Question

An organic acid is composed of carbon (45.45%), hydrogen (6.12%), and oxygen (48.44%). Its molar mass is 132.12 g/mol. Determine the molecular formula of the compound.

Answer 1

Answer:

C4H8O4

Explanation:

To determine the molecular formula, first, let us obtain the empirical formula. This is illustrated below:

From the question given, we obtained the following information:

C = 45.45%

H = 6.12%

O = 48.44%

Divide the above by their molar mass

C = 45.45/12 = 3.7875

H = 6.12/1 = 6.12

O = 48.44/16 = 3.0275

Divide by the smallest

C = 3.7875/3.0275 = 1

H = 6.12/3.0275 = 2

O = 3.0275/3.0275 = 1

The empirical formula is CH2O

The molecular formula is given by [CH2O]n

[CH2O]n = 132.12

[12 + (2x1) + 16]n = 132.12

30n = 132.12

Divide both side by the coefficient of n i.e 30

n = 132.12/30 = 4

The molecular formula is [CH2O]n = [CH2O]4 = C4H8O4

Answer 2

Answer:

The molecular formula is C5H8O4

Explanation:

Step 1: Data given

Suppose the mass of the compound is 100 grams

The compound contains:

45.45 % Carbon = 45.45 grams

6.12 % hydrogen = 6.12 grams

48.44 % oxygen = 48.44 grams

Molar mass of C = 12.01 g/mol

Molar mass of H = 1.01 g/mol

Molar mass of O = 16.0 g/mol

Step 2: Calculate moles

Moles = mass / molar mass

Moles C = 45.45 grams / 12.01 g/mol

Moles C = 3.784 moles

Moles H = 6.12 grams / 1.01 g/mol

Moles H = 6.059 moles

Moles O = 48.44 grams / 16.0 g/mol

Moles O = 3.028 moles

Step 4: Calculate mol ratio

We divide by the smallest amount of moles

C: 3.784 / 3.028 = 1.25

H: 6.059 / 3.028 = 2

O: 3.028 / 3.028 = 1

The empirical formula is C5H8O4

The molar mass of this empirical formula is 132.12 g/mol

This means the empirical formula is also the molecular formula

The molecular formula is C5H8O4