1. In what form is oxygen commonly present in natural water?
A.
As dissolved molecular oxygen
B.
As solid oxygen crystals
C.
As dissolved ozone only
D.
As free oxygen ions
Correct Answer:
As dissolved molecular oxygen
Explanation:
Oxygen is present in natural water mainly as dissolved molecular oxygen, O2.
2. Which gas dissolved in water is essential for the survival of fish?
A.
Nitrogen
B.
Oxygen
C.
Hydrogen
D.
Helium
Correct Answer:
Oxygen
Explanation:
Aquatic animals such as fish use dissolved oxygen in water for respiration.
3. Oxygen is best described as what type of gas in water?
A.
Highly soluble gas
B.
Slightly soluble gas
C.
Completely insoluble gas
D.
Solid gas
Correct Answer:
Slightly soluble gas
Explanation:
Molecular oxygen is only slightly soluble in water, but the dissolved amount supports aquatic life.
4. What generally happens to the solubility of oxygen in water when temperature increases?
A.
It increases greatly
B.
It decreases
C.
It remains exactly unchanged
D.
It becomes infinite
Correct Answer:
It decreases
Explanation:
The solubility of oxygen in water generally decreases as the temperature of water rises.
5. What generally happens to the amount of oxygen dissolved in water when pressure increases?
A.
It decreases
B.
It increases
C.
It becomes zero
D.
It changes into hydrogen
Correct Answer:
It increases
Explanation:
Higher pressure generally increases the solubility of gases such as oxygen in water.
6. Which water sample is likely to contain more dissolved oxygen, assuming other conditions are similar?
A.
Cold water
B.
Boiling water
C.
Very hot water
D.
Steam
Correct Answer:
Cold water
Explanation:
Oxygen is more soluble in cold water than in warm or hot water.
7. Dissolved oxygen in water is mainly used by aquatic organisms for which process?
A.
Respiration
B.
Photosynthesis only
C.
Melting
D.
Freezing
Correct Answer:
Respiration
Explanation:
Aquatic organisms consume dissolved oxygen during respiration to obtain energy.
8. Which natural process can add oxygen to water?
A.
Contact with air
B.
Complete sealing from air
C.
Removal of all surface movement
D.
Conversion of oxygen into a solid
Correct Answer:
Contact with air
Explanation:
Oxygen from the atmosphere can dissolve in water when water comes into contact with air.
9. Why can aquatic life be harmed in warm, stagnant water?
A.
Warm water generally contains less dissolved oxygen
B.
Warm water contains only solid oxygen
C.
Stagnant water produces unlimited oxygen
D.
Oxygen becomes completely insoluble in all water
Correct Answer:
Warm water generally contains less dissolved oxygen
Explanation:
Higher temperature lowers oxygen solubility, and stagnant water may receive less oxygen from the atmosphere.
10. Which statement about oxygen in water is correct?
A.
Oxygen can dissolve in water in molecular form
B.
Oxygen is present only as a solid in water
C.
Water cannot contain dissolved gases
D.
Dissolved oxygen is always absent from natural water
Correct Answer:
Oxygen can dissolve in water in molecular form
Explanation:
Molecular oxygen, O2, dissolves in water and is commonly present as dissolved oxygen.
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