Aqueous solutions of $Na_2S_2O_3$ on reaction with $Cl_2$ gives

What is the number of moles of electrons gained by one mole of oxidizing agent in the following redox reaction?
$Zn_{(s)} + 2HCl_{(aq)} \longrightarrow ZnCl_2(aq) + H_2(g)$

$KMnO_4$ oxidises oxalic acid to $CO_2$ in acidic medium. The equivalent weight of $KMnO_4$ is $(Mn = 55, K = 39, O = 16)$:

What is the equivalent mass of $IO_4^-$ when it is converted into $I_2$ in an acidic medium?

The number of moles of electrons required to reduce $0.2 \ mol$ of $Cr_2O_7^{2-}$ to $Cr^{3+}$ is:

How many electrons are lost in the following transformation?
$3Fe + 4H_2O \to Fe_3O_4 + 4H_2$