Q1: How does life exist on earth?
Ans: Life exists on earth due to presence of equilibrium phenomenon taking place in atmosphere.
Example: A natural process in which we take oxygen and exhale (CO₂)
Q2: How different environmental systems can exist?
Ans: Many environmental systems depend for their existence on delicate equilibrium phenomenon.
Q3: Define Reactants?
Ans: Substances that combine during a chemical reaction are called Reactants.
Q4: Define Products?
Ans: New substances form in a chemical reaction is called Products.
Q5: Give an example of reactants and products? Ans: Consider the reaction:
2H₂ + O₂ 2H₂O
In above reaction H₂, O₂ are reactants while H₂O is a product.
Q6: What are Irreversible reactions? Give few characteristics of them?
Ans: “Those reactions in which products do not recombine to form reactants are called Irreversible reactions.”
(i) These reactions proceed in one direction only.
(ii) Reactants are completely converted into products.
(iii) It is represented by a single arrow between the reactants and products.
Q7: Define Chemical Equilibrium State?
Ans: When the rate of forward reaction takes place at the rate of reverse reaction, the composition of the reaction mixture remains constant; it is called Chemical Equilibrium State.
Q8: Give the Characteristics of Reversible reaction? Ans: Reversible Reaction shows Following Characteristics: –
(i) Products recombine to form reactants.
(ii) It proceeds in both ways.
(iii) Reaction never goes to completion in reversible reaction.
(iv) It attains the dynamic equilibrium.
(v) Maximum yield of the products is obtained.
Q9: How Dynamic equilibrium is established?
Ans: If a reversible reaction is allowed to continue for considerable time without changing the conditions and rates of forward reaction and rate of reverse reaction becomes equal but take place in opposite directions this is called dynamic equilibrium.
Q10: Why at equilibrium state reaction does not stop? Ans: It is because of dynamic equilibrium.
Q11: Why equilibrium state is attainable from either way?
Ans: The concentration of specie at equilibrium stage attains the same values whether we start the reaction in the vessel in the forward direction or backward direction.
Q12: What is relationship between Active mass and Rate of reaction?
Ans: Active mass represents the concentration in mole dm¯³ and it is expressed as square brackets ( ). Rate of reaction is change in concentration of reactant or product divided by the time taken to the change. It is expressed as R=∆c/∆t. So, when active mass of substance change then rate also change.
Q13: Derive the equilibrium constant expression for the synthesis of ammonia from nitrogen and hydrogen?
Ans: The reaction for synthesis of ammonia is as:
N₂ + 3H₂ 2NH₃
Rf = Kf [N₂][H₂]³ Rr = Kr [NH₃]²
The expression for equilibrium constant of reaction is:
Kc = [NH₃]² [N₂][H₂]³
Q14: Write the equilibrium constant expression for two following reaction:-
(i) H₂ + I₂ ↔2HI
Ans: Rf = Kf [H₂][I₂] = Rate of forward reaction Rr = Kr [HI]² = Rate of reverse reaction
Kc = [HI]² = Equilibrium constant expression
(ii) CO + 3H₂ CH₄ + H₂O
Ans: Rf = Kf [CO][H₂]³ = Rate of forward reaction Rr = Kr [CH₄][H₂O] = Rate of reverse reaction
Kc = [CH₄][H₂O] = Equilibrium constant expression
Q15: How direction of a reaction can be predicted?
Ans: Direction of chemical reaction at any particular moment can be predict by knowing the numerical values of equilibrium constant of a chemical reaction and comparing this with reaction quotient.
Q16: How can you know that a reaction has achieved an equilibrium state?
Ans: If the value of forward becomes equal to reverse the reaction is said to in equilibrium state thus, Qc = Kc such reactions have comparable amounts of reactants and products at equilibrium position.
Q17: What are the characteristics of a reaction that establish equilibrium state at once? Ans: There are following important characteristics of such reactions:
(i) The reaction is reversible.
(ii) Rates of forward and reverse reaction become equal.
(iii) Amount of reaction and products remains the same.
(iv) It can be disturbed and achieved again under specific condition.
