Water
Chemistry · 50 practice questions
Water as a product of the combustion of hydrogen and its composition by volume; water as a solvent and dissolved atmospheric gases and their biological significance; hard and soft water (temporary and permanent hardness, methods of softening); treatment of water for town supply; water of crystallization, efflorescence, deliquescence and hygroscopy (examples and uses).
- Identify the various uses of water.
- Identify effects of dissolved atmospheric gases in water.
- Distinguish between the properties of hard and soft water and determine the causes and removal of hardness.
- Describe the processes involved in treating water for town supply.
- Distinguish between efflorescence, deliquescence and hygroscopy and identify compounds exhibiting these phenomena.
Try a few questions
- Practice question 1
By mass, water, H₂O (H = 1, O = 16, molar mass = 18), is composed of approximately
- A.89% hydrogen and 11% oxygen
- B.50% hydrogen and 50% oxygen
- C.11% hydrogen and 89% oxygen
- D.2% hydrogen and 98% oxygen
Show the answer
C. 11% hydrogen and 89% oxygen
Hydrogen contributes 2 ÷ 18 ≈ 11.1% of the mass, with oxygen making up the remaining 16 ÷ 18 ≈ 88.9%.
- Practice question 2
Sedimentation, as a stage in water treatment, mainly allows
- A.dissolved salts to be removed from the water
- B.harmful micro-organisms to be killed
- C.suspended solid particles to settle out of the water under gravity
- D.dissolved gases to be removed from the water
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C. suspended solid particles to settle out of the water under gravity
Sedimentation relies simply on gravity to let heavier suspended particles sink and settle out.
- Practice question 3
Chlorination, as a stage in water treatment, mainly serves to
- A.remove dissolved calcium and magnesium salts
- B.kill or disinfect harmful micro-organisms present in the water
- C.remove suspended solid particles from the water
- D.add a pleasant taste to the water
Show the answer
B. kill or disinfect harmful micro-organisms present in the water
Chlorine is added specifically to destroy disease-causing micro-organisms in the water supply.
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