Chemistry Exam 3
The pH of water and most solutions changes drastically when a small amount of acid or base is added. However, when an acid or a base is added to a buffer solution, there is little change in pH.
A buffer solution maintains the pH of a solution by neutralizing small amounts of added acid or base.
69. Calculate the pH of each solution given the following: A. [H3O+]=1×10−4 M B. [H3O+]=3×10−9 M C. [OH−]=1×10−5 M D. [OH−]=2.5×10−11 M E. [H3O+]=6.7×10−8 M F. [OH−]=8.2×10−4 M
A. 4.0 B. 8.5 C. 9.0 D. 3.40 E. 7.17 F. 10.92
44. Write the formula for the conjugate acid for each of the following bases: A. CO 2−3 B. H2O C. H2PO −4 D. Br− E. ClO −4
A. HCO −3 B. H3O+ C. H3PO4 D. HBr E. HClO4
42. Identify the reactant that is a Brønsted-Lowry acid and the reactant that is a Brønsted-Lowry base in each of the following: A. HI(aq)+H2O(l) → I−(aq)+H3O+(aq) B. F−(aq)+H2O(l)⇄HF(aq)+OH−(aq) C. H2S(aq)+C2H5—NH2(aq)⇄ HS−(aq)+C2H5—NH +3(aq)
A. HI is the acid (hydrogen ion donor), and H2O is the base (hydrogen ion acceptor). B. H2O is the acid (hydrogen ion donor), and F− is the base (hydrogen ion acceptor). C. H2S is the acid (hydrogen ion donor), and H2H5—NH2 is the base (hydrogen ion acceptor).
50. Identify the weaker acid in each of the following pairs: A. HCl or HSO −4 B. HNO2 or HF C. HCO −3 or NH +4
A. HSO −4 B. HF C. HCO −3
37. Write formulas for each of the following acids and bases: A. rubidium hydroxide B. hydrofluoric acid C. phosphoric acid D. lithium hydroxide E. ammonium hydroxide F. periodic acid
A. RbOH B. HF C. H3PO4 D. LiOH E. NH4OH F. HIO4
90. Solution A has a pH of 4.5, and solution B has a pH of 6.7. (11.6) A. Which solution is more acidic? B. What is the [H3O+] in each? C. What is the [OH−] in each?
A. Solution A B. Solution A [H3O+]=3×10−5M; Solution B [H3O+]=2×10−7M C. Solution A [OH−]=3×10−10M; Solution B [OH−]=5×10−8M
55. Answer True or False for each of the following: A strong acid: A. is completely dissociated in aqueous solution B. has a small value of Ka C. has a strong conjugate base D. has a weak conjugate base E. is slightly dissociated in aqueous solution
A. True B. False C. False D. True E. False
60. Indicate whether each of the following solutions is acidic, basic, or neutral: A. [H3O+]=2.0×10−5 M B. [H3O+]=1.4×10−9 M C. [OH−]=8.0×10−3 M D. [OH−]=3.5×10−10 M
A. acidic B. basic C. basic D. acidic
Why does bread grow mold more quickly at room temperature than in the refrigerator?
At room temperature, the reactions involved in the growth of bread mold will proceed at a faster rate than at the lower temperature of the refrigerator.
TRUE OR FALSE: Reactions with low activation energies go faster than reactions with high activation energies.
TRUE
Which theory indicates that a reaction takes place only when molecules collide with the proper orientation and sufficient energy?
The collision theory
What is meant by the rate of a reaction?
The rate of the reaction indicates how fast the products form or how fast the reactants are used up.
73. What is the molarity of an HCl solution if 28.6 mL of a 0.175 M NaOH solution is needed to titrate a 25.0-mL sample of the HCl solution?
0.200 M HCl solution
98. A solution of 0.205 M NaOH is used to titrate 20.0 mL of a H2SO4 solution. If 45.6 mL of the NaOH solution is required to reach the endpoint, what is the molarity of the H2SO4 solution? (11.7) H2SO4(aq)+2NaOH(aq) → 2H2O(l)+Na2SO4(aq)
0.234 M H2SO4
77. What is the molarity of a solution of HCl if 5.00 mL of the HCl solution is titrated with 28.6 mL of a 0.145 NaOH solution? HCl(aq)+NaOH(aq) → H2O(l)+NaCl(aq)
0.829 M HCl solution
49. Identify the stronger acid in each of the following pairs: A. HBr or HNO2 B. H3PO4 or HSO −4 C. HCN or H2CO3
A. HBr B. HSO −4 C. H2CO3
71. Write the balanced equation for the reaction between H2SO4(aq) and K2CO3(s).
H2SO4(aq) + K2CO3(s) → CO2(g) + H2O(l) + K2SO4(aq)
Why are the concentrations of H3O+ and OH− equal in pure water?
In pure water, [H3O+]=[OH−] because one of each is produced every time a hydrogen ion is transferred from one water molecule to another.
13. What is the numerical value of Kc for the following reaction if the equilibrium mixture contains 0.030 M N2O4 and 0.21 M NO2? N2O4(g)⇄2NO2(g)
Kc= 1.5
46. When ammonium chloride dissolves in water, the ammonium ion, NH +4, acts as an acid. Write a balanced equation for the reaction of the ammonium ion with water.
