CHM 122Practice Problems –Exam 1
You must read your textbook, study your notes, homework and quizzes. Do Not assume the problems on the exam will be exactly the same.
- Which one of the following statements does not describe the equilibrium state?
A) Equilibrium is dynamic and there is no net conversion to reactants and products.
B) The concentration of the reactants is equal to the concentration of the products.
C) The concentration of the reactants and products reach a constant level.
D) The rate of the forward reaction is equal to the rate of the reverse reaction.
2.The equilibrium equation is also known as the law of
A) coefficients.
B) constant concentration.
C) dynamic equilibrium.
D) mass action.
3.Which of the following changes in reaction conditions will not alter the composition of a homogeneous equilibrium mixture of gases?
A) addition of a catalyst
B) addition of reactants or products
C) decreasing the temperature
D) increasing the pressure or volume
4.The following pictures represent the initial state and the equilibrium state for the gaseous state reaction of A2 molecules (shaded spheres) with B atoms (unshaded spheres) to give AB molecules.
If the volume of the equilibrium mixture is decreased, what will happen to the number of AB molecules and the number of B atoms?
A) The number of AB molecules and the number of B atoms will both decrease.
B) The number of AB molecules will increase; the number of B atoms will decrease.
C) The number of AB molecules will decrease; the number of B atoms will increase.
D) The number of AB molecules and the number of B atoms will both increase.
5.When dissolved in water, which of the following compounds is an Arrhenius acid?
A) HCN
B) NaOH
C)NaF
D) CH3CH2OH
6.Which Br∅nsted-Lowry acid has the strongest conjugate base?
A) HBr
B) HClO4
C) HF
D) HI
7.The following pictures represent aqueous solutions of binary acids of the type HA where the water molecules have been omitted for clarity.
Arrange the acids in order of increasing acid strength.
A) D < C < A < B
B) D < C < B < A
C) D < B < A < C
D) D < A < C < B
8.SO3 reacts with H2O to form H2SO4. Which picture below correctly represents the curved arrow notation for the initial Lewis acid-Lewis base interaction in this reaction; what is the Lewis acid and the Lewis base?
A) Picture (1) is correct; H2O is the Lewis acid and SO3 is the Lewis base.
B) Picture (1) is correct; SO3 is the Lewis acid and H2O is the Lewis base.
C) Picture (2) is correct; H2O is the Lewis acid and SO3 is the Lewis base.
D) Picture (2) is correct; SO3 is the Lewis acid and H2O is the Lewis base.
Question II
One step in the manufacture of sulfuric acid is the oxidation of sulfur dioxide, 2SO2(g) + O2(g) 2SO3(g). If Kp for this reaction is 3.30 at 1000K. What is the value of Kc at the same temperature?
Kc = 275
Question III
At 1400K, Kc = 2.5 x 10-3 for the reaction
CH4(g) + 2H2S(g) CS2(g) + 4H2(g)
A 10.0 L reaction vessel at 1400K contains 2.0 mol of CH4, 3.0 mol of CS2, 3.0 mol of H2 and 4.0 mol of H2S. Is the reaction mixture at equilibrium? If in which reaction does the reaction proceed to reach equilibrium?
Qc > Kc
Qc = 7.6 x 10-2
Question IV
Consider the following reaction at equilibrium: C(s) + 2 H2(g) ⇌ CH4(g)△H° = – 74.8 kJ . Use Le Chatelier’s principle to predict the equilbirum concentration of H2(g) when:
- C solid is removed
- CH4 is added: Also account for the value of Qc
- Temperature is decreased: Also account for the value of Kc
- A catalyst is added
Question V
If you mixed equal concentration of reactants and products, would the equilibrium proceed to right or to the left? Explain why by using the information from table 14.1
- H2CO3(aq) + HSO4-(aq) H2SO4(aq) + HCO3-(aq)
- HF(aq) + Cl-(aq) HCl(aq) + F-(aq)
Question VI
Determine the ammonia concentration of a 0.20 M aqueous solution that has a pH of 11.00. Write the balanced equation for the dissociation of NH3.
Kb = 1.8 x10-5
[NH3] = 0.019M
Question VII
Calculate the pH and the concentration of all species present (H3O+, -OH, HIO3 and IO3-) in 0.0500 M HIO3. Ka = 1.7 x 10-1
x = 0.04M
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