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A farmer can buy urea, CO(NH₂)₂, ammonium nitrate, NH₄NO₃, or ammonium sulphate, (NH₄)₂SO₄.

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A farmer can buy urea, $\text{CO(NH}_2)_2$ , ammonium nitrate, $\text{NH}_4\text{NO}_3$ , or ammonium sulphate, $(\text{NH}_4)_2\text{SO}_4$ . Find the mass percent of nitrogen in each. Which gives the most nitrogen for each kilogram? Use $\text{H} = 1$ , $\text{C} = 12$ , $\text{N} = 14$ , $\text{O} = 16$ and $\text{S} = 32$ .

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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A farmer can buy urea, CO(NH₂)₂, ammonium nitrate, NH₄NO₃, or ammonium sulphate, (NH₄)₂SO₄.

The worked solution

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