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ElectrochemistryLesson 5Balancing Half Reactions
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Core Concepts
What is reduced and oxidized?What gains or loses electrons?What
are the oxidizing and reducing agents? 2H+ + As2O3 + 2NO3- + 2H2O
2H3AsO4 + N2O3
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Core Concepts
What is reduced and oxidized?What gains or loses electrons?What
are the oxidizing and reducing agents? 2H+ + As2O3 + 2NO3- + 2H2O
2H3AsO4 + N2O3
You must use oxidation #'s
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Core Concepts
What is reduced and oxidized?What gains or loses electrons?What
are the oxidizing and reducing agents? +3 +5 +5 +32H+ + As2O3 +
2NO3- + 2H2O 2H3AsO4 + N2O3
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Core Concepts
What is reduced and oxidized?What gains or loses electrons?What
are the oxidizing and reducing agents? +3 +5 +5 +32H+ + As2O3 +
2NO3- + 2H2O 2H3AsO4 + N2O3
oxidizedreduced
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Core Concepts
What is reduced and oxidized?What gains or loses electrons?What
are the oxidizing and reducing agents? +3 +5 +5 +32H+ + As2O3 +
2NO3- + 2H2O 2H3AsO4 + N2O3
oxidizedreducedloses e'sgains e's
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Core Concepts
What is reduced and oxidized?What gains or loses electrons?What
are the oxidizing and reducing agents? +3 +5 +5 +32H+ + As2O3 +
2NO3- + 2H2O 2H3AsO4 + N2O3
oxidizedreducedloses e'sgains e'sred agentox agent
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PdCl2 reacts with Mn but not Br-.
Write the spontaneous reaction.
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PdCl2 reacts with Mn but not Br-.
Write the spontaneous reaction.
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PdCl2 reacts with Mn but not Br-.
Write the spontaneous reaction.
Pd2++ Mn(s) Pd(s) + Mn2+
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PdCl2 reacts with Mn but not Br-.
Write the spontaneous reaction.
Pd2++ Mn(s) Pd(s) + Mn2+
Rank the oxidizing agents in decreasing strength.
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PdCl2 reacts with Mn but not Br-.
Write the spontaneous reaction.
Pd2++ Mn(s) Pd(s) + Mn2+
Rank the oxidizing agents in decreasing strength.
Pd2+
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PdCl2 reacts with Mn but not Br-.
Write the spontaneous reaction.
Pd2++ Mn(s) Pd(s) + Mn2+
Rank the oxidizing agents in decreasing strength.
Br-
Pd2+
Mn
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PdCl2 reacts with Mn but not Br-.
Write the spontaneous reaction.
Pd2++ Mn(s) Pd(s) + Mn2+
Rank the oxidizing agents in decreasing strength.
Br2Br-
Pd2+
Mn
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PdCl2 reacts with Mn but not Br-.
Write the spontaneous reaction.
Pd2++ Mn(s) Pd(s) + Mn2+
Rank the oxidizing agents in decreasing strength.
Br2Br-
Pd2+
Mn2+Mn
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PdCl2 reacts with Mn but not Br-.
Write the spontaneous reaction.
Pd2++ Mn(s) Pd(s) + Mn2+
Rank the oxidizing agents in decreasing strength.
Br2Br-
Pd2+Pd
Mn2+Mn
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PdCl2 reacts with Mn but not Br-.
Write the spontaneous reaction.
Pd2++ Mn(s) Pd(s) + Mn2+
Rank the oxidizing agents in decreasing strength.
Br2Br-
Pd2+Pd
Mn2+Mn
Br2Pd2+Mn2+
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PdCl2 reacts with Mn but not Br-.
Write the spontaneous reaction.
Pd2++ Mn(s) Pd(s) + Mn2+
Rank the reducing agents in decreasing strength.
Br2Br-
Pd2+Pd
Mn2+Mn
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PdCl2 reacts with Mn but not Br-.
Write the spontaneous reaction.
Pd2++ Mn(s) Pd(s) + Mn2+
Rank the reducing agents in decreasing strength.
