Page 149 - Basic physical chemistry for the atmospheric sciences

Oxidation-reduction reactions 1 3 5

Is this a spontaneous reaction?
6 . 2 2. What is the value of the equilibrium constant for the redox
reaction given in Exercise . 2 1 ? What do you conclude from
6
this value?
6.23 . Calculate the initial electric potential difference i n an elec­
trochemical cell at 250K, and the initial change in the Gibbs
free energy (.:lG) associated with the redox reaction
2
Cd(s) + Cu + (aq)� Cd 2 + (aq) + Cu(s)
when the species are present in the following concentrations
z
z
[Cd(s)] = 3 . 00 M , [Cu + (aq)] = 1 . 50 M, [Cd + (aq)] = 0.500 M ,
and [Cu(s)] = 0.750 M . Is the reaction spontaneous ?
6.24. Automob l e batteries often consist of six cells connected in
i
series. The following redox reaction occurs in each cell
Pb(s) + Pb0 (s) + 4H + (aq) + 2SO� - ( aq)�
2
2PbSOis) + 2H20(1)
What is the maximum voltage that this battery can generate
under standard conditions?
2
6.25. The cell potential when a Mn(s) - Mn + ( aq) couple is linked
to an H + (aq) - H (g) couple is 1 . 0 1 V at 25°C when both the
2
2
1
n
Mn(s) and the Mn + ( aq) are present in concentratio s of . 0
M and the partial pressure of the H 2 (g) is 1 . 0 atm. What is
the concentration of H + (aq)? [Note: This problem indicates
how an electrochemical cell that involves H + ( aq) can be
used to measure [H + (aq)] , and therefore the pH of a solu­
tion. This is the basis of a pH meter.]
6 . 2 6. Calculate the standard electrode potential for the half­
reaction

HS03(aq) + H20(1)� HSC}.j(aq) + 2H + (aq) + 2e ...
I s this reaction spontaneous under standard conditions?
6.2 . What is the ratio of [Fe2+ (aq)] to [FeH (aq)] that will e in
b
7
equilibrium at 25°C with seawater that has a redox potential
of 0.600 V ?
6.28. H2S(aq) + H 0 3 (aq)� S(s) + O (g) + H20(1) is an unbal­
N
N
anced redox reaction. What is the gram-equivalent weight
of H 2 S(aq) and HN0 3 (aq)?