The mass of iron converted into $Fe_3O_4$ by the action of $18\text{ g}$ of steam is : (Given: Molar mass of $H$,$O$ and Fe are $1$,$16$ and $56\text{ g mol}^{-1}$ respectively). Assume iron is present in excess: (in $\text{ g}$)

At $STP$,for complete combustion of $3\, g$ of $C_2H_6$,the required volume of $O_2$ will be - ............. $litre$.

$A$ sample of a metal oxide has the formula $M_{0.83}O_{1.00}$. The metal $M$ can exist in two oxidation states,$+2$ and $+3$. In the sample of $M_{0.83}O_{1.00}$,the percentage of metal ions existing in the $+2$ oxidation state is $.........\%$ (nearest integer).

$4.4 \ g$ of a gas at $STP$ occupies a volume of $2.24 \ L$. The gas can be:

How many moles of potassium chlorate need to be heated to produce $5.6 \, L$ of oxygen at $STP$?

The molarity of a $NaOH$ solution prepared by dissolving $4 \ g$ of it in $250 \ mL$ of water is: (in $M$)