SCH 4U
Acid-Base Equilibrium
Student Name
Total 30
CLEARLY MARK THE LETTER OF THE BEST ANSWER.
1.
Which of the following 0.10 mol/L aqueous solutions gives the lowest pH? a) b) c)
2.
H3PO4 (pK a1 = 2.12) HF (pK a = 3.45)
-10
What is the pH of 0.010 mol/L HCN(aq) (K a = 4.9 10 )? a) b)
3.
CH3COOH (pK a = 4.75) d) HIO3 (pK a = 0.77) e) Since all are acids, acids, the pH is the same same for all solutions. solutions.
5.65 2.00
c) d)
4.65 6.69
e)
9.31
When 500 mL of 0.120 mol/L KOH (aq) is mixed with 500 mL of 0.0480 mol/L Ba(OH) 2 (aq), the pH of the resulting solution is a) b)
4.
13.03 12.92
b) H3PO4
a) HC2O4-1 and H2O b) HC2O4-1 and H3O+1
13.23
c) HC l
d) H2CO3
H3O+1 (aq) + C2O42- (aq) c) H2O and C2O42d) HC2O4-1 and C2O42-
In the following reaction, which is a Brønsted-Lowry Brønsted-Lowr y base? HC2O4-1 (aq) + H2O (l) a) HC2O4-1
7.
e)
For the following reaction, which of the following is a conjugate acid-base pair? HC2O4-1 (aq) + H2O (l)
6.
14.00 13.33
Which of the following is a strong acid? a) HF
5.
c) d)
b) H2O
H3O+1 (aq) + C2O42- (aq) c) H3O+1
d) None of these
When KNO 2 is dissolved in water, which of the following is the principal acid-base equilibrium? a) K(H2O)6+(aq) K(H2O)5OH(aq) + H+(aq) b) HNO2(aq) H+ (aq) + NO2- (aq) c) NO2- (aq) + H2O(l) HNO2(aq) + OH- (aq) d) NO2- (aq) + H2O(l) HNO3(aq) + H+ (aq)
8.
A Brønsted-Lowry base is defined as a substance that a) acts as a proton donor. b) increases [H+] when placed in water. c) acts as a proton acceptor. d) decreases [H+] when placed in water.
9.
For the following reaction, which of the following is a conjugate acid-base pair? H2PO4- (aq) + NH3 (aq)
HPO42- (aq) + NH4+ (aq)
a) H2PO4- and NH3 b) HPO42- and NH4+ c) H2PO4- and HPO42d) None of the above 10.
Which of the following reactions corresponds to hydrolysis of NH 4+ in water solution? a. NH4+ (aq) + OH – (aq) NH3(aq) + H2O(l) + b. NH4 (aq) + H2O(l) NH3(aq) + H3O+(aq) c. NH4+ (aq) + H2O(l) NH52+(aq) + OH –(aq) d NH4+ (aq) NH2+(aq) + H2(g)
11.
What is the conjugate a) OH-1 b) HCO3+
12.
of HCO3-1? c) H2CO3 d) H3CO3+
e) CO32 –
What is the pH of an aqueous solution at 25.0 oC in which [OH-] is 0.00250 a) +2.60 b) –11.4
13.
base
The magnitude of
c) –2.60 d) –2.25 K w indicates
mol/L.
e) +11.4
that __________.
a) water autoionizes very slowly b) water autoionizes very quickly c) water autoionizes only to a very small extent d) the autoionization of water is exothermic e) water autoionizes completely 14.
Which of the following solutes, when dissolved in water to 1.0 mol/L, gives the solution with the highest pH? a) HNO2 b) NaC l
15.
e) HC l
The pH of a 0.0025 mol/L aqueous solution of calcium hydroxide, Ca(OH)2, is: a) 11.70 b) 12.00
16.
c) NaNO2 d) NH4C l
c) 12.40 d) 2.30
e) 11.10
The pH of 0.20 mol/L CH3NH2 (aq) is 11.93. What is the value of K b for CH3NH2? a) 8.5 × 10-3 b) 1.7 × 10-3
c) 1.4 × 10-5 d) 3.8 × 10-4
e) 7.2 × 10-5
17.
