CHEMISTRY Class XI Chapter : Equilibrium Free Notes

 CHEMISTRY Class XI Chapter : Equilibrium Free Notes

CHEMISTRY Class XI Chapter : Equilibrium 

1. Define dynamic equilibrium.

Ans 1. When the reactants in a closed vessel at a particular temperature react to give products, the concentrations of the reactants keep on decreasing, while those of products keep on increasing for sometime after which there is no change in the concentrations of either the reactants or products. This stage of the system is the dynamic equilibrium. 

2. Name the three group into which chemical equilibrium can be classified.

Ans 2. Chemical equilibrium can be classified into three groups – 

(i) The reaction that proceeds nearly to completion and only negligible concentrations of the reactants are left. 

(ii) The reactions in which only small amounts of products are formed and most of the reactants remain unchanged at equilibrium stage. 

(iii) The reactions in which the concentrations of the reactants and products are comparable, when the system is in equilibrium. 

3. What is physical equilibrium? Give an example.

Ans 3. Physical equilibrium is an equilibrium between two different physical states of same substance e.g. H2 O(s)  H2O(l) 

 

 4. What is meant by the statement ‘Equilibrium is dynamic in nature’?

Ans 4. At equilibrium, reaction does not stop rather it still continues, the equilibrium is dynamic in nature. It appears to stop because rate of forward reaction is equal to the rate of backward reaction.

5. On what factor does the boiling point of the liquid depends? 

Ans 5. Boiling point depends on the atmospheric pressure. 

6. State Henry’s law. 

Ans 6. The mass of a gas dissolved in a given mass of a solvent at any temperature is proportional to the gas above the solvent. 

7. What happens to the boiling point of water at high altitude? 

Ans 7. Boiling point of water depends on the altitude of the place. At high altitude atmosp here pressure thetore is less boiling point decreases.

8. On which factor does the concentration of solute in a saturated solution depends?

Ans 8. The concentration of solute in a saturated solution depends upon the temperature. Sugar (soln.)  sugar (solid). 

9. Mention the general characteristics of equilibria involving physical processes. 

Ans 9. (a) For solid  liquid equilibrium, there is only one temperature at 1 atm at which two phases can co-exist. If there is no exchange of heat with the surroundings, the mass of the two phases remain constant. 

(b) For liquid  vapors equilibrium, the vapors pressure is constant at a given temperature. 

(c) For dissolution of solids in liquids, the solubility is constant at a given temperature. 

(d) For dissolution of gases in liquids, the concentration of a gas in liquid is proportional to pressure of the gas over the liquid.  

10. What conclusion is drawn from the following – Solid  Liquid H2O(s)  H2O (l)

Ans 10. Melting point is fixed at constant pressure. 

State the law of chemical equilibrium. 

At a given temperature, the product of concentrations of the reaction products raised to the respective stoichiometric coefficient in the balanced chemical equation divided by the product of concentrations of the reactants raised to their individual stoichiometric coefficients has a constant value. This is known as the equilibrium law or law of chemical equilibrium.  

On what factors does the value of the equilibrium constant of a reaction depend?

The equilibrium constant of a reaction depends upon 

(i) Temperature 

(ii) Pressure, & 

(iii) Stoichiometry of the reaction 

State Le chatelier’s principle.

It states that a change in any of the factors that determine the equilibrium conditions of a system will cause the system to change in such a manner so as to reduce or to counteract the effect of the change. 

Can a catalyst change the position of equilibrium in a reaction?

No, a catalyst cannot change the position of equilibrium in a chemical reaction. A catalyst, however, affects the rate of reaction. 

What is the effect of reducing the volume on the system described below? 2C(s) + O2(g)  2CO(g) 

The forward reaction is accompanied by increase in volume. Hence according to Chatelier’s principle, reducing the volume will shift the equilibrium in the forward direction. 

Why the addition of inert gas does not change the equilibrium? 

It is because the addition of inert gas at constant volume does not change the partial pressures or the molar concentrations of the substance involved in the reaction. 

What happens when the temperature increases for a reaction?

The equilibrium constant for an exothermic reaction ( ) ∆ − H ve decreases as the temperature increases. 

The equilibrium constant of a reaction increases with rise in temperature. Is the reaction exo – or endothermic?

The equilibrium constant increases with a rise in temperature. Therefore, the reaction is endothermic. 

Can a catalyst change the position of equilibrium in a reaction? 

No, a catalyst cannot change the position of equilibrium in a chemical reaction. A catalyst affects the rate of reaction. 

If Qc < Kc, when we continuously remove the product, what would be the direction of the reaction?

Continuous removal of a product maintains Qc at a value less than Kc and reaction continues to move in the forward direction.

Define strong and weak electrolyte.

Those electrolytes which dissociate almost completely into ions in aqueous solutions are Known as strong electrolytes while those which show poor dissociation into ions in aqueous solutions are called weak electrolytes. 

Define Buffer solution

The solutions which resist change in pH on dilution or with the addition of small amounts of acid or alkali are called Buffer solutions. 

Define solubility product.

The solubility product of a salt at a given temperature is equal to the product of the concentration of its ions in the saturated solution, with each concentration term raised to the power equal to the number of ions produced on dissociation of one mole of the substance. 

When is a solution called unsaturated? 

When the ionic product is less than the solubility product the solution is unsaturated. 

How does dilution with water affect the pH of a buffer solution?

Dilution with water has no effect on the pH of any buffer. This is because pH of a buffer depends on the ratio of the salt, acid or salt base and dilution does not affect this ratio.