Question

To neutralize 200 ml sample of water should not require more than _________ ml of 0.1 normal NaOH.

(a) 1

(b) 2

(c) 3

(d) 4

The question was posed to me in an international level competition.

Enquiry is from Quality of Water topic in portion Water of Concrete Technology

Answer 1

The correct answer is:

(b) 2

Explanation: This type of question is typically related to the neutralization of acidity in water using a known concentration of sodium hydroxide (NaOH).

To find the correct amount of NaOH needed to neutralize the sample, we consider the typical assumption that the water sample has a moderate amount of acidity (such as carbonic acid or other weak acids) that can be neutralized by the NaOH. For the standard concentration of NaOH (0.1 N), it is expected that neutralizing 200 ml of water would require around 2 ml of 0.1 N NaOH to bring it to a neutral pH (pH 7).

This is based on common water quality testing practices in concrete technology, where the pH of water is tested to ensure that it doesn't affect the quality of concrete, which is sensitive to high acidity.