The mass of $500 \, cm^3$ of a gas at $STP$ is $0.581 \, g$. If the gas is a hydrocarbon,what is the gas?

The oxide of a metal has the molecular formula $M_2O_3$. If the equivalent mass of the metal is $9$,what is the molecular mass of the oxide?

Which symbol replaced the unit of atomic mass,$amu$?

If $M_1$ and $M_2$ are the molecular weights of $Al(OH)_3$ and $H_3PO_3$ respectively,find their equivalent weights in the following reaction:
$Al(OH)_3 + 2H_3PO_3 \to Al(OH)(H_2PO_3)_2 + 2H_2O$

The approximate atomic weight of an element is $26.89$. If its equivalent weight is $8.9$,the exact atomic weight of the element would be:

$0.126 \ g$ of an acid is needed to completely neutralise $20 \ mL$ of $0.1 \ N$ $NaOH$ solution. The equivalent weight of the acid is: