You have it.
Take a 100 g sample which gives you 40 g C, 6.71 g H and (100-40-6.71) g O.
You go from there. Post your work if you get stuck.
lactic acid is the avid responsible for the sour test in spit milk. on the basis of combustion analysis, it's percentage composition by mass is 40.00% carbon, 6.71%hydrogen and x% oxygen.
a. Calculate the empirical formula of lactic acid
b. The molar mass of lactic acid is 90g/mol. Determine the molecular formula
So I know the first step would be to find the # of g? And then concern that into moles then find the ratio between moles. And then for b you would find the g/mol in the empirical formula and divide it by the molar mass to find how many fit within the molecular formula.
So b makes sense to me, but I'm not sure how to go from the % to the number of g with that little information. Is it just 40g of C and 6.71g of hydrogen, then add those and take away a 100 to find O? That's all I can think of doing, but I don't get why.
Thank you very much
1 answer