Put the species in order from strongest reducing agent 1 to

Put the species in order, from strongest reducing agent (#1) to the weakest reducing agent (#6). You may consult a table of standard reduction potentials.

Co(s), Cl^-(aq), F^-(aq), K(s), Hg₂²⁺(aq), Zn(s)

Solution

Co(s)    ------>   2e-    +     Co2+      +0.28V

2Cl-(aq) ------>   2e-    +     Cl2    -1.36V

2F-(aq) ------>   2e-    +      F2    [-2.87V]

K(s) ------>   1e-    +   K+         [+2.93V]

Hg22+(aq)   + 2e- ------>    Hg2      [+0.79V] (the opposite reaction will be used for reduction)

Zn(s)   ------>   2e-    +     Zn2+(aq)         [+0.76V]

Higher the standered oxidation potentioal, stronger the reducing power and vice versa.
Hence, reducing order can be given as:
1. K(s)   >   2. Co(s)   > 3. Zn(s)     >     4. Hg22+    >      5. Cl-      >     6. F-