Given that the abundances of isotopes $^{54}Fe$,$^{56}Fe$ and $^{57}Fe$ are $5 \%$,$90 \%$ and $5 \%$,respectively,the atomic mass of $Fe$ is

$4 \, g$ 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 ...... .

The specific heat of a metal is $0.16$,its approximate atomic weight would be

Match the following substances in List-$I$ with their equivalent weights in List-$II$ ($M$ = Formula weight):

List-$I$ (Substance)	List-$II$ (Equivalent weight)
$A. Na_2CO_3$	$I. M/5$
$B. KMnO_4 / H^+$	$II. M/3$
$C. K_2Cr_2O_7 / H^+$	$III. M/2$
$D. KMnO_4 / H_2O$	$IV. M/6$

When the weights of two elements combine with each other,their ratio is the ratio of their ......

In order to prepare one litre of a $1 \ N$ (normal) solution of $KMnO_4$,how many grams of $KMnO_4$ are required if the solution is used in an acidic medium for oxidation?