For what ratio of volumes should $0.4 \, M \ HCl$ and $0.9 \, M \ HCl$ be mixed to obtain a solution of $0.7 \, M \ HCl$?

The mass of $BaCO_3$ produced when excess $CO_2$ is bubbled through a solution of $0.205 \ mol$ $Ba(OH)_2$ is ............ $g$.

How many moles of potassium chlorate $(KClO_3)$ are required to be heated to produce $11.2 \text{ L}$ of oxygen gas at $STP$?

$1\, g$ of a carbonate $(M_{2}CO_{3})$ on treatment with excess $HCl$ produces $0.01186\, mol$ of $CO_{2}.$ The molar mass of $M_{2}CO_{3}$ in $g\, mol^{-1}$ is:

$24 \ g$ of $Mg$ metal reacts with water. How many moles of $H_2$ will be liberated? ............. $mol$

When $262 \ g$ of xenon (atomic mass $= 131$) reacted completely with $152 \ g$ of fluorine (atomic mass $= 19$),a mixture of $XeF_2$ and $XeF_6$ was produced. The molar ratio $XeF_2 : XeF_6$ is