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Exam 1 Results:
Mean: 71%
Range: 39.5%-93.5%
Median: 72%
Other Bio-LS Class
Mean 72%
Please read Chapter 4 and
complete problems.
Please see me for help.
There are 3-classes of chemical reactions that
occur in aqueous solution.
1. Precipitation Reaction-– an insoluble solid is
formed from specific cation-anion combinations.
2. Acid-Base Reaction-– a protons donor
substance reacts with a hydroxide donor substance
forming a salt and water.
Precipitation
Involves Substances
Cations
Anions
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 to obtain the net ionic equation
Involves Substances
Involves Substances
H+ ions
OH- ions
Combine to Form
Insoluble
Precipitate
Salt and H2O
3. Oxidation-Reduction Reaction-electron donor
Learning Check: Does a precipitate form?
Write the net M/I and net ionic equation for
the reaction of silver nitrate with sodium
chromate.
Oxidation
Reduction
Combine to Form
Predicted by
substances react with react with substances that accept
electrons.
Acid-Base
Neutralization
Solubility
Rules
Oxidation Reduction
Which is the
Loss of e-
Gain of e-
Which is called
Reducing
Agent
Oxidizing
Agent
Write the net ionic equation for the reaction of
silver nitrate with sodium chromate.
Solubility Rules
Soluble Ionic Compounds
Exceptions
+
Salts of:
Group IA and NH4
NO3C2H3O2ClO3- and ClO4Cl-, Br-, ISO42-
Insoluble Ionic Compounds
Salts of:
Will a precipitate form when Mg(NO3)2 is added to
NaOH?
None
None
None
None
Ag+, Pb2+, Cu+, Hg22+
Ca2+, Sr2+, Ba2+ Ag+, Pb2+
A precipitation reaction will occur if can occur.
Use the solubility table to judge if it can occur.
Exceptions
OHCO3PO43-
Group IA, Ca2+, Sr2+, Ba2+
Salts of Group IA and NH4+
Salts of Group IA and NH4+
Salts of Group IA,
NH4+, Ba2+ Ca2+, Sr2+
S2-
There are 3-classes of chemical reactions that
occur in aqueous solution.
Will a precipitate form when Mg(NO3)2 is added to
NaOH?
1. Write a balanced equation
2. Ask whether any combination of ions will be insoluble
from a solubity table. If so, the reaction will occur.
3. Write the molecular, ionic and net ionic equations
Note ionic species exchanged---called a metathesis reaction
Molecular Equation
Mg(NO3)2 + 2NaOH ==> Mg(OH)2 + 2NaNO3
Ionic Equation
1. Precipitation Reaction-– an insoluble solid is
formed from specific cation-anion combinations.
2. Acid-Base Reaction-– a protons donor
substance reacts with a hydroxide donor substance
forming a salt and water.
3. Oxidation-Reduction Reaction-electron donor
Mg2+ + 2NO32- + 2Na+ + 2OH- ==> Mg
substances react with react with substances that accept
electrons.
Net Ionic Equation
Mg2+ + 2OH- ==> Mg(OH)2 (s)
Precipitation
Involves Substances
Cations
Anions
Acid-Base
Neutralization
Oxidation
Reduction
Involves Substances
Involves Substances
H+ ions
OH- ions
Combine to Form
Combine to Form
Insoluble
Precipitate
Salt and H2O
Predicted by
Solubility
Rules
2. Acid-Base Reactions
Oxidation Reduction
Which is the
Loss of e-
Gain of e-
Which is called
Reducing
Agent
Oxidizing
Agent
The effects of acid rain on a statue of George Washington
taken in 1935 (left) and 2001 (right) marble.
Properties of Acids and Bases
Acid
Acids: 200 Million Tons H2SO4
•
•
•
•
Acrid sour taste
React with metals giving ion + H2 gas
Changes plant dye litmus from blue to red
React with carbonates and bicarbonates to
produce CO2 gas
Base
Bases: 50 Million Tons NaOH
•
•
•
•
Bitter taste
Slippery feel
Changes plant dye litmus from red to blue
React and neutralizes the effects of acids
Acids are substances that produce H+ when
dissolved in water.
