CHEM 123 SAPLING LEARNING
QUESTIONS & CERTIFIED
Quiz____?
The rate of a reaction is studied by measuring the concentration of the reactant and the
concentration of the product as a function of time. The results are shown in the graph.
A graph with time on the x axis and concentration on the y axis. A red curve labeled X,
starts at a concentration of zero at time zero. The concentration of X increases as time
increases. The shape of the curve is concave down. A blue curve labeled Y, starts at some
concentration above zero at time zero and decreases as time increases. The shape of the
curve is concave up. The final concentration of Y is near zero. The final concentration of X
is approximately twice the initial concentration of Y.
Which chemical equation is consistent with the graph? -
Answer✓✓
Y⟶2X
Solution
When a reaction progresses overtime, the concentrations of reactants are expected to
decrease because reactants are consumed in the reaction. The concentration of prooducts
are expected to increase with time because products are formed in the reaction.
In the graph, the concentration of Y is decreasing and the concentration of X is increasing.
Thus, Y is the reactant and X is the product.
The graph shows that the final concentration of the reactant Y is approximately zero, and
that the final concentration of the product X is approximately twice the initial concentration
of the reactant Y. This indicates that 2 mol of X are formed for every 1 mole of Y
consumed.
Thus, the chemical equation that is consistent with the graph is
Y⟶2X
1
, Quiz____?
Consider the following generic reaction.
X+Y⟶Z
Each reaction container contains a mixture of X and Y. -
Answer✓✓
A container contains 8 red spheres and 8 blue spheres that are evenly dispersed throughout
the container.
Solution
The collision theory is based on the assumption that for a reaction to occur, the reacting
compounds have to come in contact or collide with one another. The rate at which a
chemical reaction proceeds is proportional to the frequency of effective collisions.
As the concentration of the reactants increase, the frequency with which they collide
increases, leading to an increase in the reaction rate. Therefore, the reaction in the
container with eight molecules of each reactant will be faster than the reaction in the
container with only two molecules of each reactant.
In the third container, the reactants are not in contact with each other at all, meaning the
reaction in this container will be the slowest, if it happens at all.
Quiz____?
The concentration of X over time is shown in the graph.
A graph with time on the x axis and the concentration of X on the y axis. The curve is
concave down. There are three points labeled on the curve 1, 2, and 3, where point 1 is
closest to time zero.
Is X a reactant or product of the reaction?
How is the reaction rate changing as time progresses?
What conclusion can be drawn about the average rate of the reaction between points 1 and
2 and between points 2 and 3? -
Answer✓✓
2
, product
slowing down
The rate of the reaction between points 1 and 2 is faster than the rate of reaction between
points 2 and 3 because the concentration of reactants decreases.
Solution
In a chemical reaction, the reactant concentration decreases with time as the reactant is
consumed and the product concentration increases as the product is formed.
The graph shows that the concentration of X increases with time. Thus, X is a product.
The rate of the reaction can be expressed in terms of the concentration of X
reaction rate=+1/𝑎 * Δ[X]/Δ𝑡
where Δ[X] is the change in concentration, Δ𝑡 is the change in time and 𝑎 is the coefficient
of X in the balanced equation of the reaction.
Based on the shape of the curve, the change in the concentration of X is decreasing (getting
smaller) over time. Since X is a product, that means that the reaction is slowing down.
This can be observed by comparing the rate of the reaction between points 1 and 2 and
points 2 and 3 on the graph. The rate at which X is formed is greater between points 1 and
2 than between points 2 and 3, meaning the reaction is faster between points 1 and 2 than
between points 2 and 3. This decrease in rate is most likely due to a decrease in the
concentration of the reactants (not shown on the graph).
Quiz____?
After 20 min, a reactant has decomposed to 85% of its original concentration.
Which order would the reaction need to be to allow you to solve for the rate constant, 𝑘 ,
with only this information? -
Answer✓✓
first order
Quiz____?
