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Chem 210 Spring 2020 - EXAM 1
Name___________________________________
MULTIPLE CHOICE. 1 pt each. Choose the one alternative that best completes the statement or answers the question.
1) Which of the following substances has the greatest solubility in water?
A) NiCO3 , Ksp = 1.3 × 10–7
1)
B) MgCO3 , Ksp = 3.5 × 10–8
C) CuBr, Ksp = 5.0 × 10–9
D) AgCN, Ksp = 2.2 × 10–16
E) AgIO3 , Ksp = 3.1 × 10–8
2) Write the ion product expression for calcium phosphate, Ca3 (PO4 )2 .
2)
A)
B)
C)
D)
E) None of these choices are correct.
3) What volume of 0.500 M H 2 SO4 is needed to react completely with 20.0 mL of 0.400 M
LiOH?
A) 12.5 mL
B) 32.0 mL
C) 8.00 mL
D) 4.00 mL
3)
E) 16.0 mL
4) When a weak acid is titrated with a strong base, the pH at the equivalence point
4)
A) is greater than 7.0.
B) is equal to 7.0.
C) is equal to the pKa of the acid.
D) is equal to 14.0 – pKb , where pKb is that of the base.
E) is less than 7.0.
5) Which, if any, of the following aqueous mixtures would be a buffer system?
A) HSO4 – , HSO3 –
B) H 2 CO3 , HCO3 –
C) H 2 PO4 – , HCO3 –
D) CH3 COOH, NaH2 PO4
E) None of these choices are correct.
1
5)
6) Which one of the following is a strong acid?
6)
A) CH3 COOH
B) H 2 CO3
C) H 2 SO3
D) H 3 PO4
E) H 2 SO4
7) Which of the following liquids contains the strongest acid?
7)
A) 0.1 M HD, pH = 7.22
B) 0.1 M HJ, pH = 11.88
C) pure water
D) 0.1 M HE, pH = 8.34
E) 0.1 M HA, pH = 6.85
8) What is the [OH– ] for a solution at 25°C that has [H3 O +] = 2.35 × 10–3 M?
A) 4.26 × 10–12 M
8)
B) 2.35 × 10–11 M
C) 2.35 × 10–17 M
D) 4.26 × 10–5 M
E) None of these choices are correct.
9) What is the pH of a 0.00200 M HClO4 solution?
9)
A) 0.995
B) 6.215
C) 1.378
D) 2.699
E) None of these choices are correct.
10) What is the value of Kb for the cyanide anion, CN– ? Ka(HCN) = 6.2 × 10–10
A) 3.8 × 10–4
10)
B) 6.2 × 104
C) 1.6 × 10–5
D) 1.6 × 10–4
E) 3.8 × 10–5
11) When a chemical system is at equilibrium,
11)
A) the reaction quotient,
, has reached a maximum.
B) the concentrations of the reactants and products have reached constant values.
C) the reaction quotient, , has reached a minimum.
D) the forward and reverse reactions have stopped.
E) the concentrations of the reactants are equal to the concentrations of the products.
2
12) Which of the following has an effect on the magnitude of the equilibrium constant?
12)
A) increasing the pressure, in a gas-phase reaction
B) adding a catalyst
C) removing products as they are formed
D) change in temperature
E) adding more of a reactant
13) The solubility of silver chromate is 0.0287 g/1.0 L of solution. What is the Ksp for
13)
Ag2CrO4 ?
A) < 1.0 × 10–13
B) 9.5 × 10–5
C) 6.5 × 10–13
D) 2.6 × 10–12
E) 2.4 × 10–5
14) The solubility of aluminum hydroxide in water ________ when dilute nitric acid is
14)
added to it.
A) increases
B) does not change
C) first increases, then decreases
D) first decreases, then increases
E) decreases
15) A sample of a monoprotic acid (HA) weighing 0.384 g is dissolved in water and the
15)
solution is titrated with aqueous NaOH. If 30.0 mL of 0.100 M NaOH is required to
reach the equivalence point, what is the molar mass of HA?
A) 211 g/mol
B) 37.0 g/mol
C) 81.0 g/mol
D) 128 g/mol
E) 20.3 g/mol
16) What is the pH of a buffer that consists of 0.20 M NaH2 PO4 and 0.40 M Na2 HPO4 ?
For NaH2PO4 , Ka = 6.2 × 10–8
A) 6.51
B) 7.90
C) 7.51
D) 6.91
E) 8.13
17) Which one of the following will give a solution with a pH > 7, but is not an Arrhenius
base in the strict sense?
A) CH4
B) NaOH
C) CH3 NH2
3
D) CO2
16)
E) Ca(OH) 2
17)
18) The hydrated Al3+ ion, Al(H2 O)6 3+, is a weak acid in water. What are the products of its
18)
reaction with H2O?
