Practicals

Question 1

Make up a volumetric solution

Answer 1

1. Weigh the sample bottle containing the solid on a (2 dp) balance.
2. Transfer solid to beaker and reweigh sample bottle.
3. Record the difference in mass.
4. Add distilled water and stir with a glass rod until all the solid has dissolved.
5. Transfer to a volumetric flask with washings.
6. Make up to the 250cm3
   mark with distilled water.
7. Invert flask.

Question 2

Titration

Answer 2

1. Pour approximately 100cm3
   of the standard
   solution of known concentration into a beaker.
2. Fill the burette with the standard solution of
   known concentration.
3. Pour approximately 100cm3
   of the solution with
   unknown concentration into a second beaker.
4. Using a pipette filler and pipette to transfer
   exactly 25cm3
   of solution into a 250cm3
   conical
   flask.
5. Add two to three drops of phenolphthalein
   indicator to the solution in the conical flask and
   note the initial colour of the indicator.
6. Record the initial burette reading.
7. Titrate the contents of the conical flask by
   adding solution to it from the burette until the
   indicator undergoes a definite, permanent
   colour change. Adding dropwise nearer the end. Record the final burette reading
   in your table of results. Calculate the titre
   volume (change in volume in the burette).
8. Repeat, calculate and record the volume of
   solution used in the titration in a table (titre
   volume). Repeat until two concordant results
   are obtained. Record all of the results that you
   obtain.

Question 3

Measurement of an enthalpy change.

Answer 3

1. Weigh out between 3.90-4.10 g of anhydrous copperIl) sulfate in a dry, stoppered weighing bottle. Keep the stock of solid in a closed container during weighing. The precise mass should be recorded.
2. Construct a suitable table of results to allow you to record temperatures at minute intervals up to 15 minutes.
3. Using a measuring cylinder, place 25 cm’ of deionised (or distilled) water into a polystyrene cup and record its initial temperature (t=0).
   Start the timer and then continue to record the temperature each minute, for three minutes.
4. At the fourth minute, add the powdered anhydrous copper(Il)
   sulfate to the water in the polystyrene cup and but do not record the temperature. At the fifth minute continue the temperature readings at minute intervals, up to fifteen minutes. Stir the solution in the polystyrene cup as this is done.
5. Plot a graph of temperature (on the y-axis) against time. Draw two separate best fit lines; one, which joins the points before the addition, and one, which joins the points after the addition.
   Extrapolate both lines to the fourth minute. (see diagram)
6. Use your graph to determine the temperature change at the fourth minute, which theoretically should have occurred immediately on addition of the solid. final - initial!
   (q=mcdeltat)
   n=m/mr
   q/n = deltah

Question 4

Investigation of how the rate of a reaction changes with temperature

Answer 4

*Measure 10 cm3 of 0.2M hydrochloric acid and 10 cm3 of sodium thiosulfate in separate clean measuring
cylinders. Put the solutions in separate boiling tubes
*Choose a temperature to investigate use water bath to get the two solutions to that temperature by
placing the boiling tubes in the water bath.
*Place the flask on the centre of the large cross; first add the sodium thiosulfate to the flask. Then add the hydrochloric acid and start the stopwatch and swirl to mix the solutions.
*Stop the clock when the cross disappears and note the time.
*Repeat the experiment for four more different temperatures (maximum temperature should be 70 oC)

• 1/time taken is a measure of the rate
• plot of 1/time against volumes/concentrations of A or plot
  log(1/time) vs log(volume or concentration of A)
• description of interpreting order from shape of 1/time vs
  volume or concentration graph / gradient of log plot gives
  order / allow interpretation of time vs concentration graph
  / ratio between change in concentration and change in
  rate (e.g, 2x[A] = 2 x rate so 1st order)

Question 5

Identification of ions: Group 2 ions or NH4+

Answer 5

a) Place about 10 drops of 0.1 mol dm–3 metal ion solution in a test tube.
b) Add about 10 drops of 0.6 mol dm–3 sodium hydroxide solution, mixing well.
c) Continue to add sodium hydroxide solution, dropwise with gentle shaking, until in excess

repeat with sulfuric acid

Question 6

Test for ammonium ions

Answer 6

a) Place about 10 drops of 0.1 mol dm–3 ammonium chloride in a test tube.
b) Add about 10 drops of 0.4 mol dm–3 sodium hydroxide solution. Shake the mixture.
c) Warm the mixture in the test tube gently using a water bath.
d) Test the fumes released from the mixture by holding a piece of damp red litmus paper in the mouth of the test tube.

