Chemical Equilibrium - Home of Knowledge

Chemical Equilibrium

Chemical Equilibrium

 

Q1. Describe a reversible reaction with the help of an example and graph.

Answer: Reversible reaction:  A reaction in which the products recombine to form reactants is called reversible reaction. OR  a reaction that proceed both in forward as well as reverse direction is called reversible reaction.

Representation: A reversible reaction is represented by a double arrow between reactants and products.

Explanation: The reversible reaction proceeds in both ways, i.e. forward and reverse. So a reversible reaction is one which can be made to proceed in either direction depending upon the conditions. It proceeds in either direction depending upon the conditions. These reactions usually carried out in a closed vessel. In a reversible reaction the equilibrium is the ultimate goal. These reactions cannot reach to completion.

General reaction for a reversible reaction:

A+B ⇔  C+D

(Reactants)   ⇔    (Products)

 

Example:

N2(g) + 3H2(g) ⇔   2NH3(g)

 

H2 + I2 ⇔  2HI

 

CaCO3 (g)  CaO(s) + CO2(g)

 

Question 2: What are irreversible reactions? What are their properties?

Answer: Irreversible reactions : A reaction in which the products cannot recombine to form reactants is called irreversible reaction.  OR   A reaction which takes place in one direction only under same conditions is called an irreversible reaction.

 Representation: Irreversible reaction is represented by a single arrow ( → ) from reactants to products.

General Reaction:

A + B  → C + D

(Reactants)  (Products)

Example: 2H2 + O2  →  2H2O

2Na(s) + 2H2O(l) → 2NaOH(l) + H2(g)

* Irreversible reactions are supposed to completion.

* These reactions are mostly carried out in open vessels.

* These reactions proceed only in one direction. i,e forward direction.

 

Question 3 :Define Chemical reaction? What do you know about reactants and products?

Answer: Chemical reaction : A process in which atoms of the same or different elements rearrange themselves to form a new substance.

Reactants: The substances that combine in a chemical reaction are called reactants.

Products: The new substances formed after completion of a reaction are called products.

Example, when H2 and O2 (reactants) combine they form H2O (product).

           2H2 + O2  →  2H2O

 

Question 4 : Defferentiate between reversible and irreversible reaction? OR write down the characteristic properties of reversible and irreversible reactions?

Answer:

Reversible Reaction

*products recombine to form reactants

*proceed both in forward as well as reverse direction

* A reversible reaction is represented by a double arrow between reactants and products.

* These reactions usually carried out in a closed vessel.

* These reactions cannot reach to completion.

*Example: N2(g) + 3H2(g)    2NH3(g)

Irreversible reaction

* Products cannot recombine to form reactants.

* These reactions proceed only in one direction. i,e forward direction.

* Irreversible reaction is represented by a single arrow ( → ) from reactants to products.

* These reactions are mostly carried out in open vessels.

* Irreversible reactions are supposed to completion

* 2H2 + O2  →  2H2O

 

Question 5 : Define chemical equilibrium state? Write down the types of chemical equilibrium?

Answer:  Chemical Equilibrium: Equilibrium means balance. when the rate of the forward reaction takes place at the rate of reverse reaction, the composition of the reaction mixture remains constant, it is called a chemical equilibrium state.  “OR”  A state in reversible reaction when two opposing reactions takes place at the same rate And the concentration of reactants and products donot change with time is called state of chemical equilibrium. A chemical reaction is in equilibrium when there is no tendency for the quantities of reactants and products to change.

Types of Chemical equilibrium: There are two types of chemical equilibrium.

Static equilibrium : When reaction ceases to proceed, it is called static equilibrium. This happens mostly in physical phenomenon. For example, a building remains standing rather than falling down because all the forces acting on it are balanced. This is an example of static equilibrium.

NaOH + HCl  NaCl + H2O

Graphite  ⇐⇒ Diamond.

dynamic equilibrium : When reaction does not stop, only the rates of forward and reverse reactions become equal to each other but take place in opposite directions. This is called dynamic equilibrium state. Dynamic means reaction is still continuing.

Example: N2(g) + 3H2(g)     2NH3(g)

 At dynamic equilibrium state : Rate of forward reaction = Rate of reverse reaction.

In a reversible reaction, dynamic equilibrium is established before the completion of reaction. It is represented graphically in figure below. At initial stage, the rate of forward reaction is very fast and reverse reaction is taking place at a negligible rate. But gradually forward reaction slows down and reverse reaction speeds up. Eventually, both reactions attain the same rate, it is called a dynamic equilibrium state.

