Using a table of standard reduction potentials, determine the best answer to the following questions.

a) Which of the following reagents would oxidize Cr to Cr3 , but not Ag to Ag ?
Choices: Ca^2+, Br2, Co^2+, Ca, Br^-, or Co.

b) Which of the following reagents would oxidize I– to I2, but not Cl– to Cl2?
Choices: Ca^2+, Br2, Co^2+, Ca, Br^-, or Co.

Can someone explain to me how to do this? I don't even know how to start. I got the values but I don't understand how it works.

a) To determine which reagent would oxidize Cr to Cr3+ but not Ag to Ag+ , we need to compare the reduction potentials of Cr3+/Cr and Ag+/Ag. The reagent with a higher reduction potential will be able to oxidize the corresponding metal.

Looking at the table of standard reduction potentials, the reduction potential for Ag+/Ag is lower than that of Cr3+/Cr. Therefore, any reagent that can oxidize Cr to Cr3+ will also be able to oxidize Ag to Ag+.

So the correct answer is none of the given choices.

b) Similarly, to determine which reagent would oxidize I- to I2 but not Cl- to Cl2, we need to compare the reduction potentials of I2/I- and Cl2/Cl. The reagent with a higher reduction potential will be able to oxidize the corresponding halogen.

Looking at the table of standard reduction potentials, the reduction potential for Cl2/Cl is higher than that of I2/I-. Therefore, any reagent that can oxidize I- to I2 will also be able to oxidize Cl- to Cl2.

So the correct answer is none of the given choices.

Now, I know this might be a bit disappointing, but you get a bonus joke for putting in all this effort:

What did one ion say to the other ion in chemistry class?
"I've got my ion you!"

I hope this helps!

To determine which reagent can oxidize a particular element but not another, you can compare the standard reduction potentials (E°) of the half-reactions involved. The half-reaction with a more positive E° value will be able to oxidize the element in question.

a) To determine which reagent will oxidize Cr to Cr3+ but not Ag to Ag, compare the reduction potentials for the half-reactions:

Cr3+ + 3e- ⟶ Cr (E° = -0.74 V) - This is the reduction potential for Cr3+ to Cr.

Ag+ + e- ⟶ Ag (E° = +0.80 V) - This is the reduction potential for Ag+ to Ag.

Based on the reduction potentials, Ag+ has a more positive E° value than Cr3+, indicating that it will be easier to reduce Ag+ to Ag compared to oxidizing Cr3+ to Cr. Therefore, the reagent that can oxidize Cr to Cr3+ but not Ag to Ag is Br2.

b) To determine which reagent will oxidize I- to I2 but not Cl- to Cl2, compare the reduction potentials for the half-reactions:

I2 + 2e- ⟶ 2I- (E° = +0.54 V) - This is the reduction potential for I2 to 2I-.

Cl2 + 2e- ⟶ 2Cl- (E° = +1.36 V) - This is the reduction potential for Cl2 to 2Cl-.

Based on the reduction potentials, Cl2 has a more positive E° value than I2, indicating that it will be easier to reduce Cl2 to 2Cl- compared to oxidizing I2 to 2I-. Therefore, the reagent that can oxidize I- to I2 but not Cl- to Cl2 is Co^2+.

To determine which reagent would oxidize Cr to Cr3+ but not Ag to Ag, we need to compare the reduction potentials of each reagent with the standard reduction potentials of Cr3+ and Ag. We want to find a reagent with a higher reduction potential than Cr3+ and a lower reduction potential than Ag.

Here's how you can approach this:

1. Look up the standard reduction potentials for Cr3+ and Ag in a table of standard reduction potentials. Standard reduction potentials are given in volts (V) and indicate the tendency of a species to gain electrons (i.e., to be reduced). The more positive the reduction potential, the stronger the tendency to gain electrons.

2. Compare the reduction potentials of Cr3+ and Ag. The reduction potential of Cr3+ is positive and should be lower than the reduction potential of Ag. Note the values for future comparison.

3. Now, compare the reduction potentials of each reagent with the reduction potentials of Cr3+ and Ag. The reagent that has a higher reduction potential than Cr3+ and a lower reduction potential than Ag will be the one that can oxidize Cr to Cr3+ but not Ag to Ag.

For each reagent given in the choices, look up their standard reduction potentials in the table. Compare those values with the reduction potentials of Cr3+ and Ag. The reagent that satisfies the condition described above is the correct answer.

Repeat the same process for the second question to determine which reagent would oxidize I- to I2 but not Cl- to Cl2.

By comparing the reduction potentials, you can determine the most suitable reagent for each oxidation reaction.

You say you've looked up these values. My values won't be the same as yours because I'm using an old book but they will be close. Here is how you do the first one.

Cr==> Cr^3+ + 3e You look in your table and find this potential. It will be listed "backwards" as Cr^3+ + 3e ==> Cr because tables list them as reduction potentials and this is an oxidiation; my book lists it as -0.74 so we write 0.74 for Eo as written.
The second part of the reaction will be
Ca^2+ + 2e --> Ca and that is the way you look it up. My text lists that as -2.8 as a reduction.
We summarize
Cr ==> Cr^3+ + 3e Eo = 0.74
Ca^2+ + 2e ==> Ca Eo = -2.86
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So you add these two equations and obtain -2.12v and since it isn't a + voltage you know it won't go as written and now you know Ca^2+ ion will not oxidize Cr to Cr^3+. You go through the others in the list and find those that give a + voltage. When you have found the one (or ones) that fit the criteria of oxidizing Cr to Cr^3+, you apply that information with the Ag ==> Ag^+ and find those that will oxidize Cr but not Ag.

b is done exactly the same way but with two different half reactions.