chemistry - water purification

Question 1

how can you test the pH of a sample of water?

Answer 1

use universal indicator paper or a digital pH probe

Question 2

what would you expect the colour and pH of a sample of pure water to be?

Answer 2

green and pH 7

Question 3

how can you find the mass of salt dissolved in a sample of water?

Answer 3

• weigh an empty evaporating basin
• fill with a sample of water and heat with a bunsen burner until all the water evaporates
• reweigh the evaporating basin and subtract the empty basin weight to find the mass of salts that were dissolved

Question 4

how can you purify a sample of water?

Answer 4

distillation

Question 5

describe how a sample of water can be purified by distillation?

Answer 5

• first test the pH. Add alkali/acid as necessary to obtain pH 7
• place the water sample in a conical flask and connect the flask to distillation apparatus (including a condenser)
• as the water in the flashing is heated, it evaporates and enters the condenser as steam
• cold water around the condenser cools the steam, which condenses to form water before it is collected in a beaker

Question 6

how could you test that the water collected from a distillation experiment is pure water?

Answer 6

• check the pH is still pH 7
• determine the boiling point and check it matches that if water (100°C)