A molecule of a compound is composed of at least two types of atoms.
Explanation:
A molecule is defined as when two or more atoms of an element combine together by the bonds by sharing the electrons as O^2 (oxygen molecule)
A compound is a molecule when two different types of atom joined by chemical bonds as covalent, ionic or coordinate bonds as NH^3 ( ammonia)
Solubility of a compound in water can be referred to as the amount of the compound that can be dissolved in 1 L of the solvent (water) at any given temperature. Solubility of a compound can be expressed in the units of g/L or mg/L.
Given that the solubility of calcium carbonate in water = 14 mg/L
We have to calculate the volume of water that can dissolve 11 g of calcium carbonate.
Converting 11 g calcium carbonate to mg:

Volume of water that would dissolve 11000 mg calcium carbonate
= 
=785.7 L
Rounding the volume 785.7 L to two significant figures, we get 790 L water.
Therefore, we would need 790 L water to completely dissolve 11 g of calcium carbonate.
A specific combination of bonded atoms which always react in the same way, regardless of the particular carbon skeleton is known as the functional group. These are specific groups of atoms or bonds within organic molecules that accounts for the characteristic chemical reactions of those molecules. Examples of functional groups are the Carbonyl group, alkyl Halides, aldehydes and ketones among others.
C14H18N2O5
In limiting reactions and chemical reactions.