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

Equivalent weight of $H_3PO_2$ when it disproportionates into $PH_3$ and $H_3PO_3$ is:

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

$2KMnO_4 + 3H_2SO_4 + 5H_2O_2 \rightarrow K_2SO_4 + 2MnSO_4 + 8H_2O + 5O_2$. Find the normality of $H_2O_2$ solution,if $20 \ mL$ of it is required to react completely with $16 \ mL$ of $0.02 \ M \ KMnO_4$ solution. (Molar mass of $KMnO_4 = 158 \ g \ mol^{-1}$)

Assign $A, B, C, D$ for the given type of reaction: $CuSO_4$ (solution) + $ZnCl_2$ (solution) $\longrightarrow$ No reaction.

When $CuSO_4$ reacts with $KI$,the oxidation number of $Cu$ changes by