The present atomic weight scale is based on

The equivalent weight of an acid:

Write about atomic mass.

$4 \, g$ of copper is dissolved in concentrated $HNO_3$. Upon strong heating of the resulting copper nitrate solution,$5 \, g$ of its oxide is obtained. The equivalent weight of copper is ...... .

Hydrazine reacts with $KIO_3$ in the presence of $HCl$ as:
$N_2H_4 + IO_3^- + 2H^+ + Cl^- \rightarrow ICl + N_2 + 3H_2O$
The equivalent masses of $N_2H_4$ and $KIO_3$ respectively are:

If $m_1 \ g$ of metal $A$ displaces $m_2 \ g$ of another metal $B$ from its salt solution,and their equivalent weights are $E_1$ and $E_2$ respectively,how is the equivalent weight of $A$ expressed?