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Showing posts with label 11th Class Chemistry Notes. Show all posts
Showing posts with label 11th Class Chemistry Notes. Show all posts

Saturday, 6 January 2018

Class 11 Chapter 6 - Thermodynamics

Class 11 Chapter 6: Thermodynamics


            A system is that part of universe in which we made observations is called system.


            All remaining part of the universe, other than system is called surroundings.
Universe = System + Surroundings

Types of System:

            The system is classified on the basis of movement of energy and matter inside or outside the system. I.e. open system, closed system and isolated system.

     1.     Open System:

A system in which exchange of matter and energy between the system and surroundings take place, is called open system.
Example:- Reaction in open beaker.

     2.     Closed System:

A system in which exchange of energy between the system and surroundings take place but there is no exchange of matter between the system and surroundings takes place, is called closed system.
Example:- Reaction in closed conducting vessel of steel.

     3.     Isolated System:

A system, in which no exchange of matter and energy between the system and surroundings take place, is called isolated system.
Example:- Reaction in isolated vessel like thermos flask.

The state of the system

            In chemistry, the state of thermodynamic system is described by the measurable or macroscopic i.e. bulk properties of the thermodynamic system.
To learn better, if someone asks, how we can describe the state of a gas?
So to answer this question, we describe the state of a gas by getting information about pressure (p), volume (V), temperature (T) and amount (n) etc. of gas.
So, these variables i.e. p, V, T are known as state variables or state functions.
Why these variables (p, V, T) are called state variables or state functions?
These variables are called state variables or state functions because their values depends only on the state of the system and do not depend on how they are reached on that point.

Internal Energy

            Sum of all energies (like chemical, electrical, mechanical etc.) of the system is called internal energy (U) of the system.
Now question is when internal energy of the system changes?
Internal energy of the system changes when,
·        Heat passes into or heat passes out of the system.
·        Work is done on the system or work is done by the system.
·        Matter enters the system or matter leaves the system.

     i.       Work

Before learning about effect of work on internal energy we first understand what is Adiabatic system.

Adiabatic system

            Adiabatic system is a system which does not allow transfer of heat through its boundary; means heat can not enters or leave the system.

Work on adiabatic system

            If 1kJ mechanical work done (case 1) on the system and 1kJ electrical work done (case 2) on the system than change in temperature is same in bath cases.
So, amount of work done on the system produces the same change of state no matter how this work was done.
            U = U2 – U1 = Wad
            U = internal energy
            U2 = internal energy at state 2 (final state)
U1 = internal energy at state 1 (initial state)
Wad = adiabatic work
Sign of Wad
a.     If Wad is positive, then work is done on the system.
b.     If Wad is negative, then work is done by the system.

      ii.     Heat

What is heat?

The exchange of energy due to difference in temperature is called heat.

If system allows exchange of heat (conducting walls of the system) then change in internal energy depends on amount of heat transfer between system and surroundings at constant volume when no work is done.
            U = q
            U = internal energy
            q = heat
            Sign of q
a.     q is positive, if heat is transferred from the surroundings to the system.
b.     q is negative, if heat is transferred from the system to surroundings.

Sunday, 17 September 2017

Structure of Atom Class 11 MCQ

Structure of Atom MCQ

Structure of Atom Chemistry Question Answers
These are some of the random multiple question answers from Structure of Atom... 

1. Who discovered anode rays :

 J. Stanley
 J. J. Thomson

2. Neutron was discovered by :


3. Radioactive isotope of hydrogen has ________ number of neutrons :


4. Cathode rays are deflected by :

 A magnetic field only
 An electric field only
 By Both
 By None

5. Cathode rays have :

 Mass Only
 Charge Only
 Mass and Charge Both
 No Charge and No Mass

6. Mass of atom is mainly constituted by :

 Neutrons and neutrino
 Neutrons and electrons
 Neutrons and protons
 Protons and electrons

7. Ratio of mass of proton and electron is :

 None of these

8. Atomic number of an element is equal to the number of  :

 Electron and Proton

9. Size of nucleus is :

 10-8 m
 10-10 m
 10-12 m
10-15 m

10. Who modifies Bohr’s model :


Also read Chemistry Notes of this chapter at below link...
11 Class Chapter 2- Structure of Atom

Friday, 15 September 2017

Some Basic Concepts of Chemistry Class 11 MCQ

Some Basic Concepts of Chemistry Class 11 MCQ

some basic concepts of chemistry mcq

These are some of the random multiple question answers from Some Basic Concept of Chemistry...

