Answer to Question #90859 in General Chemistry for acadia carlson

Question

Lactic acid, the substance that causes sour milk to taste as it does, has a formula weight of 74. It consists of 48.63% C and 8.18% H, with the rest being oxygen. Calculate the empirical and molecular formulas of lactic acid, arranging the atomic symbols in alphabetical order.

Answer 1

$\% O= 100 \% - (48.63 \% + 8.18\%)=43.19 \%$

$\dfrac{74g/mol*48.63\%}{12g/mol*100\%}=2.998(~3)atoms(C)$

$\dfrac {74g/mol*8.18\%}{1g/mol*100\%}=6.05 atoms(H)$

$\dfrac{74g/mol*43.19 \%}{16g/mol*100\%}$ ~ 3 atoms(O)

molecular formula of lactic acid: C3H6O3