When an element forms its oxide,oxygen constitutes $20\%$ of its weight in the oxide. What is the equivalent weight of the element?

On what basis is the modern atomic mass standard defined?

Among $10^{-9} \ g$ (each) of the following elements,which one will have the highest number of atoms?
Element: $Pb, Po, Pr$ and $Pt$

Write about Formula Mass.

$0.1914 \ g$ of an organic acid is dissolved in approx. $20 \ mL$ of water. $25 \ mL$ of $0.12 \ N$ $NaOH$ is required for the complete neutralization of the acid solution. The equivalent weight of the acid is

Chlorine has two naturally occurring isotopes,${}^{35}Cl$ and ${}^{37}Cl$. If the atomic mass of $Cl$ is $35.45$,the ratio of natural abundance of ${}^{35}Cl$ and ${}^{37}Cl$ is closest to (in $: 1$)