 

For example, in case of reaction between hydrogen and iodine vapours, some of the molecules react with each other to give hydrogen iodide.

 

H2 + I2 →  2HI

At the same time, some of the hydrogen iodide molecules decompose back to hydrogen and iodine.

2HI →  H2 + I2

concentration of the reactants is higher than that of the products, the rate of the forward reaction is fast than the reverse reaction. As the reaction proceeds, the concentration of reactants will gradually decrease while that of product will increase, consequently the rate of the forward reaction will go on decreasing and the reverse reaction will go on increasing and ultimately the two rates will become equal to each other. Thus, the equilibrium will set up and concentration of various species (H2,I2,HI) becomes constant. It is represented as

H2 + I2  2HI

 

Examples of Equilibrium:

Example 1: Our existence is based on the equilibrium process taking place in atmosphere. We inhale oxygen and exhale carbon dioxide during respiration , while plants inhale Carbon dioxide and exhale Oxygen during photosynthesis. These two processes are responsible for the existence of life on earth. These two processes takes place through equilibrium phenomenon.

Example 2: Concentration of gases in lake water is governed by the principles of equilibrium.

Example 3: The lives of aquatic plants and animals are indirectly related to concentration of dissolved oxygen in water.

Question 6: What are the macroscopic characters of forward and reverse reactions?

Answer:

Forward Reaction Reverse Reaction
   

1. It is a reaction in which reactants react to form products.

2. It takes place from left to right.

3. At initial stage, the rate of forward reaction is very fast.

4. It slows down gradually

1. It is a reaction in which products react to produce reactants.

2. It takes place from right to left.

3. In the beginning, the rate of reverse reaction is negligible.

4. It speeds up gradually.

 

Question 7: Write down the macroscopic characteristics of dynamic equilibrium?

Answer: Macroscopic characteristics of dynamic equilibrium:

A few important characteristic features of dynamic equilibrium are given below:

  1. An equilibrium is achievable only in a closed system (in which substances can neither leave nor enter).
  2. At equilibrium state, a reaction does not stop. Forward and reverse reactions keep on taking place at the same rate but in opposite direction.
  3. At equilibrium state, the amount (concentration) of reactants and products do not change. Even physical properties like colour, density, etc. remain the same.
  4. 4. An equilibrium state is attainable from either way, i.e. starting from reactants or from products.
  5. An equilibrium state can be disturbed and again achieved under the given conditions of concentration, pressure and temperature.

 

Question 8: State the law of Mass Action and derive the expression for equilibrium constant for a general reaction?

Answer: LAW OF MASS ACTION: Cato Maximilian Guldberg and Peter Waage in 1869 put forward this law.

Statement OR Definition : “The rate at which a substance reacts is directly proportional to its active mass and the rate of a reaction is directly proportional to the product of the active masses of the reacting substances”.  OR

The rate of a reaction is directly proportional to the product of the molar concentration of each reacting substance raised to a power equal to the number of times the particular substance appears in the balanced chemical equation.

 

Active mass : Generally, an active mass is considered as the molar concentration having units of mol dm-3, expressed as square brackets [ ]. It represent the concentration of reactants and products in mol.dm-3

 

For example, consider a reversible reaction of the type

 

A+B    C+D

(Reactants)   (Products)

Suppose [A], [B], [C] and [D] are the molar concentrations (mol dm-3) of A, B, C and D respectively.

According to the Law of Mass Action:

The rate of the forward reaction a [ A ] [ B ]

= kf [ A ] [ B ]

 

Similarly,

The rate of the reverse reaction a [ C ] [ D ]

= kr [ C ] [ D ]

 

where kf and kr are the proportionality constant called specific rate constants of the forward and the reverse reactions, respectively.

At equilibrium state:

The rate of forward reaction = The rate of reverse reaction

kf [ A ] [ B ] = kr [ C ] [ D ]

Kf / Kr = [ C ] [ D ] ∕ [ A ] [ B ]   (where Kf /Kr = Kc )

 

Kc is called equilibrium constant. It is represented as:

 

Kc = [ C ] [ D ] ∕ [ A ] [ B ]

 

Law of Mass Action describes the relationship between active masses of the reactants and the rate of a reaction.

 

Derivation of the Expression for Equilibrium Constant for General Reaction:

 

Let us apply the law of Mass Action for a general reaction.

