EXAM Review #2
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CHM 142
#1
Given the reaction below, which of the following would cause an increase in the
concentration of reactant(s)?
2HF(g) ⇋ F2 (g) + H2 (g)
ΔH = -12.0 kJ/mol
I.
II.
III.
IV.
removal of H2
addition of HF
Increasing the temp of the reaction
An increase in the volume of the container
A.
B.
C.
D.
E.
I only
II only
III only
IV only
III and IV
#1 ANSWER
Given the reaction below, which of the following would cause an increase in the
concentration of reactant(s)?
2HF(g) ⇋ F2 (g) + H2 (g) +HEAT ΔH = -12.0 kJ/mol
I.
II.
III.
IV.
removal of H2 remove product → shift to products
addition of HF add reactant → shift to products
Increasing the temp of the reaction add product → shift to reactants
An increase in the volume of the container no effect (same # moles on each side)
A.
B.
C.
D.
E.
I only
II only
III only
IV only
III and IV
“The System always kicks back”
1. Con󰇹󰈩󰈞t󰈸󰇽󰉄i󰈡n
Add reactants → shift to PRODUCTS
Add products → shift to REACTANTS
Remove products → shift to
PRODUCTS
Remove reactants → shift to
= Le Chatelier's principle
2. Pre󰈻󰈼󰉉r󰇵/Vol󰉉󰈚󰇵
3. Tem󰈥󰈩󰈹󰇽tu󰈸󰈩
Decrease volume (increase
pressure) → shift to THE SIDE WITH
Temp increase → shift to PRODUCTS
(endo) or to REACTANTS (exo)
Increase volume
(decrease pressure) → shift to THE
Temp decrease → shift to
REACTANTS (endo) or PRODUCTS (exo)
THE FEWER MOLES
SIDE WITH THE MORE MOLES
REACTANTS
*Explanations in speaker notes below*
#2
The value of K for the formation of H2 (g) + Cl2 (g) ⇋ 2HCl (g) is 2.13
Determine the reaction quotient, Q, and which way the reaction will shift if
H2= 15 mol, Cl2= 4 mol, and HCl = 9 mol in a 1.00 L vessel at 10°C.
A.
B.
C.
D.
E.
Q = 1.35, shift to form more reactants
Q = 1.35, shift to form more products
Q = 0.15, shift to form more reactants
Q = 0.15, shift to form more products
Can not be determined.
#2 ANSWER
Q = Keq at equilibrium!!!
The value of K for the formation of H2 (g) + Cl2 (g) ⇋ 2HCl (g) is 2.13
Determine the reaction quotient, Q, and which way the reaction will shift if
H2= 15 mol, Cl2= 4 mol, and HCl = 9 mol in a 1.00 L vessel at 10°C.
A.
B.
C.
D.
E.
Q = 1.35, shift to form more reactants
Q = 1.35, shift to form more products
Q = 0.15, shift to form more reactants
Q = 0.15, shift to form more products
Can not be determined.
#3
An aqueous solution is considered to be acidic if:
The hydroxide ion concentration is 10-6 M.
The hydrogen ion concentration is 10-8 M.
The hydroxide and hydrogen ion concentration are equal.
They hydroxide ion concentration is greater than the hydrogen ion
concentration.
E. The hydroxide ion concentration is 10-10 M.
A.
B.
C.
D.
#3 ANSWER
An aqueous solution is considered to be acidic if:
The hydroxide ion concentration is 10-6 M.
The hydrogen ion concentration is 10-8 M.
The hydroxide and hydrogen ion concentration are equal.
They hydroxide ion concentration is greater than the hydrogen ion
concentration.
E. The hydroxide ion concentration is 10-10 M.
A.
B.
C.
D.
#4
When [H+] = 4.0 × 10-9 M in water at 25°C, then pOH = ________
A.
B.
C.
D.
E.
8.40
-8.40
7.00
5.60
- 6.1
#4 ANSWER
When [H+] = 4.0 × 10-9 M in water at 25°C, then pOH = ________
A.
B.
C.
D.
E.
8.40
-8.40
7.00
5.60
- 6.1
#5
Use the following acid ionization constants to identify the correct
decreasing order of conjugate base strengths (strongest to weakest).
