Required Practicals Flashcards
Describe the titration practical
1) Use a pipette to transfer 25cm^3 of an alkali of known
concentration (e.g Sodium hydroxide) into a conical flask
- Conical flasks reduce the risk of splashing
2) Add 5 drops of an indicator ( e.g methyl orange) to the
alkaline in the conical flask
3) Place the conical flask on a white tile to clearly see a
colour change more clearly
4) Now fill a burette with your acid ( e.g Sulfuric acid)
5) Add the acid to the alkali until the solution has changed colour, ( yellow to red for methyl orange)
indicating that the solution is neutral
Make sure you stir the solution to make sure the acid and alkali fully mix
7) Read the volume of acid added added from the burette
Make sure your eye is at level with the surface of the liquid, as it naturally curves and the burette is read from the bottom of the meniscus
** Repeats are often taken until you get 2 readings within a 0.1cm^3 range, and then a mean is taken **
In a titration practical, which substance goes in a pipette?
- The substance with a known concentration
In a titration practical, which substance goes in a burette
- The acid
What colour change occurs in during neutralisation with methyl orange indicator
- Yellow to Red
Describe a method for making pure copper sulfate crystals from copper carbonate and dilute sulfuric acid. Name all the apparatus used
- Place 25cm³ of dilute Sulfuric acid in a beaker
- Using a spatula, place in Copper Carbonate one
spoon at a time, stirring until it is in excess
(when no more gas is being given off) - Using filter paper and a funnel, filter off the excess
calcium carbonate - Heat off half of the remaining volume of Copper
Sulfate in an evaporating dish - Finally, leave the solution to crystalise, producing
pure Copper Sulfate crystals
Describe how you would perform the electrolysis of Copper II Chloride
- Pour 50cm³ of Copper Chloride solution into a
beaker - Place a plastic dish with 2 holes over the beaker
- Insert a graphite rod into each hole, connected to a
power pack by crocodile clips (these are the
electrodes) - Switch the power supply on at 4V
- The cathode (negative electrode) will be coated with
Copper as it’s less reactive than Hydrogen - The anode (positive electrode) will have bubbles of a
gas around it (Chlorine, as it’s a halide)
Why are electrodes made of carbon graphite?
They are inert and won’t react with the solution
Why must 2 electrodes not touch each other?
It would produce a short circuit
What is the test for Chlorine?
It bleaches damp blue litmus paper
What products are discharged in the electrolysis of Copper II Chloride solution?
Chlorine and Copper
Describe how you would perform the electrolysis of Sodium Chloride solution
- Place 50cm³ of NaCl solution in a beaker
- Place a plastic dish with 2 holes over the beaker
- Insert a graphite rod into each hole, connected to a
power pack by crocodile clips (these are the
electrodes) - Switch the power supply on at 4V
- At the positive electrode, Chlorine gas forms
- At the negative electrode, Hydrogen forms as it’s less
reactive than Sodium
What are the three products made in the electrolysis of Sodium Chloride solution?
Hydrogen, Chlorine and Sodium Hydroxide
Describe the temperature changes practical
- Use a measuring cylinder to measure 30cm³ of dilute
HCL and transfer it into a polystyrene cup - Place the cup in a beaker to prevent it toppling
- Use a thermometer to measure the starting
temperature of the acid - Use a measuring cylinder to measure 5cm³ of NaOH
solution, and transfer this to the cup - Fit a plastic lid into the cup, and place a thermometer
in through the lid
The bulb of the thermometer must be in the solution - Stir the solution with the thermometer
- As the reaction is exothermic, there will be a
temperature increase - Measure the temperature rise on the thermometer
until the reading stops changing
*Repeat the experiment increasing the volume of
NaOH solution by 5cm³ until 40cm³ *
Why does the maximum temperature in the reaction decrease after adding a large volume of NaOH?
(Temperature Changes practical)
A greater volume means that the energy released is now spread out into a greater volume
Why is a polystyrene cup used in the Temperature Changes experiment?
To reduce heat loss, as polystyrene is a good insulator