H 2O
HA(g) ==>
H+
+
A-
Acid donates H+
A- is symbol for
halide anion
Bases are substances that produce OH- when
dissolved in water.
H 2O
MOH(s) ==> OH- + M+
Bases donate OH-
M+ is symbol for
metal cation
Both are strong electrolytes!
We must memorize common strong acids and
strong bases. All are strong electrolytes that
dissociate completely in solution.
Strong Bases
Strong Acids
hydrochloric acid HCl
hydrobromic acid HBr
hydroiodic acid
HI
nitric acid
HNO3
sulfuric acid
H2SO4
perchloric acid HClO4
H-X acids
Oxide containing acids
lithium hydroxide:
LiOH
sodium hydroxide:
NaOH
potassium hydroxide: KOH
calcium hydroxide
Ca(OH)2
strontium hydroxide Sr(OH)2
barium hydroxide
Ba(OH)2
Group I and II Hydroxides
Acids and bases can be classified as strong or
weak. We use arrows to symbolize the difference.
Anything not strong is weak!
Common Weak Acids and Their Anions
100% ionized = strong electrolyte = ==> arrow
Acid
HF
CH3COOH
Anion
FCH3COO-
Anion Name
fluoride ion
acetate ion
HCN
HNO2
H2CO3
H2SO3
CNNO2CO32SO32-
cyanide ion
nitrite ion
carbonate ion
sulfite ion
H3PO4
(COOH)2
PO43(COO)22-
phosphate ion
oxalate ion
Strong Acid
H2SO4(aq) ==> 2H+(aq) + SO42-(aq)
Strong Base
KOH(aq) ==> OH-(aq) + K+ (aq)
<20% ionized = weak electrolyte = <==> arrow
Weak Acid
HNO2(aq) <==> H+(aq) + NO2-(aq)
Weak Base
NH4OH(aq) <==> OH-(aq) + NH4+ (aq)
Determining the Molarity of H+ Ions in Aqueous
Solutions of Acids
Determining the Molarity of H+ Ions in Aqueous
Solutions of Strong Acids or Bases
Nitric acid is a major chemical in the fertilizer and
explosives industries. In aqueous solution, each
molecule dissociates and the H becomes a
solvated H+ ion. What is the molarity of H+(aq) in
1.4M nitric acid?
Nitric acid is a major chemical in the fertilizer and
explosives industries. In aqueous solution, each
molecule dissociates and the H becomes a solvated H+
ion. What is the molarity of H+(aq) in 1.4M nitric acid?
What is the H+ molarity of 0.70 M H2SO4?
Of H+ .466 M H3PO4?
One mole of H+(aq) is released per mole of nitric acid (HNO3)
HNO3(l)
H 2O
H+(aq) + NO3-(aq)
1.4M HNO3(aq) is 1.4M H+(aq).
What is the molarity of H+ in a 0.70 M H2SO4?
Of 2.5 M NaOH ?
What is the molarity of H+ in a 0.466 M H3PO4?
Acids and bases react in a must know chemical
reaction called a “neutralization reaction” to form a
salt and water.
Chemists use general symbols to represent the
“neutralization reaction” to form a salt and water.
NaOH (aq) + HCl (aq) ==> H2O + Na+ + ClNaOH (aq) + HCl (aq) ==> H2O + Na+ + Clbase
+ acid
base
+ acid
==> Water + salt
==> Water + salt
MOH (aq) + HX (aq) ==> H2O + Na+ + Cl-
A salt is an ionic compound whose cation comes
from a parent base and whose anion comes from
a parent acid:
Learning check: write the molecular, ionic and net
equation for the neutralization between calcium
hydroxide and sulfuric acid.
Alkali
Metal Cation
Halide
Anion
Learning check: Write molecular, ionic and net
equations for the following acid base neutralization
reactions.
1. The molecular equation
shows all reactants and products as undissociated compounds.
strontium hydroxide(aq) + perchloric acid(aq)
Ca(OH)2 (aq) + H2SO4 (aq) ===> 2H2O + CaSO4
2. The total ionic equation
barium hydroxide(aq) + sulfuric acid(aq)
shows all of the soluble ionic substances dissociated into ions.
