Question

A 25 ml sample was diluted to 250 ml with odourless distilled water so that the odour of the sample no longer perceivable. What was the Threshold odour number ?
1. 11
2. 10
3. 25
4. 05

Answer 1

Correct Answer - Option 2 : 10

Concept:

Odour and taste are expressed by threshold odour number (T.O.N.) as it represents the dilution ratio at which odour can not be detected.

\(T.O.N. = \frac{{A + B}}{A} = \frac{{volume\ of\ diluted\ sample}}{{Volume\ of\ undiluted\ sample}}\)

where A = Volume of water sample undiluted 

B = volume of distilled water required to be added to remove the odour.

Calculation:

Given,

A + B = 250 ml

A = 25 ml

\(T.O.N. = \frac{{A + B}}{A} = \frac{{250}}{{25}}\)

T.O.N. = 10

• Generally in these question volume of water to be added (B), is given.
• But In the question, it is given " sample was diluted to ", which means that the final volume of the sample after dilution(A+B) is given