 

Aa + Bb ⇔ Cc + dD

 

This reaction consists of two reactions; forward and reverse reactions. According to this law, the rate of a chemical reaction is directly proportional to the product of the molar concentrations of its reactants raised to power equal to their number of moles in the balanced chemical equation of the reaction.

Let us first discuss the forward reaction. A and B are the reactants whereas ‘a’ and ‘b’ are their number of moles.

The rate of forward reaction according to law of Mass Action is:

 

Rf α [A]a [B]b

Rf = Kf [A]a [B]b

 

where Kf is the rate constant for the forward reaction. Similarly, the rate of the reverse reaction Rr, is directly proportional to the

product of [C]c [D]d, where ‘c’ and ‘d’ are the number of moles as given in the balanced chemical equation. Thus,

 

Rr α [C]c [D]d

Rr = Kr [C]c [D]d

 

where kr is the rate constant for the reverse reaction . We know that at equilibrium state the rates of both the reactions are equal.

 

The rate of forward the reaction = The rate of the reverse reaction

 

Such as:              Rf = Rr

 

and putting the values of Rf and Rr

    Kf [A]a [B]b = Kr [C]c [D]d

 

By taking the constants on one side and variables on other side of the equation , the above equation becomes:

 

Kf/Kr = [C]c [D]d ∕ [A]a [B]b

Kc = [C]c [D]d ∕ [A]a [B]b

 

Where Kc = Kf / Kr is called equilibrium constant.

 

This expression is for chemical equilibrium constant. All the reversible reactions can be expressed in this form. Such as:

When nitrogen reacts with oxygen to form nitrogen monoxide, the reversible reaction is as follows.

 

N2 + O2  2NO

The rate of forward reaction   Rf = Kf [N2] [O2]

 

The rate of reverse reaction   Rr = Kr [NO]2

The equilibrium constant expression for for this reaction is :

 

Kc = [NO]2   [N2] [O2]

 

For the reaction of Hydrogen with nitrogen to ammonia, the balanced chemical equation is :

 

N2 + 3H2  ⇔ 2NH3

For the reaction

The rate of forward reaction    Rf = Kf [N2] [H2]3

The rate of reverse reaction        Rr = Kr [NH3]2

 

The equilibrium constant expression for for this reaction is :

 

Kc = [NH3]2   ∕  [N2] [H2]3

 

 

Question 9: Define equilibrium constant? What is the unit of Kc?

 

Answer: Equilibrium Constant:

 

Equilibrium constant is a ratio of the product of concentration of products raised to the power of coefficient to the product of concentration of reactants raised to the power of coefficient as expressed in the balance chemical equation.

 

Kc =  Product of concentration of products raised to the power of coefficients  ∕ Product of concentration of reactants raised to the power of coefficients

 

It is conventional to write the products as numerator and reactants as denominator. By knowing, the balanced chemical equation for a reversible reaction we can write the equilibrium expression. Thus, we can calculate the numerical value of by putting actual equilibrium concentrations of the reactants and products into equilibrium expression. The value of Kc depends only on temperature, it does not depend on the initial concentrations of the reactants and the products. A few problems have been solved

to make the concept clear.

 

Unit of Kc :

Kc has no units in reactions with equal number of moles on both sides of the equation. This is because concentration units cancel out in the expression for Kc, e.g., for the reaction:

 

H2 + I2 2HI

Kc = [HI]2  ∕  [H2] [I2]     UNITS : (mol.dm-3)2 ∕(mol.dm-3) (mol.dm-3) = no units.

 

For reaction in which number of moles of reactants and products are not equal in the balanced chemical equation, Kc of course , have units, e.g., for the reaction:

N2 + 3H2  2NH3

 

Kc = [NH3]2  ∕  [N2] [H2]3 = (mol.dm-3)2  ∕  (mol.dm-3) (mol.dm-3)3  =  mol-2. dm6 OR (dm3∕mol) 2

 

 

Question 10: What is the importance of equilibrium constant?

 

Answer: Importance OR applications of equilibrium equilibrium constant:

Knowledge of equilibrium constant for a given reaction is very helpful aid in laboratory analysis as well as in industry. By knowing the numerical value of Kc of a reaction , direction as well as extent of the reaction can be predicted.

 

Direction of reaction:

Direction of a reaction at a particular moment can be predicted by inserting the concentration of reactants and products at that particular moment in the equilibrium expression.