The pH of 1.0 mol/L HCO2H(aq) is 1.88. What is the percent ionization of HCO 2H? a) 1.3% b) 50%
18.
c) 1.8% d) 94%
Which of the following is the strongest acid? a) HClO2 (pKa = 2.00) b) HCN (pKa = 9.32)
19.
e) 13%
c) HF (pKa = 3.46) d) CH3COOH (pKa = 4.75)
e) HNO2 (pKa = 3.34)
The solution at the equivalence point in a titration of 0.10 mol/L NH 3(aq) with 0.10 mol/L HC l (aq) is best described as: a) a solution of pH = 7.00 d) a 0.10 mol/L solution of NH4C l b) a 0.050 mol/L solution of NH 4C l e) a 1:1 buffer solution c) a solution containing equal concentrations of NH 3 and NH4C l
20.
If one were to prepare a buffer solution using pyridine (C5H5N, Kb = 1.8 × 10-9 ) and pyridinium chloride (C 5H5NHCl), its pH would be in the approximate range: a) 7.7 to 9.7 b) 9.3 to 11.3
21.
c) 4.3 to 6.3 d) 11.1 to 13.1
e) 2.9 to 4.9
If the pH of a solution of a salt is 5.0, the salt must be one which could be formed from the neutralization of a) a strong acid and a strong base. b) a strong acid and a weak base.
22.
23.
c) a weak acid and a strong base. d) HCl and NaOH. -5
Which indicator (identified by a letter) could be used to titrate aqueous NH 3 (Kb = 1.8 x 10 ) with HC l solution of equal concentration? Indicator
Colour Range
Color-Change pH
a)
Pink-yellow
1.2 - 2.8
b)
Blue-yellow
5.2 – 6.2
c)
Yellow-purple
6.5 - 7.8
d)
Colorless-red
8.3 - 9.9
e)
none of these
The following titration curve is the kind of curve expected for the titration of a ____ acid with a ____ base.
a) strong, strong b) weak, strong c) strong, weak d) weak, weak e) none of these
24.
-1
What is the hydronium ion concentration in a solution which has [OH ] = 1.0 x 10 a) 1.0 x 10-12 mol/L b) 12 mol/L
c) 1.0 x 10-2 mol/L d) 1.0 x 10-7 mol/L
-2
e) 1.0 x 10-16 mol/L
mol/L?
25.
Identify the INCORRECT statement: a) As the pH increases the hydroxide ion concentration decreases. b) As the pH increases the hydronium ion concentration decreases. c) As the pH increases the Kw of water remains the same. d) As the pH increases the product [H3O+][OH-] remains constant. e) As the pH increases the solution becomes less acidic and more alkaline.
26.
Calculate the pH of a 0.136 mol/L solution of aqueous sodium fluoride, NaF. -4 (HF has a Ka value of 3.5 × 10 ) a) 2.16 b) 8.73
27.
b) NH3
c) HI
c) 6.67 x 10-10 mol/L, 9.18 d) 6.67 10-11 mol/L, 10.18
If the auto-dissociation constant of water, K w, at 40°C is 2.92 × 10 neutral solution in water at 40 °C? a) 1.00 x 10-7 mol/L -14 b) 2.92 x 10 mol/L
30.
d) H3PO4
What is the hydroxide ion concentration and pH for the hydrochloric acid solution that has a -4 hydronium ion concentration of 1.50 x 10 mol/L? a) 6.67 x 10-10 mol/L, 4.82 b) 6.67 10-11 mol/L, 3.82
29.
e) 8.30
Which of the following can behave as a Brønsted-Lowry acid or as a Brønsted-Lowry base in aqueous solution? a) HSO3-1
28.
c) 5.71 d) 11.84
-14
+
then what is [H ] for a
c) 1.00 x 10-14 mol/L -7 d) 1.71 x 10 mol/L
What is the pH of 0.10 mol/L sodium acetate (NaAc) solution? The K a of acetic acid -5 (HAc) is 1.8 x 10 . a) 1.0 b) 8.9
c) 0.10 d) 5.1
e) 7.0
