Chapter 23
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What is reduction?
1) gain of electrons 2) decrease in oxidation number
What is oxidation?
1) loss of electrons 2) increase in oxidation number
What is the oxidation number of an uncombined element?
0
What is the oxidation number of combined hydrogen?
+1
What is the oxidation number of combined oxygen?
-2
What is the oxidation number of an ion of an element?
ionic charge
Give an example of a reducing agent.
1) iron(II) ions, Fe²⁺(aq) 2) ethanedioic acid, (COOH)₂(aq)
What is a voltaic cell?
converts chemical energy into electrical energy
What does a half-cell contain?
the chemical species present in a redox half-equation
What are the different types of half-cells?
1) metal/metal ion half-cells 2) ion/ion half-cells 3) ion/metal ion half-cells
How is the equilibrium in a half-cell written?
1) forward reaction = reduction 2) reverse reaction = oxidation
What is standard electrode potential E?
the tendency to be reduced + gain electrons
What is the standard electrode potential of a standard hydrogen electrode?
0V
How do you measure a standard electrode potential?
1) connect half-cell to standard hydrogen electrode 2) connect two solutions with a salt bridge
The more negative the E value, the…?
1) greater the tendency to lose electrons + undergo oxidation 2) less the tendency to gain electrons + undergo reduction
The more positive the E value, the…?
1) greater the tendency to gain electrons + undergo reduction 2) less the tendency to lose electrons + undergo oxidation
Do metals have positive or negative E values?
negative
Do non-metals have positve or negative E values?
positive
E꜀ₑₗₗ =
E(positive electrode) - E(negative electrode)