Question

The taste of sour milk is lactic acid. What is the molecular formula for lactic acid if the percent composition is 40.00% C, 6.71% H, 53.29% O, and the approximate molar mass is 90 g/mol?

Answer 1

Answer:

C3H6O3

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, O=16).

For C,40/12=3.33. For H,6.71/1=6.71

For O,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 O,3.33/3.33=1.

Emperical formula=CH2O

Molecular formula=(CH2O)n=90

(12+2*1+16)n=90

30n=90, n=3

molecular formula=(CH2O)3

molecular formula of lactic acid=C3H6O3.