The density of a gas at $STP$ is $2.86 \, g \, L^{-1}$. Which of the following is the gas?

The active mass of $64 \ g$ of $HI$ in a $2 \ L$ flask is......

The amount of calcium oxide produced on heating $150 \ kg$ of limestone ($75 \%$ pure) is $........... \ kg$ $(Nearest \ integer)$. Given: Molar mass (in $g \ mol^{-1}$) of $Ca = 40, O = 16, C = 12$.

The weight of calcium oxide formed by burning $20 \ g$ of calcium in excess oxygen is $.... \ g$

$A$ mixture of gases contains $H_2$ and $O_2$ gases in the ratio of $1 : 4$ $(w/w)$. What is the molar ratio of the two gases in the mixture?

What is the concentration of sugar $(C_{12}H_{22}O_{11})$ in $mol \ L^{-1}$ if its $20 \ g$ are dissolved in enough water to make a final volume up to $2 \ L$?