Chapter 4 Chemistry
Review
Aqueous Reactions and Solution Stoichiometry
By: Enid Truong and Alyisha Bouges
Electrolytes
A substance whose aqueous solution contains
ions. The more ions present the stronger the
solution. Ex:NaCl
Nonelectrolyte: a substance that does not form ions Ex:
C12H22O11
Strong vs. Weak
Strong = completely ionized, all Ionic
compounds and the strong molecular acids
Weak = some amount ionizes, weak acids
and bases
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Electrolytes
Dissolution?
When an ionic compound dissolves in water.
Solvation?
When water molecules surround an ion to stop them
from rebonding.
Denoted with an aqueous phase abbreviation: (aq)
Precipitates
A reaction that results in the formation of an
insoluble product are called Precipitation
Reactions.
A precipitate is an insoluble solid that is
formed in a reaction
Ex:KI (aq) + Pb(NO3)2 (aq) ---> PbI2 (s) + 2KNO3 (aq)
Solubility Rules!
Which of the pair is insoluble (will be solid)?
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Na2SO4 or BaS
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KOH or CaCl2
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MgCrO4 or LiClO3
Solubility Rules!
Net Ionics
CaCl2 (aq) + Na2CO3 (aq) ---> CaCO3 (s) + 2NaCl (aq)
Write the net ionic and find the precipitation
reaction that occurs when aqueous solutions
of Calcium Chloride and Sodium Carbonate
are mixed.(as seen above)
Ca^2+(aq) + CO3^2+(aq) ------> CaCO3(s)
Acids vs. Bases
Acids:
H+
Proton donor
Ex: HCl(monoprotic)
H2SO4(diprotic)
H3P(triprotic)
Bases:
OHProton acceptor
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Strong acids and
bases are strong
electrolytes, so
they ionizes
completely.
Weak acids and
bases do not.
Acids vs. Bases
Ways to remember:
Our favorite for strong acids:
http://www.youtube.com/watch?v=jPil
rd7b1B8
Something new for strong bases: The Thumb
Rule
(AKA: The Rule of Thumb)
Neutralization Reactions
When you add an acid to a base, the result is
water and a salt.
Ex: HCl (aq) + NaOH (aq) ---> H2O (l) + NaCl (aq)
Try one!! Magnesium hydroxide and
hydrochloric acid. What do they form?
H2O(l) + MgCl2(aq)
Acid-Base Gas Formations
Sulfide ion and Carbonate ions both from gas
when they react with acids. For example:
2HCl(aq) + Na2S(aq) --->H2S(g) + 2NaCl(aq)
But what does this produce?
Na2SO3(aq) + HCl(aq)----> ?
NaCl(aq) + H2SO4
H2O(l) + SO2(g)
Oxidation-Reduction
AKA :REDOX Reactions
Oxidation - the LOSS of electrons by a substance.
Reduction - the GAIN of electrons by a substance
Great way to memorize this: LEO says GER (Lose Electron
Oxidizes/ Gains Electrons Reduces)
Which one reduces and which one oxidizes? :
Ca(s) + 2 H^+(aq) ---> Ca2^+(aq) + H2(g)
oxidized!
Oxidation Numbers
1) For an Atom in its elemental form, the oxidation number
is always zero
EX: H2 has an oxidation number of 0
2) For any Monatomic ion the oxidation number equals the
charge on the ion
EX: K+ has an oxidation number of +1 and S2has an oxidation number of -2
Oxidation Numbers
3) Nonmetals usually have negative oxidation numbers, but
they can be positive with some exceptions:
1) The oxidation number of oxygen is usually -2 in both
ionic and molecular compounds. The exception is in
peroxides (O2)^2-, giving each oxygen a charge of 1-.
For ex: BaO2 ; (1)(-2) + (2)(x) = 0 ; O = -1
2) The oxidation of Hydrogen is usually +1 when bonded
to nonmetals and -1 with metals
For ex: NaH ; Na is a metal, so in this case, the ox.
number of H is -1
Oxidation Numbers
3) The oxidation number of fluorine is -1 in all
compounds. Other halogens have an ox. number of 1- in
most binary compounds, but when combined with
oxygen, they have positive ox. numbers.
4) The sum of the oxidation numbers of all atoms in a
neutral compound is zero. The sum of the ox. number of
polyatomic ions equals the charge of the ion.
For ex: (Cr2O7)^ -2
Cr is unknown, but we know O has an oxidation number
of -2, so (x)(2) + (-2)(7) = -2. Cr = -1
Molarity
Molarity (M) = Moles solution / volume of
solution in liters
Problem: What is the molar concentration of
K+ ions in a o.o15M solution of potassium
carbonate?
0.030M
Dilution and Titration
McVc = MdVd (where c = concentrate & d =
dilute)
Titration: a method scientists often use to
determine the concentration of a particular
solute in a solution..
MaVaIa = MbVbIb (M stands for molarity, V
stands for volume, I stand for ions, a = acids
and b = base) To find "I" look at the amount of H+ and OHions
Activity Series
Take out your Super Secret Periodic Tables and
turn to page 39.
This is your table of the activity series.
Which is a list of metals arranged in order of
decreasing ease of oxidation and to form
compounds.
Any metal on the list can be oxidized by the
element below it!
Activity Series
Now answer this:
If you add copper to a solution with silver
present, will there be a reaction?
Yes!
Now what if gold were added to the same
solution?
No!