class ninth

1 Write down the name of the discovery against the name of each scientists:

Name of the scientists Scientific discovery
1 Jabar bin haiyan HNO3 , H2SO4, HCl
2 Yaqoob Al Kundi Concept of one metal
3 Empedocles Concept of four elements
4 Bohr Atomic model
5 Dalton Atomic Theory
6 Faraday \Law of Electrolysis

2. Multiple choice questions are given below. Please tick (√) on the right choice.
(i) Sulphuric acid was discovered by
a. Al Jahiz b. Berzelius
c. Jabar Bin Haiyan√ d. Aristotle
(ii) The information obtained from observation is called a
a. fact √ b.theory
c. principle or law d.knowledge of science
(iii)The western Scientists think universe
a. is created by an idol b. comes in to being on its on √
c. is created by Almighty Allah d. is imaginary
(iv) A hypothesis is tested by
a observation b.experiment
c. comparison with scientific laws d. comparison with other theories
(v) Inferences are deduced
a. through collection of information b. by thoughtful considerations
c. by coordinating with the previous information√ d. by all three factors mentioned above

3. Define Science?
Answer: Science
The knowledge obtained through observations and experiments is
called science. Or The search of man for collecting knowledge and integrating
it is called science.
4. Which part of the universe is studied in chemistry?
Answer: matter.
5. Which disciplines of chemistry were known to the ancient civilizations?
Answer: (i) Some of the oldest societies were familiar with chemical material extracted
from herbs .
(ii)They were also familiar with metallurgy, Physical properties of matter and color.
(iii) They were also familiar with the techniques of using dyes and paper making.
6. Explain different branches if chemistry.
Answer: Organic Chemistry:
The branch of chemistry in which we study the compounds of carbon. Or Study of hydrocarbons and their derivatives is called organic chemistry.
In organic chemistry:
The study of all elements and their compounds except compounds of carbon is called inorganic chemistry.
Analytical chemistry.
It is that branch of chemistry which discusses the analytical methods for getting information about compounds and chemical processes Or It deals with the study of determining the kind and quantity of substance present in a matter
Biochemistry:
It is the study of chemical compounds and their reactions occurring in living things Or Study of molecular components of cell.
Industrial chemistry:
The application of chemical knowledge, technology in
Industry and preparation of industrial products is called industrial chemistry.
Environmental chemistry:
Study of environmental problems and their solution i-e to
remove the ill elements is called environmental chemistry.
Nuclear chemistry:
Study of nuclear emissions and processes related is
Nuclear chemistry
Physical chemistry:
It is the branch of chemistry which deals with the physical properties and physical behavior of material things Or Branch of chemistry which deals with the principles and laws that describe matter and energy.
7. Why has science been divided into different disciplines?
Answer: We have divided science into different disciplines just for our convenience because no one can have grip or command on all of the scientific knowledge at the same time.
8. Show the relationship of different disciplines of science with the help of a diagram.
Answer:

Diagram
Physical Chemistry

Physics
Chemistry
Biochemistry
Biology
Geological Chemistry
Geology























9. What is the scientific method?
Answer: It is scientific approach which helps to collect facts. The scientific method includes the following four steps .Observation .Inference. Prediction and Experiment.
10. Explain the cyclic process of experiment observation, inference and prediction.
Answer: Observation:
It is made by using all of the five senses; one may use scientific
instruments /Apparatus like thermometer, burette ,Graduated cylinder etc.
Inference:
Correlating the facts with the previous information /Knowledge that we already have and thus jumping to hypothesis.
Prediction:
It is the process in which we deduced testable facts from the hypothesis.
Experiment:
Especially designed instruments are used to test the validity of hypothesis.
11. Difference between a law and a theory.
Answer:
Theory
Law
Not a permanent conclusion
Permanent conclusion
Can be modified
One can not modify it easily
When hypothesis are found correct by experiments then it becomes a theory,
It is based on theory. Or When a theory prevails for a longer period of time then it becomes law
Scientists can disagree only it is with out experimental proof Or on the basis of contradictory results of the experiments performed by them in laboratory.
Universally accepted.
12. Why hypothesis is formulated?
Answer: The scientists speculate regarding particular phenomenon without assumption of its truth is called hypothesis, according to them it may be the possible answer to a problem .It becomes the start point for investigations and research.

