COMPETITION FOCUS

Among the following, the number of elements showing only one non-zero oxidation state is $\mathrm{O}, \mathrm{F}, \mathrm{Cl}, \mathrm{N}, \mathrm{P}, \mathrm{Sn}, \mathrm{Tl}, \mathrm{Na}, \mathrm{Ti}$.
 

The difference in the oxidation numbers of the two types of sulphur atoms in ${\mathrm{Na}}_2{\mathrm{S}}_4{\mathrm{O}}_6$ is

How many moles of electrons are involved in the conversion of $1$ mole of ${\mathrm{Cr}}_2{{\mathrm{O}}_7}^{2-}$ ions to ${\mathrm{Cr}}^{3+}$ ions?

The oxidation number of $\mathrm{Mn}$ in the product of alkaline oxidative fusion of ${\mathrm{MnO}}_2$ is. 

How many moles of iodine are liberated when $2$ moles of potassium permanganate react with potassium iodide?

Reaction of ${\mathrm{Br}}_2$ with ${\mathrm{Na}}_2{\mathrm{CO}}_3$ in aqueous solution gives sodium bromide and sodium bromate with evolution of ${\mathrm{CO}}_2$ gas. The number of sodium bromide molecules involved in the balanced chemical equation is 

Consider the following list of reagents: Acidified ${\mathrm{K}}_2{\mathrm{Cr}}_2{\mathrm{O}}_7,$ alkaline ${\mathrm{KMnO}}_4,$ ${\mathrm{CuSO}}_4,$ ${\mathrm{H}}_2{\mathrm{O}}_2,$ ${\mathrm{Cl}}_2$, ${\mathrm{O}}_3$, ${\mathrm{FeCl}}_3$, ${\mathrm{HNO}}_3$. The total number of reagents that can oxidise aqueous iodide to iodine are 

How many grams of potassium dichromate are required to oxidise $20.0 \mathrm{g}$ of ${\mathrm{Fe}}^{2+}$ in ${\mathrm{FeSO}}_4$ to ${\mathrm{Fe}}^{3+}$ if the reaction is carried out in an acidic medium ? (Molar mass of ${\mathrm{K}}_2{\mathrm{Cr}}_2{\mathrm{O}}_7$ and ${\mathrm{FeSO}}_4$ are $294$ and $152$ respectively)

Round off your answer to the nearest integer.