If a gaseous mixture contains $20\%$ $H_2$ by weight,what is the number of moles of $H_2$ in $100 \ g$ of the mixture (in $mol$)?

What is the number of moles of $Cl$ atoms and $N$ atoms respectively present in $n$ moles of tear gas?

Calculate the number of atoms in the following: $(i)$ $52 \ mol$ of $Ar$ $(ii)$ $52 \ u$ of $He$ $(iii)$ $52 \ g$ of $He$

What is the concentration of water?

Calculate the number of atoms of oxygen present in $176 \ g$ of $CO_2$.

Among the following,choose the ones with an equal number of atoms.
$A$. $212 \ g$ of $Na_2CO_3(s)$ [molar mass $= 106 \ g/mol$]
$B$. $248 \ g$ of $Na_2O(s)$ [molar mass $= 62 \ g/mol$]
$C$. $240 \ g$ of $NaOH(s)$ [molar mass $= 40 \ g/mol$]
$D$. $12 \ g$ of $H_2(g)$ [molar mass $= 2 \ g/mol$]
$E$. $220 \ g$ of $CO_2(g)$ [molar mass $= 44 \ g/mol$]
Choose the correct answer from the options given below.