NH +4(aq)+H2O(l)⇄NH3(aq)+H3O+(aq)
Naming Bases:
Typical Arrhenius bases are named as hydroxides.
81. a. One of the conjugate acid-base pairs that buffers the blood plasma is H2PO4−/HPO42−. The Kafor H2PO4− is 6.2 × 10−8. What is the pH of a buffer that is prepared from 0.10 M H2PO4− and 0.50 M HPO42−? b. What is the pH of a buffer made from 0.10 M formic acid (HCHO2) and 0.010 M formate (CHO2−)? The Ka for formic acid is 1.8 × 10−4.
a. pH = 7.91 b. pH = 2.74
65. a. Calculate the pH of a sample of bile that has [OH−] = 1.3 × 10−6 M. b. What is the pH of egg whites with [OH−] = 1.2 × 10−5 M?
a. pH = 8.11 b. pH = 9.08
A Brønsted-Lowry base is a substance that
accepts H+.
Arrhenius bases:
are ionic compounds that dissociate into cations and hydroxide ions (OH−) when they dissolve in water. - Most Arrhenius bases are formed from Groups 1A (1) and 2A (2) metals, such as NaOH, KOH, LiOH, and Ca(OH)2.
A Brønsted-Lowry acid is a substance that
donates H+.
92. What is the pH of a solution prepared by dissolving 2.5 g of HCl in water to make 425 mL of solution? (11.6)
pH=0.80
Arrhenius acids:
substances that produce hydrogen ions (H+) when they dissolve in water. - Acids dissolve in water to produce hydrogen ions, along with a negative ion that may be a simple nonmetal anion or a polyatomic ion.
78. If 38.2 mL of a 0.163 M KOH solution is required to titrate 25.0 mL of a H2SO4solution, what is the molarity of the H2SO4 solution? H2SO4(aq)+2KOH(aq) → 2H2O(l)+K2SO4(aq)
0.124 M H2SO4 solution
79. A solution of 0.204 M NaOH is used to titrate 50.0 mL of a 0.0224 M H3PO4solution. What volume, in milliliters, of the NaOH solution is required? H3PO4(aq)+3NaOH(aq) → 3H2O(l)+Na3PO4(aq)
16.5 mL
61. Calculate the [H3O+] of each aqueous solution with the following [OH−]: A. coffee, 1.0×10−9 M B. soap, 1.0×10−6 M C. cleanser, 2.0×10−5 M D. lemon juice, 4.0×10−13 M
A. 1.0×10−5M B. 1.0×10−8M C. 5.0×10−10M D. 2.5×10−2M
62. Calculate the [OH−] of each aqueous solution with the following [H3O+]: A. stomach acid, 4.0×10−2 M B. urine, 5.0×10−6 M C. orange juice, 2.0×10−4 M D. bile, 7.9×10−9 M
A. 2.5×10−13M B. 2.0×10−9M C. 5.0×10−11M D. 1.3×10−6M
74. Complete and balance the equation for each of the following reactions: A. HBr(aq)+ZnCO3(s) → B. HCl(aq)+Zn(s) → C. HCl(aq)+NaHCO3(s) → D. H2SO4(aq)+Mg(OH)2(s) →
A. 2HBr(aq)+ZnCO3(s) → CO2(g)+H2O(l)+ZnBr2(aq) B. 2HCl(aq)+Zn(s) → H2(g)+ZnCl2(aq) C. HCl(aq)+NaHCO3(s) → CO2(g)+H2O(l)+NaCl(aq) D. H2SO4(aq)+Mg(OH)2(s) → 2H2O(l)+MgSO4(aq)
75. Balance each of the following neutralization reactions: A. HCl(aq)+Mg(OH)2(s) → H2O(l)+MgCl2(aq) B. H3PO4(aq)+LiOH(aq) → H2O(l)+Li3PO4(aq)
A. 2HCl(aq)+Mg(OH)2(s) → 2H2O(l)+MgCl2(aq) B. H3PO4(aq)+3LiOH(aq) → 3H2O(l)+Li3PO4(aq)
83. Consider the buffer system of hydrofluoric acid, HF, and its salt, NaF. HF(aq)+H2O(l)⇄H3O+(aq)+F−(aq) A. The purpose of this buffer system is to: 1. maintain [HF] 2. maintain [F−] 3. maintain pH B. The salt of the weak acid is needed to: 1. provide the conjugate base 2. neutralize added H3O+ 3. provide the conjugate acid C. If OH− is added, it is neutralized by: 1. the salt 2. H2O 3. H3O+ D. When H3O+ is added, the equilibrium shifts in the direction of the: 1. reactants 2. products 3. does not change
A. 3 B. 1 and 2 C. 3 D. 1
97. Calculate the volume, in milliliters, of a 0.150 M NaOH solution that will completely neutralize each of the following: (11.7) A. 25.0 mL of a 0.288 M HCl solution B. 10.0 mL of a 0.560 M H2SO4 solution
A. 48.0 mL of NaOH solution B. 74.7 mL of NaOH solution
56. Consider the following acids and their dissociation constants: H2SO3(aq)+H2O(l)⇄H3O+(aq)+HSO −3(aq)Ka=1.2×10−2 HS−(aq)+H2O(l)⇄H3O+(aq)+S2−(aq)Ka=1.3×10−19 A. Which is the stronger acid, H2SO3 or HS−? B. What is the conjugate base of H2SO3? C. Which acid has the weaker conjugate base? D. Which acid has the stronger conjugate base? E. Which acid produces more ions?
