Question

A fat is composed of long chains of carbon and hydrogen atoms. In a reaction with a strong base, a fat forms a soap and glycerol. What is the empirical formula of a fat containing 77.60 % carbon, 11.45 % oxygen, and 10.95 % hydrogen? What is its molecular formula if its molecular mass is 1253 g/mol?

Answer 1

Answer:

Empirical formula is C₉H₁₅O

Molecular formula = C₈₁H₁₃₅O ₉

Explanation:

Percentage of carbon = 77.60%

Percentage of oxygen = 11.45%

Percentage of hydrogen = 10.95%

Molecular weight = 1253 g/mol

Molecular formula = ?

Empirical formula = ?

Solution:

Number of gram atoms of C = 77.60 g /12g/mol =6.5

Number of gram atoms of O = 11.45 g / 16 g/mol = 0.72

Number of gram atoms of H = 10.95 g / 1.008 g/mol= 10.9

Atomic ratio:

C               :            H                 :    O

6.5/0.72   :       10.9/0.72         :   0.72/0.72

     9          :            15              :         1

C : H : O = 9 : 15 : 1

Empirical formula is C₉H₁₅O

Molecular formula:

Molecular formula = n (empirical formula)

n = molar mass of compound / empirical formula mass

n = 1253 / 139

n = 9

Molecular formula = n (empirical formula)

Molecular formula = 9 (C₉H₁₅O )

Molecular formula = C₈₁H₁₃₅O ₉