Dulong and Petit's law is valid only for

The equivalent mass of iodine in the following reaction is $I_2 + 2S_2O_3^{2-} \longrightarrow 2I^{-} + S_4O_6^{2-}$

An element has three isotopes and their isotopic weights are $11, 12, 13$ units,and their percentage of occurrence in nature is $80 \%, 15 \%, 5 \%$ respectively. Then the average atomic weight of the element will be $:-$

In Victor Mayer’s method,$0.2 \ g$ of an organic substance displaced $56 \ mL$ of air at $STP$. The molecular weight of the compound is:

$x_1 \, g$ of a compound combines with $O_2$ to give $x_2 \, g$ of oxide. The equivalent mass of the compound is .........

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