HF Ka = 7.2×10-4
HNO2 Ka = 4.5×10-4
HCN Ka = 6.2×10-10
A.
B.
C.
D.
E.
CN- > NO2- > FF- > NO2- > CNNO2- > F- > CNNO2- > CN- > FF- > CN- > NO2-
#5 ANSWER
Use the following acid ionization constants to identify the correct
decreasing order of conjugate base strengths (strongest to weakest).
HF Ka = 7.2×10-4 highest Ka = strongest acid = weakest conjugate base
HNO2 Ka = 4.5×10-4
HCN Ka = 6.2×10-10 smallest Ka = weakests acid = strongest conjugate base
A.
B.
C.
D.
E.
CN- > NO2- > FF- > NO2- > CNNO2- > F- > CNNO2- > CN- > FF- > CN- > NO2-
☆ The larger the Ka, the STRONGER the acid =
the WEAKER the conjugate base
☆ The smaller the Ka, the WEAKER the acid =
the STRONGER the conjugate base
#6
Which of the following is NOT a conjugate acid-base pair?
A.
B.
C.
D.
E.
NH3 and NH2HNO3 and HNO2
HI and IH2PO4- and HPO42H2O and OH-
#6 ANSWER
Which of the following is NOT a conjugate acid-base pair?
A.
B.
C.
D.
E.
NH3 and NH2HNO3 and HNO2
HI and IH2PO4- and HPO42H2O and OH-
#7
Calculate the pH of a solution that initially contains 2.00 M of a weak acid,
nitrous acid (HNO2). The Ka for nitrous acid is 4.5 × 10-4.
HNO2 ⇆ H+ + NO2A.
B.
C.
D.
E.
2.5
1.5
2.7
2.3
3.4
#7 ANSWER
Calculate the pH of a solution that initially contains 2.00 M of a weak acid,
nitrous acid (HNO2). The Ka for nitrous acid is 4.5 × 10-4.
HNO2 ⇆ H+ + NO2A.
B.
C.
D.
E.
2.5
1.5
2.7
2.3
3.4
Use approximation (get rid
of the X in the denominator)
because x/[HA]i ≤ 5%
In this case, (0.03)/(2.00M)
x 100 = 1.5% ≤ 5%
#8
For the following reaction:
HNO3 + NH3 ⇌ NH4+ + NO3Which compound is the strongest base and to which side does
equilibrium lie?
A.
B.
C.
D.
E.
NH3 is the strongest base and equilibrium lies to the left
NH4+ is the strongest base and equilibrium lies to the right
NO3- is the strongest base and equilibrium lies to the right
NH3 is the strongest base and equilibrium lies to the right
NO3- is the strongest base and equilibrium lies to the left
#8 Answer
For the following reaction:
HNO3 + NH3 ⇌ NH4+ + NO3Which compound is the strongest base and to which side does
equilibrium lie?
A.
B.
C.
D.
E.
NH3 is the strongest base and equilibrium lies to the left
NH4+ is the strongest base and equilibrium lies to the right
NO3- is the strongest base and equilibrium lies to the right
NH3 is the strongest base and equilibrium lies to the right
NO3- is the strongest base and equilibrium lies to the left
#9
Which of the following will have the highest pH?
A.
B.
C.
D.
E.
0.5 M KOH
0.5 M Ca(OH)2
1.0 M KOH
0.75 M Ca(OH)2
0.75 M KOH
#9 Answer
Which of the following will have the highest pH?
A.
B.
C.
D.
E.
0.5 M KOH
0.5 M Ca(OH)2
1.0 M KOH
0.75 M Ca(OH)2
0.75 M KOH
#10
The Keq for the reaction 2NO + O2 ⇌ 2NO2 is 5.4 x 1013 at 480°C.
What is Keq for the reaction 4NO2 ⇌ 4NO + 2O2 ?
A.
B.
C.
D.
E.
3.4 x 10-28
3.7 x 10-14
2.9 x 1027
1.8 x 10-14
1.1 x 1014
#10 Answer
The Keq for the reaction 2NO + O2 ⇌ 2NO2 is 5.4 x 1013 at 480°C.
What is Keq for the reaction 4NO2 ⇌ 4NO + 2O2 ?
A.
B.
C.
D.
E.
