Video Transcript
Ammonia can be reacted with bromine
to produce nitrogen and hydrogen bromide. The reaction can be described with
the following equation: two NH3 gas plus three Br2 gas react to form N2 gas plus six
HBr gas. Which of the following correctly
shows which reactant is the oxidizing agent, which reactant is the reducing agent,
and how the reactants are either oxidized or reduced to make the products?
This question is asking us to
identify which of the reactants is the oxidizing agent and which of the reactants is
the reducing agent in this reaction between ammonia and bromine. Let’s clear some space to discuss a
few important terms.
Oxidization can be defined as a
chemical process that increases the oxygen percentage or decreases the hydrogen
percentage in a substance. Conversely, reduction can be
defined as a chemical process that decreases the oxygen percentage or increases the
hydrogen percentage in a substance. A reactant that oxidizes another
reactant is known as an oxidizing agent, whereas a reactant that reduces another
reactant is known as a reducing agent.
If we look at the chemical equation
provided, we can quickly see that the element oxygen does not play a part in this
reaction. However, three hydrogen atoms exist
in each molecule of ammonia. So, we can look for a gain or loss
of hydrogen to help us answer this question. During the chemical reaction,
ammonia loses hydrogen and forms nitrogen gas, or N2. We can also see that bromine gas is
converted into hydrogen bromide, or HBr, by gaining hydrogen. By using our definition of
reduction, we can say that bromine was reduced because it gained hydrogen. Likewise, using our definition of
oxidization, we can say that ammonia was oxidized because it lost hydrogen during
the reaction. Based on our discussion so far, we
can eliminate answer choices (B) and (C) because these answer choices show that
ammonia was reduced. But we know now that it was
oxidized.
Since ammonia was oxidized, Br2
must be the oxidizing agent. And since Br2 was reduced, NH3 must
be the reducing agent. Knowing this allows us to eliminate
answer choice (A), which has the labels for oxidizing agent and reducing agent
reversed.
So, which diagram correctly shows
which reactant is the oxidizing agent, which reactant is the reducing agent, and how
the reactants are either oxidized or reduced to make the products? The correct answer is the diagram
in answer choice (D).