Al(H2 O)6 3+(aq) + H2 O(l) →?
A) Al(H2 O)5 3+(aq) + 2H2 O(l)
B) Al(H2 O)5 OH2+(aq) + H3 O +(aq)
C) Al(H2 O)6 2+(aq) + H3 O +(aq)
D) Al(H2 O)6 OH2+(aq) + H3 O +(aq)
E) Al(H2 O)6 H 4+(aq) + OH– (aq)
19) Carbon monoxide and chlorine combine in an equilibrium reaction to produce the highly
19)
toxic product, phosgene (COCl2)
CO(g) + Cl 2(g)
COCl2 (g)
If the equilibrium constant for this reaction is Kc = 248, predict, if possible, what will
happen when the reactants and product are combined with the concentrations shown.
[CO] = [Cl2] = 0.0200 M; [COCl2 ] = 0.0992 M
A) The reaction will proceed to the left.
B) The reaction will proceed to the right.
C) The reaction is at equilibrium, and no change in concentrations will occur.
D) The temperature needs to be specified before a prediction can be made.
E) The container volume needs to be specified before a prediction can be made.
20) Which one of the following substances will give an aqueous solution of pH < 7?
20)
A) KI
B) CH3 OH
C) CH3 COONa
D) Na2 CO3
E) NH4 Br
21) Formic acid, which is a component of insect venom, has a Ka = 1.8 × 10–4. What is the
[H3 O+] in a solution that is initially 0.10 M formic acid, HCOOH?
21)
A) 8.4 × 10–3 M
B) 1.8 × 10–5 M
C) 1.8 × 10–6 M
D) 4.2 × 10–3 M
E) 1.8 × 10–4 M
22) What is the [H3 O +] for a solution at 25°C that has pOH = 5.640?
A) 2.29 × 10–6 M
B) 4.27 × 10–11 M
C) 8.360 M
D) 4.37 × 10–9 M
E) 2.34 × 10–4 M
4
22)
23) Consider the reactions of cadmium with the thiosulfate anion.
K1 = 8.3 × 103
Cd2+(aq) + S2 O32–(aq)
Cd(S2O3 )(aq)
Cd(S2 O3)(aq) + S2 O32–(aq)
Cd(S2O3 )2 2–(aq) K2 = 2.5 × 102
What is the value for the equilibrium constant for the following reaction?
Cd2+(aq) + 2S2 O32–(aq)
Cd(S2O3 )2 2–(aq)
B) 0.030
D) 33
A) 8.1 × 103
C) 2.1 × 106
23)
E) 8.6 × 103
24) The reaction of nitrogen with oxygen to form nitrogen monoxide can be represented by
24)
the following equation.
N2(g) + O2(g)
2NO(g)
At 2000°C, the equilibrium constant, Kc, has a value of 4.10 × 10 –4. What is the value of
Kp ?
A) 7.65 × 10–2
B) 7.75
C) 4.10 × 10–4
D) 2.17 × 10–8
E) None of these choices are correct.
25) An acetic acid buffer containing 0.50 M CH3 COOH and 0.50 M CH3 COONa has a pH
of 4.74. What will the pH be after 0.0020 mol of HCl has been added to 100.0 mL of the
buffer?
A) 4.71
B) 4.77
C) 4.68
D) 4.62
E) None of these choices are correct.
5
25)
SHORT ANSWER. Points assigned for each question. Show your work. Significant figures and rounding count.
26) 5 pts. A solution is prepared by adding 500 mL of 0.3 M NaClO to 500 mL of 0.4
M HClO. What is the pH of this solution? Ka = 3.5 x 10-8
6
26)
27) 5 pts. A 35.0-mL sample of 0.20 M LiOH is titrated with 0.25 M HCl. What is
the pH of the solution after 23.0 mL of HCl have been added to the base?
7
27)
28) 10 pts. A 10.0-mL sample of 0.75 M CH3 CH2 COOH is titrated with 0.30 M
NaOH. Calculate the pH at 0.00mL of NaOH; at equivalence; at pKa; after 22.00
mL of NaOH have been added and after 35.00 mL of NaOH have been added.
Ka = 1.3 × 10–5
8
28)
Answer Key
Testname: SP20_210_EXAM1
1) A
2) D
3) C
4) A
5) B
6) E
7) E
8) A
9) D
10) C
11) B
12) D
13) D
14) A
15) D
16) C
17) C
18) B
19) C
20) E
21) D
22) D
23) C
24) C
25) A
26) The pH will be less than the pKa of hypochlorous acid.
27) 12.33
28) 5.75
29) 7.8 atm
10