3.4 x 10-28
3.7 x 10-14
2.9 x 1027
1.8 x 10-14
1.1 x 1014
#11
What is the percent ionization of a 0.125-M solution of nitrous acid
with a pH of 2.09.
A.
B.
C.
D.
E.
81%
21%
6.5%
0.39%
13%
#11 Answer
What is the percent ionization of a 0.125-M solution of nitrous acid
with a pH of 2.09.
A.
B.
C.
D.
E.
81%
21%
6.5%
0.39%
13%
#12
For the reaction N2O4 ⇌ 2NO2 , Keq= 4.64 x 10-3. If the initial
concentration of N2O4 is 0.0367 M what is the concentration of
both gases at equilibrium.
A.
B.
C.
D.
E.
[N2O4]= 0.0307 M ; [NO2]= 0.0119 M
[N2O4]= 0.0367 M ; [NO2]= 0.00596 M
[N2O4]= 0.0119 M ; [NO2]= 0.0307 M
[N2O4]= 0.00596 M ; [NO2]= 0.0367 M
[N2O4]= 0.0307 M ; [NO2]= 0.00596 M
#12 Answer
For the reaction N2O4 ⇌ 2NO2 , Keq= 4.64 x 10-3. If the initial
concentration of N2O4 is 0.0367 M what is the concentration of
both gases at equilibrium.
A.
B.
C.
D.
E.
[N2O4]= 0.0307 M ; [NO2]= 0.0119 M
[N2O4]= 0.0367 M ; [NO2]= 0.00596 M
[N2O4]= 0.0119 M ; [NO2]= 0.0307 M
[N2O4]= 0.00596 M ; [NO2]= 0.0367 M
[N2O4]= 0.0307 M ; [NO2]= 0.00596 M
4
#13
Which of the following is false about water?
A.
B.
C.
D.
E.
Water can either donate or accept a proton.
The autoionization of water equation is H2O + H2O ⇌ H3O+ + OHThe ion-product constant of water (Kw) is 1.0 x 10-7
Kw = [H+][OH-]
All of the above are true
#13 Answer
Which of the following is false about water?
A.
B.
C.
D.
E.
Water can either donate or accept a proton.
The autoionization of water equation is H2O + H2O ⇌ H3O+ + OHThe ion-product constant of water (Kw) is 1.0 x 10-7
Kw = [H+][OH-]
All of the above are true
#14
At equilibrium of a certain reaction, the products are greatly
favored. Which of the following are true.
A.
B.
C.
D.
E.
K << 1
K >>1
Q <<1
K=Q
B and D are true
#14 Answer
At equilibrium of a certain reaction, the products are greatly
favored. Which of the following are true.
A.
B.
C.
D.
E.
K << 1
K >>1
Q <<1
K=Q
B and D are true
#15
When the reversible reaction N2(g) + O2(g) <--> 2NO(g) has
reached a state of equilibrium,
A. No further reactions occur
B. The total moles of products must equal the remaining moles of
reactant
C. The addition of a catalyst will cause formation of more NO
D. The concentration of each substance in the system will be
constant
#15 ANSWER
When the reversible reaction N2(g) + O2(g) <--> 2NO(g) has
reached a state of equilibrium,
A. No further reactions occur forward/reverse occurs simultaneously
B. The total moles of products must equal the remaining moles of
reactant equilibrium may favor more reactants/products
C. The addition of a catalyst will cause formation of more NO
catalyst lowers activation energy but doesn’t affect concentrations
D. The concentration of each substance in the system will be
constant
#16
In which of the following equilibria is HPO42- acting as a
Bronsted-Lowry base?
#16 ANSWER
In which of the following equilibria is HPO42- acting as a
Bronsted-Lowry base?
#17
Which of the following salts will not form a neutral solution in
water?
A. NaClO4
B. NaNO3
C. NaF
D. NaI
E. NaCl
#17 ANSWER
Which of the following salts will not form a neutral solution in
water?
A. NaClO4
B. NaNO3
C. NaF
D. NaI
E. NaCl
#18
The reaction quotient, Qc, for a reaction has a value of 75 while the
equilibrium constant, Kc, has a value of 195. Which of the following
statements is accurate?
