Question

What is the difference between the formula of acetate and ethanoate?

Answer 1

There are many compounds which have two names persisting to their existence. One name is the one given by the chemical engineers or scientists before IUPAC, which they used normally as a household name because IUPAC names were too complex for general people.

Complete answer:
Ethanoate is a keto compound as we can see by the suffix in the end -ate. By starting with ‘ethane’ we can say that the number of carbons in the parent chain is two.
Also in ester compounds, the alkyl group is attached to the oxygen that is attached to the carbon belonging to the parent chain. As there is no prefix, we can say that a hydrogen atom must be attached with the above mentioned oxygen atom.
Therefore, the formula for ethanoate must be $C{H_3} - COOH$

Acetate is the name of a compound according to old nomenclature which was the general name for the compound which was acid and also known as acetic acid.
Now, the formula for acetic acid is $C{H_3} - COOH$ .
As we can see that both he compounds, acetate and acetic acid have same formula but what the difference is that while naming the acetic acid, the carbon having oxygen double bond and a bond with OH is not counted while naming, therefore, it was known for its acidic properties but in IUPAC nomenclature both the carbons were counted while naming them.
There is no difference in the formula of acetate and ethanoate.

Note:
Ethanoate and acetate are also known as carboxylic acid. Acetate ion is the popular ion which is very acidic and high electronegative because of two oxygen atoms and one alkyl group.