heating
4. use low bunsen burner flame to keep the mixture boiling for a while and don’t allow any vapours to escape
5 remove flame and distil some of the solution

Question 5

chlorination of 2-methylpropan-2-ol using concentrated HCl

Answer 5

1. measure a volume of 2-methylpropan-2-ol inn a measuring cylinder and weigh its mass
2. pour the alcohol into a separating funnel and reweigh empty measuring cylinder to find out mass of alcohol used
3. in fume cupboard, at portions of HCl to separating funnel ad after each portion avert the flask and open tap to release pressure
4. star the flask in the fume cupboard for some time and shake at intervals
5. allow layers to separate then dispose the aqueous layer
6. add sodium hydogencarbonate to neutralise the remaining acid and open tap to release co2
7. allow layers to separate and again remove the lower aqueous layer and run the organic layer into a conical flask
8. add anhydrous sodium sulphate to dry the liquid and let it stand until liquid become clear.9. decant the liquid into distillation flask
9. distil
   10 measure the mass of the 2-chloro-2-methylpropane

Question 6

to determine the enthalpy range of a reaction using Hess’s Law

Answer 6

1. wash the equipment with the solution to be used
2. dry the cup after washing
3. put polystyrene cup into a beaker for insulation and support
4. measure out the volumes of solution with volumetric pipette and transfer to insulated cup
5. clamp thermometer making sure the bulb is immersed into the solution
6. measure the initial temperatures of both solutions- do his for every miniature for 3 minute
7. at minute 3 transfer the second solution into the cup
8. stir the mixture and record temperature every minute after the addition of the second solution
9. plot a graph with extrapolation

Question 7

finding the Ka value for a weak acid

Answer 7

1. transfer a volume of acid into a conical flask with a volumetric pipette
2. measure initial pH of acid
3. add alkali in small amounts noting the volume added using burette
4. stir the mixture to equalise the pH
5. record the pH
6. repeat the steps 3 to 5 but when end point is approaching add in smaller volumes of alkali
7. add until alkali is in excess
8. plot a titration curve
   at half the neutralisation volume the concentration of HA is equalled to a- so Ka= H+ concentration

Question 8

investigating electrochemical cells

Answer 8

1. place a copper strip into a beaker wit copper sulphate
2. place zinc strip into a beaker with zinc sulfate
3. use a strip of filter paper soaked in potassium nitrate solution for the salt bridge
4. connect the half cells using crocodile clips and leads provided to the voltmeter

Question 9

redox titrations

Answer 9

1. weigh the tablets
2. grind up the tablet with sulphuric acid using pestle and mortar 3 through a funnel and transfer the the paste into volumetric flask.
   3 add sulfruic acd=id to make up the mark. shake the flask. the iron ions would be dissolved in the solution
3. titrate some of the solution with potassium manganate. the end point is marked by the first permanent purple colour

Question 10

prepare a titration metal complex

Answer 10

1. add hydrated copper sulfate to a weighing boat and weigh
2. transfer the copper sulfate into a test tube and weigh the empty weighing boat
3. add some water to the test tube and place in a water bath
4. stir gently to dissolve the copper sulfate
5. remove test tube from the water bath and in a fume cupboard add some ammonia solution to the copper sulfate
6. pour the solution into a beaker containing ethanol and stir it and place in ice bath
7. using a Buchner funner and flask filter the crystals and using col ethanol rinse the washing into the Buchner funnel
8. rinse the crystals with cold ethanol
9. scare the crystals onto a filter paper and place another on top gently pressing it to dry it
10. weigh the mass of the crystals

Question 11

rates of reaction: following the rate of the iodine propanone reaction by titrimetric method

Answer 11

1. in a bear add the same volume and concentration of propanone and sulfuric acid
2. add iodine solution to the beaker and start the clock and swirl
3. using a pipette remove a sample of the mixture and transfer it to a conical flask
4. add sodium hydrogen carbonate to stop the reaction (quench). record the time it is added
5. titrate the iodine present in the flask with sodium thiosulfate solution. when the colour turns pale yellow add starch . the end point of the reaction is when the blue turns colourless
6. every 5 minutes remove another 10cm3 of the sample and repeat the steps 4 and 5

Question 12

rates of reaction: clock reaction

Answer 12

1. measure a volume of potassium iodide solution into a small beaker standing on white tile
2. add a volume of sodium thiosulfate to the potassium iodide
3. add 10 drops of starch which will act as an indicator
4. measure a volume of sodium peroxodisulfate solution and pour this to the mixture and start the clock
5. stop the clock when the blue colour appears in the beaker and note the time
6. repeat steps 1 to 5 using the volumes of the different chemicals in the table given

Question 13

finding the activation energy of a reaction

Answer 13

1. pipette a volume of phenol solution and bromide solution into a boiling tube
2. add a few drops of methyl red indicator
3. into a second boiling tube add a volume of sulfuric acid
4. play the two boiling tubes into water bath at 20c
5. when the substances have reached the water temperature mix the contents into one boiling tube ad swirl and start the clock
6. place in the water bath and stop the clock when the red methyl indicator disappears
7. repeat the experiment at different temperatures

Question 14

recrystallisation

Answer 14

1. dissolve crude solid in minimum value of hot solvent
2. filter off the residue while the solution is hot
3. let solution cool at room temperature so that crystal lattice reforms gradually
4. cool solution in ice bath
5. filter pure solid under reduced pressure leaving impurities in solution (Buchner funnel)
6. let solid air dry to remove traces of solvent