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Reactions in Aqueous Solution
Chapter 4
Dr. Ali Bumajdad
Chapter 4 Topics
Solution Stoichiometry
• Solution
•Electrolytes, acids and bases
•Precipitation reactions and solubility rules
•Molecular eqn., ionic eqn & net ionic eqn.
•Oxidation reduction reactions
(Redox Reactions)
•Molarity and Dilution
•Solution Stoichiometry (gravimetric analysis,
titrations, limiting reactant….etc)
Dr. Ali Bumajdad
Solution
•solution is a homogenous mixture of 2 or more
substances
•solute is(are) the substance(s) present in the
smaller amount(s)
•solvent is the substance present in the larger amount
Solution
Solvent
Solute
Soft drink (l)
H2O
Sugar, CO2
Air (g)
N2
O2, Ar, CH4
Soft Solder (s)
Pb
Sn
Dr. Ali Bumajdad
Electrolytes, acids and bases
•Electrolyte is a substance when dissolved in water
results in a solution that can conduct electricity.
•Why? Because it gives ion when dissolve in water
•Nonelectrolyte is a substance when dissolved results
in a solution that does not conduct electricity.
•Why? Because it does not dissociates into ions
nonelectrolyte
weak electrolyte
strong electrolyte
Dissociation or Ionization?
Cations (+) and Anions (-)
•Strong Electrolyte: 100% dissociation
H 2O
NaCl (s)
HCl (l)
H 2O
NaOH (l)
Na+ (aq) + Cl- (aq)
H+ (aq) + Cl- (aq)
H 2O
Na+ (aq) + OH- (aq)
Soluble salt
Strong acid
Strong Base
•Weak Electrolyte: not completely dissociated
CH3COOH
NH3 + H2O
0.1M
CH3COO- (aq) + H+ (aq) Weak acid
NH4+ (aq) + OH- (aq)
1%
1%
Weak base
Dr. Ali Bumajdad
•Non-electrolyte: No dissociation into ions
Example: Sugar, ethanol (CH3CH2OH)
C6H12O6 (s)
H 2O
C6H12O6 (aq)
(Note that sugar and ethanol (CH3CH2OH) soluble
in water but do not gives ions when dissolved)
Q) Which of the following is not a strong electrolytes:
1) KCl
2)LiOH
3)NaNO3
4)NH3
5)Suger
6)H2SO4
7)HCl
8)HNO3
9)KOH
10)HC2H3O2
11) H2O
12) HF
13)HBr
14) H3PO4
Dr. Ali Bumajdad
Acids
•Have a sour taste. Vinegar owes its taste to acetic acid. Citrus
fruits contain citric acid.
•React with certain metals to produce hydrogen gas.
2HCl (aq) + Mg (s)
MgCl2 (aq) + H2 (g)
•React with carbonates and bicarbonates to produce carbon
dioxide gas
2HCl (aq) + CaCO3 (s)
CaCl2 (aq) + CO2 (g) + H2O (l)
•Aqueous acid solutions conduct electricity.
Dr. Ali Bumajdad
Bases
•Have a bitter taste.
•Feel slippery. Many soaps contain bases.
•Aqueous base solutions conduct electricity.
Dr. Ali Bumajdad
Arrhenius acid is a substance that produces H+ (H3O+) in water
Arrhenius base is a substance that produces OH- in water
Dr. Ali Bumajdad
A Brønsted acid is a proton donor
A Brønsted base is a proton acceptor
base
acid
acid
base
A Brønsted acid must contain at least one
ionizable proton!