For a general reaction this expression can be given as : Kc = [Products] /[Reactants]

For our easiness we Consider a gaseous reversible reaction between hydrogen and iodine to form hydrogen iodide.

H2 + I2  2HI     Kc 57.0 at 700k (at equilibrium)

Now This value of Kc is helpful in determining the direction in which a reaction will shift in order to achieve the equilibrium. For this purpose we have to withdraw the samples from the reaction mixtures and determine the concentrations of H2, I2, and HI. Suppose concentrations of the components the mixture are:

[H2]t = 0.10 mol.dm-3 , [I2]t = 0.20 mol.dm-3 and [HI]t = 0.40 mol.dm-3 .

The subscript ‘ t ’ with the concentration symbols means that the concentrations are measured at some time t, not necessarily at erquilibrium. When we put these concentrations into the equilibrium constant expression, we obtain a value called the reaction quotient Qc . The reaction quotient for this reaction is calculated as :

Qc = [HI]2t  ∕  [H2]t + [I2]t = (0.40)2 ∕ (0.10)(0.20) = 8.0

 

As the numerical value of Qc (8.0) is less than Kc (57.0) , the reaction is not at equilibrium. It requires more concentration of product. Therefore reaction will move in the forward direction.

The reaction quotient Qc is useful because it predicts the direction of the reaction by comparing the value of Qc with Kc.

Thus we can make the following generalization about the direction of the reaction.

 

If Qc < Kc ; the reaction goes from left to right, i.e., in forward direction to attain equilibrium.

 

If Qc > Kc ; the reaction goes from right to left, i.e., in reverse direction to attain equilibrium.

 

If Qc = Kc ; forward and reverse reactions take place at equal rates i.e., equilibrium has been attained.

 

(ii) Predicting Extent of a Reaction

Numerical value of the equilibrium constant predicts the extent of a reaction. It indicates to which extent reactants are converted to products. In fact, it measures how far a reaction proceeds before establishing equilibrium state. In general, there are three possibilities of predicting extent of reactions as explained below.

A very high value of equilibrium constant

 A very small value of equilibrium constant

 A moderate value of equilibrium constant

 

Large numerical value of Kc: The large value of Kc indicates that at equilibrium position the reaction mixture consists of almost all products and reactants are negligible. The reaction has almost gone to completion. For example, oxidation of carbon monoxide goes to completion at 1000 K.

2CO + O2  ⇔  2CO2   Kc = 2.2×1022

 

(b) Small numerical value of Kc: When the Kc value of reaction is small, it indicates that the equilibrium has established with a very small conversion of reactants to products. At equilibrium position, almost all reactants are present but amount of products is negligible. Such type of reactions never go to completion.

For example:

2NH3 ⇔  N2 + 3H2   Kc = 3.0 × 10-9

 

(c) Numerical value of Kc is neither small nor large. Such reactions have comparable amounts of reactants and products at equilibrium position. For example:

N2O4  2NO2  Kc = 0.211

 

Question 10: Define Le Chatellier’s principle?

Answer: If you impose a change in concentration, temperature or pressure on a chemical system at equilibrium, the system responds in a way that opposes the change.

 

Short Questions

  1. What are irreversible reactions? Give a few characteristics of them?

Answer: Irreversible reactions : A reaction in which the products cannot recombine to form reactants is called irreversible reaction.  OR   A reaction which takes place in one direction only under same conditions is called an irreversible reaction.

Representation: Irreversible reaction is represented by a single arrow ( → ) from reactants to products.

General Reaction:

A + B  → C + D

(Reactants)  (Products)

Example: 2H2 + O2  →  2H2O

2Na(s) + 2H2O(l) → 2NaOH(l) + H2(g)

* Irreversible reactions are supposed to completion.

* These reactions are mostly carried out in open vessels.

* These reactions proceed only in one direction. i,e forward direction.

  1. Define chemical equilibrium state.

Answer: Chemical Equilibrium: Equilibrium means balance. when the rate of the forward reaction takes place at the rate of reverse reaction, the composition of the reaction mixture remains constant, it is called a chemical equilibrium state.  “OR”  A state in reversible reaction when two opposing reactions takes place at the same rate And the concentration of reactants and products donot change with time is called state of chemical equilibrium. A chemical reaction is in equilibrium when there is no tendency for the quantities of reactants and products to change.

 

  1. Give the characteristics of reversible reaction.

Answer: Characteristics of Reversible Reaction:

*products recombine to form reactants

*proceed both in forward as well as reverse direction

* A reversible reaction is represented by a double arrow between reactants and products.

