Which species will reduce Ag+ but not Fe2+?
1. H2
2. Cr
3. V
4. Pt
5. Au
H2
it was V
To determine which species will reduce Ag+ but not Fe2+, we need to consider the reduction potential of each species. The reduction potential is a measure of the tendency of a species to gain electrons and undergo reduction.
Ag+ can be reduced to Ag by accepting an electron, while Fe2+ can be reduced to Fe by accepting two electrons. Therefore, we need to find a species that has a higher reduction potential than Ag+ but a lower reduction potential than Fe2+.
To find the reduction potential for each species, we can refer to a standard reduction potential table. This table lists the reduction potentials of various species at standard conditions (25°C, 1 M concentration).
Let's check the reduction potentials for each species:
1. H2: The reduction potential for the H2/H+ couple is -0.42 V.
2. Cr: The reduction potential for the Cr3+/Cr couple is -0.74 V.
3. V: The reduction potential for the V3+/V couple is -1.18 V.
4. Pt: The reduction potential for the Pt2+/Pt couple is -1.20 V.
5. Au: The reduction potential for the Au3+/Au couple is +1.50 V.
Based on the reduction potentials, we can see that Au has the highest reduction potential, followed by Pt, V, Cr, and H2. Since Au has a higher reduction potential than Ag+, it can reduce Ag+ to Ag. Additionally, Au also has a higher reduction potential than Fe2+, indicating that it can also reduce Fe2+ to Fe.
Therefore, the correct answer is option 5. Au.