Ca2+ + 2OH- + 2H+ + SO42- ===> 2H2O + Ca2+ + SO42-
Nitric acid(aq) + barium hydroxide(aq)
Ca2+ and SO42- are spectator ions---they just watch!
3. The net ionic equation
eliminate spectator ions and show actual chemical change
H+(aq) + OH- (aq) ===> H2O(l)
Acetic acid(aq) + potassium hydroxide
Writing Ionic Equations for Acid-Base Reactions
strontium hydroxide(aq) + perchloric acid(aq)
(a) Sr(OH)2(aq)+2HClO4(aq)
2H2O(l)+Sr(ClO4)2(aq)
(b) Sr2+(aq)+2OH-(aq)+ 2H+(aq)+2ClO4-(aq)
2H2O(l)+Sr2+(aq)+2ClO4-(aq)
(c) 2OH-(aq)+ 2H+(aq)
2H2O(l)
NaOH(aq) + CH3COOH(aq)
CH3COONa(aq) + H2O
Weak acid is not dissociated!
Na+(aq)+ OH-(aq) + CH3COOH(aq)
CH3COO-(aq) + Na+(aq) + H2O(l)
2H2O(l) + BaSO4(aq)
Ba2+(aq) + 2OH-(aq)+ 2H+(aq)+ SO42-(aq)
2H2O(l)+Ba2+(aq)+SO42-(aq)
(c) 2OH-(aq)+ 2H+(aq)
Molecular equation
Total ionic equation
barium hydroxide(aq) + sulfuric acid(aq)
(b) Ba(OH)2(aq) + H2SO4(aq)
Weak acids dissociate to a very small extent and
this fact is reflected in their equations as well
using a double-arrow (<==>).
Net ionic equation
OH-(aq) + CH3COOH(aq)
CH3COO-(aq) + H2O(l)
2H2O(l)
Learning Check: Acids and Bases
1. Name and characterize each as a base, acid or salt?
HF(g), HI(aq), LiOH(aq), Mg(OH)2, Na2SO4 CH3COONH4
Chemists symbolize the reactions of acids with
water two equivalent ways. Don’t let it bug you.
H+ representation
H3O+ Representation
2. Name and classify the following as strong, weak acid or base?
H 2O
HClO4, Sr(OH)2, HClO2, NH3(g), H3PO4(aq), H2SO4(aq), HNO3
(aq)
HCl(g) ===> H+ + Cl-
HCl(g) + H2O => H3O+ + Cl-
3. Write the M/I/NI equation for the reactions of a) hydrochloric
acid with calcium hydroxide and b) phosphoric acid with
sodium hydroxide
H 2O
HNO3(l) ===> H+ + NO3-
HNO3(g) + H2O => H3O+ + NO3-
4. What acids and bases were reacted to form the following
salts? Show using balanced equations.
HA(g) ===> H+ + A-
1) NaNO2
2) CaSO4
3) Mg(PO4)2
Quiz 3
H 2O
Generalized Acid HA
HA(g) + H2O => H3O+ + AGeneralized Acid HA
Given the following reaction: N2(g) + H2(g) ==> NH3(g)
Mol Mass (g/mol): N2 = 28.01; H2 = 2.016; NH3 = 17.03
(1) Balance the equation: N2(g) + H2(g) => NH3(g) (1.5 pts).
Please put your books away!
Full-sheet of paper with name on top!
Time is 10 minutes
(2) If 1.0 g of N2 is reacted with excess H2, how many
moles of NH3 can be produced? (2 pts)
(3) If 1.0 g of H2 is reacted with excess N2, how many
moles of NH3 can be produced? (1.5pts)
(4) Suppose reacting 2.0 g of N2 with excess H2 produces
2.4 g of NH3, while reacting 2.0 g of H2 with excess N2
produces 11 g of NH3. If 2.0 g of N2 is reacted with 2.0 g
of H2, is N2 or H2 the limiting reagent? (1 pt)
(5) How many H atoms are in 1.0 g of NH3? (4 pts)