PAGs Flashcards
PAG 2.2 Setting up for a titration
Set up:
Pour 50cm3 of sodium carbonate into a dry clean beaker
Rinse burette several times with distilled water
Use some sodium carbonate to rinse the burette above and below the tap, discard the rinsings and repeat this twice more
Fill burette with sodium carbonate above the 0 mark using a funnel ( remove funnel after )
Open the tap to allow the sodium carbonate to flow through the burette until it is at the 0 mark
Record the level of solution in the burette, make sure the bottom of the meniscus is where the reading is taken from
Take the first reading with the meniscus at eye level
Then take a reading from the bottom of the meniscus to nearest 0.05 cm3 and make a note of the reading
Rinse pipette with distilled water and then 2 - 3 more times with the dilute hydrochloric acid
Rinse conical flask with distilled water
Transfer exactly 25cm3 of the hydrochloric acid into the pipette using the pipette filler
Drain the pipette into the conical flask and touch the tip on the side of the flask to get the last drop out
Add 2 - 3 drops of methyl orange to the flask and swirl
Note the colour of the solution using a white tile under the flask
PAG 2.2 method for titration
Method
Carry out a rough titration by allowing the sodium carbonate to drain quickly into the flask while swirling
When the colour chain is persistent then slow down the flow and add 0.05cm3 at a time until the end point is reached
Swirl the flask continuously until this is achieved
Note the burette reading
Empty and wash conical flask
Add another 25cm3 sample of hydrochloric acid with 2 - 3 drops of indicator
For the accurate titration, rapidly add sodium carbonate solution until it reaches the approximate amount needed to activate the indicator, stop it 2cm3 above this value
As the end point is approached, swirl the conical flask and add the sodium carbonate solution dropwise from the burette
After each drop, rinse the tip of the burette with distilled water, swirl the flask and rinse the side of the conical flask with distilled water
When a permanent colour change occurs note the reading
Repeat the accurate titrations until two readings are concordant ( both within 0.1cm3 of eachother )
PAG 2.2 making a standard solution
Procedure
Must know the exact mass of sodium carbonate which will be dissolved in a known volume of water
This can be done via the weighing by difference method
Using a spatula weigh out approximately 2.6g of anhydrous sodium carbonate
Record the mass of the sodium carbonate with the container used to contain it
Transfer the solid to an 100cm3 beaker
Re weigh and record the mass of the used container
Then find out the exact mass of anhydrous sodium carbonate using the equation:
Initial mass - used boat mass = mass of anhydrous sodium carbonate
Dissolve the sodium carbonate in distilled water
Stir the solution thoroughly until the solution is completely dissolved
Pour solution down a glass rod into a funnel and into a 250cm3 volumetric flask, raise the funnel so that it drain smoothly
Rinse the glass rod with distilled water to make sure the sodium carbonate solution is all transferred, add the rinse to flask and do this 2 - 3 times, make sure to only use a small amount of water so that the solution does not go above the 250cm3 mark
This should also be done with the funnel
Add further distilled water until the solution reaches the 250cm3 mark, observing the meniscus at eye level
Label flask clearly, including the exact concentration of the solution
PAG 1.1 Determination of the composition of copper(II) carbonate basic
Set up the apparatus as shown in the diagram below.
Weigh approximately 1.5 g of CuCO3•Cu(OH)2(s). Record the exact mass. Use the correct number of decimals and the correct unit.
Add the solid to the conical flask and replace the bung.
Using a 50 cm3 measuring cylinder, measure out 50 cm3 of 1.0 mol dm–3 H2SO4(aq) (this is an excess).
Remove the bung from the conical flask, quickly add the acid to the flask, and immediately replace the bung.
Collect the gas in the 250 cm3 measuring cylinder and record the final volume of carbon dioxide using an appropriate format.
If you have time, repeat the experiment.
PAG 3.1 Enthalpy change for a displacement reaction
Weigh out roughly 2 g of zinc (this is a large excess so the exact mass is not important).