Dr. Ali Bumajdad
Monoprotic acids
HCl
H+ + Cl-
HNO3
H+ + NO3H+ + CH3COO-
CH3COOH
Strong electrolyte, strong acid
Strong electrolyte, strong acid
Weak electrolyte, weak acid
Diprotic acids
H2SO4
H+ + HSO4-
Strong electrolyte, strong acid
HSO4-
H+ + SO42-
Weak electrolyte, weak acid
Triprotic acids
H3PO4
H2PO4HPO42-
H+ + H2PO4H+ + HPO42H+ + PO43-
Weak electrolyte, weak acid
Weak electrolyte, weak acid
Weak electrolyte, weak acid
Dr. Ali Bumajdad
Q) Identify each of the following species as a Brønsted
acid, base, or both. (a) HI, (b) CH3COO-, (c) H2PO4HI (aq)
H+ (aq) + I- (aq)
CH3COO- (aq) + H+ (aq)
H2PO4- (aq)
Brønsted acid
CH3COOH (aq)
H+ (aq) + HPO42- (aq)
H2PO4- (aq) + H+ (aq)
H3PO4 (aq)
Brønsted base
Brønsted acid
Brønsted base
Dr. Ali Bumajdad
Acid- Base Equilibria
1) Arrhenius Definition:
+
 Acid: Substance when dissolved in water increaseH
 Base: Substance when dissolved in water increaseOH
2) BrØnsted-Lowry Definition:
+
 Acid: Substance that donateH
+
 Base: Substance that acceptH
3) Lewis Definition:
 Acid: Electron-pair acceptor
 Base: Electron pair donor
Dr. Ali Bumajdad
Neutralization Reaction
acid + base
HCl (aq) + NaOH (aq)
H+ + Cl- + Na+ + OHH+ + OH-
salt + water
NaCl (aq) + H2O
Na+ + Cl- + H2O
H2O
Dr. Ali Bumajdad

A weak acid is a weak electrolyte
A strong acid is a strong electrolyte
A weak base is a weak electrolyte
A strong base is a strong electrolyte
Dr. Ali Bumajdad
•Hydration the process in which an ion is surrounded
by water molecules
d-
d+
H2O
Dr. Ali Bumajdad
Dr. Ali Bumajdad
Precipitation reactions and solubility rules
Precipitate: insoluble solid that separates from solution
PbI2
Dr. Ali Bumajdad
Solubility Rules
soluble salts
cation salts
1) alkali metals salts
e.g. NaCl
2) ammonium ion salts
e.g. (NH4)2SO4
Soluble salts with exceptions
All chlorides, bromides,
Iodides except those of
Ag+, Pb2+ and Hg22+
e.g. MgI2
(SO42-)
Anions salts
1) nitrate ion salts
e.g. KNO3
2) chlorate ion salts
e.g. NaClO3
3) perchlorate ion salts
e.g. KClO4
4) acetate ion salts
e.g. Cu(C2H3O2)2
All sulfates
except
those of
Ag+, Ca2+, Sr2+, Ba2+
Pb2+, and Hg2+
e.g. MgSO4
insoluble salts with exceptions
All metals oxides except
those of
alkali metals, Ca2+, Sr2+, Ba2+
e.g. MgO
All hydroxides except
those of
alkali metals, Ca2+, Sr2+, Ba2+
e.g. Be(OH)2
All carbonates (CO32-), phosphates
( PO43-), sulfides (S2-) and sulfites
(SO32-), and chromate (CrO42-)
except those of
NH4+, alkali metals
e.g. CaCO3
Dr. Ali Bumajdad
Q) Soluble or not:
a) Na2S
c) AgBr
Soluble
Not Soluble
e) Cu(C2H3O2)2
Soluble
b) FeCO3
Not Soluble
d) ZnO
Not Soluble
f) PbSO4
Not Soluble
g) Ni(OH)2 Not Soluble
Dr. Ali Bumajdad
Molecular eqn., ionic eqn & net ionic eqn.
Writing Net Ionic Equations
1. Write the balanced molecular equation.
2. Write the ionic equation showing the strong electrolytes
completely dissociated into cations and anions.
3. Cancel the spectator ions on both sides of the ionic equation
Q) Write the net ionic equation for the reaction of silver
nitrate with sodium chloride.
