H Chem Redox Rxns 2015.notebook
Oxidation Reduction Reactions
(red­ox rxns)
objectives:
(#4‐3) How do chemicals undergo an oxidation reduction reaction?
(#4‐3a) I can identify if a reaction is oxidation/reduction
(#4‐ 3b) I can identify which species in a reaction is being oxidized or reduced.
(#4‐ 3c) I can balance a "simple" redox reaction. Simple: Non‐ oxygen based. (#4‐3d) I can determine the voltage of a redox reaction.
(#4‐3e) I can determine the spontaneity based upon a chemical voltage.
also
I can write half reactions and model the reaction.
Nov 22­9:16 AM
1
H Chem Redox Rxns 2015.notebook
Oxidation Reduction Reactions
(a.k.a. RedOx rxns)
Atoms/ions gain and lose charge in reaction
• e­ are transfered from one species to another
• must occur simultaneously
First, must determine the oxidation state(charges)
oxidation state: the apparent charge on an atom
Oxidation State Rules
• 0 is alway 0­2 when bonded to other atom (except F)
• H is always H+l when bonded to other atom (usually)
not bonded • elements by self have 0 charge if
diatomic (super 7)
• use ion sheet or periodic table
Practice: write oxidation state O2
HF Cu
Fe
Al
NO2
AgNO3
FeCl2
Cl2
try these:
NaHCO3
SO4­2
Nov 22­6:11 AM
2
H Chem Redox Rxns 2015.notebook
Oxidation Reduction Reactions
(redox rxns)
Atoms/ions gain and lose charge in reaction
ou
y
lp
r
he be
to em
rem
Check for REDOX: write charges (oxidation state) above each to see what happens to the charge. Label Reduction and Oxidation.
Cu + AgNO3 Cu(NO3)2 + Ag
Nov 22­6:11 AM
3
H Chem Redox Rxns 2015.notebook
Oxidation Reduction Reactions
(redox rxns)
Types: Determine oxidation and reduction
Metal Replaces Metal ion
Cu + AgNO3 Cu(NO3)2 + Ag
Non­Metal Replaces NonMetal ion
NaCl + F2 NaF + Cl2
Combustion
CH4 + O2 C4H8 + O2 Synthesis (often redox) Na + Cl2 NaCl
Decompostion (often redox) KClO3 KCl + O2
Nov 22­6:11 AM
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H Chem Redox Rxns 2015.notebook
3 equations to depict reaction:
molecular, ionic and net ionic
molecular:
Cu + 2AgNO3 Cu(NO3)2 + 2Ag
ionic: Cu0 + 2Ag+1 + 2NO3­1 Cu+2 + 2NO3­1 + 2Ag0 (show any ions dissociated)
spectator ion: ion that does not change on either side and is not part of the reaction
(remove spectator ions ­­ cross off NO3­1 ­­ same on both sides)
net ionic: Cu0 + 2Ag+1 Cu+2 + 2Ag0
l l tua
ac mica
e
ch ction
rea
balancing 1/2 reactions separate the species, add e­ to balance
Cu0 Cu+2 + 2e­
lose e­ ­­ Ox.
gain e­ ­­Red.
net ionic:
2e­ +
2Ag+1 2Ag0 Cu0 + 2Ag+1 Cu+2 + 2Ag0
Nov 22­6:21 AM
5
H Chem Redox Rxns 2015.notebook
3 equations to depict reaction:
molecular, ionic and net ionic
molecular:
Cu + 2AgNO3 Cu(NO3)2 + 2Ag
ionic: Cu0 + 2Ag+1 + 2NO3­1 Cu+2 + 2NO3­1 + 2Ag0 (show any ions dissociated)
spectator ion: ion that does not change on either side and is not part of the reaction
(remove spectator ions ­­ cross off NO3­1 ­­ same on both sides)
Cu0 + 2Ag+1 Cu+2 + 2Ag0
net ionic: l l tua
ac mica
e
ch ction
rea
balancing 1/2 reactions separate the species, add e­ to balance
Cu0 Cu+2 + 2e­
lose e­ ­­ Ox.
gain e­ ­­Red.
net ionic:
2e­ +
2Ag+1 2Ag0 Cu0 + 2Ag+1 Cu+2 + 2Ag0
Nov 22­6:21 AM
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H Chem Redox Rxns 2015.notebook
Write the molecular, ionic, and net ionic equation
Write the half reactions.
Determine the voltage and if the reaction is spontaneous.
Na + FeCl2 Nov 22­12:10 PM
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H Chem Redox Rxns 2015.notebook
Write the molecular, ionic, and net ionic equation
Write the half reactions.