Pipette 25 cm3 of the 0.500 mol dm-3 copper sulphate solution into a clean, dry polystyrene cup that is inside a beaker (for stability).
Place a lid on the cup, put it under a tripod and put a thermometer (-10 to 110°C) through the hole so that the thermometer is within the tripod. Stir and record the temperature every minute in table.
At precisely 4 minutes, add the zinc to the cup and then continue stirring and record the temperature every minute until at least 12 minutes have passed (or until it has been falling for at least 5 minutes)
PAG 3.2 finding enthalpy change for a displacement reaction
Into two separate clean, dry polystyrene cups in beakers under a tripod, pipette 25 cm3 of the 1.0 mol dm-3 hydrochloric acid and the 1.0 mol dm-3 sodium hydroxide solution
Place a thermometer (-10 to 50°C) into each the cup through a cardboard lid within a tripod.
Record the temperature of both solutions for 3 minutes and record these and their average.
At precisely 4 minutes, add the solutions together. Continue stirring and record the temperature every minute until at least 12 minutes have passed (or until it has been falling for at least 5 minutes).
PAG 3.3 enthalpy change for combustion
Weigh a spirit burner (with its lid), record the mass to the nearest 0.01 g and note the name of the alcohol.
Using a 50 cm3 measuring cylinder, measure 100 cm3 of water into a beaker.
Record the initial temperature of the water to the nearest 0.5°C.
Set up the apparatus as shown in the diagram.
Light the burner using a lighted splint and burn the alcohol whilst stirring the water CAREFULLY with the thermometer.
After approximately three minutes extinguish the flame. Immediately record the maximum temperature reached by the water to the nearest 0.5°C.
Reweigh the spirit burner and record the mass to the nearest 0.01 g
Repeat steps 1–7 for the different alcohols in the other spirit burners. Think about what you will
have to control in order to ensure your results are comparable.
PAG 7.1 identification of an alkene and haloalkane
Identification of an alkene:
Add 10 drops of bromine water.
Add one drop of the substance.
Agitate the test tube from side to side to ensure mixing.
Record your observations in a suitable format.
Identification of a haloalkane:
Set up a small water bath: Half fill a 250cm3 beaker with warm water (50–60°C) from a kettle.
For each of the haloalkanes, in a separate test tube:
Add five drops of the haloalkane
Add 1 cm3 ethanol and 1 cm3 0.05 mol dm–3 silver nitrate solution to each tube.
Agitate the test tube from side to side to ensure mixing.
Place the tubes in the water bath for 2–3 minutes.
Record any observations in a suitable format
PAG 7.2 identification of primary, secondary and tertiary alcohol and identification of an aldehyde
Identification of a primary, secondary, tertiary alcohol:
Using a spotting tile/well plate, add 3 drops of acidified 0.100 mol dm–3 potassium dichromate(VI) solution in each of four adjacent wells.
Add 2 drops of each alcohol separately to the first three wells – the fourth well is a control to help observe the colour change(s).
Observe the colour change(s) over 5-10 minutes.
Record any observations in a suitable format.
Disposal instructions: Immediately after your observations have been noted, immerse the spotting
tile/well plate in a washing-up bowl of water – this will help minimise any staining of the spotting tile/well plate
PAG 7.2 identification of a carboxylic acid
Separately for 0.1 mol dm–3 ethanoic acid and distilled/deionised water
Add 10 drops to a well in a spotting tile/well plate.
Measure the pH of the drop using pH paper.
Add a small spatula measure of sodium carbonate.
Once there is no further sign of reaction, measure the pH of the resultant solution.
