Chemical Equilibrium

Question 1

Irreversible chemical reaction

Answer 1

i) A reaction that proceeds only in one
direction is called as Irreversible
chemical reaction
ii) The products are stable and do not
convert back into the reactants in
these reaction.
iii) These are represented by full headed arrow
iv) Reactants may be completely
converted into products in these
reactions.
Examples:
a) 2H2 + O2 → 2H2O
b) NaOH + HCl → NaCl + H2O

Question 2

Reversible chemical reaction

Answer 2

i) A reaction that proceeds in two
directions is called as Reversible
chemical reaction.
ii) The products are unstable and
convert back into the reactants
iii) These are represented by two
oppositely directed half headed
arrows.
iv) Reactants are never completely
converted into products in these
reactions.
Examples:
a) PCl5 ⇇ PCl3 + Cl2
b) N2 +3H2 ⇇ 2NH3.

Question 3

Chemical Equilibrium is a Dynamic Equilibrium:

Answer 3

A type of equilibrium in which two opposing processes are proceeding at the equal rate is called dynamic equilibrium. Since, two opposing processes i.e forward and backward reactions are not stopped but proceeds at equal rate at equilibrium.

Question 4

Characteristics Of Chemical Equilibrium:

Answer 4

Following are the characteristics of chemical equilibrium.
At the state of equilibrium
i) Rate of forward and backward reactions becomes equal.
ii) The concentration of reactants and products becomes constant.
iii) The progress of reaction ceases.
iv) This state is attained for the reversible reaction no matter in which direction the reaction is proceeding.
v) At equilibrium, both reactants and products are present in different ratios.
Example:
Lets consider the reversible reaction between H2 gas and Iodine vapours to form HI at 450oC. The equilibrium is established when rising Curve of the
products [HI] and falling curve of the reactants [H2] and [I2] become parallel to time axis (x-axis). It is shown in
the following fig.
H2(g) +I2(g)
450𝑜𝐶⇇ 2HI(g)
Note: This reaction attains equilibrium, no matter it is started by combination of H2 and I2 or by decomposition of HI.