A. H2SO3 B. HSO −3 C. H2SO3 D. HS− E. H2SO3
95. Complete and balance each of the following: (11.7) A. H2SO4(aq)+ZnCO3(s) → B. HNO3(aq)+Al(s) →
A. H2SO4(aq) + ZnCO3(s) → CO2(g) + H2O(l)+ZnSO4(aq) B. 6HNO3(aq)+2Al(s) → 3H2(g)+2Al(NO3)3(aq)
76. Write a balanced equation for the neutralization of each of the following: A. H2SO4(aq) and NaOH(aq) B. HCl(aq) and Fe(OH)3(s) C. H2CO3(aq) and Mg(OH)2(s)
A. H2SO4(aq)+2NaOH(aq) → 2H2O(l)+Na2SO4(aq) B. 3HCl(aq)+Fe(OH)3(s) → 3H2O(l)+FeCl3(aq) C. H2CO3(aq)+Mg(OH)2(s) → 2H2O(l)+MgCO3(s)
87. Using Table 11.3, identify the stronger acid in each of the following pairs: (11.3) A. HF or HCN B. H3O+ or H2S C. HNO2 or HC2H3O2 D. H2O or HCO −3
A. HF B. H3O+ C. HNO2 D. HCO −3
94. Using Table 11.3, identify the conjugate acid-base pairs in each of the following equations and whether the equilibrium mixture contains mostly products or mostly reactants: (11.2, 11.3) A. NH3(aq)+HNO3(aq)⇄NH +4(aq)+NO −3(aq) B. HBr(aq)+H2O(l)⇄H3O+(aq)+Br−(aq)
A. HNO3/NO −3 and NH +4/NH3; equilibrium mixture contains mostly products B. HBr/Br− and H3O+/H2O; equilibrium mixture contains mostly products
89. Calculate the [H3O+] and [OH−] for a solution with each of the following pH values: (11.6) A. 3.00 B. 6.2 C. 8.85 D. 11.00
A. [H3O+]=1.0×10−3M;[OH−]=1.0×10−11M B. [H3O+]=6×10−7M;[OH−]=2×10−8M C. [H3O+]=1.4×10−9M;[OH−]=7.1×10−6M D. [H3O+]=1.0×10−11M;[OH−]=1.0×10−3M
96. Determine each of the following for a 0.050 M KOH solution: (11.6, 11.7) A. [H3O+] B. pH C. the balanced equation for the reaction with H2SO4 D. milliliters of KOH solution required to neutralize 40.0 mL of a 0.035 M H2SO4solution
A. [H3O+]=2.0×10−13M B. pH=12.70 C. 2KOH(aq)+H2SO4(aq) → 2H2O(l)+K2SO4(aq) D. 56 mL of the KOH solution
85. Identify each of the following as an acid or a base: (11.1) A. H2SO4 B. RbOH C. Ca(OH)2 D. HI
A. acid B. base C. base D. acid
86. Identify each of the following as an acid, base, or salt, and give its name: (11.1) A. HBrO2 B. CsOH C. Mg(NO3)2 D. HClO4
A. acid, bromous acid B. base, cesium hydroxide C. salt, magnesium nitrate D. acid, perchloric acid
99. A buffer solution is made by dissolving H3PO4 and NaH2PO4 in water. (11.8) A. Write an equation that shows how this buffer neutralizes added acid. B. Write an equation that shows how this buffer neutralizes added base. C. Calculate the pH of this buffer if it contains 0.50 M H3PO4 and 0.20 M H2PO −4.The Ka for H3PO4 is 7.5×10−3.
A. acid: H2PO −4(aq)+H3O+(aq) → H3PO4(aq)+H2O(l) B. base: H3PO4(aq)+OH−(aq) → H2PO −4(aq)+H2O(l) C. pH=1.72
68. State whether each of the following solutions is acidic, basic, or neutral: A. blood plasma, pH 7.38 B. vinegar, pH 2.8 C. coffee, pH 5.52 D. tomatoes, pH 4.2 E. chocolate cake, pH 7.6
A. basic B. acidic C. acidic D. acidic E. basic
88. Determine the pH for each of the following solutions: (11.6) A. [H3O+]=2.0×10−8M B. [H3O+]=5.0×10−2M C. [OH−]=3.5×10−4M D. [OH−]=0.0054M
A. pH=7.70 B. pH=1.30 C. pH=10.54 D. pH=11.73
51. Predict whether each of the following reactions contains mostly reactants or products at equilibrium: A. H2CO3(aq)+H2O(l)⇄HCO −3(aq)+H3O+(aq) B. NH +4(aq)+H2O(l)⇄NH3(aq)+H3O+(aq) C. HNO2(aq)+NH3(aq)⇄NO −2(aq)+NH +4(aq)
A. reactants B. reactants C. products
Acids and Metals: Acids react with certain metals to produce hydrogen gas (H2) and a salt.
Active metals include potassium, sodium, calcium, magnesium, aluminum, zinc, iron, and tin. In these single replacement reactions, the metal ion replaces the hydrogen in the acid.
A solution with a pH of 3 is 10 times more acidic than a solution with pH 4. Explain.
