Who is called the father of chemistry?

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

If $1 \ g$ of each of the following gases are taken at $STP$,which of the gases will occupy $(a)$ greatest volume and $(b)$ smallest volume? $CO, H_2O, CH_4, NO$

Substance $A_2B_{(g)}$ can undergo decomposition to form two sets of products. If the molar ratio of $A_{2(g)}$ to $A_{(g)}$ is $5 : 3$ in a set of product gases,then the energy involved in the decomposition of $1 \, \text{mole}$ of $A_2B_{(g)}$ is:
$A_2B_{(g)} \to A_{2(g)} + B_{(g)}; \Delta H^o = 40 \, \text{kJ/mol}$
$A_2B_{(g)} \to A_{(g)} + AB_{(g)}; \Delta H^o = 50 \, \text{kJ/mol}$

Air contains $23\% \, O_2$ and $77\% \, N_2$ by weight. What is the percentage of $O_2$ by volume?

$A$ gas has a density of $2.68 \ g/L$ at $STP$. Identify the gas.