A. The reaction must proceed to the left
B. The reaction must proceed to the right
C. The concentration of the products will be much smaller than the
concentration of the reactions at equilibrium
D. The concentration of the products will be = to the concentration of
the reactants
#18 ANSWER
The reaction quotient, Qc, for a reaction has a value of 75 while the
equilibrium constant, Kc, has a value of 195. Which of the following
statements is accurate?
A. The reaction must proceed to the left
B. The reaction must proceed to the right
C. The concentration of the products will be much smaller than the
concentration of the reactions at equilibrium
D. The concentration of the products will be = to the concentration of
the reactants
#19
Rank the following from strongest to weakest acid:
HNO₂
H2SO₄
HPO₄⁻²
A.
B.
C.
D.
E.
H₂SO₄ → HNO₂ → HPO₄⁻²
HPO₄⁻² → H₂SO₄ → HNO₂
HNO₂ → H2SO₄ → HPO₄⁻²
H2SO₄ → HPO₄⁻² → HNO₂
HPO₄⁻² → HNO₂ → H₂SO₄
#19 ANSWER
Rank the following from strongest to weakest acid:
HNO₂
H2SO₄
HPO₄⁻²
A.
B.
C.
D.
E.
H₂SO₄ → HNO₂ → HPO₄⁻²
HPO₄⁻² → H₂SO₄ → HNO₂
HNO₂ → H2SO₄ → HPO₄⁻²
H2SO₄ → HPO₄⁻² → HNO₂
HPO₄⁻² → HNO₂ → H₂SO₄
#20
What is the pH of a 0.20 M solution of ammonia? The Kb value for
ammonia is 1.8×10–5
A.
B.
C.
D.
E.
9.56
9.26
4.74
11.28
2.72
#20 ANSWER
What is the pH of a 0.20 M solution of ammonia? The Kb value for
ammonia is 1.8 × 10–5
A.
B.
C.
D.
E.
9.56
9.26
4.74
11.28
2.72
Goodluck!!
You got this!
EXTRA practice on
the following slides :)
Extra #21
Which of the following are true of catalyst?
I.
II.
III.
IV.
They enhance the rate of forward and reverse reactions
They alter the equilibrium constant, K
They do not change the position of equilibrium
They so not affect how quickly equilibrium is reached
A.
B.
C.
D.
E.
I and II
II only
III and I
IV only
III and II
Extra #21 ANSWER
Which of the following are true of catalyst?
I.
II.
III.
IV.
They enhance the rate of forward and reverse reactions TRUE
They alter the equilibrium constant, K
FALSE (do not alter K)
They do not change the position of equilibrium
TRUE
They so not affect how quickly equilibrium is reached FALSE (they affect it)
A.
B.
C.
D.
E.
I and II
II only
III and I
IV only
III and II
Extra #22
Which of the following is false?
I.
II.
III.
IV.
V.
Strong acids/bases fully dissociate
Weak do notably dissociate
The first hydrogen lost in a polyprotic acid is the most acidic
Strong acids/bases represent an equilibrium condition, they have double arrows in their equation
Weak bases generally don’t contain hydroxide
A.
B.
C.
D.
E.
I and II
III only
IV only
V only
IV and V
Extra #22 ANSWER
Which of the following is false?
I.
II.
III.
IV.
V.
Strong acids/bases fully dissociate
TRUE
Weak do notably dissociate
TRUE
The first hydrogen lost in a polyprotic acid is the most acidic
TRUE
Strong acids/bases represent an equilibrium condition, they have double arrows in their equation FALSE
Weak bases generally don’t contain hydroxide
TRUE
A.
B.
C.
D.
E.
I and II
III only
IV only
V only
IV and V
Strong acids/bases are not
represented by “⇋” because
they are not an equilibrium
condition. They dissociate
completely and do not require
an ICE table!
Extra #23
What property will the salt AlBr3 have in water?
A.
B.
C.
D.
E.
Neutral
Acidic
Basic
Amphiprotic
Can not be determined
Extra #23 ANSWER
What property will the salt AlBr3 have in water?
A.
B.
C.
D.
E.
Neutral
Acidic
Basic
Amphiprotic
Can not be determined
1)
2)
3)
Split the salt up into its two ions
a) Al3+
b) BrDetermine the property of each ion
a) Al3+ → cation → transition metal → acts acidic
b) Br- → anion →comes from strong acid → acts
neutral
Compare acidities
a) If acidic and neutral, the acidic will outweigh the
neutral
Extra #24
What is the pH of a 0.400 M HCl solution?
