3.5g of a certain compound x, known to be made of carbon, hydrogen, and perhaps oxygen, and to have a molecular molar mass of 150g/mol is burned completely in excess oxygen, and the mass of the products carefully measured .

product

carbon dioxide 5.13g

water 2.10g

use this information to find the molecular formula of x

C₅H₁₀O₅

Explanation:

1. Calculate the mass of each element in 2.78 mg of X.

(a) Mass of C

(b) Mass of H

(c) Mass of O

Mass of O = 3.5 - 1.400 - 0.2349 = 1.87 g

2. Calculate the moles of each element

3. Calculate the molar ratios

Divide all moles by the smallest number of moles.

4. Round the ratios to the nearest integer

C:H:O = 1:2:1

5. Write the empirical formula

The empirical formula is CH₂O.

6. Calculate the molecular formula.

EF Mass = (12.01 + 2.016  + 16.00) u  = 30.03 u

The molecular formula is an integral multiple of the empirical formula.

MF = (EF)ₙ

MF = (CH₂O)₅ = C₅H₁₀O₅

The molecular formula of X is C₅H₁₀O₅.

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