Question 7

Test for carbonate ions: aqueous solution

Answer 7

1. Add an equal, small volume of dilute hydrochloric acid to sodium
   carbonate solution in a test tube.
2. Use a delivery tube to transfer the gas produced into a second test tube containing a small volume of calcium hydroxide solution (limewater).
3. Put a stopper into the test tube containing the calcium hydroxide
   solution (limewater).
4. The limewater will go cloudy if carbonate ions present.

Question 8

Test for sulfate ions: aqueous solution

Answer 8

1. Add an equal volume of dilute hydrochloric acid then an equal volume of barium chloride solution to the solution.
2. Barium sulphate formed (white precipitate). Barium sulfate is an
   insoluble salt.
3. Add a small volume of dilute HCl.
4. As precipitate does not dissolve, sulphate or hydrogensulfate ions are
   present.

Question 9

Test for halide ions: aqueous solution

Answer 9

1. Add a small volume of dilute nitric acid to the solution of potassium chloride.
2. Add 2 cm of silver nitrate to the solution. Record any observations.
3. Swirl the tubes to ensure that the precipitates formed in each case are evenly
   distributed and then divide the contents of each tube in half.
   Allows further
   identification tests as
   initial precipitates can be
   hard to distinguish.
4. To one half of the contents, add an excess of dilute aqueous ammonia solution
   and observe what happens. Record your observations.
5. To the other half, working in a fume cupboard, add an excess of concentrated
   ammonia solution and observe what happens. Record your observations.
6. Repeat with solutions of potassium bromide and potassium iodide in new,
   separate test tubes.

Question 10

Test for group 7 ions: solid salts

Answer 10

1. Place a small spatula measure of solid potassium chloride in a dry test tube in a test tube rack.
2. Working in a fume cupboard, add a few drops of concentrated sulfuric acid. Record any observations.
3. Test any gas evolved with moist blue litmus or universal indicator paper.
4. Repeat the experiment with solid potassium bromide and solid potassium iodide, recording any observations.

Question 11

Once i know the method of these, make sure to know the precautions and reasons for the method.

Answer 11

:)))

Question 12

Preparation of cyclohexene by the dehydration and distillation of cyclohexanol.

Answer 12

1. Acidify the potassium manganate(VII) solution combining a volume of a regular laboratory concentration with an equal volume of dilute
   sulfuric acid.
2. Pour the mixture into a pear-shaped/round flask, with a still head containing a thermometer.
3. Attached to a condenser with a ice cooled collecting vessel.
4. Add a few anti-bumping granules.
5. Heat the flask gently.
6. Collect sample at boiling point of the desired product.
7. The cooled collection vessel is essential to reduce evaporation of the product.

Question 13

Preparation of ethanal by the oxidation and distillation of ethanol.

Answer 13

Make the oxidising agent by dissolving potassium dichromate (VI) in dilute
sulfuric acid. The concentration of the potassium dichromate(VI) should be
approximately 1 g in every 10 cm3
of this dilute acid.
2. Using a 25 cm3
measuring cylinder, carefully measure out 12 cm3
of the
acidified potassium dichromate(VI) solution and pour this into a boiling tube.
3. Cool the boiling tube in a beaker of cold water.
4. Using a 10 cm3
measuring cylinder, carefully measure out 2 cm3
of ethanol.
5. Using a teat pipette, slowly add the 2 cm3
of ethanol dropwise, to the oxidising
agent in the cooled boiling tube, shaking the tube gently to mix the contents.
6. Add a few anti-bumping granules to the boiling tube and attach to it a bung
fitted with a right-angled glass delivery tube.
7. Clamp the boiling tube at about 450 in a beaker of water so that the delivery
tube goes to a test tube which is immersed in cold water in a beaker.
8. Gently heat the beaker of water containing the ethanol to slowly distil off
approximately 5 cm3 of liquid distillate.
9. Use Tollen’s reagent to test the distillate for ethanal. (Should produce a silver
mirror).

Question 14

Testing for alcohol: metal

Answer 14

1. Add a small piece of metallic sodium to alcohol.
2. Produces hydrogen gas which is shown by ‘squeaky pop’ test.
3. Dispose any excess sodium safely using the beaker of ethanol provided. (Sodium will completely react with the excess ethanol in order to be safely washed away because if any water comes into contact with the sodium there is a serious fire risk.

