Electrochemistry

The standard electrode potential \(\mathrm{(M^{3+}/M^{2+})}\) for V, Cr, Mn & Co are \(-\)0.26 V, \(-\)0.41 V, + 1.57 V and + 1.97 V, respectively. The metal ions which can liberate \(\mathrm{H_2}\) from a dilute acid are :