Download Acid-Base Reactions

Topic 4 Solutions and Aqueous Reactions
General Properties of Aqueous Solution
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Solute vs. solvent
Process of dissolving
strong/weak/non electrolyte
Strong acids/bases
Molarity = (moles of solute) / (liters of solution)
Dilution
1. If you were to draw diagrams representing aqueous solutions of each of the following ionic
compounds, how many anions would you show if the diagram contained six cations?
(a) NiSO4 6
(b) Ca(NO3)2 12
(c) Na3PO4
2
(d) Al2(SO4)3 9
2. The total concentration of ions in a 0.250 M solution of HCl is __________.
A) essentially zero
B) 0.125 M
C) 0.250 M
D) 0.500 M
3. A weak electrolyte exists predominantly as __________ in solution.
A) atoms
B) ions
C) molecules
D) electrons
E) 0.750 M
E) an isotope
4. Which of the following are strong electrolytes?
NH 3
HC2 H 3 O 2
HCl
KCl
5. What is the concentration (M) of KCl in a solution made by mixing 25.0 mL of 0.100 M KCl
with 50.0 mL of 0.100 M KCl?
A) 0.100
B) 0.0500
C) 0.0333
D) 0.0250
E) 125
6. How many grams of NaOH (MW = 40.0) are there in 500.0 mL of a 0.175 M NaOH solution?
3
A) 2.19  10-3
B) 114
C) 14.0
D) 3.50
E) 3.50  10
7. There are __________ mol of bromide ions in 0.500 L of a 0.300 M solution of AlBr 3 .
A) 0.150
B) 0.0500
C) 0.450
D) 0.167
E) 0.500
8. What are the molar concentrations of each of the ions present in a 0.025 M aqueous solution
of calcium nitrate?
Calcium nitrate is composed of calcium (Ca2+) ions and nitrate ions NO3–, so its chemical
formula is Ca(NO3)2. Because there are two NO3– ions for each Ca2+ ion in the compound, each
mole of Ca(NO3)2 that dissolves dissociates into 1 mol of Ca2+ and 2 mol of NO3–. Thus, a
solution that is 0.025 M in Ca(NO3)2 is 0.025 M in Ca2+ and 2  0.025 M = 0.050 M in NO–:
9. What is the molar concentration of K+ ions in a 0.015 M solution of potassium carbonate?
0.030 M K+
10. a) How many grams of Na2SO4 are there in 15 mL of 0.50 M Na2SO4?
1.1 g
b) How many milliliters of 0.50 M Na2SO4 solution are needed to provide 0.038 mol of this salt?
76 mL
11. What volume of 2.50 M lead(II) nitrate solution contains 0.0500 mol of Pb2+?
0.0200 L = 20.0 mL
b) How many milliliters of 5.0 M K2Cr2O7 solution must be diluted to prepare 250 mL of 0.10 M
solution?
5.0 mL
12. How would you prepare 450 mL of 0.10M H3PO4 starting with 3.0M H3PO4?
McVc = MdVd
(3.0M) V = (0.10M)(0.450L)
V = 0.015 L (or 15mL)
Place 15mL of 3.0M H3PO4 in a flask. Add enough water to make 450mL of solution.
13. Label each as strong, weak or non electrolyte:
CaCl2 strong electrolyte (ionic compound)
HNO3 strong electrolyte (strong acid)
C2H5OH (ethanol) nonelectrolyte (molecular compound, not acid/base)
HCOOH (formic acid) weak electrolyte (weak acid)
KOH strong electrolyte (ionic compound)
Ca(NO3)2 (calcium nitrate) strong electrolyte (ionic compound)
C6H12O6 (glucose) nonelectrolyte (molecular compound, not acid/base)
CH3COONa (sodium acetate) strong electrolyte (ionic compound)
CH3COOH (acetic acid) weak electrolyte (weak acid)
Precipitation Reactions
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Solubility guidelines (Table 4.1)
Soluble = aq
Insoluble = s (slightly soluble)
Metathesis reactions (double replacement reactions)
Types of equations:
Molecular/Formula equations show all chemical formulas
Complete ionic equations show all ions
Net ionic equations only include ions involved in reaction (spectator ions are removed)