AgNO3 (aq) + NaCl (aq)
AgCl (s) + NaNO3 (aq)
Ag+ + NO3- + Na+ + Cl-
AgCl (s) + Na+ + NO3-
Ag+ + Cl-
AgCl (s)
Dr. Ali Bumajdad
precipitate
Pb(NO3)2 (aq) + 2NaI (aq)
PbI2 (s) + 2NaNO3 (aq)
molecular equation
Pb2+ + 2NO3- + 2Na+ + 2I-
PbI2 (s) + 2Na+ + 2NO3-
ionic equation
Pb2+ + 2I-
PbI2 (s)
net ionic equation
PbI2
Na+ and NO3- are spectator ions
Dr. Ali Bumajdad
Sa. Ex. 4.8: what happen when the following pairs mixed:
a) KNO3 and BaCl2
2KNO3 (aq) + BaCl2 (aq)
b) Na2SO4 and Pb(NO3)2
Na2SO4 (aq) + Pb(NO3)2 (aq)
Ba(NO3)2 (aq) + 2KCl (aq)
No net ionic eqn.
No reaction
2NaNO3 (aq) + PbSO4 (s)
reaction
c) KOH and Fe(NO3)3
3KOH (aq) + Fe(NO3)3 (aq)
3KNO3 (aq) + Fe(OH)3 (s)
reaction
Dr. Ali Bumajdad
Sa. Ex. 4.9: Write the molecular, complete ionic and net
ionic equations for the following mixed chemicals:
1) Potassium Chloride added to silver nitrate
2) Potassium hydroxide added to iron (III) nitrate
Dr. Ali Bumajdad
Q) Write the molecular, complete ionic and net ionic
equations for the following mixed chemicals:
• K2CrO4 and Ba(NO3)2
• HCl and NaOH
• HC2H3O2 and KOH
Dr. Ali Bumajdad
Oxidation-Reduction Reactions
Redox Reactions
(electron transfer reactions)
2Mg (s) + O2 (g)
2MgO (s)
• Oxidation: Loss of electrons
2Mg
2Mg2+ + 4e-
neutral
Cation
Oxidation half-reaction (lose e-)
We can say : Oxidation of Mg or Mg is oxidized
We can say : Mg is a reducing agent
• Reduction: Gain of electrons
O2 + 4eneutral
2O2-
Reduction half-reaction (gain e-)
anion
We can say : reduction of O2 or O2 is reduced
We can say : O2 is oxidation agent
• Redox reaction: Gaining and losing of electrons
2Mg + O2 + 4e2Mg + O2
2Mg2+ + 2O2- + 4e2MgO
Dr. Ali Bumajdad
• Oxidizing agent:
Reactant reduced
• Oxidizing agent:
Reactant that gain electrons
Reactant oxidized
• Reducing agent: Reactant that lost electrons
• Reducing agent:
Dr. Ali Bumajdad
Oxidation number
The charge the atom would have in a molecule (or an
ionic compound) if electrons were completely transferred.
1. O.N. of free elements is zero.
Na, Be, K, Pb, H2, O2, P4 = 0
2. O.N. of monatomic ions = the charge on the ion.
Li+, Li = +1; Fe3+, Fe = +3; O2-, O = -2
3. The sum of O.N. in a molecule is Zero
H2O = 2(+1) +(-2) =0
4. The sum of O.N. in a polyatomic ion = the charge on ion.
SO4-2 = (X) +4(-2) =-2
5. Group IA metals = +1, IIA metals = +2
Dr. Ali Bumajdad
6. F O.N. = -1.
7. H O.N. = +1, except with metals in binary compounds = –1.
8. O O.N. = -2, except in H2O2 and O22- = –1.
9. When encounter conflict in rules 6, 7, 8 the higher one
take precedence.
Dr. Ali Bumajdad
Figure 4.10 The oxidation numbers of elements in their compounds
Q) Zinc reacts with copper sulfate to form copper metal.
What is the reducing agent in the reaction?
Zn (s) + CuSO4 (aq)
ZnSO4 (aq) + Cu (s)
Zn2+ + 2e- Zn is oxidized
Zn
Cu2+ + 2e-
Zn is the reducing agent
Cu Cu2+ is reduced Cu2+ is the oxidizing agent
Q) Copper wire reacts with silver nitrate to form silver metal.
What is the oxidizing agent in the reaction?
Cu (s) + 2AgNO3 (aq)
Cu
Ag+ + 1e-
Cu(NO3)2 (aq) + 2Ag (s)
Cu2+ + 2e- Cu is oxidized
Ag Ag+ is reduced
Cu is the reducing agent
Ag+ is the oxidizing agent
Dr. Ali Bumajdad
Q) What are the oxidation numbers
of all the elements in the following ?
