Question

Define “equivalence point”. Why is it necessary to plot the first and second derivative curves to obtain the pKa of the carboxylic acid?

Answer 1

Many people tend to confuse between end point and equivalence point

equivalence point -

equivalence point is a point in a chemical reaction where both the reacting species taking part in the reaction are equivalent to each other

Equivalence point is not same as end point always

End point is called when we use a indicator for the reaction and the indicator indicates us that reaction is complete

Now why do we need the second derivative curve for carboxylic acid?

So when we plot certain graph the equivalence point doesn't show a sharp change and we get a linear graph for the equivalence point

In such cases when we use first derivative we get the slope of every point at that point and hence it becomes easier for us to find the end point

And during the second derivative of carboxylic acid pka we get a sharp peak for equivalence point which tells us about the pka of carboxylic acid

So we use first and second derivative curve for cases like carboxylic acid

I hope this helps. If you have any query or want more detailed explanation, feel free to ask in the comments section below.