Question 15

Test for an alcohol: potassium dichromate

Answer 15

1. To determine between alcohols, add acidified potassium dichromate to the solution.
2. Primary and secondary alcohols will reduced from orange dichromate(VI) ions to green chromiumIII) ions.
3. It will remain orange if a tertiary alcohol is

Question 16

Test for an aldehyde: Fehling’s solution

Answer 16

1. In a clean test tube mix together equal volumes of Fehling’s solution A (blue aqueous solution of copper(II) sulfate pentahydrate
   crystals) and Fehling’s solution B (clear solution of aqueous potassium sodium tartrate and a strong alkali). The resultant Fehling’s test
   reagent should be a clear dark blue solution.
2. Add 5 drops of this test reagent to a test tube along with a few anti-bumping granules, then add the aldehyde.
3. Warm gently for around two minutes in a beaker of hot water, gradually bring the beaker of water to boiling and maintain this
   temperature for a few minutes.
4. Carefully lift the test tube out of the boiling water and allow its contents to stand for several minutes.
5. A brick red precipitate formed if an aldehyde is present.

Question 17

Test for an alkene: bromine water

Answer 17

1. Add about 1 cm3
   of bromine water to 2 drops alkene.
2. Shake the contents of the tube vigorously from side to side.
3. Bromine water decolourised from orange if an alkene is present.

Question 18

Test for a carboxylic acid

Answer 18

1. Place spatula of solid sodium carbonate in a test tube and add about 2 cm3
   of dilute ethanoic acid using a pipette.
2. Collect the gas produced and bubble through limewater (calcium hydroxide). It will turns cloudy if a carboxylic acid is present as CO2 is
   produced.

Question 19

Test for a halogenoalkane: sodium hydroxide and silver nitrate

Answer 19

1. Using a teat pipette, add 5 drops of 1-bromobutane to about 1cm3
   of sodium hydroxide solution in a test tube. (OH- ions replace the Br
   by nucleophilic substitution).
2. Warm the contents of the test tube for a few minutes in a beaker filled with hot water at approximately 60°C.
3. Acidify the contents of the test tube by adding 2cm3
   of dilute nitric acid and then add about 1cm3 of silver nitrate solution. (Nitric acid
   removes carbonate and hydroxide impurities which would form precipitates. Silver Bromide precipitate then forms).

Question 20

Initial rate method: ‘Iodine Clock’ experiment

Answer 20

1. Fill the 50 cm3
   burette with potassium iodide solution.
2. Transfer 10.0 cm3
   of hydrogen peroxide solution from a burette to a 100 cm3
   beaker
3. Use a 50 cm3 measuring cylinder to add 25 cm3 of sulfuric acid to a 250 cm3
   beaker.
4. Use a 25 cm3
   measuring cylinder to add 20 cm3 of distilled (deionised) water
   into the 250 cm3 beaker.
5. Use a plastic dropping pipette to add about 1 cm3 of starch solution to this
   beaker.
6. Use the burette to add 5.0 cm3 of potassium iodide solution to the mixture in the
   250 cm3
   beaker.
7. Finally, add 5.0 cm3
   of sodium thiosulfate solution from a burette to the mixture
   in the 250 cm3
   beaker.
8. Stir the mixture in the 250 cm3
   beaker. Pour the hydrogen peroxide solution
   from the 100 cm3
   beaker into the 250 cm3
   beaker and immediately start the
   timer.
9. Stop the timer when the mixture in the 250 cm3
   beaker turns blue-black.
   Record the time.
10. Rinse the 250 cm3
    beaker with distilled (deionised) water and dry it with a
    paper towel.
11. Repeat steps in four further experiments changing the concentration of
    potassium iodide.
12. Plot a graph of initial rate (y) versus concentration (x) to determine the order.

Question 21

Continuous monitoring method

Answer 21

1. Add 50 cm3 of 0.8 moldm-3 hydrochloric acid to a conical flask.
2. Set up the gas syringe or alternative gas collection equipment.
3. Add a 6 cm strip of magnesium ribbon to the conical flask, place the
   bung firmly into the top of the flask and start the timer.
4. Record the volume of hydrogen gas collected every 15 seconds for 2.5
   minutes.
5. Alter the concentration of HCl and repeat steps (1) to (4).

Question 22

Setting up an electrochemical cell: zinc and copper

Answer 22

1. Clean a piece of copper and a piece of zinc using emery paper or fine grade
   sandpaper.
2. Degrease the metal pieces using some cotton wool and propanone.
3. Place the copper into a 100 cm3
   beaker with about 50 cm3
   of 1.0 mol dm-3
   CuSO4
   solution.
4. Place the zinc into a 100 cm3
   beaker with about 50 cm3
   of 1.0 mol dm-3 ZnSO4
   solution.
5. Lightly plug one end of a plastic U-tube with cotton wool and fill the tube with the
   solution of 2.0 mol dm-3 sodium chloride solution (NaCl), then plug other end.
6. Join the two beakers with U-tube so that the plugged ends are in the separate
   beakers.
7. Connect the Cu(s)|Cu2+
   (aq) and Zn(s)|Zn2+
   (aq) half-cells by connecting the metals
   using crocodile clips and leads. Include a voltmeter in the circuit in order to read
   off the voltage.

