What is the proportion of acid and alkalis permitted in the water used in construction ?
- AA 100 ml sample of water should be neutralized by not more than 2 ml of 0·1 normal NaOH of 10 ml of 0·1 normal HCl
- BA 200 ml sample of water should be neutralized by not more than 2 ml of 0·1 normal NaOH of 10 ml of 0·1 normal HClCorrect
- CA 300 ml sample of water should be neutralized by not more than 2 ml of 0·1 normal NaOH of 10 ml of 0·1 normal HCl
- DA 50 ml sample of water should be neutralized by not more than 2 ml of 0·1 normal NaOH of 10 ml of 0·1 normal HCl
Solution
Concept
Permissible acidity and alkalinity of mixing water
Step-by-step solution
1. IS 456: 200 ml of water should not require more than 2 ml of 0.1 N NaOH to neutralise it (acidity limit). 2. 200 ml of water should not require more than 10 ml of 0.1 N HCl to neutralise it (alkalinity limit), with phenolphthalein or methyl orange as indicator.
Explanation
The code tests a 200 ml sample for both acidity and alkalinity.
Why the other options are wrong
The other options use a sample volume of 50, 100 or 300 ml, which is not the standard test volume.
Shortcut
200 ml sample; 2 ml NaOH; 10 ml HCl.
Correct answer: B) A 200 ml sample of water should be neutralized by not more than 2 ml of 0·1 normal NaOH of 10 ml of 0·1 normal HCl