How many moles of $KMnO_4$ are required to oxidize $1 \ mol$ of $Fe(C_2O_4)$ in an acidic medium?

Which of the following is a redox reaction?
$(i) \, CdCl_2 + 2 KOH \longrightarrow Cd(OH)_2 + 2 KCl$
$(ii) \, BaCl_2 + K_2SO_4 \longrightarrow BaSO_4 + 2 KCl$
$(iii) \, CaCO_3 \longrightarrow CaO + CO_2$
$(iv) \, 2 Ca + O_2 \longrightarrow 2 CaO$

In the titration of $KMnO_{4}$ and oxalic acid in acidic medium,the change in oxidation number of carbon at the end point is

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

The reaction of sulphur in alkaline medium is given below:
$S_{8(s)} + a OH^{-}_{(aq)} \rightarrow b S^{2-}_{(aq)} + c S_{2}{O_{3}}^{2-}_{(aq)} + d H_{2}O_{(\ell)}$
The value of '$a$' is ............ (Integer answer)

$KMnO_4 + HCl \rightarrow MnCl_2 + Cl_2 + KCl + H_2O$. In the above reaction,how many moles of $H_2O$ would be formed for each mole of $Cl_2$ liberated?