A.
B.
C.
D.
E.
7.1
13.6
3.0
0.222
0.398
Extra #24 ANSWER
What is the pH of a 0.400 M HCl solution?
A.
B.
C.
D.
E.
7.1
13.6
3.0
0.222
0.398
Extra #25
An equilibrium that strongly favors products has ____
A.
B.
C.
D.
E.
A value of K << 1
A value of K >> 1
A value of Q >> 1
A value of Q << 1
K=Q
Extra #25 ANSWER
An equilibrium that strongly favors products has ____
A.
B.
C.
D.
E.
A value of K << 1
A value of K >> 1
A value of Q >> 1
A value of Q << 1
K=Q
K = products/reactants
If products are big, then the
K value is very big!
Extra #26
What is the Kb for the benzoate ion, given that the Ka for benzoic acid is
6.46 x 10-5?
A.
B.
C.
D.
E.
1.55 x 10-10
6.46 x 109
6.46 x 10-19
3.52 x 10-9
7.43 x 10-5
Extra #26 ANSWER
What is the Kb for the benzoate ion, given that the Ka for benzoic acid is
6.46 x 10-5?
A.
B.
C.
D.
E.
1.55 x 10-10
6.46 x 109
6.46 x 10-19
3.52 x 10-9
7.43 x 10-5
Extra #27
Which statement, A–D, is not correct? If all are correct, respond E. Pure
water at 25°C has __________
A.
B.
C.
D.
E.
Kw = 1.0 × 10–14.
pOH = 7.
[H3O+] = [OH–]
pH = 7.
A–D are all correct.
Extra #27 ANSWER
Which statement, A–D, is not correct? If all are correct, respond E. Pure
water at 25°C has __________
A.
B.
C.
D.
E.
Kw = 1.0 × 10–14.
pOH = 7.
[H3O+] = [OH–]
pH = 7.
A–D are all correct.
pOH = pH for pure
water! They add up to
be 14.
Kw is the
autoionization
constant for water.
[H3O+] has to be = to
[OH-] in order for the
pH and pOH to be 7
Extra #28
In the following reaction in aqueous solution, the acid reactant is ________
and its conjugate base product is ________.
CH3NH2 + HSO4- ⟷ CH3NH3+ + SO42A.
B.
C.
D.
E.
CH3NH2; SO42HSO4-; H3O+
CH3NH2; CH3NH3+
HSO4-; CH3NH3+
HSO4-; SO42-
Extra #28 ANSWER
In the following reaction in aqueous solution, the acid reactant is ________
and its conjugate base product is ________.
CH3NH2 + HSO4- ⟷ CH3NH3+ + SO42A.
B.
C.
D.
E.
CH3NH2; SO42HSO4-; H3O+
CH3NH2; CH3NH3+
HSO4-; CH3NH3+
HSO4-; SO42-
CH3NH2 + HSO4- ⟷ CH3NH3+ + SO42Base
Acid
C.A.
C.B.
Extra #29
The equilibrium constant for the formation of hydrogen iodide from
hydrogen and iodine is 45.0 at a certain temperature.
H2(g) + I2(s) ⟷ 2HI(g)
Which of the following is true regarding this equilibrium?
I. The reaction is product-favored.
A. II and III
II. The reaction is reactant-favored.
B. II and IV
III. Equilibrium lies to the right.
C. I and IV
IV. Equilibrium lies to the left.
D. I and III
E. None are true, as the concentrations
of reactants and products are
essentially the same
Extra #29 ANSWER
The equilibrium constant for the formation of hydrogen iodide from
hydrogen and iodine is 45.0 at a certain temperature.
H2(g) + I2(s) ⟷ 2HI(g)
Which of the following is true regarding this equilibrium?
