A student reduces 12.3 g of nitrobenzene (123 g/mol) with zinc (65 g/mol)…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
A student reduces of nitrobenzene () with zinc (). In a neutral medium (zinc and ammonium chloride), the product is N-phenylhydroxylamine, (), and each nitrobenzene takes 4 electrons. In an alkaline medium (zinc and sodium hydroxide), the product is hydrazobenzene, (), and two nitrobenzene molecules take 10 electrons together. Each zinc atom gives 2 electrons. Find the mass of zinc and the mass of product for each medium. Take the yields as 100 %.
Need a reminder? The key ideaShow
Silver cyanide gives an isocyanide and potassium cyanide gives a nitrile. A nitrile is reduced to a primary amine with one more carbon than the halide. An isocyanide is hydrolysed by acid to a primary amine and formic acid, and is reduced to a secondary amine. Nitrobenzene takes 6, 4 or 5 electrons in an acidic, neutral or alkaline medium, and each atom of zinc or tin gives 2 electrons.
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. Nitrobenzene. .
Step 2. Neutral, zinc. of zinc, which is .
Step 3. Neutral, product. .
Step 4. Alkaline, zinc. , which is .
Step 5. Alkaline, product. , and .
Answer: , , and .
Check. Alkaline reduction needs more zinc, since 5 electrons are taken for each nitrobenzene, against 4. Yet it gives the lightest mass of product, because two nitrobenzene molecules make one product molecule.
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