1. If a matter has definite volume and definite shape, then it is :

All of the Above

2. Mole is SI unit of :

Amount of Substance
Luminous intensity

3. A measured temperature is 100 0F on Fahrenheit scale, then what is this reading be on Celsius scale :

11.2 0C

78 0C

102.7 0C

37.8 0C

4. What amount of H­2O produced by combustion of 32 g of CH4 :

36 g
18 g
72 g
90 g

5. How many moles of CH4 is needed to get 44 gram CO2 after combustion :

0.5 mol of Methane
1 mol of Methane
2 mol of Methane
4 mol of Methane

6. Calculate the mass per cent of the solute, when a solution is prepared by adding 4 gram of substance A to 36 gram of water :


7. What is molarity of  NaOH in the Solution, that is prepared by adding 2 gram NaOH in water to get 500 mL of the solution :

0.4 M
1.0 M
0.1 M
4.0 M

8. A measured temperature is 44 0C on Celsius scale, then what is this reading be on Fahrenheit scale :

111.2 0F

88.8 0F

32 0F

199.8 0F

9. Dalton in 1803, gives :

Law of conservation of mass

Law of definite proportion

Law of multiple proportion

Gay Lussac’s law of gaseous volume

10. The prefix 10-15 is :


View below video on Some Basic Concept of Chemistry Quiz

Also read Chemistry Notes of this chapter at below link...

11 Class Chapter 1- Some Basic Concept of Chemistry Notes

Tuesday, 23 June 2015

11 Class Chapter 5- States Of Matter

States Of Matter

·       Water exists in three state i.e. solid (ice), liquid (portable water), gas (steam, vapors).
·       In these three states water has different physical properties but same chemical composition i.e. H2O
·       Also characteristics of these states of water depend on the molecular energy and how molecules aggregate.
·       As molecules change its physical state (from liquid to gas, gas to liquid, solid to gas etc.) there is no change in chemical properties of the substance but some changes may occur in rate of chemical reaction.

Intermolecular Forces:

                             These are forces of attraction and/or repulsion between the interacting particles i.e. atom or molecules.
Dutch Scientist J. Van der Waals (1837-1923) explains deviation of the real gases from ideal behavior with intermolecular forces, so intermolecular forces are also called as van der waals forces.
Example: Hydrogen bonding which is strong dipole-dipole interaction.

Dispersion Forces

                             If an atom gets instantaneous dipole (i.e. Atom has more electron density in right or left hand side) then its nearby atom become induced dipole, so these two temporary dipole attract each other. This attraction force is known as dispersion forces.
·       As these forces were first proposed by F. London so these forces are also known as London forces.

Dipole-Dipole Forces

                                    This type of force act between the molecules which have permanent dipole. Dipole of these molecule possess some partial charges (denoted by delta that is delta positive or delta negative)
Example: HCl molecule, where H possess delta positive and Cl possess delta negative.

Dipole-Induced Dipole Forces

                                             These attractive forces act between polar and non-polar molecules where polar molecules have permanent dipole, which induced the dipole and non-polar molecule by deforming electronic cloud of non-polar molecule.
·       As polarisability increases, strength of the attractive interaction also increases.


                           It is a type of dipole-dipole interaction present in molecules with high polar N-H, O-H and H-F bonds.

Thermal Energy

                           It is the energy of the body arise due to the motion of its atoms and molecules.
·       Thermal energy is directly proportional to temperature of the substances.