An increase or decrease of one pH unit changes the [H3O+] by a factor of 10. Thus a pH of 3 is 10 times more acidic than a pH of 4.
acid dissociation constant, Ka
As with other dissociation expressions, the molar concentration of the products is divided by the molar concentration of the reactants. -Weak acids have small Kavalues. However, strong acids, which are essentially 100% dissociated, have very large Ka values
82. Which of the following represents a buffer system? Explain. A. NaOH and NaCl B. H2CO3 and NaHCO3 C. HF and KF D. KCl and NaCl
B. and C. are buffer systems. b contains the weak acid H2CO3 and its salt NaHCO3. c contains HF, a weak acid, and its salt, KF.
57. Phosphoric acid dissociates to form hydronium ion and dihydrogen phosphate. Phosphoric acid has a Ka of 7.5×10−3. Write the equation for the reaction and the acid dissociation expression for phosphoric acid.
H3PO4(aq)+H2O(l)⇄H3O+(aq)+H2PO −4(aq)
Why does a neutral solution have a pH of 7.0?
In a neutral solution, the [H3O+] is 1.0×10−7M and the pH is 7.00, which is the negative value of the power of 10.
In an acidic solution, how does the concentration of H3O+ compare to the concentration of OH−?
In an acidic solution, the [H3O+] is greater than the [OH−]
By rearranging the Ka expression to give [H3O+], we can obtain the ratio of the acetic acid/acetate buffer.
In this rearrangement of Ka, the weak acid is in the numerator and the conjugate base in the denominator.
14. What is the numerical value of Kc for the following reaction if the equilibrium mixture contains 0.51 M CO, 0.30 M H2,1.8 M CH4, and 2.0 M H2O? CO(g)+3H2(g)⇄CH4(g)+H2O(g)
Kc= 260
When we alter any of the conditions of a system at equilibrium, the rates of the forward and reverse reactions may no longer be equal. We say that a stress is placed on the equilibrium. Then the system responds by changing the rate of the forward or reverse reaction in the direction that relieves that stress to reestablish equilibrium. We can use?
Le Châtelier's principle, which states that when a system at equilibrium is disturbed, the system will shift in the direction that will reduce that stress.
52. Write an equation for the acid-base reaction between ammonium ion and sulfate ion. Why does the equilibrium mixture contain mostly reactants?
NH+4(aq)+SO2−4(aq)⇄NH3(aq)+HO−4(aq) The equilibrium mixture contains mostly reactants because NH +4 is a weaker acid than HSO −4, and SO 2−4 is a weaker base than NH3.
Effect of a Catalyst on Equilibrium:
Sometimes a catalyst is added to a reaction to speed up a reaction by lowering the activation energy. As a result, the rates of both the forward and reverse reactions increase. The time required to reach equilibrium is shorter, but the same ratios of products and reactants are attained. Therefore, a catalyst speeds up the forward and reverse reactions, but it has no effect on the equilibrium mixture.
Acid-Base Titration:
Suppose we need to find the molarity of a solution of HCl, which has an unknown concentration. We can do this by a laboratory procedure called titration in which we neutralize an acid sample with a known amount of base. In a titration, we place a measured volume of the acid in a flask and add a few drops of an indicator, such as phenolphthalein. An indicator is a compound that dramatically changes color when pH of the solution changes. In an acidic solution, phenolphthalein is colorless. Then we fill a buret with a NaOH solution of known molarity and carefully add NaOH solution to neutralize the acid in the flask (see Figure11.6). We know that neutralization has taken place when the phenolphthalein in the solution changes from colorless to pink. This is called the neutralization endpoint. From the measured volume of the NaOH solution and its molarity, we calculate the number of moles of NaOH, the moles of acid, and use the measured volume of acid to calculate its concentration.
Acids and Hydroxides: Neutralization = is a reaction between a strong or weak acid with a strong base to produce a water and a salt.
The H+ of the acid and the OH− of the base combine to form water. The salt is the combination of the cation from the base and the anion from the acid. We can write the following equation for the neutralization reaction between HCl and NaOH:
Acids React with Carbonates or Bicarbonates: When an acid is added to a carbonate or bicarbonate, the products are carbon dioxide gas, water, and a salt.
The acid reacts with CO 2−3 or HCO −3 to produce carbonic acid, H2CO3, which breaks down rapidly to CO2 and H2O.
2. In the following reaction, what happens to the number of collisions when more Br2(g) molecules are added? H2(g)+Br2(g) → 2HBr(g)
The number of collisions will increase when the number of Br2 molecules is increased.
As a reaction progresses, the rate of the forward reaction decreases and that of the reverse reaction increases. At equilibrium, the rates of the forward and reverse reactions are equal.
When molecules begin to react, the rate of the forward reaction is faster than the rate of the reverse reaction. As reactants are consumed and products accumulate, the rate of the forward reaction decreases, and the rate of the reverse reaction increases.
16. When ethene (C2H4) reacts with water vapor, ethanol (C2H6O) is produced. If an equilibrium mixture contains 0.020 M C2H4 and 0.015 M H2O, what is the equilibrium concentration of C2H6O? At 327 °C, the Kc is 9.0 × 103. C2H4(g) + H2O(g) ⇄ C2H6O(g)
[C2H6O] = 2.7 M
30. The equilibrium constant, Kc, for the decomposition of COCl2 to CO and Cl2 is 0.68. If an equilibrium mixture contains 0.40 M CO and 0.74 M Cl2, what is the molar concentration of COCl2? COCl2(g)⇄CO(g)+Cl2(g)
[COCl2]= 0.44 M
18. The equilibrium constant, Kc, for this reaction is 54. H2(g)+I2(g)⇄2HI(g) If the equilibrium mixture contains 0.015 M I2 and 0.030 M HI, what is the molar concentration of H2?
