Arrange the following in the order of increasing mass (atomic mass: $O = 16, Cu = 63, N = 14$)
$I.$ one atom of oxygen
$II.$ one atom of nitrogen
$III.$ $1 \times 10^{-10}$ mole of oxygen
$IV.$ $1 \times 10^{-10}$ mole of copper

The number of oxygen atoms in a solution prepared by dissolving $34.2 \ g$ of sucrose in $90 \ g$ of water is:

$K_2CS_3$ can be called potassium:

$10 \ mL$ of $2 \ M$ $NaOH$ solution is added to $20 \ mL$ of $1 \ M$ $HCl$ solution kept in a beaker. Now,$10 \ mL$ of this mixture is poured into a volumetric flask of $100 \ mL$ containing $2 \ moles$ of $HCl$ and made the volume up to the mark with distilled water. The solution in this flask is $:$

Chlorophyll extracted from the crushed green leaves was dissolved in water to make $2 \, L$ solution of $Mg$ of concentration $48 \, ppm$. The number of atoms of $Mg$ in this solution is $x \times 10^{20}$ atoms. The value of $x$ is (Nearest Integer) (Given : Atomic mass of $Mg$ is $24 \, g \, mol^{-1}$,$N_{A} = 6.02 \times 10^{23} \, mol^{-1}$)

What is $Rasavidya$?