13. Write in detail how science has improved our daily life?
Answer: Science is playing very important role in order to bring the comfort in mans life .
Advancement in Agricultural field:
Grate advancement ids made in order to get more yield of crops to fulfill the requirement of huge population of world .Good quality pesticides and artificial fertilizer are made.
In the field of energy;
Different techniques are devised by scientific knowledge to obtain energy e.g. tidal energy, Nuclear energy, solar energy, energy obtained by using refusal.
Medicinal Field:
Different kind of medicines are invented /made for the curing of different diseases. So prolonged mans life up to some extent.
Transport facility:
Fastest means of transport services like bullet train(Magnetic train ) and passenger air crafts are used for traveling nowadays.
14. Which incident of life was responsible for the beginning of the subject of chemistry?
Answer: It was combustion phenomenon/process that was responsible for the beginning of the subject of chemistry.
15. What was Greek’s concept of elements?
Answer: The Greek philosopher Empedocles introduced the concept of four elements i-e Fire, Air, Earth, Water .According to him the elements were not interconvert able.
16. Who were Alchemists and what was their belief?
Answer: There was a concept of in Muslim era that inferior metal like iron copper could be made superior one (Gold) by the application of physical and chemical processes, Scientists following this concept were called Alchemists and this branch is called Alchemy.
17. Write a note on the discoveries of Jabar Bin Haiyan in chemistry.
Answer: The credit of all the following goes to Jabar bin haiyan
He explained calcinations and reduction
He improved the method of evaporation ,melting ,Sublimation , Distillation and crystallization,
He extracted Antimony and Arsenic from their sulphide ore
He worked on metallurgy.
He discovered methods for preparing varnish.
He prepared Concentrated Acetic Acid (CH3COOH)
He developed then process of golden script writing.
He prepared Hydrochloric acid, Nitric acid, Sulphuric acid.
He prepared aqua Regia (royal water having ability of dissolving gold)
He developed glass industry.
18. What facilities are provided by chemistry to man kind?
Answer: Some of the following major facilities are given below.
Agricultural development:
Due to study of soil chemistry one can select the crop to sow ,and would get more yield secondly production of fertilizers and there use has given better results in addition to chemical methods are used to normalize the acidic or high basics level of soil.
Medicinal field:
Chemical drugs are formulated by biochemist and organic chemistry
for the cure of deceases
Doctors are using radioactive elements and isotopes for treatment
of various diseases.

Industrial field:
Cement, Iron, brick, and glass are produced on mass scale and are
utilized in making buildings .houses, bridges etc.
In the field of energy:
By using nuclear technology we can make use of nuclear reaction s to produce electricity for our use.
War weapons:
Different kind s of weapons like nuclear, chemical, biological etc are made by the chemist (Chemical Scientists) which can be used for self defense.


19. How is chemistry proved to be dangerous for our lives?
Answer: 1.Smoke emissions from industries are proved to be dangerous for our health.
2. Industrial effluent when mixed with water lines goes to main water, so become
Serious threat to marine life and effect fish populations and eating affected fishes,
Cause serious problems.
3. War weapons made by man are infact the most dangerous threat to
Human beings because weapons of mass destructions are specially made to kill
Large number of peoples in seconds.
20. Why has Islam put so much emphasis to pay attention to the study of natural phenomena?
Answer: Because by this they would become able to under stand the sovereignty of Allah and mystery of universe and reason of creation .By studying natural phenomenon man became able to devise new inventions so he can make life comfortable.



Fill in the blanks:
(i) Molecular mass of an element or a compound is found relative to the mass C-12.
(ii) Ionic compounds are represented by their Formula unit.
(iii) One mole of hydrogen chloride gas contains12.044x1023.
(iv) A chemical reaction in which the products react to give back the reactants is called reversible reaction.
(v) The molecular formula of a substance tells actual number of atoms present in the molecule of that substance.
(vi) Empirical formula of a compound is also called its simplest formula.
(vii) One mole of ozone (O3) contains 18.068x1023 number of oxygen atoms.
Which of the following quantities will contain a mole of oxygen gas?
(i) 32 g of O2 (√) (ii) 14 g of CO (iii) 16 g of O2
3. Which of the following equations are correct in all respects?
Al2O3 (s) _________________ 2Al (s) + 3O2 (g)
Al2O3 (s) __________________2Al (s) + 3/2O2 (g)
Al2O3 (s) __________________2Al (s) + O2 (g) + O (g)
2Al2O3 (s) _________________4Al (s) + 3O2 (g) (√)
C2H6 (g) + O2 (g) _______________ _2CO2 (g) + H2O (g)
C2H6 (g) + 7O (g) ________________2CO2 (g) + 3H2O (g)
2C2H6 (g) + 7O2 (g) _____________ 4CO2 (g) + 6H2O (g)
4. The molecular formula of oxalic acid is CH2O2 which of the following formula
represents its empirical formula.
(i) CH2O2 (ii) CHO (iii) CHO2 (√) (iv) C2HO2
5. Hydrogen peroxide (H2O2) and water (H2O) contain hydrogen 5.93%
and 11.2% respectively. Show that the data illustrates the law of
Multiple proportions.
Answer: Solution:

H2O
H2O2
% of Hydrogen = 2/18 x 100= 11.11%
% of Oxygen = 16/18 x 100 = 88.88%
H : O
11.11 : 88.88 ( dividing by the lesser)
11.11 11.11
1 : 8
% of Hydrogen = 2/34 x 100= 5.882%
% of Oxygen = 32/34 x 100= 94.117%
H : O
5.88 : 94.77 ( dividing by the lesser)
5.88 5.88
1 : 16
Comparing % of oxygen in both cases
Oxygen in water H2O : Oxygen in water H2O2
8 : 16 (dividing by the lesser)
8 8
1 : 2
As the ratio is simple hence law of multiple proportions is proved.






