Chemistry Paper 1 Required Practicals + Relevant info to them

Question 1

How to make a soluble salt using an acid e.g. using copper oxide and sulfuric acid

Answer 1

• Set up a tripod, gauze, bunsen and beaker and pour a fixed amount of dilute sulfuric acid
• Gently heat until almost boiling and add the copper oxide and stir with a glass rod
• The copper oxide will react and seem to disappear turning the solution blue
• Continue until powder still remains after stirring (all acid has reacted)
• Filter the solution to remove the excess copper oxide
• Take the filtrate (copper sulfate solution) and put it in an evaporating dish over a water bath on a tripod, bunsen etc.
• Heat gently until half the solution remains
• Stop heating and leave the solution to cool to let the rest of the water evaporate
• After 24hrs, scrape the crystals off and pat dry

Question 2

What is the limiting reageant (reactant) in the soluble salt experiment and what is in excess

Answer 2

• Limiting reageant - acid
• Excess - metal oxide/carbonate
• This is becase the metal compound is added until no more reacts so that means all of the acid has been used up
• We don’t want anymore acid at the end as it would contaminate the salt so it is all reacted

Question 3

How to make a standard solution

Answer 3

• Measure desired mass of soluble solid
• Add the minimum amount of water needed to dissolve the solid
• Transfer the solution to a volumetric flask using a funnel and add the rinsings as well
• Add water until it reaches the volume line
• Stopper and invert to mix

Question 4

Procedure for carrying out a titration of sulfuric acid and sodium hydroxide to find the concentration of the acid

Answer 4

1. Use a pipette to transfer 25cm3 of sodium hydroxide into a conical flask
2. Add 5 drops of indicator e.g. methyl orange
3. Place the conical flask on a white tile so a colour change can be seen clearly
4. Fill a burette with sulfuric acid
5. Add acid until a colour change, stop and swirl swirl to mix, and if it stays that colour, it is neutral otherwise continue. Record the volume of acid used and this is the rough titre value
6. Repeat but when you get to the rough titre value, add very slowly and repeat until you get at least 3 concordant results

Question 5

What pH does phenolphthalein change at and to what colours

Answer 5

• From colourless to pink
• At a pH of 8.2
• So it is colourless in acid, pink in alkali

Question 6

What pH does methyl orange change at and to what colours

Answer 6

• Red in acid yellow in alkali
• Changes colour between pH of 3 and 4.2

Question 7

Required pratical for the electrolysis of copper (II) chloride solution

Answer 7

• Set up beaker with 50cm3 of the solution
• Add a petri dish with 2 holes and put graphite electrodes in them
• Attach them to a power pakc and make sure they don’t touch
• Once it is turned on, the cathode will be coated in copper
• The anode will have bubbles of chlorine around it and this can be proved as it turns damp blue litmus paper white

Question 8

Required pratical for the electrolysis of sodium chloride solution

Answer 8

• Set up beaker with 50cm3 of the solution
• Add a petri dish with 2 holes and put graphite electrodes in them
• Attach them to a power pakc and make sure they don’t touch
• At the anode, there are bubbles of chlorine as it is a halogen
• At the cathode, there are bubbles of hydrogen

Question 9

Variables for the neutralisation exothermic reaction of HCl and NaOH

Answer 9

• Independent - volume of sodium hydroxide
• Dependent - max temp reached
• Control - voulme of HCl and concentration of both HCl and NaOH

Question 10

Method for experiment for exothermic reaction of HCl and NaOH

Answer 10

• Measure 30cm3 of dilute HCl using measuirng cylinder and pour in a polystyrene cup
• Stand the cup inside a beaker to stop it falling over
• Use a thermometer to measure the initial temp of the HCl
• Pour 5cm3 NaOH into the cup and put a lid with a thermometer and stir
• The temperature will increase and record the temp change
• Rinse out cup and repeat with increasing volumes of NaOH
• Repeat whole thing to find a mean

Question 11

Explain the results of the exothermic experiment with HCl and NaOH

Answer 11

• As the volume of NaOH increases, the max temp increases as more particles react with the HCl
• After a certain point, the temperature decreases due to there being too much NaOH(in excess) and some that doesn’t react
• This means the energy released is spread out into a larger volume and the cold NaOH absorbs the heat energy lowering the temp