Q18: If reaction quotient Qᴄ of a reaction is more than Kᴄ what will be the direction of reaction? Ans: If reaction quotient Qc is large than equilibrium Kc the reaction will go from right to left.
Q19: An industry was established based on reversible reaction……..reasons of its failure being a chemist?
Ans: There are following certain reasons of failure of reaction:
(i) Reaction is reversible so, products recombine to form reactants and dynamic equilibrium is established.
(ii) Reaction condition like temperature, pressure and catalyst are not satisfied.
Q20: Define Static Equilibrium. Give example?
Ans: When reaction ceases to proceed it is called Static Equilibrium. It occurs in physical phenomenon.
Example: A building remains standing rather than falling down.
Q21: Why do rates of forward reactions slows down when reversible reaction approaches the equilibrium stage?
Ans: As reaction proceed, concentration of reactants decreases with time, so rate of reaction slows down gradually.
Q22: Under what conditions Kᴄ has no units?
Ans: When number of moles of reactants and products are equal then Kc has no units.
H₂ + I₂ 2HI
Kc = [HI]² = (mol.dm¯³)² = No units. [H₂][I₂] (mol.dm¯³)(mol.dm¯³)
Q23: What will be the units of Kᴄ in following reactions?
N₂ + 3H₂ 2NH₃
Ans:Kc = [NH₃]² = (mol.dm¯³)² = 1 = mol¯²dm⁶ [N₂][H₂]³ (mol.dm¯³)(mol.dm¯³)³ (mol.dm¯³)²
Q24: How can we write equilibrium constant expression for a reaction?
Ans: It is conventional to write product side in numerator and reactants as denominator.
Example: N₂ + O₂ 2NO Kc = [NO]²
Q25: Difference Between Forward and Reverse Reaction?
(i) In which reactant react to form products.
In which product react to form reactant.
(ii) It takes place from left to right.
It takes place from right to left.
(iii) It slows down gradually.
It speedup gradually.
Q26: Who gave law of Mass action?
Ans: Guldberg and waage in 1869 put forward law of mass action.
Q27: Name a factor on which Kᴄ depends?
Ans: The value of Kᴄ depends only on temperature. It does not depend upon initial concentration of reactants and products.
Q28: What are the major Components of atmosphere?
Ans: Nitrogen and Oxygen are the major components of atmosphere.
Q29: Give the Importance of Nitrogen in Industry?
Ans: It is used to manufacture ammonia which is further used in nitrogenous fertilizer. Example: Urea
Q30: How is Oxygen important in preparation of Sulphuric acid?
Ans: Oxygen is used to prepare Sulphur dioxide. Sulphur dioxide is used in preparation of Sulphuric acid (H₂SO₄)
Q31: Name a King of chemical?
Ans: H₂SO₄ is called King of chemicals.
Q32: Derive equilibrium constant expression for ionization of Hydrochloric acid? Ans: Hydrochloric acid ionizes in aqueous solution as:
HCl H⁺ + Cl¯
Kc = [H⁺][Cl¯]
Q33: Give Kᴄ of following reaction?
N₂ + O₂ 2NO
Ans: Rf = Kf [N₂][O₂] = Rate of forward reaction.
Rf = Kf [NO]² = Rate of reverse reaction.
Kc = [NO]² = Equilibrium constant expression.
Q34: Define Chemical Reaction?
Ans: When substance (reactants) combines to form new substances (products) it is called Chemical Reaction. Reaction and Products are separated by arrow ( )
Q35: What are different Types of chemical reactions? Ans: There are two types of chemical reaction: –
(i) Reversible Reactions. (never complete)
(ii) Irreversible Reactions. (goes to completion)
Q36: What is Haber’s process?
Ans: Ammonia is synthesized by Haber’s process under certain condition of temperature, pressure and catalyst.
N₂ + 3H₂ 2NH₃
Q37: Why is dynamic equilibrium established in closed vessel?
Ans: Because products formed in reversible reaction will not escape out in closed vessel.
Q38: Define Kf and Kr?
Ans: Kf is specific rate constant for forward reaction. While Kr is specific rate constant for reverse reaction.
Q39: Define Reaction quotient?
Ans: Reaction quotient is [Products] = ratio at any moment of reversible reaction. It is denoted by Qᴄ.