Required Practicals Flashcards
C4 required practical titrations
1.In a clean, dry pipette, transfer 25cm3 of an alkali into a conical flask
2.Add a few drops of indicator to the alkali ( methyl orange or phenolphthalein )
3.Fill a clean, dry burette with acid
4.Note the starting volume
5.Add acid into the conical flask and swirl
6When thr indicator starts to change colour, add the acid dropwise amd swirl
7.When the colour change lasts 10msecs, stop adding acid, note the new volume
8.Calculate the titre and repeat until two concordant results are obtained
C6 required practical electrolysis of an aqueous solution ( NOT NEEDED )
- Set up apparatus as shown in picture. Clean the
electrodes lightly using emery paper. - Half fill a 100 cm3 beaker with one of the solutions.
- Connect the circuit as shown in the picture. The light bulb is present to check that the circuit is working correctly.
- Look for bubbling at each electrode. If there is bubbling at the positive electrode, test the gas by holding a piece of litmus paper in the solution at that electrode using tweezers.
- If there is bubbling at both electrodes and you have identified both gases, turn off the cell and start with the next solution.
- If there is not bubbling at both electrodes, then leave the cell connected for 5 minutes and then disconnect and study the electrodes for evidence of a metal coating.
C7 required practical temperature changes to determine if a reaction is exothermic or endothermic
1 Use the first measuring cylinder to measure 25 cm3 of the sodium hydroxide solution and pour this into the polystyrene cup.
2 Stand the polystyrene cup in the 250 cm3 beaker.
3 In the second measuring cylinder, measure 25 cm3 of hydrochloric acid.
4 Using the thermometer, measure the temperature of the sodium hydroxide every 30 seconds whilst gently stirring.
5 After exactly 2 minutes add the hydrochloric acid and continue to stir and to record the temperature of the solution every 30 seconds for 10 minutes.
6 Repeat this experiment twice:
• with 25 cm3 of copper(II) sulfate and iron filings
• with 25 cm3 potassium hydroxide and nitric acid.
C5 required practical making a copper salt
1 Using a measuring cylinder, measure 20 cm3 of acid into the beaker.
2 Stand the beaker on a tripod and gauze and warm gently until it is almost boiling. Turn off the
Bunsen burner.
3 Add half a spatula of copper(II) oxide power into the acid and stir using the glass rod.
4 Continue adding the copper(II) oxide until no more dissolves. When the copper(II) oxide disappears the solution is clear blue.
5 Allow the apparatus to cool completely and then filter the mixture and discard the residue.
6 Pour the filtrate into an evaporating basin. Evaporate this gently using a water bath (250cm3 beaker with boiling water) on the tripod and gauze (see diagram). Stop heating once crystals start to form.
7 Remove the evaporating basin from the heat and leave to crystallise.
8 Record what you observed when:
• Copper(II) oxide was first added to the acid.
• Excess copper(II) oxide was added.
• The salt was left to crystallise.
C8 concentration and rate of reaction ( measuring gas )
1.Put a 3 cm magnesium strip in in the conical flask
2.Add 50 cm cubed of hydrochloric acid in the flask
Use marble chips as a catalyst
3.The hydrochloric acid should be in excess because the magnesium is the limiting reactant
4.The reaction will release hydrogen
5.The hydrogen will go into the beehive shelf and go into the gas cylinder and put it out indicating the volume of gas
C8 required practical ( cross disapearing )
- Put a laminated cross on the desk and a conical flask over it
- Prepare the conical flask or 50cm3 thiosulfste solution of a concetrstion of 40g/cm3 and 10cm3 of 2 moles of HCl
- Measure the time it takes for the laminated cross to disappear
- Change the concentration of sodium thiosulfate by increasing the volume of water in the flask
- For each concentration repeat stepes 1 - 4
