Name: ________________________ Class: ___________________ Date: __________
SCH4U Chapter 8 review
Multiple Choice
Identify the choice that best completes the statement or answers the question.
____
1. Which statement does not describe a characteristic of acidic solutions?
A) They react with metals to form hydrogen gas.
B) They turn phenolphthalein pink.
C) They do not react with fatty acids.
D) They are made from non-metal oxides.
E) They conduct electricity.
____
2. Which statement does not describe a characteristic of basic solutions?
A) They turn litmus paper blue.
B) They react with ammonium chloride to produce ammonia gas.
C) They react with carbonates to form carbon dioxide gas.
D) They feel slippery.
E) They taste bitter.
____
3. What is the Arrhenius definition of an acid?
A) a substance that donates protons
B) a substance that accepts protons
C) a substance that dissolves in water to form OH− ions
D) a substance that dissolves in water to form H+ ions
E) none of the above
____
4. What is the Brønstead-Lowry definition of a base?
A) a substance that donates protons
B) a substance that accepts protons
C) a substance that dissolves in water to form OH− ions
D) a substance that dissolves in water to form H+ ions
E) none of the above
____
5. What is the formula of a hydronium ion?
A) H3O+(aq)
B) OH−(aq)
C) H+(aq)
D) H2O+(aq)
E) H4O2+
____
6. Which compound is a strong acid?
A) HClO(aq)
B) HIO3(aq)
C) HClO4(aq)
D) HC2H3O2(aq)
E) NaOH
____
7. Which compound is not a strong base?
A) ammonium hydroxide
B) sodium hydroxide
C) barium hydroxide
D) magnesium hydroxide
E) cesium hydroxide
____
8. Which acid or base is not a good electrolyte?
A) H2SO4(aq)
B) KOH(aq)
C) HBr(aq)
D) NH2CONH2(aq)
E) All acids and bases are good electrolytes.
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ID: A
Name: ________________________
____
ID: A
9. What is the conjugate acid of H2PO4−(aq)?
A) H3O+(aq)
B) OH−(aq)
C) H3PO4(aq)
D) HPO42−(aq)
E) PO43−(aq)
____ 10. What is the conjugate base of HSO4−(aq)?
A) H3O+(aq)
B) OH−(aq)
C) H2SO4(aq)
D) SO42−−(aq)
E) This compound does not have a conjugate base.
____ 11. Which term describes a substance that acts as a proton donor and a proton acceptor?
A) amphoteric
B) monoprotic
C) polyprotic
D) buffer
E) acid-base
____ 12. What is the most important factor for determining the strength of binary acids across a period in the periodic
table?
A) strength of the bond
B) number of oxygen atoms
C) electronegativity
D) number of hydrogen atoms
E) size of the nucleus
____ 13. Which equation below is incorrect.
A) KaKb = Kw
B) Kw = [OH-][H30+]
C) Kw = [OH-]+[H30+]
D) pH=-log[H30+]
E) [H30+] = 10-pH
____ 14. Based on your knowledge of the relative strength of oxoacids, which acid is the strongest acid?
A) HIO(aq)
B) HIO2(aq)
C) HIO3(aq)
D) HIO4(aq)
E) These acids are all the same strength.
____ 15. What is the concentration of hydroxide ions in a solution of 0.350 mol/L HI(aq)?
A) 0.350 mol/L
B) 0.175 mol/L
C) 2.86 × 10−14 mol/L
D) 0.650 mol/L
E) 1.30 mol/L
____ 16. A solution contains 6.3 × 10−5 hydronium ions. What is the pH of the solution?
A) 4.20
B) 5.00
C) 6.30
D) 9.80
E) 8.10
____ 17. A solution has a pOH of 5.23. What is the concentration of hydroxide ions in the solution?
A) 1.0 × 10−14
B) 1.7 × 10−9
C) 1.0 × 10−7
D) 5.9 × 10−6
E) none of the above
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Name: ________________________
ID: A
____ 18. A solution has a pH of 4.65. What is the concentration of hydroxide ions in the solution?
A) 1.0 × 10−14
B) 4.5 × 10−10
C) 1.0 × 10−7
D) 2.2 × 10−5
E) none of the above
____ 19. Identify the weakest acid.
A) HCN
Ka = 6.2 × 10−10
B) HCOOH
Ka = 1.8 × 10−4
C) HNO2
Ka = 7.2 × 10−4
D) HF
Ka = 6.6 × 10−4
E) All acids are the same strength, as long as they have a dissociable hydrogen ion.
Short Answer
For the following questions, write the most appropriate answer in the space provided.
