$20 \, mL$ of $0.02 \, M \, K_2Cr_2O_7$ solution is used for the titration of $10 \, mL$ of $Fe^{2+}$ solution in the acidic medium. The molarity of $Fe^{2+}$ solution is ........... $\times 10^{-2} \, M$ (Nearest Integer).

Which of the following are non-metal displacement reactions?
$(A)$ $Ca_{(s)} + 2 H_2 O_{(l)} \longrightarrow Ca(OH)_{2(aq)} + H_{2(g)}$
$(B)$ $V_2 O_{5(s)} + 5 Ca_{(s)} \stackrel{\Delta}{\longrightarrow} 2 V_{(s)} + 5 CaO_{(s)}$
$(C)$ $2 Fe_{(s)} + 3 H_2 O_{(g)} \stackrel{\Delta}{\longrightarrow} Fe_2 O_{3(s)} + 3 H_{2(g)}$
$(D)$ $Cr_2 O_{3(s)} + 2 Al_{(s)} \stackrel{\Delta}{\longrightarrow} Al_2 O_{3(s)} + 2 Cr_{(s)}$

Assign $A, B, C, D$ from the given type of reaction.
$CaSO_4 + Pb(NO_3)_2 \longrightarrow PbSO_4 \downarrow + Ca(NO_3)_2$

Which of the following reactants can be reduced by $SO_2$ in the given reactions?
$(I)$ $O_3 \to$ product
$(II)$ $Cr_2O_7^{2-} \xrightarrow{H^{+}} $ product
$(III)$ $MnO_4^{-} \xrightarrow{H^{+}} $ product
$(IV)$ $H_2S \to$ product

$Fe^{3+}$ 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 $H_2SO_4$

Which of the following is not a redox reaction?