[H2]= 1.1×10−3 M
67. What are the [H3O+] and [OH−] of cola that has a pH of 3.17?
[H3O+] = 6.8 × 10−4 M [OH−] = 1.5 × 10−11 M
27. The Kc for the following reaction is 5.0 at 100 °C. If an equilibrium mixture contains 0.50 M NO2, what is the molar concentration of N2O4? 2NO2(g)⇄N2O4(g)
[N2O4]= 1.3 M
91. What is the [OH−] in a solution that contains 0.225 g of NaOH in 0.250 L of solution? (11.7)
[OH−]=0.0225M
59. a. What is the [H3O+] of an ammonia cleaning solution with [OH−] = 4.0 × 10−4 M? Is the solution acidic, basic, or neutral? b. The [H3O+] of tomato juice is 6.3 × 10−5 M. What is the [OH−] of the juice? Is the tomato juice acidic, basic, or neutral?
a. [H3O+] = 2.5 × 10−11 M, basic b. [OH−] = 1.6 × 10−10 M, acidic
63. a. What is the pH of bleach with [H3O+] = 4.2 × 10−12 M? b. What is the pH of a borax solution with [H3O+] = 6.1 × 10−10 M?
a. pH = 11.38 b. pH = 9.21
84. Nitrous acid has a Ka of 4.5×10−4. What is the pH of a buffer solution containing 0.10MHNO2 and 0.10MNO −2?
pH=3.35
Why does doubling the reactants increase the rate of reaction?
the rate of a reaction increases when the concentration of the reactants increases. When there are more reacting molecules, more collisions that form products can occur, and the reaction goes faster
47. Does the equilibrium mixture of the following reaction contain mostly reactants or products? HF(aq)+H2O(l)⇄H3O+(aq)+F−(aq)
we see that HF is a weaker acid than H3O+ and that H2O is a weaker base than F−. Thus, the equilibrium mixture contains mostly reactants. HF(aq)Weakeracid+H2O(l)Weakerbase⇄H3O+Strongeracid(aq)+F−(aq)Strongerbase
How would temperature play a role in slowing down the rate of a reaction?
we slow down a reaction by decreasing the temperature.
40. Identify the conjugate acid-base pairs in the following reaction: HBr(aq)+NH3(aq) → Br−(aq)+NH +4(aq)
- In the reaction, HBr loses H+ to form the product Br−. Thus HBr is the acid and Br− is its conjugate base. - In the reaction, NH3 gains H+ to form the product NH +4. Thus, NH3 is the base and NH +4 is its conjugate acid.
What speeds up a reaction by providing an alternative pathway that has a lower energy of activation?
A catalyst
When a reaction proceeds in both a forward and reverse direction, it is said to be?
A reversible reaction -That means there are two reaction rates: one is the rate of the forward reaction, and the other is the rate of the reverse reaction.
What is meant by the term reversible reaction?
A reversible reaction is one in which a forward reaction converts reactants to products, whereas a reverse reaction converts products to reactants.
What is meant by the phrase "A strong acid has a weak conjugate base"?
A strong acid is a good hydrogen ion donor, whereas its conjugate base is a poor hydrogen ion acceptor.
Weak acids are weak electrolytes because they dissociate slightly in water, forming only a small amount of H3O+ ions.
A weak acid has a strong conjugate base, which is why the reverse reaction is more prevalent. Even at high concentrations, weak acids produce low concentrations of H3O+ ions. We write the equation for a weak acid in an aqueous solution with a double arrow to indicate that the forward and reverse reactions are at equilibrium. HC2H3O2(aq)+H2O(l)⇄C2H3O −2(aq)+H3O+(aq)
4. Complete each of the following with change or do not change, faster or slower, equal or not equal: A. Before equilibrium is reached, the concentrations of the reactants and products . B. Initially, reactants placed in a container have a rate of reaction than the rate of reaction of the products. C. At equilibrium, the rate of the forward reaction is to the rate of the reverse reaction.
A. Before equilibrium is reached, the concentrations of the reactants and products change. B. Initially, reactants placed in a container have a faster rate of reaction than the rate of reaction of the products. C. At equilibrium, the rate of the forward reaction is equal to the rate of the reverse reaction.
23. Hydrogen chloride can be made by reacting hydrogen gas and chlorine gas. H2(g)+Cl2(g)+heat⇄2HCl(g) For each of the following changes at equilibrium, indicate whether the equilibrium shifts in the direction of the product, the reactants, or does not change: A. adding more H2(g) B. increasing the temperature C. removing some HCl(g) D. adding a catalyst E. removing some Cl2(g)
A. Equilibrium shifts in the direction of the product. B. Equilibrium shifts in the direction of the product. C. Equilibrium shifts in the direction of the product. D. No shift in equilibrium occurs. E. Equilibrium shifts in the direction of the reactants.
