Question

A student wants to investigate the amount of ascorbic acid in orange juice, with a simple NaOH titration. What other substances and compounds of the juice might interfere with the result, to which extent?

Answer 1

As we know in the titration method, the acid and base neutralizes each other and we can find the amount of one chemical entity by knowing the amount of other chemical species required to neutralize the first compound or the compound of which we need to find the concentration.

Complete Step By Step Answer:
To solve this question, first we need to understand the chemical composition of the orange juice or most importantly the acids present in the orange juice that will interfere in the activity of the NaOH.
So, let’s see,
First of all, as we know that NaOH is a very strong base and it readily neutralizes acids.
Since, orange juice contains many other acids in addition to ascorbic acid such as citric acid, malic acid and the other acid present in the orange juice, so there will be more utilization of the Base NaOH and this will give us wrong concentration of the ascorbic acid
Secondly, the pigments present in the orange juice will interfere in this titration process. As the pigments present in the orange juice such as carotenoids are colored and they will make it difficult to identify the end point color change.

Note:
So from the above discussion we can see that the many different acids like citric acid, malic acid etc. and the pigments such as carotenoids present in the orange juice interferes in the acid base titration of the ascorbic acid with NaOH i.e. sodium hydroxide base.