Question

do lemons ,oranges and grapes have two types of acids? (in lemons and oranges both citric and ascorbic, and in grapes both tartaric and ascorbic)

Answer 1

There are many acids present in fruits such as lemons, grapes and oranges. But only one or two are in significant percentage.
Lemons have highest percentage of citric acid followed by ascorbic acid and then malic acid.
Oranges have highest amount of ascorbic acid with smaller amounts of folic, citric, malic and oxalic acid.
Grapes have tartaric, malic and citric acid significantly.