Chemistry

01. Gravimetric analysis

  • 00:21 What does ‘weigh accurately a mass of approximately 0.3g’ actually mean?
  • 00:54 Why don’t we use tap water?
  • 01:01 Why don’t we add the acid before the water? 
  • 01:11 What initial observations suggest there was a chloride in the original solid?
  • 01:20 Why do we add more silver nitrate solution? 
  • 01:25 Why is a hotplate preferable?
  • 01:34 What is the likely composition of the filtrate?
  • 01:43 Why do we wash the precipitate with the wash-solution?
  • 01:48 Why is it more effective to do this step quickly?
  • 01:59 Why is it important to test the filtrate?
  • 02:18 How do you know that all the water has left the solid? 

  • access to balance – ideally 3 decimal place (minimum 2 decimal place)

  • access to drying oven

  • 2x250 cm3 beaker 

  • 2x100 cm3 beaker

  • spatula 

  • 10 cm3 measuring cylinder 

  • 3 x dropping pipette

  • bunsen burner, tripod and gauze or electric hotplate

  • filter funnel 

  • filter paper 

  • wash-bottle

  • sample of unknown chloride

  • de-ionised water 

  • 0.5 mol dm‒3 AgNO3 solution

  • 6 mol dm‒3 HNO3 solution

  • 2 mol dm‒3 HCl solution

  • wash-solution – 4 cm3 of 6 mol dm‒3 HNO3 per dm3 deionised water

  • it is assumed that appropriate safety glasses are worn at all times

Hazard Risk Control measure

0.5 mol dm-3 AgNO3 solution: corrosive.

Contact with skin or eyes.

Eye: flood with tap water (10min). See doctor. Skin: rinse with plenty of water. If more than small burn, see doctor.

6 mol dm-3 HNO3 solution: corrosive.

Contact with skin or eyes

Eye: flood with tap water (10min). See doctor. Skin: dry with paper towel then drenched with plenty of water

2 mol dm-3 HCl solution : irritant.

Contact with skin or eyes

Eye: flood with tap water (10min) then see doctor. Skin: drench with plenty of water. If blistering occurs, see doctor