How many atoms are present in a $(i)$ $H_2S$ molecule and $(ii)$ $PO_4^{3-}$ ion?

When $3.00 \,g$ of carbon is burnt in $8.00 \,g$ of oxygen,$11.00 \,g$ of carbon dioxide is produced. What mass of carbon dioxide will be formed when $3.00 \,g$ of carbon is burnt in $50.00 \,g$ of oxygen? Which law of chemical combination will govern your answer?

Define the atomic mass unit.

Why is it not possible to see an atom with naked eyes?

In a reaction,$5.3 \, g$ of sodium carbonate reacted with $6 \, g$ of acetic acid. The products were $2.2 \, g$ of carbon dioxide,$0.9 \, g$ of water,and $8.2 \, g$ of sodium acetate. Show that these observations are in agreement with the law of conservation of mass.
$\text{Sodium carbonate} + \text{Acetic acid} \to \text{Sodium acetate} + \text{Carbon dioxide} + \text{Water}$

Calculate the number of molecules of sulphur $(S_8)$ present in $16 \, g$ of solid sulphur.