$Fe^{3+}$ is reduced to $Fe^{2+}$ by using:
$A$. $H_2O_2$ in presence of $NaOH$
$B$. $Na_2O_2$ in water
$C$. $H_2O_2$ in presence of $H_2SO_4$
$D$. $Na_2O_2$ in presence of $H_2SO_4$

If stoichiometric quantities of a $KMnO_4$ and $K_2Cr_2O_7$ mixture are added for the oxidation of $Fe^{2+}$ to $Fe^{3+}$ in an acidic medium,then $Fe^{2+}$ will be oxidized:

$A$ few drops of $KMnO_4$ solution are added to an acidic solution containing an anion. Which of the following,if present,will $NOT$ cause a change in the color of the $KMnO_4$ solution?

In the given equation,potassium dichromate acts as an oxidant in an acidic medium: $Cr_2O_7^{2-} + 14H^+ + 6e^- \rightarrow 2Cr^{3+} + 7H_2O$. The equivalent weight of $K_2Cr_2O_7$ is (Molecular weight $= M$):

Match the List-$I$ with List-$II$

List-$I$ $(\text{Redox Reaction})$	List-$II$ $(\text{Type of Redox Reaction})$
$A$. $CH_{4(g)} + 2O_{2(g)} \xrightarrow{\Delta} CO_{2(g)} + 2H_2O_{(l)}$	$I$. Disproportionation reaction
$B$. $2NaH_{(s)} \xrightarrow{\Delta} 2Na_{(s)} + H_{2(g)}$	$II$. Combination reaction
$C$. $V_2O_{5(s)} + 5Ca_{(s)} \xrightarrow{\Delta} 2V_{(s)} + 5CaO_{(s)}$	$III$. Decomposition reaction
$D$. $2H_2O_{2(aq)} \xrightarrow{\Delta} 2H_2O_{(l)} + O_{2(g)}$	$IV$. Displacement reaction

Choose the correct answer from the options given below:

The conversion of $2,3-$dibromobutane to $2-$butene in the presence of $Zn$ is an example of ...........