
Concept explainers
For each of the following
(a) H2(g) + Ni2+(aq) → H+(aq) + Ni(s)
(b) MnO4−(aq) + Cl−(aq) → Mn2+(aq) + Cl2(g)
(c) Cr(s) + Zn2+(aq) → Cr3+(aq) + Zn(s)
(a)

Interpretation:
For each of the given redox reactions, the half-cell reactions, the completely balanced cell reaction and the direction of spontaneous reactions has to be found.
Concept Introduction:
Redox reactions are the reactions in which both oxidation and reduction takes place simultaneously. Oxidation is the removal electron from an atom or ion. Oxidation process increases the oxidation number. Reduction is the addition of electron to an atom or ion. Reduction process decreases the oxidation number. The electrochemical reaction of zinc with copper sulphate is an example of redox reaction.
Standard reduction potential is the measure of the tendency of a species to undergo reduction. It is measured in terms of volts. The substance which is having high positive value will easily undergo reduction.
The standard electrode potential of a cell
The relation between Gibbs free energy and cell potential: The amount of energy in a system that can be converted into useful energy is defined as free energy in thermodynamics.
Free energy and the cell potential is related by the given equation.
Where,
Answer to Problem 18.65QP
(i)
The half-cell reactions are,
(ii)
The completely balanced equation is,
(iii)
The reaction will be spontaneous towards to left side of the completely balanced equation.
Explanation of Solution
(i)
To write the half-cell reactions
The half-cell reactions for the given redox reactions are,
(ii)
To write complete equation for the given redox reaction
The balanced equation for the given reaction can be represented as given below
(iii)
To determine the direction of the spontaneous reaction in the given standard state.
In the electrochemical series the position of nickel is below the hydrogen. Hence nickel will have the tendency to get oxidized. The spontaneity of the reaction depends upon the change of the free energy. Free energy and the electrode potential are related by the following equation.
In order to have a negative change in free energy the value of cell potential should be positive.
The cell potential of the given cell can be calculated by the following equation.
The one with higher positive value of reduction potential will be cathode and the one with lower value of reduction potential will be anode. In the given reaction will be spontaneous when zinc is oxidised (anode) to
(b)

Interpretation:
For each of the given redox reactions, the half-cell reactions, the completely balanced cell reaction and the direction of spontaneous reactions has to be found.
Concept Introduction:
Redox reactions are the reactions in which both oxidation and reduction takes place simultaneously. Oxidation is the removal electron from an atom or ion. Oxidation process increases the oxidation number. Reduction is the addition of electron to an atom or ion. Reduction process decreases the oxidation number. The electrochemical reaction of zinc with copper sulphate is an example of redox reaction.
Standard reduction potential is the measure of the tendency of a species to undergo reduction. It is measured in terms of volts. The substance which is having high positive value will easily undergo reduction.
The standard electrode potential of a cell
The relation between Gibbs free energy and cell potential: The amount of energy in a system that can be converted into useful energy is defined as free energy in thermodynamics.
Free energy and the cell potential is related by the given equation.
Where,
Answer to Problem 18.65QP
(i)
The half-cell reactions are,
(ii)
The completely balanced equation is,
(iii)
The reaction will be spontaneous towards to right side of the completely balanced equation.
Explanation of Solution
(i)
To write the half-cell reactions
The half-cell reactions for the given redox reactions are,
(ii)
To write complete equation for the given redox reaction
The balanced equation for the given reaction can be represented as given below
(iii)
To determine the direction of the spontaneous reaction in the given standard state.
In the electrochemical series the position of
In order to have a negative change in free energy the value of cell potential should be positive.
The cell potential of the given cell can be calculated by the following equation.
The one with higher positive value of reduction potential will be cathode and the one with lower value of reduction potential will be anode. In the given reaction will be spontaneous when the
(c)

Interpretation:
For each of the given redox reactions, the half-cell reactions, the completely balanced cell reaction and the direction of spontaneous reactions has to be found.
Concept Introduction:
Redox reactions are the reactions in which both oxidation and reduction takes place simultaneously. Oxidation is the removal electron from an atom or ion. Oxidation process increases the oxidation number. Reduction is the addition of electron to an atom or ion. Reduction process decreases the oxidation number. The electrochemical reaction of zinc with copper sulphate is an example of redox reaction.
Standard reduction potential is the measure of the tendency of a species to undergo reduction. It is measured in terms of volts. The substance which is having high positive value will easily undergo reduction.
The standard electrode potential of a cell
The relation between Gibbs free energy and cell potential: The amount of energy in a system that can be converted into useful energy is defined as free energy in thermodynamics.
Free energy and the cell potential is related by the given equation.
Where,
Answer to Problem 18.65QP
(i)
The half-cell reactions are,
(ii)
The completely balanced equation is,
(iii)
The reaction will be spontaneous towards to left side of the completely balanced equation.
Explanation of Solution
(i)
To write the half-cell reactions
The half-cell reactions for the given redox reactions are,
(ii)
To write complete equation for the given redox reaction
The balanced equation for the given reaction can be represented as given below
(iii)
To determine the direction of the spontaneous reaction in the given standard state.
In the electrochemical series the position of
In order to have a negative change in free energy the value of cell potential should be positive.
The cell potential of the given cell can be calculated by the following equation.
The one with higher positive value of reduction potential will be cathode and the one with lower value of reduction potential will be anode. In the given reaction will be spontaneous when the
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Chapter 18 Solutions
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