Which of the following best
describes the conversion of nitrogen to nitrogen oxide? A) fusion, B) Precipitation, C)
Nuclear transformation, D) Combustion, or E) Reduction.
The element nitrogen could most
commonly be found as a gas in the form of N₂. Nitrogen oxide is one of the many
nitrogen oxides, and it, too, is normally found as a gas. What we’re looking at is the
conversion of one to the other. And the first thing we need to
solve is, where did this oxygen come from? The most obvious source for oxygen
would be oxygen itself in the form of O₂. And one more NO on the right-hand
side balances this equation.
Nitrogen oxide is a common
byproduct of lightning strikes and internal combustion engines. These circumstances provide the
high energy needed to rearrange the atoms. In industrial settings, nitrogen
oxide is generated from other sources like ammonia. Now, we can have a look at the five
descriptions we’ve been given and see which one best applies to the conversion of
nitrogen to nitrogen oxide.
Fusion reactions are generally
considered to be nuclear fusion reactions, so we don’t see fusion appear much in
chemical reactions. The most popular fusion reaction in
the universe is that which goes on inside our Sun, the fusion of hydrogen nuclei to
form helium nuclei. In the conversion of nitrogen to
nitrogen oxide, all the particles retain their elemental identity. None of them fuse together, so it’s
not a fusion reaction.
A precipitation reaction is where
we produce a solid from solution. A good example of this is when we
mix together solutions of lead nitrate and potassium iodide, producing the brilliant
yellow precipitate of lead iodide. In our reaction, we’re only
producing nitrogen oxide, which would be a gas and not particularly soluble in
solution. So, we’re not dealing with a
Meanwhile, the nuclear
transformation involves a change in the composition of one or more nuclei. For instance, when thorium-234
decays via beta emission, we produce protactinium-234. In the process, one neutron in each
thorium-234 nucleus decays into a proton. In the conversion of nitrogen to
nitrogen oxide, we don’t see any nuclei change their identity. Nitrogen is always nitrogen and
oxygen is always oxygen.
Meanwhile, a combustion reaction is
one where commonly a component reacts with oxygen, although combustion can involve a
different oxidizing agent. The conversion of nitrogen to
nitrogen oxide could be via a combustion reaction. So, so far, it’s the best
description we have for this process. But just to be safe, let’s have a
look at reduction.
In a reduction reaction, components
of specific chemicals undergo a reduction in their oxidation state, commonly by
gaining of electrons. Nitrogen is our focus for this
conversion, and we start with an oxidation number of zero. In nitrogen oxide, the oxygen,
being more electronegative, will have an oxidation state of minus two, meaning that
the nitrogen must have an oxidation state of plus two. This is actually the reverse of
reduction. It’s an oxidation. We’re seeing an increase in the
oxidation number of our nitrogens. So, the conversion of nitrogen to
nitrogen oxide is not a reduction.
You may have noticed that the
oxygen in this process is being reduced, but that’s not part of the question. We’re only interested in the
conversion of nitrogen to nitrogen oxide. With all other options eliminated,
combustion rises as the best description of the conversion of nitrogen to nitrogen
oxide, although there may be cases where nitrogen would be converted to nitrogen
oxide through other means that aren’t classed as combustion.