Answer: С3Н603
Step-by-step explanation:
To find the emperical of the compound,you divide the percentage composition of each element by it's molar mass(C-12, H-1, 0-16).
For C,40/12=3.33. For H,6.71/1-6.71
For 0,53.19/16-3.33.
Then divide everything by the smallest value which is 3.33
For C,3.33/3.33-1. For H,6.71/3.33-~2.
For 0,3.33/3.33-1.
Emperical formula=CH20
Molecular formula (CH20)n=90
(12+2*1+16)n=90
30n=90, n=3
molecular formula=(CH20\3
molecular formula of lactic acid=С3H603.