Environmental chemistry: water

Written by Dr. Ayesha Nadeem (Chemistry)

Class 10 · Chemistry · 9 questions

Name: ____________________ Date: ____________

Hard water contains dissolved salts of:
- A Calcium and magnesium
- B Sodium
- C Hydrogen
- D Potassium only
Temporary hardness is removed by:
- A Filtering
- B Freezing
- C Boiling
- D Adding salt
Which of these is a water pollutant?
- A Nitrogen
- B Sewage
- C Hydrogen
- D Oxygen
Chlorine is added to drinking water to:
- A Make it hard
- B Add taste only
- C Add colour
- D Kill germs
Soap does not lather easily in:
- A Distilled water
- B Soft water
- C Rain water
- D Hard water
Water is a good solvent because it is:
- A Polar
- B Non polar
- C A metal
- D A gas
The process of removing salt from sea water is:
- A Desalination
- B Evaporation only
- C Sedimentation
- D Filtration
Ion exchange can be used to:
- A Soften hard water
- B Make water hard
- C Add oxygen
- D Add colour
Waterborne diseases such as cholera are caused by:
- A Sunlight
- B Contaminated water
- C Pure water
- D Cold weather

Answer key

1. A, 2. C, 3. B, 4. D, 5. D, 6. A, 7. A, 8. A, 9. B

Calcium and magnesium salts cause hardness.
Boiling decomposes calcium hydrogencarbonate and precipitates calcium carbonate.
Untreated sewage pollutes water.
Chlorination disinfects water.
Calcium and magnesium ions form scum with soap.
Its polarity helps dissolve ionic substances.
Desalination gives fresh water.
It swaps calcium ions for sodium ions.
Bacteria in unclean water cause cholera.