The requirement that a reversible reaction be at equilibrium is that:

- the concentrations on the two sides of the arrow be equal
- the velocity for the forward reaction equal that of the reverse reaction
- there will be as many molecules of the substances on one side of the arrow as there are molecules of the substances on the other side
- the moles of products will equal the moles of reactants

The velocity for the forward reaction equal that of the reverse reaction.

- the velocity for the forward reaction equal that of the reverse reaction

Explanation:-

Equilibrium constant is defined as the ratio of concentration of product to the concentration of reactants each raised to the power their stoichiometric ratios. It is represented by the symbol 'K'. For the general equilibrium equation:

The expression for equilibrium constant is given as:

Characteristics of equilibrium reaction:

Chemical equilibrium are attained is closed system.

The macroscopic remains constant like: volume, pressure, energy etc.

Rate of forward reaction is equal to the rate of backward reaction. The concentration of the reactants and products remain constant.They are not always equal.

the law of conservation of mass states that in a chemical reaction, the total mass of reactants is equal to the total mass of products. because atoms are only rearranged in a chemical reaction, there must be the same number of sodium atoms and chlorine atoms in both the reactants and products