14. Classify the following ionic compounds as soluble or insoluble in water:
(a) sodium carbonate (Na2CO3) Soluble
(d) lead sulfate (PbSO4) Insoluble
(b) cobalt(II) hydroxide Insoluble
(c) ammonium phosphate Soluble
(e) barium nitrate Soluble
15. Which combination will produce a precipitate?
A) NaC 2 H 3 O 2 (aq) and HCl (aq)
B) NaOH (aq) and HCl (aq)
C) AgNO 3 (aq) and Ca(C 2 H 3O 2 ) 2 (aq)
D) KOH (aq) and Mg(NO 3 ) 2 (aq)
E) NaOH (aq) and HCl (aq)
16. The net ionic equation for the reaction between aqueous solutions of HF and KOH is:
A) HF  KOH  H 2 O  K   F
B) HF  OH   H 2 O  F
C) HF  K   OH   H 2 O  KF
D) H   OH   H 2 O
E) H   F  K   OH   H 2 O  K   F
17. Combining aqueous solutions of BaI 2 and Na 2 SO 4 affords a precipitate of BaSO 4 . Which
ion(s) is/are spectator ions in the reaction?
A) Ba 2 only
B) Na  only
C) Ba 2 and SO 4 2
D) Na + and I
E) SO 4 2 and I 
18. Write the net ionic equation for the precipitation reaction that occurs when solutions of
calcium chloride and sodium carbonate are mixed.
Ca2+(aq) + CO32–(aq) → CaCO3(s)
19. The quantity of Cl– in a municipal water supply is determined by titrating the sample with
Ag+. The reaction taking place during the titration is
The end point in this type of titration is marked by a change in color of a special type of
indicator.
(a) How many grams of chloride ion are in a sample of the water if 20.2 mL of 0.100 M Ag+
is needed to react with all the chloride in the sample?
(b) If the sample has a mass of 10.0 g, what percent Cl– does it contain?
Acid-Base Reactions
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Arrhenius said Acids donate H+ , Bases donate OHBronsted-Lowry said Acids donate H+ , Bases accept H+
Strong/weak acids & bases
Neutralization reactions (Acid + Base  salt + water);
Titrations MH+VH+ = M OH-VOHNeutralization reactions with CO32-, S2- & SO32- form gases as a product
20. Which hydroxides are strong bases?
Sr(OH)2
KOH
NaOH
Ba(OH)2
21. Aqueous solutions of a compound did not form precipitates with Cl , Br  , I  , SO 4 2  ,
CO 32 , PO 4 3 , OH  , or S2  . This highly water-soluble compound produced the foul-smelling
gas H 2 S when the solution was acidified. This compound is __________.
A) Pb(NO 3 ) 2
B) (NH 4 ) 2 S
C) KBr
D) Li 2 CO 3
E) AgNO3
22. A neutralization reaction between an acid and a metal hydroxide produces __________.
A) water and a salt
B) hydrogen gas
C) oxygen gas
D) sodium hydroxide
E) ammonia
23. The reaction between strontium hydroxide and chloric acid produces __________.
A) a molecular compound and a weak electrolyte
B) two weak electrolytes
C) two strong electrolytes
D) a molecular compound and a strong electrolyte
E) two molecular compounds
24. The following diagrams represent aqueous solutions of three acids (HX, HY, and HZ) with
water molecules omitted for clarity. Rank them from strongest to weakest.
HY > HZ > HX. HY is a strong acid because it is totally ionized (no HY molecules in solution),
whereas both HX and HZ are weak acids, whose solutions consist of a mixture of molecules
and ions. Because HZ contains more H+ ions and fewer molecules than HX, it is a stronger
acid.
