At $NTP$,the density of a gas,whose molecular weight is $45$,is ............. $g \ L^{-1}$.

One litre of hard water contains $12.00 \ mg$ of $Mg^{2+}$. The milli-equivalents of washing soda $(Na_2CO_3)$ required to remove its hardness is:

The ratio of mass percentage (w/w) of $C : H$ in a hydrocarbon is $12 : 1$. It has two carbon atoms. The weight (in $g$) of $CO_2(g)$ formed when $3.38 \ g$ of this hydrocarbon is completely burnt in oxygen is : (Given : Molar mass in $g \ mol^{-1}$, $C : 12, H : 1, O : 16$)

The amount of $KMnO_4$ required to prepare $100 \ mL$ of $0.1 \ N$ solution in alkaline medium is ............... $g$.

Equal masses of methane and oxygen are mixed in an empty container at $25^\circ C$. The fraction of the total pressure exerted by oxygen is

When $10 \ g$ of $90 \%$ pure limestone is heated, the approximate volume $($in $L$ $)$ of $CO_2$ liberated at $\text{STP}$ is: