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A farmer can buy urea, CO(NH₂)₂, ammonium nitrate, NH₄NO₃, or ammonium sulphate, (NH₄)₂SO₄…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
A farmer can buy urea, , ammonium nitrate, , or ammonium sulphate, . Find the mass percent of nitrogen in each. Which gives the most nitrogen for each kilogram? Use , , , and .
Need a reminder? The key ideaShow
Mass percent of an element . Empirical formula: take , change each mass to moles, divide by the smallest, and multiply to whole numbers. Molecular formula: .
The worked solution
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Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. Molar masses. Urea: . Ammonium nitrate: . Ammonium sulphate: .
Step 2. Nitrogen. Each mole holds two nitrogen atoms, .
Step 3. Percentages. Urea: . Ammonium nitrate: . Ammonium sulphate: .
Answer: , and . Urea gives the most nitrogen for each kilogram.
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