A solution is 1.0M in AgNO3 and Fe(NO3)2.in the electrolysis of this solution using inert electrodes, the voltage is gradually increased. What is the order in which the substances in the solution would plate our or react at the cathode ? Assume that the overvoltage of hydrogen is .30V
I think Ag comes out first followed by H2, then Fe if ever.
Thank You. This question totally broke me
In the given electrolysis setup, the voltage is gradually increased. Let's analyze the reduction potentials of the substances present in the solution to determine the order in which they would plate out or react at the cathode:
1. AgNO3 (silver nitrate):
Ag+ + e- -> Ag (reduction potential: +0.80V)
2. Fe(NO3)2 (iron nitrate):
Fe2+ + 2e- -> Fe (reduction potential: -0.44V)
3. Hydrogen (H2):
2H+ + 2e- -> H2 (reduction potential: 0.00V)
Since the reduction potential of Ag+ is higher than that of both Fe2+ and H+, silver would plate out first at the cathode.
The electrolysis half-reactions to consider at the cathode are:
Ag+ + e- -> Ag (reduction potential: +0.80V)
Fe2+ + 2e- -> Fe (reduction potential: -0.44V)
2H+ + 2e- -> H2 (reduction potential: 0.00V + overvoltage: +0.30V)
Therefore, the order in which the substances in the solution would plate out or react at the cathode would be:
1. Silver (Ag)
2. Hydrogen (H2)
3. Iron (Fe)
To determine the order in which substances in the solution would plate out or react at the cathode, you need to compare the reduction potentials of the species present.
1. Start by writing the half-reactions that could occur at the cathode. In this case, we have Ag+ ions from AgNO3 and Fe2+ ions from Fe(NO3)2. The possible reduction reactions are:
Ag+ + e- → Ag (reduction potential 0.80V)
Fe2+ + 2e- → Fe (reduction potential -0.44V)
2. Next, compare the reduction potentials of the two reactions. The species with the higher reduction potential will plate out first at the cathode. In this case, Ag+ ions have a higher reduction potential (0.80V) compared to Fe2+ ions (-0.44V). Therefore, silver (Ag) will plate out first.
3. However, it's important to consider the overvoltage of hydrogen (0.30V in this case). If the overvoltage of hydrogen is lower than the reduction potential of a species, hydrogen gas will be formed instead of that species being plated out.
4. In this case, since the reduction potential of Fe2+ ions (-0.44V) is lower than the overvoltage of hydrogen (0.30V), hydrogen gas will be formed before Fe plates out. So the order at the cathode will be: hydrogen gas, silver (Ag), and then iron (Fe), if the electrolysis continues.
To summarize, the order in which substances in the solution would plate out or react at the cathode is: hydrogen gas, silver (Ag), and then iron (Fe).