Chapter 7: Air and water

Question 1

Name the two compounds used to test for the presence of water.

Answer 1

• Anhydrous copper(II) sulfate

- Anhydrous cobalt (II) chloride

Question 2

Describe the observation seen during the presence of water in an anhydrous copper (II) sulfate test.

Answer 2

The white powder turns blue.

Question 3

Describe the test and observation seen when anhydrous cobalt (II) chloride is used to test for water.

Answer 3

• add the liquid to anhydrous cobalt (II) chloride.

- The compound turns pink if water is present.

Question 4

Describe how blue copper(II) chloride paper is made.

Answer 4

Filter paper is soaked in a solution of cobalt chloride, which is pink, and the filter paper is heated until it turns blue.

Question 5

what is observed when a liquid containing water is dropped onto copper chloride paper.

Answer 5

it turns it to pink

Question 6

what are the two main methods used for water purification?

Answer 6

• filtration.

- chlorination.

Question 7

describe the process that used to treat water.

Answer 7

• filter through coarse gravel to remove large solids like rocks and leaves.
• filter through gravel and sand to remove smaller particles.
• add a small amount of chlorine to kill bacteria and microorganisms.

Question 8

list 3 uses of water at home.

Answer 8

drinking
cooking
washing

Question 9

Name 3 ways water is useful in industrial processes. give examples for each.

Answer 9

• as a solvent. Many reactions take place while reactants are dissolved in water.
  e. g ammonium nitrate, is an important fertilizer, is made by reacting ammonia solution with nitric acid solution and evaporating the water away
• As a cheap raw material:
  e. g used to produce hydrogen for use in the Haber process.
• As a coolant:
  e. g to stop furnaces from melting after the manufacture of iron.

Question 10

Name two problems arising from the lack of supply of clean water.

Answer 10

• Spread of waterborne diseases, like typhoid and cholera, because people drink water containing many microorganisms.
• Crops require water to grow. They need irrigating. without adequate supply of water they die and people starve.