Answer to Question #310908 in Chemistry for T.k

Question

An organic compound 0.246g by mass was burnt in oxygen and produced 0.198g carbon dioxide and 0.1014g water what is the empirical formula of this compound

Answer 1

Solution:

Convert to moles:

The molar mass of CO₂ is 44.01 g/mol

Therefore,

Moles of CO₂ = (0.198 g CO₂) × (1 mol CO₂ / 44.01 g CO₂) = 0.00450 mol CO₂

Schematic equation:

CO₂ → C

According to the shematic equation above:

Moles of C = Moles of CO₂ = 0.00450 mol

Moles of C = 0.00450 mol

The molar mass of C is 12.0107 g/mol

Therefore,

Mass of C = (0.00450 mol C) × (12.0107 g C / 1 mol C) = 0.054 g C

 

The molar mass of H₂O is 18.0153 g/mol

Therefore,

Moles of H₂O = (0.1014 g H₂O) × (1 mol H₂O / 18.0153 g H₂O) = 0.00563 mol H₂O

Schematic equation:

H₂O → 2H

According to the shematic equation above

Moles of H = 2 × Moles of H₂O = 2 × 0.00563 mol = 0.01126 mol

Moles of H = 0.01126 mol

The molar mass of H is 1.00784 g/mol

Therefore,

Mass of H = (0.01126 mol H) × (1.00784 g H / 1 mol H) = 0.0113 g H

Mass of H + Mass of C = 0.0113 g + 0.054 g = 0.0653 g

(Mass of H + Mass of C) < (Mass of organic compound)

Thus, the compound contains another element besides oxygen and hydrogen.

Suppose the remaining element is bromine (Br).

Then,

Mass of Br = Mass of organic compound − (Mass of H + Mass of C)

Mass of Br = 0.246 g − 0.0653 g = 0.1807 g

The molar mass of Br is 79.904 g/mol

Therefore,

Moles of Br = (0.1807 g Br) × (1 mol Br / 79.904 g Br) = 0.00226 mol Br

Moles of Br = 0.00226 mol

Divide all moles by the smallest of the results:

C: 0.00450 mol / 0.00226 mol = 1.99 = 2

H: 0.01126 mol / 0.00226 mol = 4.98 = 5

Br: 0.00226 mol / 0.00226 mol = 1

Thus, the empirical formula of organic compound is C₂H₅Br

Answer: The empirical formula of the compound is C₂H₅Br