Download II) Decomposition reactions - Parkway C-2

SUMMARY OF CHEMICAL REACTIONS
I)
Synthesis reactions
A + X -------------> AX
a. Metals react with non-metals to produce binary salts (two elements, no polyatomic)
b. Metal oxides (basic anhydrides) react with water to yield bases (metal hydroxides)
c. Non-metal oxides (acid anhydrides) react with water to yield acids (oxidation number
of non-metal does not change – do an imaginary charge check!)
d. Metal oxides react with non-metal oxides to produce a polyatomic salt
(Oxidation number of non-metal does not change – do an imaginary charge
check!)
II)
Decomposition reactions
AX -------------> A + X
a. Acids with oxygen decompose to give non-metal oxides and water Acids with oxygen
decompose to give non-metal oxides and water (oxidation number of non-metal does
not change – do an imaginary charge check!
b. Metallic hydroxides, or bases, decompose to give metal oxides and water
c. Metallic carbonates decompose to give metal oxides and carbon dioxide
d. Metallic chlorates decompose to give metal chlorides and oxygen
e. Metallic nitrates decompose to give metal nitrites and oxygen
f. Ammonium carbonate decomposes to give ammonia, water, and CO2
g. Sulfurous acid decompose to give water and sulfur dioxide
h. Carbonic acid decomposes to give water and carbon dioxide
i. Ammonium hydroxide decomposes to give ammonia and water
j. Binary compounds decompose to give two elements (with energy)
k. Hydrogen peroxide decomposes to give water and oxygen
l. Polyatomic salts not listed above can decompose to form the metal oxide and non-metal
oxide that formed them (oxidation number of non-metal does not change – do an
imaginary charge check!)
III)
Single Replacement reactions
A + BX -------------> AX + B
a.
b.
c.
d.
Active metals replace less active metals in ionic compounds in aqueous solutions
Active metals replace H in water to form metal hydroxides (bases) and H2
Active metals replace H in acids to form hydrogen gas and a salt
Active non-metals replace less active non-metals in ionic compounds in aqueous
solutions
e. Non-aqueous replacement reactions – reductions of metal oxides by hydrogen or other
gases:
- H2 + CuO → Cu + H2O (occur at high temperatures!)
- CO + Fe2O3 → Fe + CO2
IV)
Metathesis (Double Replacement reactions) – Removal of ions is the driving force
(cations change partners) to form a solid, liquid, or gas that stays whole as a molecule
– involves two ionic compounds!
AX + BY -------------> AY + BX
ONE OF YOUR PRODUCTS MUST BE FORMED AS A SOLID, LIQUID, OR GAS – THIS
IS WHAT DRIVES A DOUBLE REPLACEMENT REACTION!
a. Formation of a precipitate (solid) governed by the solubility rules
b. Formation of a gas
-
Common gases are H2S, CO2, SO2, NH3
1.
2.
3.
4.
-
Any sulfide (S-2) plus any acid forms H2S gas and a salt
Any carbonate (CO3-2) plus any acid forms CO2, HOH, and a salt
Any sulfite (SO3-2) plus any acid forms SO2, HOH, and a salt
Any ammonium (NH4+1) compound plus a soluble hydroxide form NH3,
HOH, and a salt
IMPORTANT – IF YOU CREATE NH4OH, H2CO3, AND H2SO3, THEY
WILL IMMEDIATELY BREAK DOWN INTO H2O AND A GAS – NH3,
CO2, OR SO2 - THESE THREE COMPOUNDS ARE UNSTABLE AND
CANNOT BE ISOLATED!
c. Formation of a molecule – which is a compound that does not dissociate well in water,
due to its covalent nature! It stays together as a molecule! Example – H2O!
-
Acid-base neutralization is one type – ACID PLUS BASE = WATER
PLUS SALT
d. Hydrolysis – Reverse of an acid-base neutralization – a salt reacts with water – this
will only happen with one in a trillion water molecules!
-
-
One in a trillion water molecules can break apart into H+1 and OH-1
The salt then breaks apart, and a double replacement reaction occurs, with the
salt reacting with the H+1 and the OH-1
Produces an acid and a base every time!
Salts are products of neutralization, but salts that undergo hydrolysis are not
neutral!
1. Salts of a strong acid and a weak base + H2O give an acidic solution
2. Salts of a weak acid and a strong base + H2O give a basic solution
3. Salts of a strong acid and a strong base do not undergo hydrolysis – their
solutions are neutral!
4. Salts of a weak acid and a weak base + H2O may give an acidic, basic, or
neutral solution – look at the strength of the acid or base produced (Ka or
Kb)
A COUPLE OF REMINDERS FOR REACTIONS THAT OCCUR IN WATER, WHEN YOU
GO TO WRITE IONIC REACTIONS:
i.
ii.
iii.
iv.
Strong acids ionize or dissociate 100% in water
Strong bases ionize or dissociate 100% in water
Most common (soluble) salts dissociate in water
Weak acids and water do not dissolve well in water, and should be
written as whole molecules!
STRONG ACIDS:
HClO4
HClO3
HCl
HBr
KOH
Ca(OH)2
HI
HNO3
H2SO4
STRONG BASES:
LiOH
NaOH
Sr(OH)2
Ba(OH)2
NOTE ON HIDDEN REACTIONS! LOOK FOR:
1. IF ONE COMPOUND IS AQUEOUS, THAT MEANS THAT
IT IS IN WATER, AND THE OTHER COMPOUND
MIGHT REACT WITH THAT WATER!