Br2Br-
Pd2+Pd
Mn2+Mn
MnPdBr-
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Balancing Redox Half Reactions in Acid Solution
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Balancing Redox Half Reactions in Acid Solution
Cr2O72- Cr3+
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Balancing Redox Half Reactions in Acid Solution
Cr2O72- Cr3+
1. Balance the central atom
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Balancing Redox Half Reactions in Acid Solution
Cr2O72- Cr3+
1. Balance the central atom
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Balancing Redox Half Reactions in Acid Solution
Cr2O72- 2Cr3+
1. Balance the central atom
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Balancing Redox Half Reactions in Acid Solution
Cr2O72- 2Cr3+
1. Balance the central atom2.Balance O by adding H2O
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Balancing Redox Half Reactions in Acid Solution
Cr2O72- 2Cr3+ + 7H2O
1. Balance the central atom2.Balance O by adding H2O
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Balancing Redox Half Reactions in Acid Solution
Cr2O72- 2Cr3+ + 7H2O
1. Balance the central atom2.Balance O by adding H2O3.Balance H
by adding H+
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Balancing Redox Half Reactions in Acid Solution
Cr2O72- + 14H+ 2Cr3+ + 7H2O
1. Balance the central atom2.Balance O by adding H2O3.Balance H
by adding H+
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Balancing Redox Half Reactions in Acid Solution
Cr2O72- + 14H+ 2Cr3+ + 7H2O
1. Balance the central atom2.Balance O by adding H2O3.Balance H
by adding H+4.Balance the charge by adding electrons
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Balancing Redox Half Reactions in Acid Solution +12Cr2O72- +
14H+ 2Cr3+ + 7H2O
1. Balance the central atom2.Balance O by adding H2O3.Balance H
by adding H+4.Balance the charge by adding electrons
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Balancing Redox Half Reactions in Acid Solution +12+6Cr2O72- +
14H+ 2Cr3+ + 7H2O
1. Balance the central atom2.Balance O by adding H2O3.Balance H
by adding H+4.Balance the charge by adding electrons
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Balancing Redox Half Reactions in Acid Solutionmost positive
side +12+66e- +Cr2O72- + 14H+ 2Cr3+ + 7H2O
1. Balance the central atom2.Balance O by adding H2O3.Balance H
by adding H+4.Balance the charge by adding electrons
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Balancing Redox Half Reactions in Acid Solutionmost positive
side +12+66e- +Cr2O72- + 14H+ 2Cr3+ + 7H2O
1. Balance the central atom2.Balance O by adding H2O3.Balance H
by adding H+4.Balance the charge by adding electrons5.Check
charge
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Balancing Redox Half Reactions in Acid Solutionmost positive
side +6+66e- +Cr2O72- + 14H+ 2Cr3+ + 7H2O
1. Balance the central atom2.Balance O by adding H2O3.Balance H
by adding H+4.Balance the charge by adding electrons5.Check
charge
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Balancing Redox Half Reactions in Acid Solution
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Balancing Redox Half Reactions in Acid Solution
HV2O53- H2VO3+
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Balancing Redox Half Reactions in Acid Solution
HV2O53- H2VO3+
1. Balance the central atom
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Balancing Redox Half Reactions in Acid Solution
HV2O53- 2H2VO3+
1. Balance the central atom
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Balancing Redox Half Reactions in Acid Solution
HV2O53- 2H2VO3+
1. Balance the central atom2.Balance O by adding H2O
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Balancing Redox Half Reactions in Acid Solution
H2O + HV2O53- 2H2VO3+
1. Balance the central atom2.Balance O by adding H2O
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Balancing Redox Half Reactions in Acid Solution
H2O + HV2O53- 2H2VO3+
1. Balance the central atom2.Balance O by adding H2O3.Balance H
by adding H+
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Balancing Redox Half Reactions in Acid Solution
H2O + HV2O53- + H+ 2H2VO3+
1. Balance the central atom2.Balance O by adding H2O3.Balance H
by adding H+
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Balancing Redox Half Reactions in Acid Solution
H2O + HV2O53- + H+ 2H2VO3+
1. Balance the central atom2.Balance O by adding H2O3.Balance H
by adding H+4.Balance the charge by adding electrons
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Balancing Redox Half Reactions in Acid Solution -2 H2O + HV2O53-
+ H+ 2H2VO3+
1. Balance the central atom2.Balance O by adding H2O3.Balance H
by adding H+4.Balance the charge by adding electrons
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Balancing Redox Half Reactions in Acid Solution -2 +2H2O +
HV2O53- + H+ 2H2VO3+
1. Balance the central atom2.Balance O by adding H2O3.Balance H
by adding H+4.Balance the charge by adding electrons
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Balancing Redox Half Reactions in Acid Solutionmost positive
side -2 +2H2O + HV2O53- + H+ 2H2VO3+
1. Balance the central atom2.Balance O by adding H2O3.Balance H
by adding H+4.Balance the charge by adding electrons
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Balancing Redox Half Reactions in Acid Solution -2 +2H2O +
HV2O53- + H+ 2H2VO3+ + 4e-
1. Balance the central atom2.Balance O by adding H2O3.Balance H
by adding H+4.Balance the charge by adding electrons
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Balancing Redox Half Reactions in Acid Solution -2 +2H2O +
HV2O53- + H+ 2H2VO3+ + 4e-
1. Balance the central atom2.Balance O by adding H2O3.Balance H
by adding H+4.Balance the charge by adding electrons5.Check
charge
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Balancing Redox Half Reactions in Acid Solution -2 -2H2O +
HV2O53- + H+ 2H2VO3+ + 4e-
1. Balance the central atom2.Balance O by adding H2O3.Balance H
by adding H+4.Balance the charge by adding electrons5.Check
charge
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Balancing Redox Half Reactions in Acid
SolutionHBr2O72-H2BrO2-
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Balancing Redox Half Reactions in Acid SolutionHBr2O72-
2H2BrO2-
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Balancing Redox Half Reactions in Acid SolutionHBr2O72- 2H2BrO2-
+ 3H2O
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Balancing Redox Half Reactions in Acid SolutionHBr2O72-+ 9H+
2H2BrO2- + 3H2O
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Balancing Redox Half Reactions in Acid Solution+7-2HBr2O72- +
9H+ 2H2BrO2- + 3H2O
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Balancing Redox Half Reactions in Acid Solution+7-29e- +
HBr2O72- + 9H+ 2H2BrO2- + 3H2O
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Balancing Redox Half Reactions in Acid Solution+7-29e- +
HBr2O72- + 9H+ 2H2BrO2- + 3H2O
Reduction: electrons are on the left
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Balancing Redox Half Reactions in Acid Solution-2-29e- +
HBr2O72- + 9H+ 2H2BrO2- + 3H2O
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Balancing Redox Half Reactions in Acid Solution-2-29e- +
HBr2O72- + 9H+ 2H2BrO2- + 3H2O
To balance in base solution.
