Molecular Mass and Mole Concept

Calculate the number of aluminium ions present in $0.051\mathrm{}\mathrm{g}$ of aluminium oxide. (Take avogadro number as $6.022\times {10}^{23}$)
(Hint: The mass of an ion is the same as that of an atom of the same element. Atomic mass $\mathrm{Al}=27 \mathrm{u}$)

Calculate the number of molecules of Sulphur $\left({\mathrm{S}}_8\right)$ present in $16 \mathrm{g}$ of solid sulphur (Avogadro number = $6.022\times {10}^{23}$).

What is the mass of:
(a) $0.2$ mole of oxygen atoms?
(b) $0.5$ mole of water molecules?

Convert into mole.
(a) $12 \mathrm{g}$ of oxygen gas
(b) $20 \mathrm{g}$ of water
(c) $22 \mathrm{g}$ of carbon dioxide.

What is the mass of
(a) $1$ mole of nitrogen atoms?
(b) $4$ moles of aluminium atoms (Atomic mass of aluminium $=27$)?
(c) $10$ moles of sodium sulphite $\left(\mathrm{N}{\mathrm{a}}_2\mathrm{S}{\mathrm{O}}_3\right)$?

Calculate the molar mass of the following substances.
(a) Ethyne, ${\mathrm{C}}_2{\mathrm{H}}_2$
(b) Sulphur molecule, ${\mathrm{S}}_8$ 
(c) Phosphorus molecule, ${\mathrm{P}}_4$ (Atomic mass of Phosphorus = $31 \mathrm{u}$)
(d) Hydrochloric acid, $\mathrm{H}\mathrm{C}\mathrm{l}$
(e) Nitric acid, $\mathrm{H}\mathrm{N}{\mathrm{O}}_3$.

A $0.24 \mathrm{g}$ sample of compound of oxygen and boron was found by analysis to contain $0.096 \mathrm{g}$ of boron and $0.144 \mathrm{g}$ of oxygen. Calculate the percentage composition of the compound by weight.

Which has more number of atoms, $100$ grams of sodium or $100$ grams of iron (Given, atomic mass of $\mathrm{N}\mathrm{a}=23 \mathrm{u}, \mathrm{F}\mathrm{e}=56 \mathrm{u}$, Avogadro number $=6.022\times {10}^{23}$)?

If one mole of carbon atoms weighs $12$ gram, what is the mass (in grams) of $1$ atom of carbon? (Avogadro number$=6.022\times {10}^{23}$).

Calculate the formula unit masses of $\mathrm{Z}\mathrm{n}\mathrm{O}, \mathrm{N}{\mathrm{a}}_2\mathrm{O}, {\mathrm{K}}_2\mathrm{C}{\mathrm{O}}_3,$ given atomic masses of $\mathrm{Z}\mathrm{n}=65 \mathrm{u}, \mathrm{N}\mathrm{a}=23 \mathrm{u}, \mathrm{K}=39 \mathrm{u}, \mathrm{C}=12 \mathrm{u},$ and $\mathrm{O}=16 \mathrm{u}.$

Calculate the molecular masses of ${\mathrm{H}}_2, {\mathrm{O}}_2, \mathrm{C}{\mathrm{l}}_2, \mathrm{C}{\mathrm{O}}_2, \mathrm{C}{\mathrm{H}}_4, {\mathrm{C}}_2{\mathrm{H}}_6, {\mathrm{C}}_2{\mathrm{H}}_4, \mathrm{N}{\mathrm{H}}_3, \mathrm{C}{\mathrm{H}}_3\mathrm{O}\mathrm{H}$.