An unknown substance has the composition of 77.87% C, 2.63% H and 55.62% O. The compound has a molar mass of 345.2 g/mole. What is the molecular formula?

Question

Chemistry

Madeleine Li

22 May, 11:38

An unknown substance has the composition of 77.87% C, 2.63% H and 55.62% O. The compound has a molar mass of 345.2 g/mole. What is the molecular formula?

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Answers (1)

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Coco Chanel · Answer 1

If we use 100 grams of compound:

m (C) = 0,7787 · 100 g = 77,87 g.

n (C) = 77,87 g : 12 g/mol = 6,49 mol.

m (H) = 0,0263 · 100 g = 2,63 g.

n (H) = 2,63 g : 1 g/mol = 2,63 mol.

m (O) = 0,5562 · 100 g = 55,62 g.

n (O) = 55,62 g : 16 g/mol = 3,48 mol.

n (C) : n (H) : n (O) = 6,49 mol : 2,63 mol : 3,48 mol.

n (C) : n (H) : n (O) = 2,5 : 1 : 1,33.

From molecular mass only possible is C₁₂H₉O₁₂.