Answer the following question briefly:
 
What is a chemical equilibrium? What are its characteristics?
 
Chemical equilibrium is a state of a  reaction in which the forward and backward rates of reaction are .
There is no change in the amount of reactants or products.
 
Characteristics of equilibrium:
 
i. In ________ equilibrium, the volume of all phases remains constant.
 
ii. In a system at equilibrium, observable properties such as pressure, concentration, colour, density, and ________ remain constant with time.
 
iii. Although reactions continue at equilibrium, the system appears ________ externally.