[SemonSays]

1. Tartaric acid, also known as cream of tartar, is used in baking. Its empirical formula is C2H3O3. If 1.00 mol of tartaric acid contains 3.61 x 10^24 oxygen atoms, what is the molecular formula of tartaric acid?

2. A compound has the formula C6xH5xOx, where x is a whole number. Its molar mass is 186 g/mol; what is its molecular formula?

Can someone help me figure this out? I'd really appreciate it because i have a quiz on this tomorrow that are based on these kind of questions. Smile

[allanf]

(1) the empirical formula C₂H₃O₃ means that the molecular formula is C_2nH_3nO_3n, where n is some integer.  So for one mole of the substance there are 2n moles of Carbon atoms, 3n moles of Hydrogen atoms, and 3n moles of Oxygen atoms.

You've been given the total amount of oxygen atoms, if you convert this to moles you should be able to get the molecular formula from what I said above.

(2)  The molar mass is just the sum of the masses of the atoms in the molecule, correct?  You know you have 6x Carbons where x is some unknown, 5x Hydrogens, and 1x Oxygens, if you were to add up the atomic masses for the Carbons, Hydrogens, and Oxygens you will end up with a simple expression for the molar mass in terms of x, which you then solve for (given that you know the molar mass is 186)

[SemonSays]

Allan, thank you so much.