Re: what are the chemcial elements that make up lemon juice?

I'm afraid the answer to this is not a simple one. You're correct in saying that water is H20, or two hydrogen atoms and one oxygen, but....

Lemon juice is a mixture of molecules, not just one. I'm not an expert on lemons by any stretch of the imagination, but here's what I've found out so far.

Lemon juice is going to be mainly water - it's an aqueous solution of lots of other things. As you may guess by the sharp taste of lemons, some of the other most important ingredients are acids. I found a paper about this ("ORGANIC-ACIDS IN THE JUICE OF ACID LEMON AND JAPANESE ACID CITRUS BY GAS-CHROMATOGRAPHY" in JOURNAL OF THE FACULTY OF AGRICULTURE KYUSHU UNIVERSITY, 1995, Vol.40, No.1-2, pp.39-44)

The absract of this said that "Acetate, glycolate, butyrate, oxalate, malonate, succinate, fumarate, glyoxylate, malate, tartarate, cis-aconitate and citrate were detected in the juice....with compositions and contents varied according to sampling years and species. Citrate and malate were predominant, accounting for more than 90% and 3-9% of the total detected acids, respectively. The other acids presented in traces, accounting totally for roughly less than 0.5%."

In brief, the most common acid is citric acid, followed by malaic acid, followed by a bunch of other things as well. I would think that in addition to the acids, there is probably som glucose and other sugars, as well as other types of organic molecules.

The chemical formula of citric acid is C₆H₈O₇ and that of glucose is C₆H₁₂O₆. To see pictures of the molecules you can go to www.chemfinder.com and search for each one in turn, as well as any other molecules you've heard of. This gives you lots of data on the molecules as well as the picture.

I hope this helps!