Video Transcript
The graph below shows the
concentration of oxygen gas produced during the following chemical reaction: two
H2O2 reacts to form two H2O plus O2. How long does this reaction take to
reach completion? (A) 90 seconds, (B) 120 seconds,
(C) 80 seconds, (D) 100 seconds, (E) 20 seconds.
In the reaction in this question,
hydrogen peroxide decomposes to form water and oxygen gas. The concentration of oxygen gas has
been graphed over time. We need to determine how long it
takes this reaction to reach completion. At the start of the reaction, the
concentration of oxygen is zero because no oxygen gas has been produced yet. Then, the concentration gradually
increases until the concentration stops changing when it reaches a value of one mole
per liter. When the concentration of the
reactants and products stop changing, it means the reaction has reached
completion. The graph shows that the
concentration of oxygen stopped changing after 90 seconds. So answer choice (A) is the correct
answer. It took 90 seconds for this
reaction to reach completion.
