What is the composition of the white enamel of our teeth?

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 $24 \, g \, mol^{-1}$,$N_{A} = 6.02 \times 10^{23} \, mol^{-1}$)

In a $20\%$ aqueous solution of $H_2O_2$,the mole fraction of water is $.......$.

State whether the following statements are true or false:
$(i)$ $^\circ F = \frac{9}{5} (^circ C) + 32$
$(ii)$ In $1808$,Dalton published the law of chemical combination in the journal "New System of Chemical Philosophy".
$(iii)$ If the molar mass of a dibasic acid is $100$,its equivalent mass is $200$.

Rearrange the following ($I$ to $IV$) in the order of increasing masses:
$(I)$ $0.5$ mole of $O_3$
$(II)$ $0.5 \, g$ atom of oxygen
$(III)$ $3.011 \times 10^{23}$ molecules of $O_2$
$(IV)$ $5.6 \, L$ of $CO_2$ at $STP$

The ratio of $C_p$ and $C_v$ of a gas '$X$' is $1.4$. The number of atoms of the gas '$X$' present in $11.2 \ L$ of it at $N.T.P.$ is