Compound A, a diacid that occurs in apples and other fruits has
the following composition by mass: C: 35.8%, O: 59.7%. A 2.0g
vapour of A has a volume of 334cm^3 at stp.
Compound A reacts with ethanol in the presence of concentrated
sulfuric acid under reflux to form B C8H14O5. Compound B evolves
hydrogen gas when treated with sodium metal and reacts with
acidified potassium dichromate to form Compound C which is also a
ketone.
Is the molecular formular for A C4H6O5? I can't figure out the
structures for A,B,C...Help please?
Whenever you see "apple", think of Malic acid.
http://en.wikipedia.org/wiki/Malic_acid
Alpha is :

Bravo is the di(ethylester) generated when heated under reflux
with ethanol and conc H2SO4 catalyst. The two terminal -COOH
groups of Alpha are now replaced by -COOCH2CH3.
Charlie is same as Bravo, except that the secondary
alcohol group has been oxidized to the ketone group.