Physical Chemistry

Molecularity of an elementary reaction is defined as the number of reacting species (atoms, ions, or molecules) taking part in an elementary chemical reaction which must collide simultaneously in order to bring about a chemical reaction. In the decomposition of ammonium nitrite:

Only one reacting molecule is involved in the elementary decomposition, so the reaction is unimolecular and its molecularity is one (1).

Gold number is defined as the minimum mass in milligrams of a protective colloid required to prevent coagulation of $10\text{ mL}$ of a standard gold sol on adding $1\text{ mL}$ of $10\%\text{ NaCl}$ solution.

Smaller gold number means greater protective power. Colloid A has the smallest gold number range ($0.005 - 0.01$, characteristic of gelatin), making it the most effective protective colloid.

The minimum concentration of an electrolyte in millimoles per litre (${\text{mmol L}}^{-1}$) required to cause precipitation or coagulation of a colloidal solution in two hours is defined as the coagulating value (or flocculation value) of the electrolyte. The smaller the coagulating value, the greater is the coagulating power of the electrolyte.