IB Chemistry SL 1.4.4 Empirical and Molecular Formulas Questions

Convert composition data to moles, reduce to an empirical formula, then use molar mass to obtain the molecular formula and check percentage composition.

Exam points

Derive an empirical formula by converting element masses, combustion products or percentage composition to moles and reducing to the simplest whole-number atom ratio.
Determine a molecular or formula-unit composition from an empirical formula and molar mass, and distinguish simplest ratios from actual atoms in a molecule.
Calculate percentage composition by mass from a stated chemical formula, including hydrates and adducts, with appropriate significant figures.

[Maximum number: 1]

A hydrocarbon has the empirical formula $\mathrm{C}_{3} \mathrm{H}_{7}$ . When 1.17 g of the compound is heated to $85^{\circ} \mathrm{C}$ at a pressure of 101 kPa it occupies a volume of $400 \mathrm{~cm}^{3}$ .

Deduce the molecular formula of the compound.

$\quad \mathrm{C}_{6} \mathrm{H}_{14}$ ;

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IB Chemistry SL 1.4.4 Empirical and Molecular Formulas Questions question 1