Chemistry Podcast

Saturday, 6 January 2018

Class 11 Chapter 6 - Thermodynamics

Class 11 Chapter 6: Thermodynamics

System:

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

Surroundings:

            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.
So,
            U = U2 – U1 = Wad
Where,
            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.
So,
            U = q
Where,
            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 :

 Goldstein
 Rutherford
 J. Stanley
 J. J. Thomson


2. Neutron was discovered by :

 Rutherford
 Chadwick
 Austin
 Langmuir


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

 0
 1
 2
 3


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 :

 1.8
 1.8x103
 Infinite
 None of these


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

 Proton
 Electron
 Neutron
 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 :

 Dalton
 Pauli
 Rutherford
 Sommerfeld




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 :

Solid
Liquid
Gas
All of the Above


2. Mole is SI unit of :

Current
Temperature
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 :

10%
20%
30%
40%


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 :

Atto
Femto
Peta
Tera


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


Sunday, 27 August 2017

Chemistry Formulas for Chemical Bonding



Chemistry Formulas for Chemical Bonding

 
   1.       Necessary condition for an ionic solid to be dissolved in water
                                Hydration Energy > Lattice Energy
   2.       Order of melting and boiling points of certain compounds
NaF > NaCl > NaBr > NaI;    MgO > CaO > BaO
3.       No Bond is 100% Ionic
4.       Force of attraction between two oppositely charged ions in vacuum (air) as per Coulombs Law
F = q1q2/r2
5.       Order of the Lattice Energy of some compounds
·         LiX > NaX > KX > RbX > CsX    (where X = F, Cl, Br, I)
·         MgO > CaO > SrO > BaO
·         MgCO3 > CaCO3 > SrCO3 > BaCO3
·         BaSO4 > SrSO4 > CaSO4 > MgSO4  
·         Mg(OH)2 > Ca(OH)2 > Sr(OH)2 > Ba(OH)2
·         Bivalent Ions-Bivalent Ions > Univalent Ions-Bivalent Ions or Bivalent Ions-Univalent Ions > Univalent Ions- Univalent Ions
6.       Example of some compounds which contains more than one type of bond
·         NaOH, KOH, Na2CO3  (Ionic Bond, Covalent Bond)
·         CO, NH3.BF3, [Co(NH3)3Cl3]  (Dative Bond, Covalent Bond)
·         NH4Cl, CuSO4, K4[Fe(CN)6], [Cu(NH3)4]SO4  (Dative Bond, Ionic Bond, Covalent Bond)
·         CuSO4.5H2O  (Hydrogen Bond, Dative Bond, Ionic Bond, Covalent Bond)
7.       Double bond or triple bond is always shorter than corresponding single bond
8.       As S-Orbital is smaller than P-Orbital so bond length decrease with increase in S-character
SP3  C-H  =  1.093 Å (as in Alkanes)
SP2  C-H  =  1.087 Å (as in Alkenes)
SP  C-H  =  1.057 Å (as in Alkynes)
9.       Bond length increases if size of bonded atom is increases with given atom
HI > HBr > HCl > HF
10.   Bond distance is directly proportional to Atomic size
11.   Order of bond strength (or bond energy) of different hydrogen halides
H-F > H-Cl > H-Br > H-I
12.   Bond energy is directly proportional to bond order
Triple Bond > Double Bond > Single Bond
13.   Formula of Dipole Moment
Dipole moment (µ) = Electronic Charge (e) x Distance (d)
14.   Unit of Dipole Moment
Debye (D)
1D = 1 x 10-18e.s.u. cm
SI unit of Dipole Moment is = Coulomb-Meter (C-m)
1D = 3.336 x 10-30 C-m
15.   Dipole Moment of some substances
Substance with Formula
Dipole Moment (D)
HF
1.91
H2O
1.84
SO2
1.60
NH3
1.46
NF3
0.24
CH3Cl
1.86
HCl
1.03
H2S
1.10
HBr
0.78
HI
0.38

16.   Formula to calculate percentage ionic character of covalent bond
% Ionic Character = (Observed dipole moment x 100)/Dipole moment for 100% ionic bond
17.   Order of polarizing power of cations
Li+ > Na+ > K+ > Rb+ > Cs+
Be2+ > Mg2+ > Ca2+ > Sr2+ > Ba2+
Al3+ > Mg2+ > Na+
18.   Order of polarizing power of anions
N3- > O2- > F-
P3- > S2- > Cl-
19.   Chemistry Formula of Bond Order
Bond Order = [Nb-Na]/2
Where,
                Na = Number of electrons in antibonding molecular orbitals
                Nb = Number of electrons in bonding molecular orbitals
20.   Some molecules with their bond order, bond length and bond dissociation energy
Molecule
Bond Order
Bond Length (pm)
Bond Dissociation Energy (kJ/mol)
F2
1
142
158
O2
2
121
498
N2
3
110
945

21.   Bond Order in compounds which exhibits Resonance
Bond Order = (Total No. of bonds between two atoms)/(Total No. of resonating structures)


Saturday, 19 August 2017

Science Quiz : Acids and Bases Chemistry MCQs Part 18

Science Quiz : Acids and Bases Chemistry MCQs


Science Quiz by www.ChemistryNotesInfo.com

These are some of the random multiple question answers from Acids and Bases Chemistry...

1. OH- ion is called as:

Hydronium Ion
Hydroxide Ion
Hydrate Ion
Hydrogen Ion


2. Taste of acidic food is:

Sweet
Salty
Sour
Bitter


3. H+ Ion (Hydrogen Ion) is simply a:

Proton
Neutron
Electron
Hydroxide Ion


4. Bases increases concentration of what in water:

H+ Ion
OH- Ion
Both
None


5. Which of the acid from given below choice of acids is more dangerous:

Citric Acid
Carbonic Acid
Hydrochloric Acid
None of the above


6. Which of the given below statement about Alkalis is true:

They cannot neutralise acids
They are all insoluble
They are all acids
They are all bases


7. What happens to litmus paper in basic solutions:

Red litmus paper turns blue
Blue litmus paper turns red
Pink litmus paper turns Black
Black litmus paper turns blue


8. A liquid has a pH of 6.5, so this liquid is:

Weakly acidic
Weakly alkaline
Strongly acidic
Neutral


9. A liquid has a pH of 14, so this liquid is:

Weakly acidic
Weakly alkaline
Strongly acidic
Strongly basic


10. If a solution have pH of 9, then its H+ concentration is:

1 x 10-9 moles/liter
1 x 10-18 moles/liter
1 x 109 moles/liter
1 x 1018 moles/liter



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