* These reactions usually carried out in a closed vessel.

* These reactions cannot reach to completion.

* Example : N2(g) + 3H2(g) ⇔    2NH3(g)

 

  1. How is dynamic equilibrium established?

Answer: The dynamic equilibrium establishes when the rate of forward reaction takes place at the rate of reverse reaction. There is no net change in the reaction mixture (Reactants and products). It means that the reactants and products are exist in equal amount.

 

  1. Why at equilibrium state reaction does not stop?

Answer: At equilibrium state the reaction does not stop. Only the rate of forward and reverse reaction becomes equal to each other.

 

  1. Why is equilibrium state attainable from either way?

Answer: In a reversible reaction the dynamic equilibrium is attainable from either side because these reactions may start either from reactants to products or from products to reactants.

 

  1. What is relationship between active mass and rate of reaction?

Answer: There is a direct relationship between active and the rate of reaction. I.e. by increasing the active mass the rate of reaction also increases.

 

  1. Derive equilibrium constant expression for the synthesis of ammonia from nitrogen and hydrogen.

Answer: N2 + 3H2    2NH3

For the reaction

The rate of forward reaction    Rf = Kf [N2] [H2]3

The rate of reverse reaction        Rr = Kr [NH3]2

 

The equilibrium constant expression for for this reaction is :

 

Kc = [NH3]2  ∕  [N2] [H2]3

 

  1. Write the equilibrium constant expression for the following reactions:

Answer:

(i) H2 + I2 2HI

Kc = [HI]2   ∕  [H2] [I2]     

 

(ii) CO + H2 CH4 + H2O

Kc =  [CH4] [H2O]  ∕  [CO] [H2]

 

  1. How direction of a reaction can be predicted?

Answer: Direction of a reaction at a particular moment can be predicted by inserting the concentration of reactants and products at that particular moment in the equilibrium expression.

For a general reaction this expression can be given as : Kc = [Products]  ∕  [Reactants]

 

  1. How can you know that a reaction has achieved an equilibrium state?

Answer: A reaction achieved equilibrium state when the rate of forward reaction becomes equal to the rate of reverse reaction.

Rate of forward reaction = Rate of reverse reaction.

 

  1. What are the characteristics of a reaction that establishes equilibrium state at once?

Answer: The reaction which attain the equilibrium state is called reversible reaction. In these type of reactions dynamic equilibrium establishes when the rate of forward reaction becomes equal to the rate of reverse reaction.

 

  1. If reaction quotient Qc of a reaction is more than Kc . What will be the direction of the reaction?

Answer: If Qc > Kc ; the reaction goes from right to left, i.e., in reverse direction to attain equilibrium.

 

  1. An industry was established based upon a reversible reaction. It failed to achieve products on commercial level. Can you point out the basic reasons of its failure being a chemist?

 Answer: The basic reason of its failure to achieve products on commercial scale is that, in a reversible reaction the products reacts with each other and form the reactants again.

 

 

Extensive Questions

 

  1. Describe a reversible reaction with the help of an example and graph.

Answer: Please see answer of question no.1.

 

  1. Write down the macroscopic characteristics of dynamic equilibrium.

Answer: Please see answer of question no.7.

 

  1. State the law of Mass Action and derive the expression for equilibrium constant for a general reaction.

Answer: Please see answer of question no.8.

 

  1. What is the importance of equilibrium constant?

 Answer: Please see answer of question no.10.

 

 

Test Yourself 9.1

1. Why reversible reactions never complete?

Answer: The reversible reactions never goes to completion because in these reactions the products recombine to form reactants.

2. What is a static equilibrium, explain with an example.

Answer: Static equilibrium : When reaction ceases to proceed, it is called static equilibrium. This happens mostly in physical phenomenon. For example, a building remains standing rather than falling down because all the forces acting on it are balanced. This is an example of static equilibrium.

NaOH + HCl ⇔  NaCl + H2O

Graphite  Diamond.

 

3. Why the amounts of reactants and products do not change in a reversible reaction.

Answer: In a reversible reaction dynamic equilibrium establishes during which the rate of forward reaction takes place at the rate of reverse reaction. So that amount of reactants and products donot change (remains the same).

 

Test Yourself 9.2

Question 1 : Define the law of mass action?