I. The reaction is product-favored.
A. II and III
II. The reaction is reactant-favored.
B. II and IV
III. Equilibrium lies to the right.
C. I and IV
IV. Equilibrium lies to the left.
D. I and III
(Explanation in speaker notes)
E. None are true, as the concentrations
of reactants and products are
essentially the same
Extra #30
Write the equilibrium expression, Keq, for the reaction below:
SnO2(s) + 2CO(g) ↔ Sn(s) + 2CO2(g)
A. K = [Sn][CO2] / [SnO2][CO]
B. K = [Sn][CO2]2 / [SnO2][CO]2
C. K = [CO]2 / [CO2]2
D. K = [CO2]2 / [CO]2
E. K = [SnO2][CO] / [Sn][CO2]
Extra #30 ANSWER
Write the equilibrium expression, Keq, for the reaction below:
SnO2(s) + 2CO(g) ↔ Sn(s) + 2CO2(g)
A. K = [Sn][CO2] / [SnO2][CO]
B. K = [Sn][CO2]2 / [SnO2][CO]2
C. K = [CO]2 / [CO2]2
D. K = [CO2]2 / [CO]2
E. K = [SnO2][CO] / [Sn][CO2]
Extra #31
Butyric acid is responsible for the odor in rancid butter. A solution of 0.25
M butyric acid has a pH of 2.71. What is the Ka for the acid?
A.
B.
C.
D.
E.
1.5 x 10-5
0.26
2.4 x 10-2
7.8 x 10-3
none of the above
Extra #31 ANSWER
Butyric acid is responsible for the odor in rancid butter. A solution of 0.25
M butyric acid has a pH of 2.71. What is the Ka for the acid?
A.
B.
C.
D.
E.
1.5 x 10-5
0.26
2.4 x 10-2
7.8 x 10-3
none of the above
Extra #32
The equilibrium constant for the reaction is 17.5:
What is the value of the equilibrium constant for the following reaction?
A.
B.
C.
D.
E.
1.87 x 10-4
5.71 x 10-2
17.5
306
5360
Extra #32 ANSWER
The equilibrium constant for the reaction is 17.5:
What is the value of the equilibrium constant for the following reaction?
A.
B.
C.
D.
E.
1.87 x 10-4
5.71 x 10-2
17.5
306
5360
Extra #33
Kc=.105 for the following reaction at 472℃, find Kp.
N2+3H2↔2NH3
A.
B.
C.
D.
E.
1.17E-6
2.81E-5
7.00E-5
393
199
Extra #33 ANSWER
Kc=.105 for the following reaction at 472℃, find Kp.
N2+3H2↔2NH3
A.
B.
C.
D.
E.
1.17E-6
2.81E-5
7.00E-5
393
199
Extra #34
In the following reaction in aqueous solution, the acid reactant is
________ and its conjugate base product is ________.
CH3NH2 + HSO4- ⟷ CH3NH3+ + SO42A.
B.
C.
D.
E.
CH3NH2; SO42HSO4-; H3O+
CH3NH2; CH3NH3+
HSO4-; CH3NH3+
HSO4-; SO42-
Extra #34 ANSWER
In the following reaction in aqueous solution, the acid reactant is
________ and its conjugate base product is ________.
CH3NH2 + HSO4- ⟷ CH3NH3+ + SO42A.
B.
C.
D.
E.
CH3NH2; SO42HSO4-; H3O+
CH3NH2; CH3NH3+
HSO4-; CH3NH3+
HSO4-; SO42-
Extra #35
Given that kf= 3.09E-2 for the following reaction, find Kr
2A→B where [A]= .15M and [B]=.90M at equilibrium
A.
B.
C.
D.
E.
.0052
7.7E-4
.0057
1.24
6.37
Extra #35 ANSWER
Given that kf= 3.09E-2 for the following reaction, find Kr
2A→B where [A]= .15M and [B]=.90M at equilibrium
A.
B.
C.
D.
E.
.0052
7.7E-4
.0057
1.24
6.37
Extra!!
1) Conceptual Questions. Acids, Bases, and Conjugates,
Miscellaneous
2) Recognizing Strong versus Weak Acids; Recognizing Basic
versus Nonbasic
3) pH Calculations; Relationships between pH and pOH
4) Ka: Sense + Calculations. Using Ka or pKa to Calculate [H+]
and/or pH; using pH to calculate Ka or pKa
5) Kb and pKb, Base Strength, and using Kb or pKb to Calculate
[OH-], pOH, pH, and/or [H+]
6) Recognizing Acid/Base Properties when Ionics are Dissolved
in Water