Question

Write a balanced chemical equation to show the reaction that occurs when each weak acid reacts with water. (Omit states-of-matter from your answer. Use the lowest possible whole number coefficients.)
(b) HCHO2


I've gotten a and c correct, and from that I know that WebAssign wants the reactants to be HCHO2 and H2O. I think that H3O should be a product, but I'm not quite sure. What's causing me trouble is the carbon - I don't know how that fits into the products.

Answer 1

HCHO2 probably is formic acid. It might be easier for you to see if it was written as HCOOH. It's the H on the right hand side that is the acidic hydrogen and if you look at it that way you would write HCOOH + H2O => H3O^+ + HCOO^-. Often these are written with that acidic H placed first as in HCHO2 and I expect that is what webassign wants.

HCHO2 + H2O ==> H3O^+ + CHO2^-

Answer 2

Thanks. How do I know if a substance is formic acid?

Answer 3

Actually, you don't but if the empirical formula is HCHO2 or CH2O2 and the Lewis structure looks like HCOOH it's a good bet it is formic acid. That's why they write the abbreviated formula as HCHO2 and that USUALLY means the first H written is the one that ionizes and the other H atoms listed are not involved in dissociation.