25. In a titration of 35.00 mL of 0.737 M H 2 SO 4 , __________ mL of a 0.827 M KOH solution is
required for neutralization.
A) 35.0
B) 1.12
C) 25.8
D) 62.4
E) 39.3
26. How many grams of Ca(OH)2 are needed to neutralize 25.0 mL of 0.100 M HNO3?
27. How many liters of 0.500 M HCl(aq) are needed to react completely with 0.100 mol of
Pb(NO3)2(aq), forming a precipitate of PbCl2(s)? 0.400 L
28. One commercial method used to peel potatoes is to soak them in a solution of NaOH for a
short time, remove them from the NaOH, and spray off the peel. The concentration of NaOH is
normally in the range of 3 to 6 M. The NaOH is analyzed periodically. In one such analysis, 45.7
mL of 0.500 M H2SO4 is required to neutralize a 20.0-mL sample of NaOH solution. What is the
concentration of the NaOH solution?
Oxidation-Reduction Reactions
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Oxidation = loss of electrons, Reduction = Gain of electrons (OIL RIG)
Assigning oxidation numbers
Displacement reactions (single replacement) need to be balanced for mass and charge
Activity Series
29. Which of these metals is the least easily oxidized?
Na
Au
Fe
Ca
Ag
30. What is the oxidation state of the boldfaced element in each of the following:
(a) P2O5 +5
(b) NaH -1
(c) Cr2O72– +6
(d) SnBr4 +4
(e) BaO2 -1
28. In which species does nitrogen have the highest oxidation number?
A) N2
B) NH3
C) HNO2
D) NO2-
E) NaNO3
29. Of the choices below, which would be the best for the lining of a tank intended for use in
storage of hydrochloric acid?
A) copper
B) zinc
C) nickel
D) iron
E) tin
33. Write the balanced molecular and net ionic equations for the reaction between magnesium
and cobalt(II) sulfate.
Mg(s) + CoSO4(aq) → MgSO4(aq) + Co(s)
Mg(s) + Co2+(aq) → Mg2+(aq) + Co(s)
(b) What is oxidized and what is reduced in the reaction?
Mg is oxidized and Co2+ is reduced.
34. Which of the following are oxidation-reduction reactions? (Select all that apply.)
1. (Cr2O7)2- (aq) + 2 (OH)- (aq) ---> 2 (CrO4)2- (aq) + (H2O) (l)
2. HCl(aq) + KOH(aq) ---> KCl(aq) + H2O(l)
3. O3(g) + NO(g) ---> O2(g) + NO2(g)
4. CH4(g) + 2O2(g) ---> CO2(g) + 2H2O(g)
5. 2H2O2(l) ---> 2H2O(l) + O2(g)
6. 2CuCl(aq) ---> CuCl2(aq) + Cu(s)
7. Zn(s) + 2HCl(aq) ---> ZnCl2(aq) + H2(g)
35. Which of the following metals will be oxidized by Pb(NO3)2: Zn, Cu, Fe?
Zn and Fe
36. A sample of an iron ore is dissolved in acid, and the iron is converted to Fe2+. The sample is
then titrated with 47.20 mL of 0.02240 M MnO4– solution. The oxidation-reduction reaction that
occurs during titration is as follows:
(a) How many moles of MnO4– were added to the solution? 1.057  10–3 mol MnO4–
(b) How many moles of Fe2+ were in the sample? 5.286  10–3 mol Fe2+
(c) How many grams of iron were in the sample? 0.2952 g
(d) If the sample had a mass of 0.8890 g, what is the percentage of iron in the sample? 33.21%
37. A sample of 70.5 mg of potassium phosphate is added to 15.0 mL of 0.050 M silver nitrate,
resulting in the formation of a precipitate.
(a) Write the molecular equation for the reaction.
K3PO4(aq) + 3 AgNO3(aq) → Ag3PO4(s) + 3 KNO3(aq)
(b) What is the limiting reactant in the reaction?
AgNO3
(c) Calculate the theoretical yield, in grams, of the precipitate that forms.