As compared to stream water sea water contains
- A10% less dissolved oxygen
- B20% less dissolved oxygenCorrect
- C10% more dissolved oxygen
- D20% more dissolved oxygen
Solution
Concept
Dissolved oxygen content in sea water
Formula
NONE
Step-by-step solution
1. The solubility of gases in water decreases as the concentration of dissolved salts increases. 2. High salinity in sea water reduces its capacity to retain dissolved gases compared to fresh stream water. 3. Under comparable temperature and pressure, sea water holds approximately 20% less dissolved oxygen than fresh stream water. Answer: B
Explanation
Dissolved oxygen solubility in water decreases as salinity increases. Because of its high dissolved salt concentration, seawater holds approximately 20 percent less dissolved oxygen at saturation compared to fresh stream water under the same temperature and pressure conditions.
Why the other options are wrong
A) High salinity in sea water reduces oxygen solubility by roughly 20%, not 10%. C) Sea water holds less dissolved oxygen than fresh stream water due to high dissolved salt concentration. D) Dissolved oxygen concentration decreases rather than increases with higher salinity.
Shortcut
Higher salinity decreases gas solubility: sea water holds ~20% less dissolved oxygen than fresh water.
Common mistake
Assuming seawater holds more dissolved oxygen than freshwater instead of recognizing that higher salinity reduces oxygen solubility by about 20%.
Correct answer: B) 20% less dissolved oxygen