I believe that number 27 is A
Answer: this seems like YOU need to answer on ur own.
Explanation:
Explanation:
The exact person is unkown cooper has been around for ages since 9000 BC in the Middle East are the earliest discoveries
The chemical formula of oxalic is 
When oxalic acid reacts with water, first, oxalic acid removes one proton and results in the formation of mono acids.
After that, in second step, oxalic acid in aqueous solution removes another proton which shows it is a polyprotic acid.
The chemical equations are: (the reactions occurs in two steps due to presence to hydrogen atoms).
When one proton is removed:

When another proton is removed:

The dissociation of oxalic acid in water in shown in the image.