Final Complete Notes of Chapter 9th Class X

7/27/2019 Final Complete Notes of Chapter 9th Class X

1/13

1

I-8/3, D-17/2, G-13/4

Islamabad

(0308-7894560)

Name:

Class:..

Subject: .

Notes by: M.Saqib Naveed ([email protected])

Compiled by: Wardah Zafar


2/13

2

Table of ContentsQ1:- Define reversible reaction, forward reaction, backward reaction and dynamic equilibrium? ............. 3

Q2:- Describe reversible reaction and state of equilibrium during evaporation process?........................... 3

Q3:- a). Define law of mass action. Derive its expression for the equilibrium constant. ............................ 4

b). Also describe way to write expression of Kc and unit of Kc?.................................................................... 4

Q4:- Define equilibrium constant.Also enlist factors effecting equilibrium constant. ................................. 5

Q5:- What are conditions required to get and maintain chemical equilibrium? .......................................... 5

Q6:- How we can recognize state of equilibrium? ........................................................................................ 6

Q7:- What is role of catalyst in reversible reaction? .................................................................................... 6

Q8:- How acid should be diluted? ................................................................................................................. 6

Q9:- Why water should not added to any acid? ........................................................................................... 6

Q10:- Describe application of equilibrium constant? ................................................................................... 6

Q11:- Give commercial application of reversible reaction and effective conditions to get maximum

yield? ............................................................................................................................................................. 7

Q12:- Define Le-Chatelaines principles also write its applications? ............................................................. 8

Exercise ......................................................................................................................................................... 9

Q.2: Give short answers of the following ................................................................................................. 9

Q.3: Following reaction can occur during lightning storm. For this reaction write ................................ 10

Q.4:Coal reacts with hot steam to form CO and H2.These substances reacts further in presence of a

catalyst to give methane and water vapour. .......................................................................................... 10

Q.5: Write equilibrium constant expression for each of following reactions. ........................................ 10Q.6:Determine units of equilibrium constants for these reaction. ........................................................ 11

Q.7: State the ways that equilibrium can be rcognized. ........................................................................ 12

Q.8: Describe macroscopic charcteristics of equilibrium reaction. ....................................................... 12

Think Tank ................................................................................................................................................... 13

Q.9: Bromine Chloride (BrCl) decomposes to form chlorine and bromine. For this reaction write ...... 13

Q.10: Kc expression for a reaction is given below. Write chemical equation for this reaction and derive

units of Kc. ............................................................................................................................................... 13

Q.11: For which of the following reactions are both reactants and products likely to be found when

reaction appears to be complete. Explain .............................................................................................. 13

Q.12: Cobalt chloride forms pink crystals(CoCl3.6H2O). When they are heated water is evolved and

they turn blue(CoCl3). Explain how you could use cobalt chloride as a test for water. ......................... 13


3/13

3

Chemical Equilibrium

Q1:- Define reversible reaction, forward reaction, backward reaction

and dynamic equilibrium?

Ans: - Reversible reaction:- A reaction in which the products can react together to form the

original reactants. OR

The reaction which proceeds in both forward and reverse direction is called reversible reaction.

For example: - reaction between nitrogen and hydrogen. It is represented by double arrow.

Forward reaction:- The reaction in which reactants convert into products.

Reverse reaction or backward reaction:-Reaction in which products converts into reactants.

Dynamic equilibrium:- Stage during reversible reaction in which rate of forward reaction

become equal to rate of backward reaction/reverse reaction.

Q2:- Describe reversible reaction and state of equilibrium during

evaporation process?

Ans:- In a close container when liquid evaporates and converts into vapours and vapours turns

into liquid again by process of condensation, a reversible reaction occurs.

Liquid gas.

When rate of evaporation becomes equal to rate of condensation, condition exist is called

dynamic equilibrium.


4/13

4

Q3:- a). Define law of mass action. Derive its expression for the

equilibrium constant.

b). Also describe way to write expression of Kc and unit of Kc?

Ans:- This Law was proposed by C.M Guld berg and P.waage.

Definition: Rate at which a substance reacts is directly proportional to its active mass and the

rate at which reaction proceeds is directly proportional to product of active mass of reactants.

Description of active mass:Active mass means concentration of reactants and products. Its unit

is mole/dm3. It is expressed by square brackets [ ].

Explanation:- Consider a hypothetical reversible reaction.

aA + bB cC + dD.

According to law of mass action.

Rate of forward reaction reactant

Rf [A]a

[B]b

Rf = kf[A]a

[B]b

Rate of backward reaction product

Rr

[C]c

[D]d

Rr= kr[C]c

[D]d

At equilibrium stage:-

Rate of forward reaction = rate of backward reaction.

Rf = Rr

Kf [A]a

[B]b

= Kr[C]c

[D]d


5/13

5

=

[] []

[] []

As Kc=

So Kc =[] []

[] []

Product concentration divided by reactant concentration.

b). (Solve and practice at your own. If you find any problem concern teacher)

Q4:- Define equilibrium constant.Also enlist factors effecting equilibrium

constant.

Ans :- It is the ratio of product concentration to the ratio of reactant concentration each raised to

power equal to the coefficient in the balanced chemical equation.

Factor that effect value of kc:-

a. Kc value depends upon temperature.b. Initial concentrations have no effect on kc value.

Q5:- What are conditions required to get and maintain chemical

equilibrium?

Ans:- Following conditions are required to maintain equilibrium.