Answer: “The rate at which a substance reacts is directly proportional to its active mass and the rate of a reaction is directly proportional to the product of the active masses of the reacting substances”.  OR

The rate of a reaction is directly proportional to the product of the molar concentration of each reacting substance raised to a power equal to the number of times the particular substance appears in the balanced chemical equation.

Question 2: How the active mass is reperesented?

Answer: Active mass : Generally, an active mass is considered as the molar concentration having units of mol dm-3, expressed as square brackets [ ]. It represent the concentration of reactants and products in mol.dm-3

Question3: What do you mean by equilibrium constant?

Answer: Equilibrium Constant: Equilibrium constant is a ratio of the product of concentration of products raised to the power of coefficient to the product of concentration of reactants raised to the power of coefficient as expressed in the balance chemical equation.

Kc =  Product of concentration of products raised to the power of coefficients  ∕ Product of concentration of reactants raised to the power of coefficients

Question 4 : Point out the coefficient in each of the following hypothetical reactions?

(a) 2A + 3B ⇔ 4C + 2D

(b) 4X ⇔ 2Y + 3Z

(c) 2M + 4N ⇔ 5O

Answer: (a) 2A + 3B  4C + 2D

Rate of forward reaction, Rf = Kf [A]2 [B]3

Rate of reverse reaction, Rr = Kr [C]4 [D]2

Kc = [Products] ∕[Reactants]

Kc = [C]4 [D]2  ∕  [A]2 [B]3

Coefficient for this reaction are 2,3,4 and 2.

(b) 4X ⇔ 2Y + 3Z

Rate of forward reaction, Rf = Kf [X]4

Rate of reverse reaction, Rr = Kr [Y]2 [Z]3

Kc = [Products]  ∕  [Reactants]

Kc = [Y]2 [Z]3  ∕  [X]4

Coefficient for this reaction are 4,2 and 3.

 

(c) 2M + 4N ⇔ 5O

Rate of forward reaction, Rf = Kf [M]2 [N]4

Rate of reverse reaction, Rr = Kr [O]5

Kc = [Products]  ∕  [Reactants]

Kc = [O]5 ∕  [M]2 [N]4

Coefficient for this reaction are 2, 4 and 5.

 

Question 5: Write the equilibrium constant expressions for the following reactions?

(a) 2NO2(g) ⇔ N2O4(g)

(b) PCl3(g) + Cl2(g)⇔   PCl5(g)

(c) 2SO2(g) + O2(g)  ⇔ 2SO3 (g)

 

Answer: (a) 2NO2(g)⇔   N2O4(g)

Rate of forward reaction, Rf = Kf [NO2]2

Rate of reverse reaction, Rr = Kr [N2O4]

Kc = [Products]  ∕  [Reactants]

Kc = [N2O4] ∕  [NO2]2

 

(b) PCl3(g) + Cl2(g) ⇔ PCl5(g)

Rate of forward reaction, Rf = Kf [PCl3] [Cl2]

Rate of reverse reaction, Rr = Kr [PCl5]

Kc = [Products]  ∕  [Reactants]

Kc = [PCl5] ∕ [PCl3] [Cl2]

 

(c) 2SO2(g) + O2(g)  2SO3 (g)

Rate of forward reaction, Rf = Kf [SO2]2 [O2]

Rate of reverse reaction, Rr = Kr [SO3]2

Kc = [Products] ∕[Reactants]

Kc = [SO3]2  ∕  [SO2]2 [O2]

 

 

Test Yourself 9.3:

Question 1: What do you mean by extent of reaction?

Answer: The extent of reaction is a quantity that measures the extent in which the reaction proceeds I,e to which extent the reactants are converted into products. It is usually denoted by the Greek letter ξ.

Question 2: Why the reversible reaction do not go to completion?

Answer: The reversible reactions never go to completion because in these reactions the products recombine to form reactants.

Question 3: If a reaction has large value of Kc, will it go to completion and why?

Answer: The large value of Kc shows that almost all of the reactants are converted into products and reactants are negligible. It means that the reaction almost gone to completion.

Question 4: Which type of reaction never go to completion?

Answer: The reaction which have very small value of Kc never go to completion.

OR

The reversible reaction never go to completion because in these reactions the products recombine to form reactants.

Question 5: Why the reaction mixture does not have 50% reactants and 50% products at equilibrium position?

Answer: At dynamic equilibrium only the rate of forward and reverse reaction becomes equal to each other. It is not necessary that the reaction mixture contains equal amount of reactants and products.

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