20. Label the conjugate acid-base pairs in each reaction.
a) CO32−(aq) + H2O(l) ⇔ HCO3−(aq) + OH−(aq)
b) H2SO4(aq) + H2O(l) ⇔ H3O+(aq) + HSO4−(aq)
CO32−(aq)
base 1
H2SO4(aq)
acid 1
a)
b)
+
+
H2O(l)
acid 2
H2O(l)
base 2
⇔
⇔
HCO3−(aq)
conjugate acid 1
H3O+(aq)
conjugate acid 2
OH−(aq)
conjugate base 2
HSO4−(aq)
conjugate base 1
+
+
Problem
Critical Thinking
For the following questions, write the answer in the space provided. Use complete sentences in your answer.
If the question requires mathematical calculations, show all of your work. Write a final statement that gives
your solution.
21. A solution of hydrocyanic acid has an initial concentration of 5.0 × 10−3 mol/L. What are the concentrations
of the ions at equilibrium, if Ka = 4.9 × 10−10.
Concentration (mol/L)
Initial
Change
Final
Ka =
HCN(aq)
5.0 × 10−3
−x
(5.0 × 10−3) − x
+ H2O(l)
⇔
H3O+(aq)
0.0
x
x
+ CN−(aq)
0.0
x
x
[H 3 O + ][CN − ]
[HCN]
x2
=
(5.0 × 10 −3 ) − x
= 4.9 × 10−10
Since x is very small, use an approximation.
x2
= 4.9 × 10–10
5.0 × 10 −3
x2 = 2.45 × 10–12
x = 1.6 × 10–6
The equilibrium concentrations of H3O+(aq) and CN−(aq) are 1.6 × 10−6 mol/L. The equilibrium
concentration of HCN(aq) is 5.0 × 10−3 mol/L.
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Name: ________________________
ID: A
22. Lactic acid, C3H6O3, builds up in human muscles during anaerobic exercise. If the initial concentration of
lactic acid is 0.12 mol/L and the pH is 2.39, what is Ka for lactic acid?
How to look at this. The pH is telling you the concentration of the H3O+(aq) and C3H5O3−(aq)
pH =
[H3O+] =
=
=
–log[H3O+(aq)]
10–pH
10–2.39
4.1 × 10–3 mol/L
Concentration (mol/L)
Initial
Change
Final
Ka =
C3H6O3(aq)
0.12
−4.1 × 10−3
0.116
+
H2O(l)
⇔ H3O+(aq)
0.0
4.1 × 10−3
4.1 × 10−3
C3H5O3−(aq)
0.0
4.1 × 10−3
4.1 × 10−3
+
[H 3 O + ][C 3 H 5 O 3 − ]
[C 3 H 6 O 3 ]
(4.1 × 10−3 )(4.1 × 10 −3 )
=
0.116
= 1.45 × 10−4
Therefore, Ka is 1.45 × 10−4.
23. Calculate the pH of a solution of H2CO3, with an initial concentration of 0.010 mol/L. Ka for H2CO3 is 4.2 ×
10−7, and Ka for HCO3− is 4.8 × 10−11.
Since Ka for HCO3− is so small, the amount of hydrondium ion produced by this step is negligible. Therefore,
only the first ionization step needs to be considered when determining the pH of the solution.
Concentration (mol/L)
Initial
Change
Final
Ka =
H2CO3(aq)
0.010
−x
0.010 − x
+
H2O(l)
⇔
[H 3 O + ][HCO 3 − ]
[H 2 CO 3 ]
x2
=
0.010 − x
= 4.2 × 10−7
Since x is very small, use an approximation.
x2
= 4.2 × 107
0.010
x2 = 4.2 × 109
x = 6.5 × 105
The equilibrium concentration of H3O+(aq) is 6.5× 10−5 mol/L.
pH = −log[H3O+]
= −log(6.5 × 10−5)
= 4.19
The pH of the solution is 4.19.
4
H3O+(aq)
0.0
x
x
+
HCO3−(aq)
0.0
x
x
Name: ________________________
ID: A
24. A 30.0 mL solution of a diprotic acid called oxalic acid, C2H2O4, is completely neutralized by titration with
56 mL of a 0.050 mol/L solution of potassium hydroxide. What is the concentration of the oxalic acid?
C2H2O4(aq) + 2KOH(aq) → 2H2O(l) + K2C2O4(aq)
Moles KOH that was used to
=V×C
= (0.056 L)(0.050 mol/L)
= 0.0028 mol
Moles C2H2O4 = Moles KOH ×
= 0.0028 mol KOH ×
1 mol C 2 H 2 O 4
(note 1 to 2 ratio for acid to base)
2 mol KOH
1 mol C 2 H 2 O 4
2 mol KOH
= 0.0014 mol (could look at it as half the amt of acid will be neutralized or that for every 2 mols of
base only 1 mol of acid is neutralized)
Concentration C2H2O4 =
Moles C 2 H 2 O 4
Volume C 2 H 2 O 4
0.0014 mol
=
0.030 L
= 0.047 mol/L
25. A chemist dissolved some Aspirin in water. The chemist then measured the pH of
the solution and found it to be 2.73 at 25C. What are the [H3O+] and [OH.] of
the solution?
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