Question

Question #f33dd

Answer 1

If the mass of water is 0.443 g, the empirical formula is C₇H₆O.

This method of determining an empirical formula is combustion analysis.

To get the empirical formula, we must calculate the molar ratios of each element.

See What is the empirical formula?.

You give an impossibly small value for the mass of water. I think you made a typo, and the mass is really 0.443 g.

Step 1. Determine the masses of each element.

Moles of C = 2.52 g CO₂ × `(1"mol CO₂")/(44.01"g CO₂") × (1"mol C")/(1"mol CO₂")` = 0.057 26 mol C

Mass of C = 0.057 26 mol C × `(12.01"g C")/(1"mol C")` = 0.6877 g C

Moles of H =0.443 g H₂O × `(1"mol H₂O")/(18.02"g O") × (2"mol H")/(1"mol H₂O")` = 0.049 17 mol H

Mass of H = 0.049 17 mol H × `(1.008"g H")/(1"mol H")` = 0.049 56 g H

Mass of O = 1.00 g – 0.6887 g -0.049 56 g = 0.262 g O

Step 2. Determine the moles of each element

Moles of C = 0.057 26 mol

Moles of H = 0.049 17 mol

Moles of O = 0.262 g O × `(1"mol O")/(16.00"g O")` = 0.0164 mol

Step 3. Determine the molar ratios

C:H:O = 0.05726:0.04917:0.0164 = 3.50:3.00:1 = 6.99:6.00:2 ≈ 7:6:2

Step 4. Write the empirical formula

The empirical formula of the compound is C₇H₆O₂.

Here's a schematic diagram of an apparatus for combustion analysis.