How many moles of $BaCO_3$ will contain $1.5$ moles of oxygen atoms?

How will you differentiate $0.50 \ mol$ $Na_2CO_3$ and $0.50 \ M$ $Na_2CO_3$?

$A$ flask contains $98 \ mg$ of $H_2SO_4$. If $3.01 \times 10^{20}$ molecules of $H_2SO_4$ are removed from the flask,the number of moles of $H_2SO_4$ remaining in the flask is $\left(N_A = 6.02 \times 10^{23}\right)$

The number of atoms present in $0.1 \ mol$ of a triatomic gas is: $(N_A = 6.022 \times 10^{23} \ mol^{-1})$

Calculate the following for $3 \ mol$ of ethane $(C_2H_6)$:
$(i)$ Number of moles of carbon atoms
$(ii)$ Number of moles of hydrogen atoms
$(iii)$ Number of molecules of ethane

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