Hot nitric acid oxidises arsenic(III) sulfide to arsenic acid and sulfate ions, and is itself…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
Hot nitric acid oxidises arsenic(III) sulfide to arsenic acid and sulfate ions, and is itself reduced to nitric oxide. Balance in acid, using and water.
Need a reminder? The key ideaShow
The total rise in oxidation number equals the total fall: electrons lost equal electrons gained. Match the changes first. Then balance the atoms that did not change, charge, hydrogen and oxygen.
The worked solution
Have you tried it?
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. Electrons lost. Each arsenic goes from to : a rise of 2, and there are two, so 4. Each sulfur goes from to : a rise of 8, and there are three, so 24. One loses electrons.
Step 2. Electrons gained. Each nitrogen goes from to , a gain of 3.
Step 3. Match. The smallest number that 28 and 3 divide into is 84. So 3 and 28 : .
Step 4. Charge. The left side is and the right side is . Add 10 on the left.
Step 5. Hydrogen. The right side has 18 hydrogen atoms and the left has 10. Add 4 water molecules on the left. Oxygen: on the left, and on the right.
Answer: .
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