Intermolecular forces v/s Thermal interactions

·       Intermolecular forces make molecules of the substance keep together.
·       While thermal energy of the substance make molecules keep apart.
·       These two (thermal energy and intermolecular forces) decides collectively the states of matter.
·       If intermolecular forces predominance then
·       If thermal energy predominance then

What is Troposphere

                                   It is the lowest layer of the atmosphere held to surface of the earth by gravitational forces where we live. It contains O2, CO2, N2 and water vapors etc.

Gaseous State

                     Only 11 elements ( H, O, N, F, Cl, He ,Ne, Ar, Kr, Xe, Rn exists in gaseous state under normal conditions.

Characteristic Physical Properties Of Gases

·       Gases are highly compressible.
·       Gases exert the equal pressure in all direction.
·       As compared to solid and liquids, gases have much lower density.
·       Gases don’t have definite (fix) shape and volume.
·       Gases mix completely and evenly in all proportions.

Gas Laws

Boyle’s law

                   It is also known as Pressure Volume relationship.
As per Boyle’s law, ”At constant temperature and fixed amount of gases in no. of moles, its pressure varies inversely with its volume.”
Mathematically, at constant T and n,
P1/V ……………..1
P = k1 x 1/V   =   k1/V ………..2
Where, P = Pressure, V = Volume and k = proportionality constant and value of k1 depends upon Pressure P and Volume V.
Also,    K1 = PV ………..3
According to above relation, product of pressure P and volume V remains constant, if we fixed the amount of gas at constant temperature. You read these first class chemistry notes for classes 11 at online classes by
So,  P1V1 = P2V2 = Constant  ………4
Then,   P1/ P2 = V2/V1   ……………..5
As we know, Density is equal to mass divided by volume i.e. d=m/V
So, V = m/d …………6
From equation 2 & 6,
P = k1d/m
·       d = (m/k1)/P = k’P ……………7
Where, k’ = m/k1

Charle’s Law

               This is also known as Temperature and Volume relationship.
As per Charle’s law, “At constant pressure and fixed mass of gas, Volume is directly proportional to Absolute temperature.”
Mathematically, at constant P and n,
                             V  online classes T
Also, V=k2T
Where, K2 is a constant.

Thermodynamic Scale:  

                                       Kelvin scale of the Temperature is known as the Thermodynamic Scale which is utilized in many scientific works.

Kelvin Scale

                   To obtain temperature in Kelvin scale we add 273.15 (generally 273) in Celsius temperature.
i.e. K= 273.15 + °C (degree  Celsius)

Gay Lussac’s Law

                         This law is also known as Pressure and Temperature relationship.
According to Gay Lussac’s Law “At constant Volume and fixed amount of gas, pressure is directly proportional to temperature.”
Mathematically, at constant V and n,
                             P  online classes T
Also, P=k3T
Where, K3 is a constant.

Avogadro’s Law

                        This law is also known as Volume and amount relationship.
According to Avogadro’s law “Equal volume of all the gases under same condition of pressure and Temperature contain equal no. of molecules.”
V  universities n ………….1
V=k4n ……………2
Where, V is volume, k4 is a constant and n is no. of moles of gas.

Avogadro’s Constant

One mole has 6.022x1023 no. of molecules which is called as Avogadro’s constant. As we know, mole is equal to mass divided by molar mass.
So n = m/M  ……………..3
Then from equation 2 & 3
V = k4(m/M)
M = k4. m/V
M = k4.d    {here . represents multiplication}
Where M is molar mass, m is mass and V is volume, K4 is constant and d is density.

Ideal Gas Equation

                              Combination of 3 laws (Boyles Law, Charles Law and Avogadro law) gives a single equation (PV=nRT) called as Ideal gas equation.
According to Boyle’s Law; at constant T and n,
V 1/P ……….1
According to Charles Law; at constant P and n,
V T ……….2
According to Avogadro Law; at constant T and n,
V n  ……….3
From equation 1, 2 and 3; we get,
V nT/P ……….4
Or, V =R nT/P ……….5
Also, PV = nRT  …………..6
Then, R = PV/nT  ………..7
Where, R is a gas constant which is same for all gases and known as Universal Gas Constant and equation 6, PV = nRT is known as Ideal Gas Equation.

