The following equations are intepretations of the evidence from the reactions of four metals with various cation solutions. Make a table of half-reactions and arrange the four metallic ions and the hydrogen ions in order of their decreasing tendency to react. Label the strongest oxidizing agent and reducing agent.

Question

The following equations are intepretations of the evidence from the reactions of four metals with various cation solutions. Make a table of half-reactions and arrange the four metallic ions and the hydrogen ions in order of their decreasing tendency to react. Label the strongest oxidizing agent and reducing agent.

Cd + 2H+ --> Cd2+ + H2
Hg + 2H+ --> Hg2+ + H2
Be + Cd2+ --> Be2+ + Cd
Ca2+ + Be --> Ca + Be

So I identified Cd, Hg, Be as the reducing agents and 2H+, Cd2+, Ca2+ as the oxidizing agents.

Now when making the table I can't identify which ones are the strongest and weakest. I know the method to do it. But for this question I don't know in what order they go. Can anyone help me?

Answer 1

Alex, I'm sorry but I can't help you with this. First, I don't think Hg will displace H ion to produce H2. Second, I don't see anyway of resolving if Cd is above or below Hg even if I believed that Hg would displace H. I don't believe in making up problems in which the data is not true. Are you allowed to use any other information, such as that which you posted last night (similar problem)? That might help, I don't know. From these data, you CAN say that Be is above Ca and that Be is above Cd ; also that Cd and Hg are above H, but there is no way I can see to place these two groups together.

Answer 2

OH! I just realized that Ca2+ + Be and Hg + 2H+ are actually nonspontaneous reactions.

Answer 3

Thanks for letting me know. That sure makes the problem go from impossible to a two second problem.

Answer 4

To determine the order of decreasing tendency to react, you need to consider the standard reduction potentials of the half-reactions involved. The larger the reduction potential, the stronger the oxidizing agent, while the smaller the reduction potential, the stronger the reducing agent.

First, let's identify the half-reactions:

1. Cd + 2H+ --> Cd2+ + H2
2. Hg + 2H+ --> Hg2+ + H2
3. Be + Cd2+ --> Be2+ + Cd
4. Ca2+ + Be --> Ca + Be

For each half-reaction, we need to determine the reduction potential or the standard reduction potential (E°). You can find a table of standard reduction potentials to get these values. The values represent the tendency of a species to be reduced (i.e., acting as the oxidizing agent) or to be oxidized (i.e., acting as the reducing agent). Keep in mind that the stronger the oxidizing agent, the higher the reduction potential.

Once you have the reduction potential values for each half-reaction, you can arrange them in decreasing order. The species with the highest reduction potential will be the strongest oxidizing agent, while the species with the lowest reduction potential will be the strongest reducing agent.

For example, let's say the reduction potentials are as follows:

Cd2+ (0.403 V) > Be2+ (−1.847 V) > Ca (−2.866 V) > H+ (+0.000 V) > Hg2+ (+0.789 V)

Based on these values, you can arrange the metallic ions and hydrogen ions in decreasing order of their tendency to react:

Strongest oxidizing agent: Cd2+
Decreasing tendency to react: Cd2+ > Hg2+ > H+ > Be2+ > Ca

Strongest reducing agent: Ca

Please note that the specific reduction potential values may vary depending on the reference table used, so make sure to consult the appropriate table to determine the exact order.