How many molecules are present in one gram of hydrogen? (Value $\times 10^{23}$)

The number of moles of electrons in $1 \ kg$ of electrons is .......

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

What is the weight in $g$ of $2.01 \times 10^{23}$ molecules of $CO$?

The total number of electrons in $18 \ mL$ of water (density $= 1 \ g \ mL^{-1}$) is

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