172k views
4 votes
Lactic acid, the substance that builds up in muscles during

exercise, has a molar mass of about 90 g and has a composition
of 40.0% C, 6.71% H, and the rest is oxygen. What is the
molecular formula of lactic acid?​

1 Answer

4 votes

Answer:

THE MOLECULAR FORMULA FOR THE LACTIC ACID IS C3H6O3

Step-by-step explanation:

Lactic acid is composed of carbon, hydrogen and oxygen.

It has molar mass of 90 g/mol

Constituents composition:

Carbon = 40.0 %

Hydrogen = 6.71 %

Oxygen = 100 - (40 + 6.71) = 53.29 %

First we calculate the empirical formula

1. Divide the percentage composition by its atomic mass of each element.

(C = 12 , H = 1, O = 16)

Carbon = 40 / 12= 3.333

Hydrogen = 6.71/1 = 6.71

Oxygen = 53.29 / 16 = 3.33

2. Divide each value of the element by the smallest of them.

carbon = 3.333/ 3.33 = 1

Hydrogen = 6.71 / 3.33 = 2.015

Oxygen = 3.33 / 3.33 = 1

3. The empirical formula is therefore

C H2 O

4. Calculate the molecular formula

(CH2O)n = Molar mass

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

(30)n = 90

n = 90 / 30

n = 3

The molecular formula is written as

(CH2O) 3

= C3H6O3

Hence, the molecular formula for the lactic acid is C3H6O3.

User Tom Warfield
by
8.2k points
Welcome to QAmmunity.org, where you can ask questions and receive answers from other members of our community.