2.5.3 Test (TST): Teacher-Scored Unit Test Test
Chemistry Sem 2 Name:
In this test you will apply what you have learned in the unit. Please answer
... [Show More] the
questions below. Submit this sheet to your teacher when you are done.
Question 1: Equilibrium (12 points)
i. What does it mean for a reaction to be at dynamic equilibrium? (2 points)
ii. Which line on the graph (1, 2, or 3) represents the system at dynamic
equilibrium? Explain your answer. (3 points)
iii. Describe the net rate of the reaction at equilibrium. (2 points)
b. The equilibrium constant for the reaction 2H2(g) + S2(g) 2H2S(g) is Keq =
. (3 points)
i. If a sample at equilibrium contained 0.051 M H2, 0.087 M S2, and 0.97 M H2S,
what would K
eq be for this reaction at that temperature? (2 points)
ii. What would happen to the equilibrium conditions if more S2 were added to the
system? (1 point)
c. The equilibrium constant for the reaction SO2(g) + NO2(g) NO(g) + SO3(g) is
Ke
q = . What would the equilibrium concentration of NO be in a gas
mixture that contains 1.7 M SO3, 0.070 M SO2, and 1.3 M NO2 if Keq = 10.8 at those
conditions? (2 points)
Question 2: Acids and Bases (10 points)
a. Use the acid-base reaction HBr + LiOH LiBr + H2O to answer the following
questions. (6 points)
i. Name the Arrhenius acid and Arrhenius base found in the above reaction. (2
points)
HBr is the Arrhenius acid and LiOH is the Arrhenius base.
ii. What kind of compound is LiBr? (2 points)
iii. What is this kind of acid-base reaction called? (2 points)
b. A Lewis acid accepts an electron pair, and a Lewis base donates an electron pair.
What is the Lewis acid and what is the Lewis base in the reaction H+ + NH3 NH4+?
(2 points)
c. What is the difference between a strong base and a weak base? (2 points)
Question 3: pH and pOH (6 points)
A solution has a hydrogen ion concentration of 6.3 10–10 M . (6 points) a. What is
the pH of the solution? Show your work. (3 points)
b. What is the pOH of the solution? Show your work. (3 points)
Question 4: Acid-Base Reactions (6 points)
a. The dissociation constant of the weak acid HF is K
a = . If at equilibrium
the concentrations of H+ and F– are each 2.6 10–3 M and the concentration of HF
is 0.010 M, what is Ka for HF? (3 points)
b. The reaction between HCO3– and its conjugate acid creates a very important
buffer in your blood. Explain what a buffer does. (3 points)
Question 5: Reaction Rate (16 points)
a. Some meats need to be tenderized, meaning that the muscle fibers need to be
broken down in order to make the meat easier to chew. This can be done physically
by pounding the meat with a special mallet, or it can be done chemically with a
meat tenderizer, which consists of enzymes that basically do the same thing.
Explain how the meat tenderizer works. (2 points)
A meat tenderizer acts enzymatically to break down the rubber-like elastic fibers
that make less tender cuts of meat hard to swallow.
b. Take a look at the reaction rate equation below.
Rate = k[A]2
Using this equation, what would the reaction rate be for the following set of
factors? (4 points)
Rate constant = 1 10–3 (L/mol)/s
[A] = 3 M
9 × 10⁻³ mol·L⁻¹s⁻¹
c. Hydrogen is produced industrially from methane through the reaction CH4(g)
+ H2O(g) + heat CO(g) + 3H2(g). The following diagram represents this
reaction. Use this information to answer the following questions. (10 points)
i. What would increasing the temperature do to the hydrogen yield? Explain your
answer. (2 points)
ii. What would increasing the temperature do to the reaction rate? Explain your
answer. (2 points)
iii. How would increasing the pressure affect the reaction rate? Explain your
answer. (2 points)
iv. This reaction is run using a nickel catalyst. How would adding nickel affect the
reaction rate? Explain your answer and draw nickel's effect on the energy diagram.
(4 points) [Show Less]