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A fuel gas is 82.8% carbon and 17.2% hydrogen by mass.

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A fuel gas is $82.8\%$ carbon and $17.2\%$ hydrogen by mass. Its molar mass is $58\ \text{g mol}^{-1}$ . Find its empirical formula, the empirical formula mass and the molecular formula.

Need a reminder? The key ideaShow

Mass percent of an element $= \dfrac{\text{its mass in 1 mol}}{M} \times 100$ . Empirical formula: take $100\ \text{g}$ , change each mass to moles, divide by the smallest, and multiply to whole numbers. Molecular formula: $n = \dfrac{\text{molar mass}}{\text{empirical formula mass}}$ .

The worked solution

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← Orange crystals used in the laboratory are 26.6% potassium, 35.4% chromium and 38.0% oxygen by mass.A chemist burns 0.230 g of a liquid that holds only carbon, hydrogen and oxygen. →

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A fuel gas is 82.8% carbon and 17.2% hydrogen by mass.

The worked solution

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