Oxidation - Reduction RedOx. Oxidation States z... of an element are determined from the number of...
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Transcript of Oxidation - Reduction RedOx. Oxidation States z... of an element are determined from the number of...
![Page 1: Oxidation - Reduction RedOx. Oxidation States z... of an element are determined from the number of electrons that are ______ other atoms yGained from.](https://reader035.fdocuments.us/reader035/viewer/2022062421/56649d095503460f949db925/html5/thumbnails/1.jpg)
Oxidation - Reduction
RedOx
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Oxidation States
. . . of an element are determined from the number of electrons that are ______ other atoms Gained from Lost toAND Shared with
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Rules of assigning oxidation states
Atoms have a negative oxidation state if they have the higher e-neg in the bond NH3
N=-3 H=+1 Oxidation states on
all the atoms of a molecule & compoundmust add upto equal zero
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Uncombined elementsfree state
Elements that are not bonded to a different element have oxidation states of zero.
Al(s) Cu(s) Ag(s) Cl2 O2 O3 Ne
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H2S sulfur has a -2 oxidation state
H2SO3
sulfur has a +4 oxidation state
H2SO4
sulfur has a +6 oxidation state
NOW More complicated . . .
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Assigning oxidation states to atoms in a polyatomic ion
Oxidation states on individual atoms must equal the charge on the ion
(SO4)(S+6 O4-2
)
-8+6 = -2
(S O4) = -2
(S O4-2
)
-8 = -2
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Try these . . .
hydroxide
dichromate
ammonium
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Assign oxidation states to each atom
NaOH
MnCrO4
(NH4)2SO4
K2O2
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Balancing RedOx reactionsusing oxidation states
Zn + HNO3 Zn(NO3)2 + NO2 + H2O
Go through the steps on paper…
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1. Assign oxidation states to all atoms determine the
number of e- lost and gained
+4
+3
+2
+1
0
-1
-2
-3
-4L
osin
g e- o
xida
tion
Gain e
- Reduction
![Page 11: Oxidation - Reduction RedOx. Oxidation States z... of an element are determined from the number of electrons that are ______ other atoms yGained from.](https://reader035.fdocuments.us/reader035/viewer/2022062421/56649d095503460f949db925/html5/thumbnails/11.jpg)
2. Select product coefficients that balance the e- HINT: switch #’s balance major elements with reactants
3. Balance leftovers with inventory
*coefficients must be lowest possible whole #s
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Balance - use oxidation states
Cu + HNO3 Cu(NO3)2 + H2O + NO
3Cu + 8HNO3 3Cu(NO3)2 + 4H2O + 2NO
K2Cr2O7 + H2O + S SO2 + KOH + Cr2O3
2K2Cr2O7 + 2H2O + 3S 3SO2 + 4KOH + 2Cr2O3
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Balancing net ionic rxns
Mg + Al3+ Mg2+ + Al
Al3+ and Mg+2 are ionsif they give you the charge use it! Its part of a net ionic rxn
they have removed the spectator ions.
Balance for mass and charge
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Balance . . . for mass and charge
Cu2+ + K K+ + Cu
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RedOx reactions
Chemical reactions involving an
electron transfer between
reactants
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Recognizing RedOx
assign oxidation states to the individual elements in reactants and the products
if the oxidation state changes for some of the particles it is considered a RedOx reaction
Single Replacement Reactions are ALWAYS RedOXDouble Replacement Reactions are NEVER RedOX
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In a RedOx reaction
If electrons are lost by one species in a reaction they
all MUST be gained by another!
If one atom is being oxidized another must be reduced.
In other words . . . oxidation and reduction always occur
together
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Oxidation
Oxidation results in an increase in oxidation state
Atoms that Lose e-lectrons undergo
Oxidation
Metals tend to undergo oxidation
+3 +2 +1 0 -1 -2 -3
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ReductionReduction results in a decrease
in oxidation state
Atoms which Gain e-lectrons
undergo Reduction
Non-metals tend to undergo reduction
+3 +2 +1 0 -1 -2 -3
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GeR
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RedOx: Yes or NO?
HCl + NaOH HOH + NaCl
Mg + 2HCl MgCl2 + H2
MnO2 + 4HBr MnBr2 + Br2 + 2H2O
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Al + CuCl2 ? Write a balanced equation based
on these reactants. Is this a RedOx reaction?What species is oxidized?
Reduced?
Predicting Products of Single Replacement Reactions
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Roaring Animals Often Attack
Elements that undergo oxidation cause reduction Reducing agent
Elements that undergo reduction cause oxidation Oxidizing agent
LEO GER
RA OA
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2Al + 3CuCl2 2AlCl3 + 3Cu
What is the Oxidizing Agent? Cu+2 because it gets reduced
What is the Reducing Agent? Al because it gets oxidized
These answers always come from the reactant
side
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MnO2 + 4HCl MnCl2 + Cl2 + 2H2O
Assign oxidation states to all atomsWhat species is oxidized?
How do you know?What species is reduced?
How do you know?
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What species is the oxidizing agent? Mn+4 because it gets reduced
What species is the reducing agent? Cl- because it gets oxidized
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RedOx Practice
Remember . . .+4
+3
+2
+1
0
-1
-2
-3
-4L
osin
g e- o
xida
tion
Gain e
- Reduction
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Writing half-reactions
A half reaction shows either oxidation or reduction of a RedOx reaction.
The electrons being lost (oxidation) or gained (reduction) are also shown.
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Oxidation half-reaction
Fe(s) Fe+3(aq) + 3e-
oxidation number increaseselectrons are lost
productsconservation of mass AND CHARGE
charges on both sides equal each other
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Reduction half-reaction
Sn+4 + 2e- Sn+2
oxidation number decreaseselectrons are gained
reactantsconservation of mass AND CHARGE
charges on both sides equal each other
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Balancing RedOx using 1/2 reactions
1. ASSIGN OXIDATION STATES . . .2. Write the oxidation 1/2 reaction3. Write the reduction 1/2 reaction4. Balance the two half reactions so that
the number of electrons transferred is equal
5. Use these coefficients to balance the RedOx atoms
6. Balance leftover atoms by inventory
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. . . use 1/2 reactions
KMnO4 + HCl MnCl2 + KCl + Cl2 + H2O
ZnS + O2 SO2 + ZnO
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The End
I came . . . I saw . . . I RedOxed