Equation Of State

                            Ideal gas equation is also known as equation of state because it gives relationship between 4 variables i.e. P, V, n and T. which describes state of any gas.
Let  if pressure, volume and temperature of fixed amount of ideal gas changes from P1, V1, T1 to P2, V2, T2  then,
P1V1/T1 = nR …………..8
P2V2/T2 = nR …………..9
So, from equation 8 & 9, we get
P1V1/T1 = P1V1/T1 ………..10
This above equation (eq. 10) is called Combined Gas Law.
Density And Molar Mass Of Gaseous Substances:
As per Ideal Gas Equation,
Then, n/V = P/RT
On replacing n by m/M (as mole n= mass m/ molar mass M); we obtain,
On replacing m/V by density d; we obtain,
Also, on rearrangement,
M = dRT/P
Where, M is molar mass, d is density, R is gas constant, T is temperature and P is pressure.

Dalton Law Of Partial Pressure:

According to Dalton law of partial pressure, “Total exerted pressure by mixture of all non-reactive gases is equal to the sum of partial pressure of all individual gases.”
At constant temperature T and Volume V
                             Ptotal = p1 +p2 +p3…………..
Where, Ptolal = total exerted pressure of mixture of all gases.
p1, p2, p3 etc. is pressure exerted by individual gases known as partial pressure.

Aqueous Tension

                           It is exerted by the saturated water vapors.
Pdrygas = Ptotal – Aqueous Tension

Partial Pressure In Terms Of Mole Fraction

                                                    Let at T temperature, 3 gases of Volume V exert the partial pressure p1, p2, p3. Then as per ideal gas equation,
Where, n1, n2, n3 are no. of moles.
 Also, according to Daltons law of partial pressure
Ptotal = p1 +p2 +p3
Or, Ptotal = n1RT/V + n2RT/V + n3RT/V = (n1+n2+n3)RT/V
And, on dividing p1 by PTotal , we obtain
P1/ PTotal={n1/(n1+n2+n3)}{RTV/RTV}
P1/ PTotal=n1/(n1+n2+n3) = n1/n = x1
Where, n= n1+n2+n3 and x1 is mole fraction of first gas.
So, p1=x1PTotal
Similarly, p2=x2PTotal
Then, general equation is written as-
Where, pi is partial pressure of ith gas.
xi is mole fraction of ith gas.

Kinetic Molecular Theory Of Gases

                                                     The postulates or assumption of Kinetic molecular theory of the gases are as follows:

  • ·       Gases contain atoms or molecules, as large no. of identical particles. These atoms or molecules are at large distances from each other, so that volume of gases is very high as compared to actual Volume of all molecules of gases. ‘Great compressibility of the gases is explained by these assumptions’.

  • ·       Gases occupy all available space by expansion because at ordinary pressure and temperature there are no attractive forces between gas particles.

  • ·       Gas particles always move in random and at constant motion because if gas particles are at rest and they occupy fixed positions then gas would have fixed shape, which is not observed at all.

  • ·       Gas particles move in straight lines in all the possible directions. During random motion these particles collide with each other and also collide with the walls of the container of the gas. As a result of this collision of gas particles with wall of the gas container pressure is exerted by gas.

  • ·       Collision between the gas molecules is perfectly elastic. It means total energy of the molecules don’t change that is It remains same before and after collision. Individual energy of the molecules may change due to exchange of energy between the colliding molecules, but sum of energies of all molecules remains same.

  • ·       Molecules of the gas move with the different speeds and their individual speed goes on changing due to collision of molecules but at particular temperature, distribution of speeds of molecules remains constant.

  • ·       Kinetic energy of molecules (of the gas) is directly proportional to absolute temperature because on heating gas at fixed volume, its pressure increases. As on heating molecules moves with more speed and strike with walls of the container more rapidly, so exerts more pressure.

Behavior Of Real Gases

Deviation From Ideal Gas Behavior

                                                   When we do different experiments, we find that real gases don’t follow PV=nRT Equation of ideal gases. So real gases don’t follow Boyle’s law means, if we plot graph between PV and P then we don’t get parallel straight line at all pressures with X-axis.

