Question

The concentration of dissolved oxygen $(DO)$ in cold water can go upto :

• A. 10 ppm
• B. 14 ppm
• C. 16 ppm
• D. 8 ppm

Answer 1

The Correct Option is A

To determine the concentration of dissolved oxygen (DO) in cold water, we need to understand the factors affecting the solubility of oxygen in water. Dissolved oxygen is crucial for aquatic life, and its concentration varies with temperature and pressure.

At 0°C (32°F), the solubility of oxygen is at its maximum because gases dissolve better at lower temperatures. Under standard atmospheric pressure (1 atm), the concentration of dissolved oxygen can reach up to approximately 14 ppm. As water temperature increases, the solubility of oxygen decreases. Typically, in cold water (around 4°C to 15°C), the concentration of dissolved oxygen is found to be around 10 ppm under typical natural water body conditions.

Let's evaluate the given options:

1. 10 ppm: This is a commonly observed concentration for cold water under average conditions and is a reasonable estimate for typical natural waters.
2. 14 ppm: This concentration might be observed at the coldest temperatures under ideal saturation conditions, but it is higher than what is commonly seen under normal environmental conditions.
3. 16 ppm: This concentration is higher than what would typically be dissolved in cold water under normal circumstances and is less likely under standard atmospheric conditions.
4. 8 ppm: This is possible but more typical of slightly warmer water temperatures.

Therefore, the most correct choice here is 10 ppm, which corresponds to a typical and realistic concentration for cold water under average environmental conditions. Other options either represent unsaturated states or are too high unless artificially controlled.