Pracs

Question 1

RP 2 Neutralisation - Titration

Answer 1

1. Use a pipette filler to fill a pipette with 25cm3 of NaOH and put it into a conical flask
2. Put the conical flask into a white tile
3. Clamp the burette and close the tap
4. Use a funnel to fill the burette with HCl to the 0cm3 line
5. Add 2-3 drops of phenolphthalein to the NaOH and swirl the flask
6. Open the burette tap so that the HCl comes out drop by drop and consistently swirl the flask at the same time
7. As soon as the NaOH is colourless from pink close the tap and record the volume of HCl lost

Question 2

Calorimetry

Answer 2

• lid, polystyrene cup with 25cm3 of NaOH in it, thermometer
• measure initial temp of NaOH
• HCl is added in 5cm3 intervals until 40cm3 is reached
• add the lid with the thermometer still in and stir the solution
• measure the maximum temperature reached
• repeat used 10

Question 3

Method for the effect of changing SA on rate

Answer 3

• measure 25cm3 of 1.0M of HCl into a conical flask using a measuring cylinder
• add 0.5g of large CaCO3 chips, attach a bung and delivery tube with a gas syringe
• record the volume of CO2 produced every 10s until the reaction is complete
• repeat investigation but with 1.0g of small CaCO3 chips
• plot a graph of volume CO2 against time for each experiment

Question 4

Disappearing cross

Answer 4

Sodium thiosulfate + HCl
-> forms S which is a yellow precipitate (causes colour change)

Question 5

Rate using using cotton wool

Answer 5

• place cylinder on a balance
• place wool at the top
• start timer and record mass every 10s

Question 6

RP 6 Chromotogprahy

Answer 6

1. Draw a horizontal pencil line 2 cm from the short edge of the chromatography paper. of Mark pencil spots at equal intervals across the line but not too close to the end of the paper.
2. Use a glass capillary tube to put small spot of each colouring on the pencil spots. A small spot ensures that the colouring separates clearly. Label each spot in pencil.
3. Pour about 1 cm3 of water into the beaker.
4. Suspend the paper in the beaker so that bottom edge of the paper dips into the water
5. Wait for the water solvent to travel at least three quarters of the way up the paper.
   Remove the paper and draw another pencil line at on the dry part of the paper right next to the wet edge. This is the solvent front, the distance travelled by the solvent.
6. Hang the paper up to dry thoroughly. to
7. Calculate the R, values for each spot. Rf value is calculated by distance travelled by substance/ solvent front.

Question 7

RP 1 Making Salts

Answer 7

1. Measure 20 cm3 sulfuric acid into a measuring cylinder and pour it into beaker.
2. Heat the acid gently using a Bunsen burner.
3. Add small amounts of insoluble base in this case copper oxide in excess (until no more reacts thus no more effervescence is produced).
4. Filter using filter paper and funnel the solution to remove the excess copper oxide.
5. Pour the solution into the evaporating basin.
6. Evaporate the solution using a water bath until crystals start to form.
7. Leave the evaporating basin in a cool place for at least 24 hours.
8. Gently pat the crystals dry between two pieces of filter paper.

Question 8

RP 3 Electrolysis

Answer 8

1. Add about 50cm3
   of copper chloride solution to a beaker.
2. Add the lid and insert electrodes through the holes making sure the electrodes don’t
   touch.
3. Attach crocodile leads to the electrode and connect the rods to the DC terminals of a low
   voltage power supply.
4. Set the power supply to 4V and switch the power supply on.
5. Using the forceps hold the litmus paper near the positive electrode.
6. After a few minutes turn the power supply off and observe the negative electrode.
7. Record observations at the electrodes.

Experiment repeated with sodium chloride

1. Add about 50cm3
   of sodium chloride solution to a beaker.
2. Add the lid and insert electrodes through the holes, making sure the electrodes don’t
   touch.
3. Attach crocodile leads to the electrode and connect the rods to the DC terminals of a low
   voltage power supply.
4. Set the power supply to 4V and switch the power supply on.
5. Using the forceps hold the litmus paper near the positive electrode.
6. After a few minutes turn the power supply off and observe the negative electrode. There
   should be effervescence.
7. Record observations at the electrodes.

Question 9

RP 4 Affect of Temp on Rate

Answer 9

1. Measure 25cm3 of hydrochloric acid into a polystyrene cup.
2. Place the cup inside the beaker to make it more stable.
3. Measure and record the temperature of the hydrochloric acid.
4. Measure 5cm3 of sodium hydroxide and add it to the polystyrene cup.
5. Quickly put a lid on the cup and gently stir the solution with the thermometer through the hole of lid.
6. When the reading on the thermometer stops changing and becomes fairly constant, record the temperature.
7. Repeat steps 4 and 5 to add further 5 cm3 amounts of sodium hydroxide to the cup. A minimum total of 40 cm3 needs to be added.
8. Repeat steps 1–7 to ensure reliability of results.
9. Calculate the mean maximum temperature reached for each of the sodium hydroxide volumes

Question 10

RP 5 rate or reaction using gas produced

Answer 10

1. Measure 50 cm3 of 1.0 M hydrochloric acid using one of the measuring cylinders. Pour the acid into the 100 cm3 conical flask.
2. Set up the apparatus as shown in one of the diagrams below.
3. Add a 3 cm strip of magnesium ribbon to the flask and quickly place the bung back into the flask. At the same time, start the stopwatch.
4. Record the volume of hydrogen gas given off every 10 seconds. Stop when no more gas is given off.
5. Repeat steps 1-4 using 1.5 M hydrochloric acid
6. Plot a graph of ‘volume of gas produced’ (y-axis) against ‘time’ (x-axis) . Draw two
   curves, one for each concentration of acid.

Question 11

RP 5 rate of reaction using colour

Answer 11

1. Measure 10 cm3 sodium thiosulfate solution into the conical flask.
2. Dilute the solution by adding 40 cm3
   water into the conical flask making the concentration 8 g/cm3
3. Put the conical flask on the black cross.
4. Measure 10 cm3
   of dilute hydrochloric acid.
5. Add the acid to the flask. Then quickly at the same time, swirl the flask gently and start the stopwatch.
6. Look down through the top of the flask. Stop the clock when you can no longer see the cross and record the time taken.
7. Repeat steps 1‒6 , using different volumes of sodium thiosulfate and water - 20 cm3
   sodium thiosulphate solution + 30 cm3 water, 30 cm3 sodium thiosulphate solution + 20cm3 water, 40 cm3 sodium thiosulphate + 10 cm3 water).
   This will change the concentration of sodium thiosulfate.
8. Repeat steps 1-7 twice more.
9. Calculate the mean time for each of the sodium thiosulfate concentrations.

Question 12

RP 8 Water Purification - analysing a water sample

Answer 12

1. Use universal indicator to test the pH of the water.
2. Measure and record the mass of an empty evaporating basin.
3. Pour 10 cm3 water into the evaporating basin and evaporate the water using a
   bunsen burner until the most of the water has evaporated.
4. Once the evaporating basin is cool, reweigh and record the change in mass.
5. Calculate the mass of dissolved solids in the water.

Question 13

RP 8 Water Purification - distillation

Answer 13

1. Place the water sample in a conical flask and set up the apparatus for distillation.
2. Heat the water gently using a bunsen burner until it boils. Then reduce the heat so the water boils gently.
3. Collect around 1 cm depth of water in the cooled test tube, then stop turn the bunsen burner off.
4. Analyse the water you have distilled with cobalt chloride paper.