The long way of doing this is to look up the reduction potentials of each.
Zn^2+ + 2e ==> Zn has a reduction potential of -0.763 and you want the reverse of that which is
Zn ==> Zn^2+ + 2e E = +0.763
and do likewise for
Ag ==> Ag^+ + e E = -0.8
Now look up, in succession, the possible answers. For Ca you get
Ca^2+ + 2e ==> Ca E = -2.87
Now add the Zn oxidation to the Ca^2+ reduction and you get +0.763 + (-2.87) = -2.10 which means Ca^2+ will not oxidize Zn to Zn^2+. For Ag that is
-0.8 + (-2.87) = -3.67 which means Ca^2+ will not oxidize Ag to Ag^+ either so you can mark Ca^2+ off the list. Do the same procedure for Co^2+, Br^- etc. You want the one that gives a + voltage with Zn and a negative voltage with Ag. The same process for part b.
a) Which of the following reagents would oxidize Zn to Zn2 , but not Ag to Ag ?
Answers are: Co2+ Ca2+ Br2- Br2 Co or Ca
b) Which of the following reagents would oxidize Ag to Ag , but not Cl– to Cl2?
Answers are: Co Br- Br2 Co2+ Ca2+ or Ca
1 answer
1 answer