Practicals

Question 1

Soluble salt formation

Use NaOH and HCl as example

Answer 1

1. Pipette to measure 25 cm3 of NaOH and pour into a conical flask
2. Add few drops of phenolphthalein
3. Pour the HCl solution into a burette
4. Record initial volume of HCl solution
5. Add HCl from burette into conical flask little at the time whilst swirling the conical flask
6. Once phenolphthalein starts to turn from pink to colourless- add HCl solution a drop at a time until one drop is sufficient to turn the solution colourless. Record the volume of HCl solution needed
7. Carry out the titration again using 25cm3 and exact same volume of HCl solution
8. Don’t add indicator
9. Gently heat the solution from the conical flask in an evaporating basin until its volume decreases around a half
10. Leave the evaporating basin to cool allowing crystals to form

Question 2

Ways to possible improve a titration

Answer 2

• larger beaker or conical flask - no acid spray escaping
• rinse beaker and add washings to flask - no acid left in the beaker
• more acid or less chalk - larger tires so smaller percentage error
• crush chalk, temperature, stir to speed up reaction