Common Types of Chemical Reactions. Decomposition.
22
Common Types of Chemical Reactions
-
Upload
pierce-franklin -
Category
Documents
-
view
236 -
download
0
Transcript of Common Types of Chemical Reactions. Decomposition.
Common Types of Chemical Reactions
Decomposition
Double Displacement
Single Displacement
Combustion
Combustion
Oxidation–Reduction Reactions
A chemical reaction in which an atom or ion loses electrons
to another atom or ion.
Fe (s) + Al(NO3)3 (aq) Fe(NO3)3 (aq) + Al (s)charges 0 03+ 3+
Fe: 0 +3 OxidationAl: +3 0 Reduction
Electrons
Lost 3Gained 3
“Redox” Reactions
Leo the Lion says, “Ger”OSE
LECTRON
XIDATION
AIN
LECTRON
EDUCTION
Oxidation numbers (oxidation state) are a chemist’s way of keeping track of electrons.
Assigning Oxidation Numbers
The convention is that the cation is written first in a formula, followed by the anion.
For example, in NaH, the H is H-; in HCl, the H is H+.
Assigning Oxidation Numbers
The oxidation number of a free element is always 0.
The atoms in He and N2, for example, have oxidation numbers of 0.
Assigning Oxidation Numbers
The oxidation number of a monatomic ion equals the charge of the ion.
For example, the oxidation number of Na+ is +1; the oxidation number of N3- is -3.
Assigning Oxidation Numbers
The usual oxidation number of hydrogen is +1.
The oxidation number of hydrogen is -1 in compounds containing elements that are less electronegative than hydrogen, (metals) as in CaH2.
Assigning Oxidation Numbers
The oxidation number of oxygen in compounds is usually -2.
Exceptions include OF2, since F is more electronegative than O
and BaO2, due to the structure of the peroxide ion, which is [O-O] 2-
Assigning Oxidation Numbers
The oxidation number of a Group IA element in a compound is +1
Assigning Oxidation Numbers
The oxidation number of a Group IIA element in a compound is +2
The oxidation number of a Group VIIA element in a compound is -1, except when that element is combined with one having a higher electronegativity. The oxidation number of Cl is -1 in HCl, but the oxidation number of Cl is +1 in HOCl.
The sum of the oxidation numbers of all of the atoms in a neutral compound is 0
CO2 Na2CrO4 C2H5OH
Assigning Oxidation Numbers
-2-2
+4-2-2-2-2
Carbon +4Oxygen -2
+1+1
+1+6
Sodium +1Chromium +6Oxygen -2
+1
+1
+1+1+1
-2-2-2
Carbon -2Hydrogen +1Oxygen -2
The sum of the oxidation numbers in a polyatomic ion is equal to the charge of the ion.
For example, the sum of the oxidation numbers for SO4
2- is -2.
Assigning Oxidation Numbers
PO4-3
NH4+1
ClO3-1
P2O7-4
P +5 O -2N -3 H +1Cl +5 O -2P +5 O -2
Common Types of Chemical Reactions
single displacement: A + BC AC + B
double displacement: AB + CD AD + CB
synthesis (formation): A + B AB
decomposition: AB A + B
combustion: CxHy + O2 CO2 + H2O
oxidation-reduction (redox): (a large variety)
• OXIDATIONOXIDATION—the atom loses (an) electron(s); —the atom loses (an) electron(s); increase in oxidation number.increase in oxidation number.
• REDUCTIONREDUCTION—gain of electron(s); decrease in —gain of electron(s); decrease in oxidation number.oxidation number.
(an agent facilitates something; ex. Travel agents (an agent facilitates something; ex. Travel agents don’t travel, they facilitate travel)don’t travel, they facilitate travel)
• OXIDIZING AGENTOXIDIZING AGENT—electron acceptor; —electron acceptor; speciesspecies is is reduced. reduced.
• REDUCING AGENTREDUCING AGENT—electron donor; —electron donor; speciesspecies is is oxidized.oxidized.
• OXIDATIONOXIDATION—the atom loses (an) electron(s); —the atom loses (an) electron(s); increase in oxidation number.increase in oxidation number.
• REDUCTIONREDUCTION—gain of electron(s); decrease in —gain of electron(s); decrease in oxidation number.oxidation number.
(an agent facilitates something; ex. Travel agents (an agent facilitates something; ex. Travel agents don’t travel, they facilitate travel)don’t travel, they facilitate travel)
• OXIDIZING AGENTOXIDIZING AGENT—electron acceptor; —electron acceptor; speciesspecies is is reduced. reduced.
• REDUCING AGENTREDUCING AGENT—electron donor; —electron donor; speciesspecies is is oxidized.oxidized.
Redox Terms
How to balance complicated Redox reactions:(The simple ten step method!)
1) Assign oxidation numbers to each atom2) Write the half reactions3) Balance all atoms other than H and O (you may need to bring in species from the original equation)
4) Balance the O’s with H2O5) Balance the H’s with H+
6) Balance the charges with e-
7) Multiply half reactions to make e- equal.8) Add the half reactions.9) Check your charges!
If the solution is acidic, yer finished!If the solution is basic…
10)Add as many OH- to both sides as there are H+, then “simplify”.