2. IF ONE COMPOUND IS AN ACID OR A BASE, THEN
THE OTHER COMPOUND MIGHT REACT WITH
WATER TO FORM AN ACID OR A BASE
3. NON-METAL OXIDES THAT REACT WITH WATER
4. METAL OXIDES THAT REACT WITH WATER
V)
Organic Reactions
a. Addition Reactions
b. Substitution Reaction
c. Combustion Reactions (oxidation of an organic molecule)
-
Usually have the general form:
Organic Molecule + O2 -------------> CO2 + H2O
-
Can produce CO and C with incomplete combustion (lack of O2)
Organic molecule often times is a hydrocarbon – can contain other elements,
such as N or S – nitrogen and sulfur oxides are produced
d. Esterification
e. Saponification
VI)
Reduction/Oxidation Reactions
-
-
In a reduction/Oxidation reaction, one species is oxidized (loses electrons) and
the other species is reduced (gains electrons)
The species being oxidized is called the “reducing agent” and the species
being reduced is called the “oxidizing agent”
Many oxidation/reduction reactions will occur in either acidic or basic
solution, taking advantage of H+ or OH- ions, along with H2O, to aid the
reduction/oxidation
These reactions are written and balanced using the half-reaction method
There are obvious signs to look for in a common redox reaction:
Important Oxidizing Agents (These things are reduced!)
MnO4- (acid solution)
MnO4- (basic solution)
MnO2 (acid solution)
Cr2O7-2 (acid solution)
CrO4-2 (basic solution)
HNO3, concentrated
HNO3, dilute
H2SO4, hot concentrated
Metallic Ions
Free Halogens
HClO4
Na2O2
H2O2
Perhalates, halates, halites
Formed in Reaction
Mn+2
MnO2
Mn+2
Cr+3
Cr+3
NO2
NO
SO2
Metallous Ions
Halide Ions
Cl-1
OH-1
H2O
Halogens
Important Reducing Agents (These things are oxidized!)
Halide Ions
Free Metals
Metallous Ions
Sulfite Ions, SO2
Free Halogens (dilute basic solution)
Free Halogens (concentrated basic solution)
C2O4-2
NO2-1
Sn+2
H2O2
Formed in Reaction
Halogens
Metal Ions
Metallic Ions
SO4-2
Hypohalite Ions
Halate Ions
CO2
NO3-1
Sn+4
O2
Chromium: dichromate to Cr3+ in acid solution; chromate to Cr(OH)3 in basic solution.
Dichromate ion can turn into chromate in basic solution, and chromate ion can turn into
dichromate ion in acidic solution (this is not reduction/oxidation – the Cr still retains a +6
charge)
Oxygen: hydrogen peroxide can acts as an oxidizing agent (reduced to water) and a reducing
agent (oxidized to oxygen gas).
Nitrogen: nitrate ion is an oxidizing agent only in acid solution. The reduction product is NO.
Sulfur: sulfate ion is an oxidizing agent only in acid solution. The reduction product is SO2.
VII)
Complex Ion Reactions (Coordination Chemistry)
a.
b.
c.
d.
e.
f.
Transition metal salt + ligand → complex ion
Aluminum salt + ligand → complex ion
Beryllium salt + ligand → complex ion
Both Zn+2 and Al+3 form Zn(OH)4-2 and Al(OH)4-1 when treated with excess hydroxide
Ag+1, Cu+2, Zn+2, and Cd+2 all form complexes with NH3
Infrequently seen, but has been on the AP, and used in lab:
1. Thiocyanate acts as a ligand and bonds to a transition metal
a. A drop of potassium thiocyanate is added to a solution of iron
(III) chloride:
SCN-1 + Fe+3 → Fe(SCN)+2
2. Ammonia, as a ligand, gets turned into ammonium ion, and the transition
metal is freed from being a complex ion
a. Dilute hydrochloric acid is added to a solution of diamminesilver
(I) nitrate:
H+1 + Cl-1 + [Ag(NH3)2]+2 → AgCl + NH4+1
Notice the destruction, rather than the formation, of a complex
Common ligands are: Cl-, I-1, Br-1, F-1, OH-1, H2O, C2O4-2, NH3, SCN-1, CN-1
It is a good idea to recognize the names of these ligands as well – iodo, bromo, fluoro, hydroxy, aqua,
oxalato, ammine, thiocyanato or isothiocyanato, and cyano
To determine the coordination number:
-
For aqua complexes of transition metals, C.N. = 6
For others, C.N. = cation charge x 2
VIII) Lewis Acid and Lewis Base Reactions
a. Lewis acid reacts with a Lewis base to form an adduct:
- BF3 + NH3 → F3BNH3
b. Phosphorus (V) oxytrichloride is added to water
- POCl3 + H2O → H3PO4 + Cl- + H+
c. Note that molecular phosphorus compounds form acids with water.
- PCl5 + H2O → H3PO4 + H2O + Cl- + H+
- PCl3 + H2O → H3PO3 + Cl- + H+
d. Organic bases that have unshared pairs of electrons can react with water or other H+
suppliers:
- Methylamine gas is bubbled into water:
- CH3NH2 + H2O → CH3NH3+ + OH¯