Video Transcript
In a series of experiments, a
student changes both the concentration and the temperature. The conditions for each experiment
are shown below. In which conical flask is the rate
of reaction likely to be highest?
Rate of reaction measures how
reactant or product concentration, mass, or volume changes over time. We can think of rate of reaction as
the speed of a chemical reaction. To answer this question, we need to
determine which flask will have the highest rate of reaction. In other words, we want to know
which reaction is likely to be the fastest.
Let’s consider a chemical reaction
between these two particles. Chemical reactions occur when
particles successfully collide with one another. If we can increase the number of
collisions between particles, then we can increase the rate of reaction. In the experiments, two conditions
were changed: concentration and temperature.
Let’s first consider how changing
the temperature might affect the number of collisions between particles. At this temperature, the particles
have a certain amount of energy and are moving about, colliding with one another and
the walls of the container. If we increase the temperature of
this substance, the particles will gain energy and move faster. The faster the particles move, the
more collisions they are likely to have. So increasing the temperature
increases the number of collisions, which increases the rate of reaction.
Looking at the experiment
conditions, we can see that two of the experiments were performed at 25 degrees
Celsius and two were performed at 50 degrees Celsius. Since we need to determine which
conical flask has the highest rate of reaction, and higher temperatures correspond
to higher rates of reaction, we can eliminate options (A) and (D).
Now let’s consider how
concentration might affect the number of collisions between particles. Concentration is the amount of a
substance in a particular volume. For this example, we can think of
the concentration as the number of particles in the box. Inside of the box, the particles
are colliding with one another and the walls of the container. If we add more particles to the
box, that is, we increase the concentration, there’s likely to be more collisions
between the particles. Therefore, increasing the
concentration increases the number of collisions, which increases the rate of
reaction.
Looking at the two remaining answer
choices, we see that conical flask (C) has a higher concentration than conical flask
(B). As rate of reaction increases as
the concentration increases, conical flask (C) should have a higher rate of
reaction. Therefore, the conical flask that
is likely to have the highest rate of reaction is flask (C) because this experiment
was performed with the greatest concentration and at the highest temperature.
