What is the mass in grams of $0.25 \ mol$ water (in $g$)?

The number of electrons in $2.1 \ g$-ion of $Cl^{-}$ is

What is the number of moles of sulfur atoms present in $n$ mole molecules of mustard gas?

Explain the mole concept.

If one atom of an element $X$ weighs $6.643 \times 10^{-23} \ g$,then find the number of moles of atoms in $50 \ kg$ of element $X$. (in $moles$)

Number of moles and number of molecules in $1.4187 \ L$ of $SO_2$ at $STP$ respectively are: