Required Practicals

Question 1

Describe the titration practical

Answer 1

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 **

Question 2

In a titration practical, which substance goes in a pipette?

Answer 2

• The substance with a known concentration

Question 3

In a titration practical, which substance goes in a burette

Answer 3

• The acid

Question 4

What colour change occurs in during neutralisation with methyl orange indicator

Answer 4

• Yellow to Red

Question 5

Describe a method for making pure copper sulfate crystals from copper carbonate and dilute sulfuric acid. Name all the apparatus used

Answer 5

• 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

Question 6

Describe how you would perform the electrolysis of Copper II Chloride

Answer 6

• 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)

Question 7

Why are electrodes made of carbon graphite?

Answer 7

They are inert and won’t react with the solution

Question 8

Why must 2 electrodes not touch each other?

Answer 8

It would produce a short circuit

Question 9

What is the test for Chlorine?

Answer 9

It bleaches damp blue litmus paper

Question 10

What products are discharged in the electrolysis of Copper II Chloride solution?

Answer 10

Chlorine and Copper

Question 11

Describe how you would perform the electrolysis of Sodium Chloride solution

Answer 11

• 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

Question 12

What are the three products made in the electrolysis of Sodium Chloride solution?

Answer 12

Hydrogen, Chlorine and Sodium Hydroxide

Question 13

Describe the temperature changes practical

Answer 13

• 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 *

Question 14

Why does the maximum temperature in the reaction decrease after adding a large volume of NaOH?

(Temperature Changes practical)

Answer 14

A greater volume means that the energy released is now spread out into a greater volume

Question 15

Why is a polystyrene cup used in the Temperature Changes experiment?

Answer 15

To reduce heat loss, as polystyrene is a good insulator

Question 16

In a titration, why is the pipette rinsed with distilled water, and then the known solution?

Answer 16

• Distilled water removes any unwanted substances
• Rinsing with unknown removes distilled water, which would dilute the solution, affecting
  the concentration and would be a source of error

Question 17

Why is the funnel removed from the burette

Answer 17

To prevent droplets of the unknown from dripping into it