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Balancing Redox Half Reactions in Acid Solution-2-29e- +
HBr2O72- + 9H+ 2H2BrO2- + 3H2O
To balance in base solution.
1.Balance in acid
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Balancing Redox Half Reactions in Acid Solution-2-29e- +
HBr2O72- + 9H+ 2H2BrO2- + 3H2O
To balance in base solution.
1.Balance in acid2.Add OH- to each side to neutralize H+
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Balancing Redox Half Reactions in Acid Solution-2-29e- +
HBr2O72- + 9H+ 2H2BrO2- + 3H2O 9OH- 9OH-To balance in base
solution.
1.Balance in acid2.Add OH- to each side to neutralize H+
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Balancing Redox Half Reactions in Acid Solution-2-29e- +
HBr2O72- + 9H+ 2H2BrO2- + 3H2O 9OH- 9OH-To balance in base
solution. 9H2O
1.Balance in acid2.Add OH- to each side to neutralize H+
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Balancing Redox Half Reactions in Acid Solution9e-+HBr2O72- +
9H2O 2H2BrO2- + 3H2O + 9OH- To balance in base solution.
1.Balance in acid2.Add OH- to each side to neutralize
H+3.Simplify
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Balancing Redox Half Reactions in Acid Solution 69e-+HBr2O72- +
9H2O 2H2BrO2- + 3H2O + 9OH- To balance in base solution.
1.Balance in acid2.Add OH- to each side to neutralize
H+3.Simplify
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Balancing Redox Half Reactions in Acid Solution 9e-+HBr2O72- +
6H2O 2H2BrO2- + 9OH- To balance in base solution.
1.Balance in acid2.Add OH- to each side to neutralize
H+3.Simplify
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Balancing Redox Half Reactions in Acid Solution 9e-+HBr2O72- +
6H2O 2H2BrO2- + 9OH- To balance in base solution.
1.Balance in acid2.Add OH- to each side to neutralize
H+3.Simplify4.Check charge
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Balancing Redox Half Reactions in Acid Solution-11 9e-+HBr2O72-
+ 6H2O 2H2BrO2- + 9OH- To balance in base solution.
1.Balance in acid2.Add OH- to each side to neutralize
H+3.Simplify4.Check charge
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Balancing Redox Half Reactions in Acid Solution-11-11
9e-+HBr2O72- + 6H2O 2H2BrO2- + 9OH- To balance in base
solution.
1.Balance in acid2.Add OH- to each side to neutralize
H+3.Simplify4.Check charge
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Balance in alkaline solution.
Au+ClO- HAuCl42-
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Balance in alkaline solution.
Au+4ClO- HAuCl42-
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Balance in alkaline solution.
Au+4ClO- HAuCl42-
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Balance in alkaline solution.
Au+4ClO- HAuCl42-+ 4H2O
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Balance in alkaline solution.
9H+ +Au+4ClO- HAuCl42-+ 4H2O
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Balance in alkaline solution.+5-29H+ + Au+ 4ClO- HAuCl42-+
4H2O
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Balance in alkaline solution.+5-29H+ + 7e- + Au+ 4ClO- HAuCl42-+
4H2O
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Balance in alkaline solution.-2-29H+ + 7e- + Au+ 4ClO- HAuCl42-+
4H2O
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Balance in alkaline solution.-2-29H+ + 7e- + Au+ 4ClO- HAuCl42-+
4H2O9OH-9OH-
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Balance in alkaline solution.9H+ + 7e- + Au+ 4ClO- HAuCl42-+
4H2O9OH-9OH- 9H2O
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Balance in alkaline solution.9H2O + 7e- + Au+ 4ClO- HAuCl42-+
4H2O + 9OH-
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Balance in alkaline solution.
9H2O + 7e- + Au+ 4ClO- HAuCl42-+ 4H2O + 9OH-
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Balance in alkaline solution.59H2O + 7e- + Au+ 4ClO- HAuCl42-+
4H2O + 9OH-
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Balance in alkaline solution.5H2O + 7e- + Au + 4ClO- HAuCl42-+
9OH-
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Balance in alkaline solution.-11-115H2O + 7e- + Au + 4ClO-
HAuCl42-+ 9OH-
