$X$ and $Y$ are the number of electrons involved, respectively, during the oxidation of $I^{-}$ to $I_{2}$ and $S^{2-}$ to $S$ by acidified $K_{2}Cr_{2}O_{7}$. The value of $X + Y$ is . . . . . . .

Assign $A, B, C, D$ from the given type of reaction.
$Ba(NO_3)_2 + Na_2SO_4 \longrightarrow BaSO_4 \downarrow + 2NaNO_3$

Which one of the following conversions does not involve either oxidation or reduction?

Observe the following reactions:
$(i)$ $2 KClO_{3(s)} \xrightarrow{\Delta} 2 KCl_{(s)} + 3 O_{2(g)}$
$(ii)$ $2 H_2O_{2(aq)} \xrightarrow{\Delta} 2 H_2O_{(l)} + O_{2(g)}$
$(iii)$ $AgNO_{3(aq)} + KCl_{(aq)} \longrightarrow AgCl_{(s)} + KNO_{3(aq)}$
$(iv)$ $2 Na_{(s)} + \frac{1}{2} O_{2(g)} \longrightarrow Na_2O_{(s)}$
The number of redox reactions in this list is

Assign $A, B, C, D$ from the given type of reaction.
$Ba(OH)_2 + CO_2 \longrightarrow BaCO_3 \downarrow + H_2O$

Which of the following is not correct?