Record your observations in a suitable format
PAG 7.2 identification of an aldehyde
Identification of an aldehyde:
The first step is to form Tollens’ reagent:
a. Add 2 cm3 0.05 mol dm–3 silver nitrate(V) to a test tube.
b. Add 2 drops of 0.4 mol dm–3 sodium hydroxide solution – a brown precipitate will form.
c. Add 1.0 mol dm–3 ammonia solution dropwise with gentle agitation until the precipitate has just
dissolved, to form a colourless solution
Divide the Tollens’ reagent between two test tubes.
Add 0.5 cm3 propanal to the first test tube and add 0.5 cm3 propanone to the second test tube. Gently agitate to ensure mixing.
Place the test tubes in a warm water bath (50–60°C) and leave to stand for 5-10 minutes.
Record your observations in a suitable format
PAG 4.3 identifying unknowns
Add litmus paper to each solution in a dimple tray to find pH, and then nitric acid
Add nitric acid to each test tube, the solution that produces effervescence is the sodium carbonate
Add the carbonate to each of the remaining test tubes, the one producing a yellow precipitate is the silver nitrate
Add the silver nitrate to the remaining two test tubes, the one producing a white precipitate is the sodium chloride and the one producing a yellow precipitate is the potassium iodide
PAG 5.1 synthesis of a haloalkane: preparation
Pour about 6.5 cm3 of 2-methylpropan-2-ol into a 10 cm3 measuring cylinder.
Measure the mass of the measuring cylinder and contents. 29.81g
Pour the 2-methylpropan-2-ol into a 250 cm3 conical flask.
Measure the mass of the empty measuring cylinder and use this to record the exact mass of 2-
methylpropan-2-ol you have put in the separating funnel. 2 1.5 8
Using a 50 cm3 measuring cylinder, measure about 20 cm3 of concentrated hydrochloric acid.
Over a period of about 2 minutes, add the concentrated hydrochloric acid gradually to the 2-
methylpropan-2-ol in the conical flask.
Place a mineral wool plug into the neck of the conical flask and gently swirl the mixture every few minutes for 20 minutes
PAG 5.1 synthesis of a haloalkane: separation
Using a funnel, pour the reaction mixture into a separating funnel. Ensure the tap is closed.
Allow the separating funnel to stand until the two layers have separated.
Open the tap and run the lower aqueous layer into a clean 100 cm3 conical flask.
Slowly add 10 cm3 of 5% sodium hydrogencarbonate solution to the organic layer in the separating funnel.
Put the stopper in the funnel and shake the contents gently. Carefully release the pressure build-up in the separating funnel.
Shake the contents more vigorously and again release the pressure.
Allow the two layers to separate, then remove the stopper and run off the lower aqueous layer as in Step 2 of Part 2.
Repeat steps 3–7 until no more gas is given off.
Add 10 cm3 of distilled water to the separating funnel and shake again.
Allow the layers to separate and then run off the lower aqueous layer – you can discard this layer.
Allow the organic layer to run into a clean 100 cm3 conical flask. This liquid contains the product of the reaction.
Anhydrous sodium sulfate acts as a drying agent to remove any traces of water. Add small quantities (1⁄2 spatula measures at a time) to the organic liquid. Swirl between each addition to the flask until the liquid is completely clear and the sodium sulfate no longer forms clumps.
PAG 5.1 synthesis of a haloalkane: distillation
Set up the distillation apparatus as shown.
Measure the mass of a clean, dry sample tube and lid.
Decant the impure organic product to the pear-shaped flask and add a few anti-bumping granules.
Heat the liquid in the pear-shaped flask gently with a small Bunsen Burner or spirit burner. Use a small beaker to receive any liquid impurities which distil over.
When the temperature is close to 48 °C, use the sample tube to collect the liquid. The boiling point of the product is 51 °C.
When the temperature rises above 53 °C (or there is no more liquid in the pear-shaped flask), stop the distillation.
Put the lid on the sample tube and weigh it to find the mass of product collected.
Test a few drops of the product with a few drops of 0.4 mol dm–3 HNO3(aq) and a few drops of
0.05 mol dm–3 AgNO3(aq)
