Question

Compound C with molar mass 205gmol-1 , contains 3.758g of carbon , 0.316g of hydrogen and 1.251g of oxygen. Determine the molecular formula.

Answer 1

Answer:

Molecular formula => C₁₂H₁₂O₃

Explanation:

From the question given above, the following data were obtained:

Molar mass of compound = 205gmol¯¹

Mass of Carbon (C) = 3.758 g

Mass of Hydrogen (H) = 0.316 g

Mass of Oxygen (O) = 1.251 g

Molecular formula =?

We'll begin by determining the empirical formula of the compound. This can be obtained as follow:

C = 3.758 g

H = 0.316 g

O = 1.251 g

Divide by their molar masses

C = 3.758 /12 = 0.313

H = 0.316 /1 = 0.316

O = 1.251 /16 = 0.078

Divide by the smallest.

C = 0.313 / 0.078 = 4

H = 0.316 / 0.078 = 4

O = 0.078 / 0.078 = 1

Thus, the empirical formula of the compound is C₄H₄O

Finally, we shall determine the molecular formula of the compound. This can be obtained as follow:

Molar mass of compound = 205gmol¯¹

Empirical formula => C₄H₄O

Molecular formula =>?

[C₄H₄O]ₙ = 205

[(12×4) + (4×1) +16]n = 205

[48 + 4 +16]n = 205

68n = 205

Divide both side by n

n = 205 / 68

n = 3

Molecular formula => [C₄H₄O]ₙ

Molecular formula => [C₄H₄O]₃

Molecular formula => C₁₂H₁₂O₃