To an acidified dichromate solution,a pinch of $Na_2O_2$ is added and shaken. What is observed?

Assign $A, B, C, D$ from the given type of reaction.
$Mn(OH)_2 + H_2SO_4 \longrightarrow MnSO_4 + 2H_2O$

Ferrous and ferric ions in solution may be distinguished by using

When $10 \, mL$ of an aqueous solution of $KMnO_{4}$ was titrated in acidic medium,an equal volume of $0.1 \, M$ aqueous solution of ferrous sulphate was required for complete discharge of colour. The strength of $KMnO_{4}$ in grams per litre is $...... \times 10^{-2}$. (Nearest integer)
[Atomic mass of $K=39, Mn=55, O=16$]

Acidified $KMnO_4$ can be decolourised by

Which of the following reactions are redox reactions?
$I. \, Cr_2O_7^{2-} + 2OH^- \to 2CrO_4^{2-} + H_2O$
$II. \, Zn + CuSO_4 \to ZnSO_4 + Cu$
$III. \, 2MnO_4^- + 3Mn^{2+} + 4OH^- \to 5MnO_2 + 2H_2O$
$IV. \, 2Cu^+ \to Cu + Cu^{2+}$