1. Concentration of the reactants or products should not change during a chemical reaction.2. Temperature of system should be constant during reaction.3. Pressure or volume should be constant during chemical reaction.


6/13

6

Q6:- How we can recognize state of equilibrium?

Ans: - Equilibrium states can be determined by determining concentration of reactants and

products at regular intervals. When concentration of reactants and product remains constant,

reaction is at equilibrium. For this purpose physical methods or chemical methods can be used

chemical methods or titration, spectroscopy etc.

Q7:- What is role of catalyst in reversible reaction?

Ans:- Catalyst reduce the time taken to reach equilibrium but they have no effect on position of

equilibrium.

Q8:- How acid should be diluted?

Ans:- Always add acid to water when diluting it. Never add water into acid.

Q9:- Why water should not added to any acid?

Ans:- When acid is added into water, splashes of acid produce which may harm us.

Q10:- Describe application of equilibrium constant?

Ans:- Equilibrium constant( kc) can be used to predict many important features of a chemical

reaction.

1. Determine the equilibrium concentration of equilibrium mixture. It initial concentrationsare known.

2. It is used to predict direction of a chemical reaction.3. It is used to predict extend of a chemical reaction.4. It predicts the effect of change in condition of equilibrium reaction at equilibrium state.


7/13

7

Q11:- Give commercial application of reversible reaction and effective

conditions to get maximum yield?

Ans:- Ammonia and Suphuric acid production involves Reversible reactions. In order to get

maximum production in Industry following conditions are applied to get maximum yield.

Ammonia production:- Ammonia is commercially produced by Haber process.

N2 + 3H2 2NH3

Conditions: Temperature = 450o

C ,Pressure = 200 atm

By applying above conditions we get 98% equilibrium mixture yields of ammonia. High

pressure and cooling the equilibrium mixtures favors the production of ammonia.

In normal process we get only 33% ammonia.

Sulfuric acid preparation by contact methods:- To prepare sulphuric acid commercially SO2

is required. SO2 is produced by reversible reaction.

First step: Sulphur reacts with Oxygen and SO2 is produced.

S + O2 SO2

Second step: SO2 is converted into SO3

2SO2 + O2 2SO3

Conditions: Temperature = 450oC,Pressure = 200 atm ,Catalyst: Pt or V2O5

High pressure and coolingthe equilibrium mixture produce maximum yield of SO3

3rd

step:- SO3 is converted into 100% sulfuric acid.


8/13

8

Q12:- Define Le-Chatelaines principles also write its applications?

Ans:- If a charge is imposed on concentration, temperature, pressure on a chemical system at

equilibrium, the system responds in a way that oppose the change.

APPLICATIONS:- Synthesis of ammonia and H2SO4 involve reversible reactions, so less

quality is produced under normal conditions. By applying the principle we can produce

maximum yield of ammonia and H2SO4 upto 98%.

2SO2 + O2 2SO3

Conditions: Temperature 450oC, Pressure: 200 atm , Catalyst : V2O5

N2 + 3H2 3NH3

Conditions: Temperature 4000C, Pressure: 200 atm , Catalyst : Fe

First equilibrium is established in the presence of catalyst in minimum time and then by

increasing pressure and temperature equilibrium is shifted towards right. Such conditions tend to

increase yield of Ammonia and SO3 to about 98%.


9/13

9

Exercise

Q.2: Give short answers of the following

I. Differentiate between forward and reverse reactions?

II. What is chemical equilibrium?

III. State the law of mass action.

IV. State conditions for equilibrium.

V. What is the importance of equilibrium constant for a chemical reaction?


10/13

10

Q.3: Following reaction can occur during lightning storm. For this reaction

write

3O2 2O3

a. Equilibrium constant expression

b. Determine the units of equilibrium constant

c. Forward and reverse reactions

Q.4:Coal reacts with hot steam to form CO and H2.These substances reacts

further in presence of a catalyst to give methane and water vapour.

CO + 3H2 CH4 + H2O

a. Write forward and reverse reactions for it.

b. Derive Kc expression for it.

c. Determine unit of Kc

Q.5: Write equilibrium constant expression for each of following reactions.

a. H2O H2 + O2


11/13

11

b. CO + 2H2 CH3OH

c. COCl2 CO + Cl2

d. 4HCl + O2 2Cl2 + 2H2O

Q.6:Determine units of equilibrium constants for these reaction.

a. COCl2 CO + Cl2

b. H2 + I2 2HI

c. 2H2 + O2 2H2O

d. N2 + 2O2 2NO2


12/13

12

Q.7: State the ways that equilibrium can be rcognized.

Q.8: Describe macroscopic charcteristics of equilibrium reaction.


13/13

13

Think Tank

Q.9: Bromine Chloride (BrCl) decomposes to form chlorine and bromine. For

this reaction write

I. Chemical equation

II. Kc expressionIII. Units of Kc

Q.10: Kc expression for a reaction is given below. Write chemical equation for

this reaction and derive units of Kc.

Q.11: For which of the following reactions are both reactants and products

likely to be found when reaction appears to be complete. Explain

I. C + O2 CO2II. 2HF H2 + F2

Reason:

Q.12: Cobalt chloride forms pink crystals(CoCl3.6H2O). When they are heated

water is evolved and they turn blue(CoCl3). Explain how you could use cobalt

chloride as a test for water.

CoCl3.6H2O CoCl3 + 6H2O

Final Complete Notes of Chapter 9th Class X

Documents

Transcript of Final Complete Notes of Chapter 9th Class X