Find the formula weight of the reactant if the formula weight of the product is $54 \ u$ and the percent atom economy is $75$. (in $u$)

$A$ solution contains $1.2046 \times 10^{24}$ hydrochloric acid molecules in one $dm^3$ of the solution. The strength of the solution is .......... $N$.

The amount of arsenic pentasulphide that can be obtained when $35.5 \ g$ of arsenic acid $(H_3AsO_4)$ is treated with excess $H_2S$ in the presence of conc. $HCl$ (assuming $100\%$ conversion) is $.... \ mol$.

The density (in $g \; mL^{-1}$) of a $3.60 \; M$ sulphuric acid solution that is $29 \%$ $H_2SO_4$ (molar mass $= 98 \; g \; mol^{-1}$) by mass will be

Calculate the mass in $kg$ of $4.48 \ dm^3$ of carbon dioxide $(CO_2)$ at $STP$.

What mass of $95 \%$ pure $CaCO_3$ will be required to neutralise $50 \ mL$ of $0.5 \ M \ HCl$ solution according to the following reaction? (In $g$)
$CaCO_{3(s)} + 2HCl_{(aq)} \rightarrow CaCl_{2(aq)} + CO_{2(g)} + H_2O_{(l)}$
[Calculate up to the second decimal place]