What is the value of percent atom economy if the formula weight of the product is $46 \ u$ and the sum of the formula weight of all reactants is $92 \ u$ (in $\%$)?

$12 \ g$ of $Mg$ (atomic mass $24$) on reacting completely with acid gives hydrogen gas,the volume of which at $STP$ would be ............... $L$.

Air contains $23\%$ oxygen and $77\%$ nitrogen by weight. What is the percentage by volume of $O_2$?

The conversion of oxygen to ozone occurs to the extent of $15\%$ only. The mass of ozone that can be prepared from $67.2 \ L$ of oxygen at $1 \ atm$ and $273 \ K$ will be ............ $g$.

$A$ gas mixture contains $25 \%$ He and $75 \% CH_4$ by volume at a given temperature and pressure. The percentage by mass of methane in the mixture is approximately . . . . . . (in $\%$)

If a $100 \ mL$ solution contains $X \ g$ of $Na_2CO_3$ and its concentration is $Y \ M$,then $X$ and $Y$ are respectively ...............