22. In the lower atmosphere, oxygen is converted to ozone (O3) by the energy provided from lightning. 3O2(g)+heat⇄2O3(g) For each of the following changes at equilibrium, indicate whether the equilibrium shifts in the direction of the product, the reactant, or does not change: A. adding more O2(g) B. adding more O3(g) C. increasing the temperature D. increasing the volume of the container E. adding a catalyst
A. Equilibrium shifts in the direction of the product. B. Equilibrium shifts in the direction of the reactant. C. Equilibrium shifts in the direction of the product. D. Equilibrium shifts in the direction of the reactant. E. No shift in equilibrium occurs.
28. According to Le Châtelier's principle, does the equilibrium shift in the direction of the products or the reactants when O2 is added to the equilibrium mixture of each of the following reactions? A. 3O2(g)⇄2O3(g) B. 2CO2(g)⇄2CO(g)+O2(g) C. 2SO2(g)+O2(g)⇄2SO3(g) D. 2SO2(g)+2H2O(g)⇄2H2S(g)+3O2(g)
A. Equilibrium shifts in the direction of the product. B. Equilibrium shifts in the direction of the reactant. C. Equilibrium shifts in the direction of the product. D. Equilibrium shifts in the direction of the reactants.
29. Would decreasing the volume of the container for each of the following reactions cause the equilibrium to shift in the direction of the products, the reactants, or not change? A. 3O2(g)⇄2O3(g) B. 2CO2(g)⇄2CO(g)+O2(g) C. 2SO2(g)+2H2O(g)⇄2H2S(g)+3O2(g)
A. Equilibrium shifts in the direction of the product. B. Equilibrium shifts in the direction of the reactant. C. Equilibrium shifts in the direction of the reactants.
24. For each of the following changes at equilibrium, indicate whether the equilibrium shifts in the direction of the product, the reactants, or does not change: (10.5) C2H4(g)+Cl2(g)⇄C2H4Cl2(g)+heat A. increasing the temperature B. decreasing the volume of the container C. adding a catalyst D. adding more Cl2(g)
A. Equilibrium shifts in the direction of the reactants. B. Equilibrium shifts in the direction of the product. C. There is no change in equilibrium. D. Equilibrium shifts in the direction of the product.
43. Write the formula for the conjugate base for each of the following acids: A. HF B. H2O C. H2PO −3 D. HSO −4 E. HClO2
A. F− B. OH− C. HPO 2−3 D. SO 2−4 E. ClO −2
38. In each of the following equations, identify the reactant that is a Brønsted-Lowry acid and the reactant that is a Brønsted-Lowry base: A. HBr(aq)+H2O(l) → H3O+(aq)+Br−(aq) B. CN−(aq)+H2O(l)⇄HCN(aq)+OH−(aq)
A. HBr, Brønsted-Lowry acid; H2O, Brønsted-Lowry base B. H2O, Brønsted-Lowry acid; CN−, Brønsted-Lowry base
39. A. When HNO3 reacts with water, water acts as a Brønsted-Lowry base. Write the equation for the reaction. B. When hypochlorite ion, ClO−, reacts with water, water acts as a Brønsted-Lowry acid. Write the equation for the reaction.
A. HNO3(aq) + H2O(l) ⇄ H3O+(aq) + NO3−(aq) B. ClO−(aq) + H2O(l) ⇄ HClO(aq) + OH−(aq)
1. Indicate whether each of the following changes will increase, decrease, or have no effect on the rate of reaction: A. increasing the temperature B. decreasing the number of reacting molecules C. adding a catalyst
A. Increase: A higher temperature increases the kinetic energy of the particles, which increases the number of collisions and makes more collisions effective, causing an increase in the rate of reaction. B. Decrease: Decreasing the number of reacting molecules decreases the number of collisions and the rate of the reaction. C. Increase: Adding a catalyst increases the rate of reaction by lowering the activation energy, which increases the number of collisions that form product.
45. Identify the Brønsted-Lowry acid-base pairs in each of the following equations: A. H2CO3(aq)+H2O(l)⇄HCO −3(aq)+H3O+(aq) B. HCN(aq)+NO −2(aq)⇄CN−(aq)+HNO2(aq) C. CHO −2(aq)+HF(aq)⇄HCHO2(aq)+F−(aq)
A. The conjugate acid-base pairs are H2CO3/HCO −3 and H3O+/H2O. B. The conjugate acid-base pairs are HCN/CN− and HNO2/NO −2. C. The conjugate acid-base pairs are HF/F− and HCHO2/CHO −2
41. Identify the conjugate acid-base pairs in each of the following reactions: a. HCN(aq) + SO42−(aq) ⇄ CN−(aq) + HSO4−(aq) b. H2O(l) + S2−(aq) ⇄ OH−(aq) + HS−(aq)
A. The conjugate acid-base pairs are HCN/CN− and HSO4−/SO42−. B. The conjugate acid-base pairs are H2O/OH− and HS−/S2−.
20. Methanol, CH4O, is finding use as a fuel additive. Describe the effect of each of the following changes on the equilibrium mixture for the combustion of methanol: 2CH4O(g)+3O2(g)⇄2CO2(g)+4H2O(g)+1450 kJ A. adding more CO2 B. adding more O2 C. increasing the volume of the container D. increasing the temperature E. adding a catalyst
A. When the concentration of the product CO2 increases, the equilibrium shifts in the direction of the reactants. B. When the concentration of the reactant O2 increases, the equilibrium shifts in the direction of the products. C. When the volume increases, the equilibrium shifts in the direction of the greater number of moles of gas, which is the products. D. When the temperature is increased for an exothermic reaction, the equilibrium shifts in the direction of the reactants. E. When a catalyst is added, there is no change in the equilibrium mixture.
