Answer 1

1. The rate of a chemical reaction can be determined by measuring the extent to which the concentration of a reactant decreases in the given time interval or extent to which the concentration of a product increases in the given time interval.
2. Mathematically, the rate of reaction is expressed as:
   Rate = `- ("d"["Reactant"])/"dT" = ("d"["Product"])/"dT"`
   where, d[reactant] and d[product] are the small decrease or increase in concentration during the small time interval dT.