In an analysis,the ratio of iodine to oxygen in a certain substance is $254:80$. What will be the formula of this substance? (Atomic mass $I = 127$,$O = 16$)

What is the percentage by mass of oxygen in $NaOH$? (Atomic mass of $Na=23 \ u, O=16 \ u, H=1 \ u$)

$A$ protein $'A'$ contains $0.30\, \%$ of glycine (molecular weight $75$). The minimum molar mass of the protein $'A'$ is $.......\, \times 10^{3} \, g\, mol^{-1}$ [nearest integer]

When $0.01 \ mol$ of an organic compound containing $60 \%$ carbon was burnt completely,$4.4 \ g$ of $CO_2$ was produced. The molar mass of the compound is $......... \ g \ mol^{-1}$ (Nearest integer).

What is the percentage of nitrogen in urea (in $\%$)?

$0.30 \ g$ of an organic compound containing $C$,$H$ and $O$ on combustion yields $0.44 \ g \ CO_2$ and $0.18 \ g \ H_2O$. If $1 \ mol$ of the compound weighs $60 \ g$,then the molecular formula of the compound is: