While working in the lab, you find a bottle labeled "fabric dye". since the original investigator neglected to record the identity of the substance, you decide to perform a combustion analysis to identify the compound. you have a 24.6 g sample that when burned produces 53.7 g co2 and 8.45 g h2o. what is the formula of this compound? (the compound consists of only c, h, and o.)?

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Dejanras Dejanras · Answer 1 · 2018-09-19T21:00:07+02:00

Answer is: formula of the compound is C₁₂H₈O₅.

Chemical reaction: CₐHₓO + O₂ → aCO₂ + x/2H₂O.

n(CO₂) = m(CO₂) ÷ M(CO₂).

n(CO₂) = 53.7 g ÷ 44 g/mol.

n(CO₂) = 1.22 mol.

n(H₂O) = 8.45 g ÷ 18 g/mol.

n(H₂O) = 0.47 mol.

From reaction: n(C) = n(CO₂).

m(C) = 1.22 mol · 12 g/mol.

m(C) = 14.64 g.

From chemical reaction: n(H₂O) = 2n(H).

n(H) = 2 · 0.47 mol = 0.94 mol.

m(H) = 0.94 mol · 1g/mol = 0.94 g.

m(O) = 24.6 g - 0.94 g - 14.64 g = 9.02 g.

n(O) = 9.02 ÷ 16 g/mol = 0.56 mol.

n(C) : n(H) : n(O) = 1.22 mol : 0.94 mol : 0.56 mol /0.56.

n(C) : n(H) : n(O) = 2.18 : 1.68 : 1.