At $STP$,$2.8 \, L$ of a gaseous substance weighs $5.5 \, g$. If the compound contains $N$ and $O$ atoms,its molecular formula will be ..............

Hemoglobin contains $0.34 \%$ of iron by mass. The number of $Fe$ atoms in $3.3 \ g$ of hemoglobin is. (Given : Atomic mass of $Fe$ is $56 \ u, N_A = 6.022 \times 10^{23} \ mol^{-1}$)

On complete combustion,$0.492 \ g$ of an organic compound gave $0.792 \ g$ of $CO_2$. The $\%$ of carbon in the organic compound is $..................$ (Nearest integer)

In each molecule of carbon tetrachloride,the mass percent of carbon and chlorine respectively are

An oxide of iron,which contains $69.9 \%$ iron and $30.1 \%$ dioxygen by mass,has the empirical formula:

The number of grams of oxygen in $32.2 \ g$ of $Na_2SO_4 \cdot 10H_2O$ is approximately (in $g$)