The modern basis of atomic weight is

Elements $A$ and $B$ form two compounds $B_2A_3$ and $B_2A$. $0.05$ moles of $B_2A_3$ weigh $9.0 \ g$ and $0.10$ mole of $B_2A$ weigh $10 \ g$. The atomic weights of $A$ and $B$ are:

The equivalent weight of an acid is equal to

If $74.5 \ g$ of a metallic chloride contains $35.5 \ g$ of chlorine,then the equivalent mass of the metal will be ...... .

If the weight of $1 \ L$ of a gas is $2 \ g$,then its vapor density and molecular weight are respectively .....

Naturally occurring boron has $20\%$ $_5B^{10}$ and $80\%$ $_5B^{11}$. The average atomic weight of boron is