One molecule of water has a volume of ........ $\times 10^{-23} \text{ cm}^3$? (Density of water = $1 \text{ g cm}^{-3}$)

The number of moles of $BaCO_3$ which contain $1.5$ moles of oxygen atoms is:

Which of the following has the greatest number of atoms?

Match List-$I$ with List-$II$.

List-$I$ (Mass of substance)	List-$II$ (Number of atoms)
$A$. $1.8 \text{ mg}$ water	$I$. $2 \times 10^{-4} \times N_{A}$
$B$. $9.8 \text{ mg}$ sulphuric acid	$II$. $1.5 \times 10^{-4} \times N_{A}$
$C$. $1.8 \text{ mg}$ carbon	$III$. $3 \times 10^{-4} \times N_{A}$
$D$. $5.85 \text{ mg}$ salt (NaCl)	$IV$. $7 \times 10^{-4} \times N_{A}$

Consider two sealed jars of equal volume. One contains $2 \ g$ of hydrogen at $200 \ K$ and the other contains $28 \ g$ of nitrogen at $400 \ K$. The gases in the two jars will have

Calculate the mass of $0.25 \ mol$ of iron (molar mass $= 56 \ g \ mol^{-1}$).