Final answer:
To find the standard cell potential and spontaneity of the reactions, use standard reduction potential values, subtracting the anode from the cathode potential. A positive result indicates a spontaneous reaction. This applies to calculating the potential for each given reaction. The correct option is a.
Step-by-step explanation:
To calculate the standard cell potential for each reaction and determine if the reaction is spontaneous under standard state conditions, use the standard reduction potentials for the half-reactions involved. The standard cell potential (E° cell) is determined using the formula:
E° cell = E° cathode - E° anode.
If the E° cell is positive, the reaction is spontaneous under standard state conditions; if it's negative, the reaction is non-spontaneous.
As an example, for reaction (a), find the standard reduction potential values from a table (often found in textbooks or referenced as Appendix L), for both Mg to Mg2+ and Ni2+ to Ni. The reaction with the higher reduction potential acts as the cathode.
For example:
- E° Mg2+/Mg = -2.37 V
- E° Ni2+/Ni = -0.25 V
Then calculate:
E° cell = -0.25 V - (-2.37 V) = +2.12 V
Since the E° cell is positive, reaction (a) is spontaneous under standard conditions.
Similar calculations would have to be performed for reactions (b), (c), and (d), usi ng the corresponding standard reduction potentials. The correct option is a.