Real gases in above graph show some significant deviation from ideal gas behavior. As we see-
1) Dihydrogen and helium shows positive deviation means PV value increases with increase in pressure.
2) Methane and Carbon monoxide shows negative deviation and positive deviation means first with increase in pressure, PV value decreases and reaches the minimum then starts increasing with increasing pressure.

  • ·       Real gases don’t follow Boyle’s law, Charles law and Avogadro’s law perfectly under the all conditions, So real gases liquefy when they cooled and compressed.

  • ·       Under very high pressure attraction forces start operating between molecules of gases so pressure exerted by real gases is lower than that of ideal gas, because in ideal gas there is no attraction force exists at high pressure.

Pideal=Preal+(an2/V2) …………..1
Preal = observed pressure
an2 /V2 = correction term
Where ‘a’ is constant

  • ·       Under very high pressure gas molecule don’t move freely but restricted to (V-nb) Volume, Where nb is actual Volume occupied by the gas molecules themselves. So we can write gas equation for real gases as :

{P+(an2/V2)}(V-nb)=nRT …………2
Equation 2 is known as van der walls equation.
Where n is no. of moles of the gas.
a and b is vander walls constant and value depends on gas characteristics.

  • ·       Deviation from ideal behavior from real gases is measured with compressibility factor z.

Compressibility factor,
 z = PV/nRT  …………3
If z =1 gas is ideal gas because PV = nRT
If z > 1 or z<1, gas is real gas and If z > 1 then it is more difficult to compress gas.

  • ·       Boyle’s temperature or Boyle’s point is a temperature at which real gas behaves like ideal gas under appreciable range of pressure.

  • ·       Compressibility factor is also defined as ratio between actual molar volume and calculated molar volume

                             i.e. z = Vreal / Videal
As per above discussion we say that gases behave ideally -

  • 1.   At low temperature and high pressure.

  • 2.   or, If volume occupied by the gas is very large therefore volume occupied by gas molecule can be neglected in comparison to it.

Liquification Of Gases

·       The process of converting gas into liquid is known as liquification of gas
·       The highest temperature at which gas start liquefying is known as critical temperature (Tc)
·       Volume of one mole of the gas at this critical temperature is known as critical volume (Vc)
·       Pressure at this critical temperature is known as critical pressure (Pc)
·       Gases are cooled below their critical temperature for the liquefication of gases
·       When we apply cooling as well as compression, gases liquefy easily

Liquid State

Intermolecular forces in liquids are stronger than in gases. Liquid have definite (fix) volume and they can flow and take the shape of the container in which these liquids are stored. These online education classes degree notes are published by and hosted at Vapour pressure, viscosity, surface tension are some physical properties of liquids which are described below-

Vapor Pressure

                    Pressure exerted by the vapors on the walls of the container containing liquid is known as vapour pressure.
·       Vaporization depends on temperature
·   Vapour pressure at which equilibrium is achieved between liquid phase and vapor phase is known as Saturated Vapour Pressure or Equilibrium Vapour Pressure
·      Boiling is a condition of free vaporization means vapor extends freely into the surroundings.
·       Boiling temp. at 1 atm pressure is known as Normal Boiling Point
·       Boiling temp. at 1 bar pressure is known as Standard Boiling Point
·       Temp. at which clear boundary between liquid and vapors disappear is known as Critical Temperature

Surface Tension

                         Liquids tends to minimize their surface area because molecules of the liquid on the surface experience net attractive force towards the interior of the liquid, this characteristic property of the liquid is known as Surface Tension.
Example: Mercury do not form thin film and capillary action


              It is a measure of resistance to flow that arise due to internal friction between the layers of liquid (or fluid), when they slip over one another, during the flow of liquid or fluid.
·       Force required to maintain flow of liquid layers is-
                             F=online classesAdu/dz
Where, A is area of contact,
du/dz is velocity gradient,
is coefficient of viscosity.
SI unit of is “Newton second per square meter (Nsm-2)”
cgs unit of is “poise”
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