36. Indicate whether each of the following statements is characteristic of an acid, a base, or both: A. has a sour taste B. neutralizes bases C. produces H+ ions in water D. is named barium hydroxide E. is an electrolyte
A. acid B. acid C. acid D. base E. both
34. Identify each of the following as an acid or a base, and give its name: A. H3PO4 B. NaOH Write the formula for each of the following: C. magnesium hydroxide, ingredient in antacids D. hydrobromic acid, used industrially to prepare bromide compounds
A. acid, phosphoric acid B. base, sodium hydroxide C. Mg(OH)2 D. HBr
32. Indicate how each of the following will affect the equilibrium concentration of H2O in the reaction: O2(g)+2HF(g)+76 kcal⇄OF2(g)+H2O(g) A. adding more OF2(g) B. increasing the temperature C. increasing the volume of the container D. decreasing the volume of the container E. adding a catalyst
A. decrease B. increase C. decrease D. increase E. no change
37. Name each of the following acids or bases: A. HCl B. Ca(OH)2 C. HClO4 D. Sr(OH)2 E. H2SO3 F. HBrO2
A. hydrochloric acid B. calcium hydroxide C. perchloric acid D. strontium hydroxide E. sulfurous acid F. bromous acid
33. Indicate if you would increase or decrease the volume of the container to increase the yield of the products in each of the following: A. 2H2S(g)+CH4(g)⇄CS2(g)+4H2(g) B. 2CH4(g)⇄C2H2(g)+3H2(g) C. 2H2(g)+O2(g)⇄2H2O(g)
A. increase B. increase C. decrease
3. How would each of the following change the rate of the reaction shown here? 2SO2(g)+O2(g) → 2SO3(g) A. adding some SO2(g) B. increasing the temperature C. adding a catalyst D. removing some O2(g)
A. increase B. increase C. increase D. decrease
25. For each of the following reactions, indicate if the equilibrium mixture contains mostly products, mostly reactants, or both reactants and products: A. H2(g)+Cl2(g)⇄2HCl(g) Kc=1.3×1034 B. 2NOBr(g)⇄2NO(g)+Br2(g) Kc=2.0 C. 2H2S(g)+CH4(g)⇄CS2(g)+4H2(g) Kc=5.3×10−8
A. mostly products B. both reactants and products C. mostly reactants
17. Indicate whether each of the following equilibrium mixtures contains mostly products or mostly reactants: A. Cl2(g)+NO(g)⇄2NOCl(g)Kc=3.7×108 B. 2H2(g)+S2(g)⇄2H2S(g)Kc=1.1×107 C. 3O2(g)⇄2O3(g)Kc=1.7×10−56
A. mostly products B. mostly products C. mostly reactants
6. Which of the following are at equilibrium? A. The rate of the forward reaction is twice as fast as the rate of the reverse reaction. B. The concentrations of the reactants and the products do not change. C. The rate of the reverse reaction does not change.
A. not at equilibrium B. at equilibrium C. at equilibrium
How does adding more reacting molecules affect the rate of the reaction?
Adding more reacting molecules will increase the rate of the reaction.
Why would an increase in temperature increase the rate of a reaction?
At higher temperatures, the increase in kinetic energy of the reactants makes them move faster and collide more often, and it provides more collisions with the required energy of activation.
If you want to increase the product, should you increase or decrease the volume of the container?
CONCEPT QUESTIterm-46ON: NO ANSWER PROVIDED. (a) A decrease in the volume of the container causes the system to shift in the direction of fewer moles of gas. (b) An increase in the volume of the container causes the system to shift in the direction of more moles of gas. (c) When a reaction has the same number of moles of reactants as products, a volume change does not affect the equilibrium mixture because the concentrations of the reactants and products change in the same way.
Three Conditions Required for a Reaction to Occur are?
Collision: The reactants must collide. Orientation: The reactants must align properly to break and form bonds. Energy: The collision must provide the energy of activation.
Strong acids are examples of strong electrolytes because they donate H+ so easily that their dissociation in water is essentially complete.
For example, when HCl, a strong acid, dissociates in water, H+ is transferred to H2O; the resulting solution contains essentially only the ions H3O+ and Cl−.We consider the reaction of HCl in H2O as going 100% to products. Thus, one mole of a strong acid dissociates in water to yield one mole of H3O+ and one mole of its conjugate base. We write the equation for a strong acid such as HCl with a single arrow. HCl(g)+H2O(l) → H3O+(aq)+Cl−(aq)
48. Does the equilibrium mixture for the reaction of nitric acid and water contain mostly reactants or products?
HNO3(aq) + H2O(l) → H3O+(aq) + NO3−(aq) The equilibrium mixture contains mostly products because HNO3 is a stronger acid than H3O+, and H2O is a stronger base than NO3−.
Effect of Volume Change on Equilibrium:
If there is a change in the volume of a gas mixture at equilibrium, there will also be a change in the concentrations of those gases.Decreasing the volume will increase the concentration of gases, whereas increasing the volume will decrease their concentration. Then the system responds to reestablish equilibrium.
