Water Quality Parameters MCQ with answer and solution

Concept

IS 10500:1991 gives desirable limits for drinking water. Chloride has a desirable limit of 250 mg/l.

Step-by-step solution

1. Recall the IS 10500:1991 desirable limits. 2. Iron: 0.3 mg/l, not 0.5 mg/l. 3. Chlorides: 250 mg/l, which is correct. 4. Fluorides: 1.0 mg/l, not 0.5 mg/l. 5. pH: 6.5 to 8.5, a range and not a single value of 7. 6. So the correct pair is (B).

Explanation

As per IS 10500:1991, the desirable limit of chlorides in drinking water is 250 mg/l. Higher chloride gives a salty taste. All other pairs show wrong values.

Why the other options are wrong

A: Desirable limit of iron is 0.3 mg/l. C: Desirable limit of fluoride is 1.0 mg/l. D: pH desirable range is 6.5 to 8.5, not exactly 7.

Shortcut

Remember: Chloride 250, Iron 0.3, Fluoride 1.0, pH 6.5 to 8.5.

Common mistake

Thinking pH must be exactly 7 (neutral) for drinking water.