Concept explainers
A Daniell cell consists of a zinc electrode in 1.00 L of 1.00 M ZnSO4 and a Cu electrode in 1.00 L of 1.00 M CuSO4 at 25°C. A steady current of 10.0 A is drawn from the cell. Calculate the Ecell after 1.00 h. Assume volumes to remain constant.
Interpretation:
The emf
Concept introduction:
Standard reduction potential: The voltage associated with a reduction reaction at an electrode when all solutes are 1M and all gases are at 1 atm. The hydrogen electrode is called the standard hydrogen electrode (SHE).
Standard emf:
Where both
Effect of concentration on cell Emf:
The mathematical relationship between the emf of galvanic cell and the concentration of reactants and products in a redox reaction under nonstandard-state conditions is,
As known
Dividing by –nF, the above equation becomes,
Nernst equation: The Nernst equation is used to calculate the cell voltage under nonstandard-state conditions.
Explanation of Solution
Calculation of standard emf
A Daniel (Galvanic cell) cell consists of Zinc electrode in
The cell diagram as follows,
At Anode, possible oxidation process occurs as follows,
At Cathode, possible reduction process occurs as follows,
Hence, the standard emf of the cell reaction are,
Therefore, the standard emf
As the concentration of given ions are nonstandard concentrations, the reaction spontaneity is determined by emf of a given galvanic reaction using Nernst equation.
Calculation of non-standard emf value using Nernst equation:
The reaction quotient for the given reaction is,
The concentration of pure solids and pure liquids do not appear in the expression for Q.
Hence, the reaction quotient becomes,
As to know the concentration of
Given: Current = 20.0 A; Time,
Convert Current into coulomb:
As known,
Convert number of Coulombs into mole of electrons:
The concentration of
- Convert mole of electrons into number of moles of Silver:
1 mole of
‘x’ of
Hence, the concentration of
Construct ICE table for the cell half-reaction to calculate the concentration of
The concentration of
Construct ICE table for the cell half-reaction to calculate the concentration of
The concentration of
Substitute known constant values of R, T and F into Nernst equation becomes as follows,
The number of electrons transferred in the given redox reaction is TWO (n=2) and
Obtained
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Chapter 18 Solutions
Chemistry
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