11. Calculate the numerical value of Kc if an equilibrium mixture contains 0.040 M NH3, 0.60 M H2, and 0.20 M N2. 2NH3(g) ⇄ 3H2(g) + N2(g)
Kc = 27
What is the minimum amount of energy required to break the bonds between atoms of the reactants?
The activation energy
Naming Acids:
When an acid dissolves in water to produce a hydrogen ion and a simple nonmetal anion, the prefix hydro is used before the name of the nonmetal, and its ide ending is changed to ic acid. For example: hydrogen chloride (HCl) dissolves in water to form HCl(aq), which is named hydrochloric acid. An exception: is hydrogen cyanide (HCN), which as an acid is named hydrocyanic acid. When an acid contains oxygen, it dissolves in water to produce a hydrogen ion and an oxygen-containing polyatomic anion. The most common form of an oxygen-containing acid has a name that ends with ic acid. The name of its polyatomic anion ends in ate. If the acid contains a polyatomic ion with an ite ending, its name ends in ous acid. When the acid has one oxygen atom less than the common form, the suffix ous is used and the polyatomic ion is named with an ite ending. The halogens in Group 7A (17) can form more than two oxygen-containing acids. For chlorine, the common form is chloric acid, HClO3, which contains the polyatomic ion chlorate, ClO −3. For the acid that contains one more oxygen atom than the common form, the prefix per is used; HClO4 is perchloric acid. When the polyatomic ion in the acid has one oxygen atom less than the common form, the suffix ous is used. Thus, HClO2 is chlorous acid; it contains the chlorite ion, ClO −2. The prefix hypo is used for the acid that has two oxygen atoms less than the common form; HClO is hypochlorous acid.
19. The equilibrium constant, Kc, for the following reaction is 2.0. If the equilibrium mixture contains 2.0 M NO and 1.0 M Br2, what is the molar concentration of NOBr? 2NOBr(g)⇄2NO(g)+Br2(g)
[NOBr]= 1.4 M
5. Complete the following statements with changes or does not change: a. At equilibrium, the concentration of the reactant _____. b. The rate of the forward reaction _____ as the reaction proceeds toward equilibrium.
a. At equilibrium, the concentration of the reactant does not change. b. The rate of the forward reaction changes as the reaction proceeds toward equlibrium.
21. Describe the effect of each of the following changes on the equilibrium mixture for the following reaction: 2HF(g) + Cl2(g) + 357 kJ ⇄ 2HCl(g) + F2(g) a. adding more Cl2 b. decreasing the volume of the container c. decreasing the temperature
a. When the concentration of the reactant Cl2 increases, the equilibrium shifts in the direction of the products. b. There is no change in equilibrium mixture because the moles of reactants are equal to the moles of products. c. When the temperature for an endothermic reaction decreases, the equilibrium shifts in the direction of the reactants.
35. a. Identify as an acid or a base and give the name for H2CO3. b. Write the formula for iron(III) hydroxide.
a. acid, carbonic acid b. Fe(OH)3
Substances that can act as both acids and bases are?
amphoteric -For water, the most common amphoteric substance, the acidic or basic behavior depends on the other reactant. Water donates H+ when it reacts with a stronger base, and it accepts H+ when it reacts with a stronger acid. Another example of an amphoteric substance is bicarbonate (HCO −3). With a base, HCO −3 acts as an acid and donates one H+ to give CO 2−3. However, when HCO −3 reacts with an acid, it acts as a base and accepts one H+ to form H2CO3.
In the process called dissociation:
an acid or a base separates into ions in water. -The strength of an acid is determined by the moles of H3O+ that are produced for each mole of acid that dissolves. The strength of a base is determined by the moles of OH− that are produced for each mole of base that dissolves.
when no further change takes place in the concentrations of the reactants and products, even though the two reactions continue at equal but opposite rates, this refers to?
chemical equilibrium
The equilibrium constant, Kc:
is the numerical value obtained by substituting experimentally measured molar concentrations at equilibrium into the equilibrium expression.
When a reaction has a large equilibrium constant, what does it mean?
it means that the forward reaction produced a large amount of products when equilibrium was reached. Then the equilibrium mixture contains mostly products, which makes the concentrations of the products in the numerator higher than the concentrations of the reactants in the denominator. Thus at equilibrium, this reaction has a large Kc.
The rate (or speed) of reaction is determined by?
measuring the amount of a reactant used up, or the amount of a product formed, in a certain period of time. Rate of reaction= change in concentration of reactant or product / change in time
According to the Brønsted-Lowry theory, a conjugate acid-base pair consists of?
molecules or ions related by the loss of one H+ by an acid, and the gain of one H+ by a base. Every acid-base reaction contains two conjugate acid-base pairs because an H+ is transferred in both the forward and reverse directions.
When a reaction has a small equilibrium constant, what does it mean?
the equilibrium mixture contains a high concentration of reactants and a low concentration of products. Then the equilibrium expression has a small number in the numerator and a large number in the denominator. Thus at equilibrium, this reaction has a small Kc.
What are the Factors that Affect the Rate of a Reaction?
the rate is affected by changes in temperature, changes in the concentration of the reactants, and the addition of catalysts.
When a catalyst lowers the activation energy?
the reaction occurs at a faster rate. - When activation energy is lowered, more collisions provide sufficient energy for reactants to form product. During a reaction, a catalyst is not changed or consumed.