HCO3O = -2
H = +1
3x(-2) + 1 + ? = -1
IF7
F = -1
7x(-1) + I (?) = 0
I = +7
C = +4
NaIO3
Na = +1 O = -2
3x(-2) + 1 + ? = 0
I = +5
K2Cr2O7
O = -2
K = +1
7x(-2) + 2x(+1) + 2x(Cr(?) = 0
Cr = +6
Sa. Ex. 4.16: Assign oxidation states of all the atoms in:
a) CO2
b) SF6
c) NO3-
Dr. Ali Bumajdad
Q) Assign oxidation states of all the atoms in:
a) FeCl3
b) KNO3
c) H2O2
d) Fe2(SO4)3
e) Cr2O7
f) ClO3g) Na2S4O6
Types of Oxidation-Reduction Reactions
Combination Reaction
A+B
C
0
+4 -2
0
S + O2
SO2
Decomposition Reaction
C
+1 +5 -2
2KClO3
A+B
+1 -1
0
2KCl + 3O2
Types of Oxidation-Reduction Reactions
Displacement Reaction
A + BC
0
+1
+2
Sr + 2H2O
+4
0
TiCl4 + 2Mg
0
AC + B
-1
Cl2 + 2KBr
0
Sr(OH)2 + H2 Hydrogen Displacement
0
+2
Ti + 2MgCl2
-1
Metal Displacement
0
2KCl + Br2
Halogen Displacement
Dr. Ali Bumajdad
The Activity Series for Metals
Hydrogen Displacement Reaction
M + BC
AC + B
M is metal
BC is acid or H2O
B is H2
Ca + 2H2O
Ca(OH)2 + H2
Pb + 2H2O
Pb(OH)2 + H2
Dr. Ali Bumajdad
Types of Oxidation-Reduction Reactions
Disproportionation Reaction
Element is simultaneously oxidized and reduced.
0
Cl2 + 2OH-
+1
-1
ClO- + Cl- + H2O
Chlorine Chemistry
Dr. Ali Bumajdad
Q) Classify the following reactions.
Ca2+ + CO32NH3 + H+
Zn + 2HCl
Ca + F2
CaCO3
NH4+
ZnCl2 + H2
CaF2
Precipitation, Combination
Acid-Base, Combination
Redox (H2 Displacement)
Redox, Combination
Dr. Ali Bumajdad
Chemistry in Action: Breath Analyzer
+6
3CH3CH2OH + 2K2Cr2O7 + 8H2SO4
Orange/ yellow
+3
3CH3COOH + 2Cr2(SO4)3 + 2K2SO4 + 11H2O
green
Dr. Ali Bumajdad
Sa. Ex. 4.17:
2Al(s) + 3 I2(s)
2AlI3(s)
Identify the atoms that are oxidized, reduced and
specify the oxidation and reducing agent.
Dr. Ali Bumajdad
Q)
14HCl + K2Cr2O7
2KCl + 2CrCl3 + 3Cl2 + 7H2O
Identify the atoms that are oxidized, reduced and specify the
oxidation and reducing agent.
Dr. Ali Bumajdad
Molarity and Dilution
M = molarity =
no. of moles of solute
(7)
Volume of solution in liters
M=
n
(7)
VLsolution
Q) What mass of KI is required to make 500. mL of
a 2.80 M KI solution?
= 232 g KI
Dr. Ali Bumajdad
Sa. Ex. 4.1: Calculate M for a solution prepared by dissolving
11.5 g of NaOH in enough water to make 1.50 L of solution.
=0.192 M
Sa. Ex. 4.2: Calculate M for a solution prepared by dissolving
1.56 g of HCl in enough water to make 26.8 ml of solution.