Question 23

Comparing electrode potentials of different metals:

Answer 23

1. Clean a piece of copper using emery paper or fine grade sandpaper.
2. Connect to the positive terminal of a voltmeter using a crocodile clip and one of the
   leads.
3. Cut a piece of filter paper to about the same area as the copper and moisten with
   sodium chloride solution. Place it on top of the metal.
4. Connect a second lead to the voltmeter and use the crocodile clip to connect the
   lead to a piece of a different metal.
5. Hold the metal against the filter paper. Record the voltage reading, including the
   sign.
6. Repeat with different metals and compare the electrode potentials.

Question 24

pH probe calibration:

Answer 24

1. Rinse the pH probe thoroughly with deionised (distilled) water and shake
   gently to remove excess water.
2. Place the probe in the standard pH 7.00 buffer solution provided. Record the
   pH reading.
3. Repeat this process using the standard pH 4.00 and pH 9.20 buffer
   solutions. Record the pH readings.
4. Plot a graph of your recorded pH reading (x-axis) against the pH of the buffer
   solution (y-axis).

Question 25

Measuring pH: acid-alkali mixture

Answer 25

1. Rinse a burette with 0.100 moldm-3 solution of ethanoic acid and then fill the burette with this solution. Label this burette. 2. Use the burette to transfer exactly 20.0 cm3 of ethanoic acid to a clean 100 cm3 beaker. 3. Rinse a second burette with 0.100 mol dm-3 NaOH solution and then fill this second burette with this solution. Label this burette. Ensure the jet of the burette is filled without any air bubbles. 4. Rinse the pH probe with distilled (deionised) water and clamp it so that its bulb is fully immersed in the ethanoic acid solution in the beaker. 5. Use a rod to stir the solution gently and record the pH reading in a suitable table 6. Add 2.0 cm3 of NaOH solution from the burette at a time. Stir the solution and record the pH alongside the volume of NaOH added. 7. When the end-point is being reached, add 0.20 cm3 of NaOH each time. Stir the solution and record the pH alongside the volume of NaOH added. 8. After this, continue adding 2.0 cm3 NaOH until it is in excess. Stir the solution and record the pH alongside the volume of NaOH added.

Question 26

HAVENT INCLUDE 10 (ASPIRIN) MAYBE DO SEPARATE FLASHCARDS FOR IT?

Question 27

Transition metal ions Test 1a

Answer 27

Place 10 drops of solution in a test tube. ● Add sodium hydroxide solution, shaking gently, dropwise until in excess. Record any observations. ● Do not discard this mixture.

Question 28

Transition metal ions Test 1b

Answer 28

Half fill a 250 cm3 beaker with the freshly boiled water. ● Allow the four test tubes containing the mixtures from Test 1a to stand in the beaker of hot water for about 10 minutes. ● Record any observations.

Question 29

Transition metal ions Test 2

Answer 29

Place about 10 drops of sodium carbonate solution in a test tube. ● Add about 10 drops of solution and shake the mixture gently. Record any observations.

Question 30

Transition metal ions Test 3

Answer 30

Place about 10 drops of solution in a test tube. ● Add about 10 drops of silver nitrate solution and shake the mixture gently. ● Allow the four test tubes to stand for about 10 minutes. Record any observations.

Question 31

Chromatography

Answer 31

1) Wearing gloves carefully use a pencil to draw a faint line 1 cm above the bottom of a TLC plate and mark five spots, equally spaced, along this line. 2) Use a capillary tube to apply a tiny drop of each solution to a different origin spot and allow the plate to air dry. If required repeat this process to achieve small but concentrated spots 3) Add approximately 10 cm3 of solvent to a development chamber (or suitable container with a lid) 4) Place the TLC plate into the development chamber, making sure that the level of the solvent is below the spotting line. Replace the lid and make sure it is a tight seal. 5) When the level of the solvent reaches about 1 cm from the top of the plate, remove the plate and mark the solvent front with a pencil. Allow the plate to dry in the fume cupboard. 6) Place the plate under a UV lamp in order to visualise the spots. Draw around them lightly in pencil. 7) Calculate the Rf values of the observed spots.