Given

$$E_{C{r^{2 + }}/Cr}^o$$ = -0.74 V; $$E_{MnO_4^ - /M{n^{2 + }}}^o$$ = 1.51 V

$$E_{C{r_2}O_7^{2 - }/C{r^{3 + }}}^o$$ = 1.33 V; $$E_{Cl/C{l^ - }}^o$$ = 1.36 V

Based on the data given above, strongest oxidising agent will be :

The standard reduction potentials for Zn²⁺/ Zn, Ni²⁺/ Ni, and Fe²⁺/ Fe are –0.76, –0.23 and –0.44 V respectively. The reaction

X + Y²⁺ $$\to$$ X²⁺ + Y will be spontaneous when :

The reduction potential of hydrogen half cell will be negative if :

The correct order of $$E_{{M^{2 + }}/M}^o$$ values with negative sign for the four successive elements Cr, Mn, Fe and Co is :