𝑡 (min) [A] (M)
3
QUESTIONS & CERTIFIED
Quiz____?
The rate of a reaction is studied by measuring the concentration of the reactant and the
concentration of the product as a function of time. The results are shown in the graph.
A graph with time on the x axis and concentration on the y axis. A red curve labeled X,
starts at a concentration of zero at time zero. The concentration of X increases as time
increases. The shape of the curve is concave down. A blue curve labeled Y, starts at some
concentration above zero at time zero and decreases as time increases. The shape of the
curve is concave up. The final concentration of Y is near zero. The final concentration of X
is approximately twice the initial concentration of Y.
Which chemical equation is consistent with the graph? -
Answer✓✓
Y⟶2X
Solution
When a reaction progresses overtime, the concentrations of reactants are expected to
decrease because reactants are consumed in the reaction. The concentration of prooducts
are expected to increase with time because products are formed in the reaction.
In the graph, the concentration of Y is decreasing and the concentration of X is increasing.
Thus, Y is the reactant and X is the product.
The graph shows that the final concentration of the reactant Y is approximately zero, and
that the final concentration of the product X is approximately twice the initial concentration
of the reactant Y. This indicates that 2 mol of X are formed for every 1 mole of Y
consumed.
Thus, the chemical equation that is consistent with the graph is
Y⟶2X
1
, Quiz____?
Consider the following generic reaction.
X+Y⟶Z
Each reaction container contains a mixture of X and Y. -
Answer✓✓
A container contains 8 red spheres and 8 blue spheres that are evenly dispersed throughout
the container.
Solution
The collision theory is based on the assumption that for a reaction to occur, the reacting
compounds have to come in contact or collide with one another. The rate at which a
chemical reaction proceeds is proportional to the frequency of effective collisions.
As the concentration of the reactants increase, the frequency with which they collide
increases, leading to an increase in the reaction rate. Therefore, the reaction in the
container with eight molecules of each reactant will be faster than the reaction in the
container with only two molecules of each reactant.
In the third container, the reactants are not in contact with each other at all, meaning the
reaction in this container will be the slowest, if it happens at all.
Quiz____?
The concentration of X over time is shown in the graph.
A graph with time on the x axis and the concentration of X on the y axis. The curve is
concave down. There are three points labeled on the curve 1, 2, and 3, where point 1 is
closest to time zero.
Is X a reactant or product of the reaction?
How is the reaction rate changing as time progresses?
What conclusion can be drawn about the average rate of the reaction between points 1 and
2 and between points 2 and 3? -
Answer✓✓
2
, product
slowing down
The rate of the reaction between points 1 and 2 is faster than the rate of reaction between
points 2 and 3 because the concentration of reactants decreases.
Solution
In a chemical reaction, the reactant concentration decreases with time as the reactant is
consumed and the product concentration increases as the product is formed.
The graph shows that the concentration of X increases with time. Thus, X is a product.
The rate of the reaction can be expressed in terms of the concentration of X
reaction rate=+1/𝑎 * Δ[X]/Δ𝑡
where Δ[X] is the change in concentration, Δ𝑡 is the change in time and 𝑎 is the coefficient
of X in the balanced equation of the reaction.
Based on the shape of the curve, the change in the concentration of X is decreasing (getting
smaller) over time. Since X is a product, that means that the reaction is slowing down.
This can be observed by comparing the rate of the reaction between points 1 and 2 and
points 2 and 3 on the graph. The rate at which X is formed is greater between points 1 and
2 than between points 2 and 3, meaning the reaction is faster between points 1 and 2 than
between points 2 and 3. This decrease in rate is most likely due to a decrease in the
concentration of the reactants (not shown on the graph).
Quiz____?
After 20 min, a reactant has decomposed to 85% of its original concentration.
Which order would the reaction need to be to allow you to solve for the rate constant, 𝑘 ,
with only this information? -
Answer✓✓
first order
Quiz____?
𝑡 (min) [A] (M)
3