Determine the voltage and if the reaction is spontaneous.
Na + FeCl2 Nov 22­12:10 PM
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H Chem Redox Rxns 2015.notebook
Does this reaction happen?
look at potential to lose or gain e­
Cu0 Cu+2 + 2e­ 2e­ + 2Ag+1 2Ag0 Cu0 + 2Ag+1 Cu+2 + 2Ag0
reduction potential chart: ability to gain e­ in E0(Volts)
GER
Standard Reduction Potentials
in Aqueous Solution at 25oC (based off H2 at 0 V)
compare rxn to find E0
2e­ + 2Ag+1 2Ag0 +0.80 V
same rxn: use E0 2x's e­ , but do not 2x's E0 Cu0 Cu+2 + 2e­ reverse rxn: use E0 with opposite sign
­0.34 V
+0.46 V
spontaneous
ur
cc
ill o
w
xn
= r
+ V
­ V = rxn will not occur
before
after
Nov 22­6:48 AM
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H Chem Redox Rxns 2015.notebook
Determine if Red­Ox, write ionic and net ionic eq.
remember to balance these
+1 mol.
­1
+1 0
­1
0
NaCl + F
NaF + Cl
2
2(g)
(aq)
(aq)
ionic: Na+1 + F­1 + Cl20 Na+1 + Cl­1 + F20
net ionic:
F­1 + Cl20 Cl­1 + F20
GER half reactions and E0 (reduction potential)
2F­1 F2 + 2e­
2e­+ 2 2Cl­1 Cl
2F­1 + Cl2 2Cl­1 + F2
­2.87
+1.36
­1.51 V
E0 (­) is non­spontaneous
does not occur without electric current
Nov 22­6:56 AM
10
H Chem Redox Rxns 2015.notebook
Predict products:
0
­1
+2
Zn + Cu(SO4)2 ?
Cu ­­either +1 or +2
Zn usually becomes Zn+2
Zn0 Zn+2 + 2e­ Cu+2 + 1e­
Cu+2 + 2e­
Cu+1
Cu0 SO4­1 spectator ion
general rule:
metals exchange with metals
non­metals exchange with non­metals
Standard Reduction Potentials
in Aqueous Solution at 25oC Zn0 + Cu+2 Zn+2 + Cu0 Does this happen?
Check reduction potential chart
Cu+2 + 2e­
Cu0 Zn Zn+2 + 2e­
+0.34 V
+0.76V
+1.00 V
V is (+) so spontaneous rxn
Nov 22­8:44 AM
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H Chem Redox Rxns 2015.notebook
KI + Br2 K+1 + I­1 + Br20 K+1 + Br ­1 + I20 ionic
I­1 + Br20 Br ­1 + I20 net
Standard Reduction Potentials
in Aqueous Solution at 25oC same rxn: use E0 reverse rxn: use E0 with opposite sign
+1.07
2e­ + Br20 2Br ­1 2 I­1 I20 + 2e­ ­0.53
2 I­1 + Br20 2Br ­1 +I20 +0.54 V
cur
c
o
ill
n w
rx
= + V
spontaneous
Will the reverse (opposite) reaction occur?
KBr + I2 KI + Br2 ­ V so nonspontaneous ­ 0.54V
(reaction will not occur)
Nov 22­6:48 AM
12
H Chem Redox Rxns 2015.notebook
Nov 20­2:12 PM
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H Chem Redox Rxns 2015.notebook
Write the molecular, ionic, and net ionic equation
Write the half reactions.
Determine the voltage and if the reaction is spontaneous.
Cu + AgNO3 Dec 2­9:13 AM
14
H Chem Redox Rxns 2015.notebook
Write the molecular, ionic, and net ionic equation
Write the half reactions.
Determine the voltage and if the reaction is spontaneous.
Al + Zn(NO3)2
Dec 2­9:33 AM
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H Chem Redox Rxns 2015.notebook
Nov 23­8:45 AM
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H Chem Redox Rxns 2015.notebook
Predict the products and balance
Write the net ionic equation.
Write the half reactions.
Determine the voltage and if the reaction is spontaneous.
Draw it!
Ag + Au(N03)3 Dec 2­9:48 AM
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H Chem Redox Rxns 2015.notebook
Which will occur?
Al + Na2SO4
Al + Na2SO4
Al2(SO4)3 + Na Al2(SO4)3 + Na Dec 1­7:34 AM
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H Chem Redox Rxns 2015.notebook
Dec 2­9:33 AM
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