PAPER 1 CHEMISTRY PRACTICALS

Question 1

Required Practical 1: Preparation of a Soluble Salt

Answer 1

• start with a fixed volume of dilute sulfuric acid . This is the limiting reactant.
• gently heat the acid until almost boiling
• use a spatula to add small amounts of copper oxide to the acid
• stir the solution with a glass rod
• the copper oxide will react and appear to no longer be seen
• continue adding copper oxide if the solution continues to be clear blue
• stop adding copper dioxide if some powder remains after stirring
• here the reaction has stopped as all the acid has reacted
• use filtration to remove the unreacted copper oxide
• Place the solution in an evaporating basin. Heat gently over a beaker of boiling water
• heat until around half of the solution remains
• leave the solution for 24 hours in a cool place for crystals to form
• scrape crystals onto paper towel and gently pat them dry

Question 2

required practical 2: Strong Acid & Strong Alkali Titration

Answer 2

• Use the pipette and pipette filler and place exactly 25 cm3 sodium hydroxide solution into the conical flask
• Place the conical flask on a white tile so the tip of the burette is inside the flask
• Add a few drops of a suitable indicator to the solution in the conical flask
• Perform a rough titration by taking the burette reading and running in the solution in 1 – 3 cm3 portions, while swirling the flask vigorously
• Quickly close the tap when the end-point is reached (sharp colour change) and record the volume, placing your eye level with the meniscus
• Now repeat the titration with a fresh batch of sodium hydroxide
• As the rough end-point volume is approached, add the solution from the burette one drop at a time until the indicator just changes colour
• Record the volume to the nearest 0.05cm3
• Repeat until you achieve two concordant results (two results that are within 0.1cm3 of each other) to increase accuracy

Question 3

Required Practical 3: Electrolysis of Aqueous Solutions

Answer 3

• Pour approximately 50 cm3 copper (II) chloride solution into the beaker.
• Add the petri dish lid and insert the carbon rods through the holes. The rods must not touch
  each other.
• Attach crocodile leads to the rods and then connect the rods to the terminals of a low-voltage power supply.
• Select 4V on the power supply and switch on and allow electrolysis to take place
• record the results in a suitable table

Question 4

required practical 4: Investigating temperature changes

Answer 4

1. Measure 30 cm3 dilute hydrochloric acid and put it into the polystyrene cup.
2. Stand the cup inside the beaker. This will make it more stable
3. Use the thermometer to measure the temperature of the acid. Record results in a table
4. Measure 5 cm3 sodium hydroxide solution.
5. Pour the sodium hydroxide into the polystyrene cup. Fit the lid and gently stir the solution with the thermometer through the hole.
6. Look carefully at the temperature rise on the thermometer.
7. When the reading on the thermometer stops changing, record the highest temperature
   reached in the table.
8. Repeat steps 4–7 to add further 5 cm3 amounts of sodium hydroxide to the cup each time,
   recording your temperature reading in the results table.
9. Repeat until a maximum of 40cm3 of sodium hydroxide has been added.
10. Wash out all the equipment and repeat the experiment for your second trial.