Question

A 0.2053g sample of an organic acid requires by titration, 15.0 mL of 0.1008 M
sodium hydroxide for complete neutralization.
i)what the molar mass of the acid if it is monoprotic?
ii)if the acid is composed of 5.89% H,70.6% C, and 23.5% O by mass, what is its molecular formula?

Answer 1

mols NaOH = M x L = ?
mols acid = same if it is monoprotic.
mols acid = grams/molar mass. You know grams and mols solve for molar mass.

Take a 100 g sample which gives you
5.89g H.
70.6g C
23.5g O.

Convert grams to mols.
5.89/1 = mols H
70.6/12 = mols C
23.5/16 = mols O

Now fiind the ratio of the mols to each other with the smallest value being 1.0. The easy way to do that is to divide the smallest value by itself, then divide the other numbers by the same small number. This will give you the empirical formula.

Then (empirical formula) x ? whole number = molar mass (from part 1). Solve for the whole number. The molecular formula then is
(empirical formul)_n where n = the whole number.
Post your work if you get stuck.