=1.60 M
Dr. Ali Bumajdad
Sa. Ex. 4.3: Give concentration of each type of ions :
a) 0.50 M Co(NO3)2
b) 1 M Fe(ClO4)3
Sa. Ex. 4.4: Calculate number of moles of Cl- in 1.75 L
of 1.0×10-3 M ZnCl2
Dr. Ali Bumajdad
Sa. Ex. 4.5: Typical blood serum is about 0.14 M NaCl. What
volume of blood contains 1.0 mg NaCl
=1.2 ×10-4 L
Sa. Ex. 4.6: What is the mass of K2Cr2O7 in 1 L of 0.200 M
solution
=58.8 g
Dr. Ali Bumajdad
Dilution:
preparing a less concentrated solution from a more concentrated one.
solute moles before dilution = solute moles after dilution
M before dil V before dil = M after dil V after dil
(8)
(8)
Mi Vi =Mf Vf
Only for
Dilution
Dilution
Add Solvent
Dr. Ali Bumajdad
Sa. Ex. 4.7: What volume of 16 M H2SO4 must be used to
prepare 1.5 L of 0.10 M H2SO4 solution
= 9.4 ×10-3 L
= 9.4 ml
Dr. Ali Bumajdad
Q) How would you prepare 60.0 mL of 0.2 M
HNO3 from a stock solution of 4.00 M HNO3?
MiVi = MfVf
Mi = 4.00
Vi =
Mf = 0.200
MfVf
Mi
Vf = 0.06 L
Vi = ? L
0.200 x 0.06
=
= 0.003 L = 3 mL
4.00
3 mL of acid + 57 mL of water = 60 mL of solution
Dr. Ali Bumajdad
V = 102 ml
Solution Stoichiometry
Gravimetric analysis
1. Dissolve unknown substance in water
2. React unknown with known substance to form a precipitate
3. Filter and dry precipitate
4. Weigh precipitate
5. Use chemical formula and mass of precipitate to determine
amount of unknown ion
Dr. Ali Bumajdad
Titrations
a solution of accurately known concentration added gradually
to another solution of unknown concentration until the chemical
reaction between the two solutions is complete
•Equivalence point : the point at which the reaction is complete
•Indicator : substance that changes color at (or near) the
equivalence point
no. of H
in the acid
(per formula)
nH M aicd V acid = nOHM base V base
(9)
no. of OH
in the base
(per formula)
Dr. Ali Bumajdad
no. of e
lost
(per formula)
nOx M Ox V Ox = nRedM Red V Red
(10)
no. of e
gained
(per formula)
Q) What volume of a 1.420 M NaOH solution is
required to titrate 25.00 mL of a 4.50 M H2SO4
solution?
WRITE THE CHEMICAL EQUATION!
H2SO4 + 2NaOH
2H2O + Na2SO4
= 158 mL
Dr. Ali Bumajdad
= 0.1141 M
= 16.1 ml
no. of e
lost
(per formula)
nOx M Ox V Ox = nRedM Red V Red
no. of e
gained
(per formula)
(10)
Sa. Ex. 4.10: what mass of NaCl must be added to 1.50 L
of a 0.100 M AgNO3 solution to precipitate all the Ag+ ions
in the form of AgCl
= 8.77g
Dr. Ali Bumajdad
Sa. Ex. 4.11: Calculate the mass of PbSO4 formed when 1.25 L
of 0.0500 M Pb(NO3)2 and 2.00L of 0.0250 M Na2SO4 are
mixed.
=15.2 g
Dr. Ali Bumajdad
Sa. Ex. 4.13: 28.0 ml of 0.250 M HNO3 and 53.0ml of 0.320 M
KOH are mixed. Calculate the amount of water formed. What is
the concentration of H+ or OH- in excess after the reaction goes
to completion.
= 0.00996 mol of water
= 0.123 M OH- in excess
Dr. Ali Bumajdad
Sa. Ex. 4.14: 1.3009 g of KHC8H4O4 (M.m.=204.22 g/mol)
dissolved in water and few drops of PhPh is added. The solution
is titrated with NaOH solution. The different between the final and
initial burette reading was 41.20 ml. Calculate the concentration
of NaOH solution.
= 0.1546 M
Dr. Ali Bumajdad
Sa. Ex. 4.15: Waste materials of CCl4 + HC7H5O2 = 0.3518 g
was shaken with water. The resulting aqueous solution required
10.59 ml of 0.1546 M NaOH for neutralization. Calculate the
mass % of HC7H5O2 in the waste.
=56.82%
Dr. Ali Bumajdad