6. Copper metal forms two oxides. In one oxide 1.26 g of oxygen combines with
10.0 g of copper while in the other oxide 2.52 g of oxygen reacts with 10.0 g of
Copper. Prove that these chemical combinations take place according to the
Law of multiple proportions.
Answer: Solution:
CuO
Cu2O
63.54 + 16 = 79.5
% of Cu = 63.5/79.5 x 100 = 79.87 %
% of O = 16/79.5 x 100 = 20.12 %
Cu : O
79.87 : 20.12
20.12 20.12
3.97 :1
2 x 63.54 + 16 = 143.08
% of Cu = 127.08/143.08 x 100 = 88.817 %
% of O = 16/143.08 x 100 = 11.18 %
Cu : O
79.88 : 11.18
11.18 11.18
7.94 :1
Comparing % of Cu in both cases
Cu in CuO : Cu in Cu2O
3.97 : 7.94
3.97 3.97
1 : 2
As the ratio is simple hence law of multiple proportions is proved.
7. Prove the law of reciprocal proportions with the help of following data. Methane
gas contains 75% carbon and 25% hydrogen whereas carbon dioxide contains 27.27% carbon and 72.73% oxygen and water contains 11.10% hydrogen and 88.9% oxygen.
Answer:
H2O
CH4
CO2
H2O =18 a.m.u
% of Hydrogen =11.11%
% of Oxygen = 88.88%


H : O
1 : 8
CH4 = 16
% of Carbon = 12 x 100 = 75
16
% of Hydrogen = 4 x 100
16
H : C
25 : 75
1 : 3
CO2 = 44
% of Carbon = 12 x 100 = 27.27
44
% of Oxygen = 32 x100=72.72
44
C : O
27.27 72.27
27.27 27.27
1 : 2.66
Comparing both cases

C of CO2 : O of CO2
C of CH4 : O of H2O
1 : 2.66

3 : 8 ( dividing by the lesser)
3 : 3
1 : 2.66

1: 2.66 : 1: 2.66
1_ : 1
2.66 2.66

1 x 2.66
2.66 1
1
1
Or 1: 1
As the ratio is simple hence law of multiple proportions is proved.

8: 6.92g sample of a hypothetical element (x) reacts with 0.584g of carbon. If the atomic mass of carbon is taken as 12 and four atoms of that hypothetical element react with carbon, find out of the atomic mass of the hypothetical element (x).
Answer: Solution:
0.584 of Carbon combines with = 6.92 g of hypothetical elements
12 g of carbon will need = x g of hypothetical elements
By cross multiplication we will get x
0.584 X (x) = 12 x 6.92
(x) = 12 x 6.92
0.584
(x) = 142.19 g
Since 4 atoms has mass = (x) i- e 142.19 g
So 1 atom has mass= (y) g
By cross multiplication we will get (y)
4 x (y) = 1 x 142.19
(y) = 1 x 142.19
4
(y) = 35.54 g
Answer: It is Chlorine having atomic mass 35.5 a.m.u.


9 If the atomic mass of carbon is taken as 50, what will be the atomic mass
of oxygen?
Answer: Solution:
When Carbon is 12 = Oxygen is 16
If Carbon is 50 = then Oxygen is x
By cross multiplication we will get
12 x (x) = 50 x 16
(x) = 50 x 16
12
(x) = 66.66 g
Mass of Carbon will be 66.66 a.m.u.







10 Find out the molecular mass or formula mass of the following substances.
CuSO4, KMnO4 Na2CO3, SiO2, (NH4)2 SO4, C6 H5NO2
Answer: Solutions:
1 CuSO4
1x 63+1x32+4x16=159.5amu
4 SiO2
1x28+2x16=60amu
2 KMnO4
1x 39+1x55+4x16=158 amu
5 (NH4)2 SO4
2 x ( 1x14+4x1) +1x32+4x16=132amu
3 Na2CO3
2 x 23+1x12+3x16=106amu
6 C6 H5NO2
6x 12 +5x1 + 1x14+2x16=123 amu.


11 What is the molecular mass of benzene (C6H6)? If the density of benzene is 0.880g/cm3 what will be the of molecules present in 1 cm3 of its volume? (D=M/V).
Answer: Solution:
Molecular mass of benzene =?
C 6H 6 = 6x12+6x1=78amu.
Density= 0.88 g/cm3
Volume = 1 cm 3
Mass =?
We know that d = m/v
Or m = d x v
M= 0.88 x 1
M = 0.88 g
As 78 g = 6.022 x 10 23 molecules
So 0.88 g = (x) molecules
Or (x) = 0.880 x 6.022 x 10 23
78
(x)= 67.94 molecules (Answer)
12 Which of the following will possess the maximum number of oxygen atoms?
1.0g of O2 1.0g of O3 1.0gof O
Answer: Solution:
Number of Oxygen atoms in 1 g of O
1 x 6.022 x 1023
16
= 6.022 x 1023
16
= 0.37 x 1023
Number of Oxygen atoms in 1 g of O2
2 x 1 x 6.022 x 1023
32
= 6.022 x 1023
16
= 0.37 x 1023

Number of Oxygen atoms in 1 g of O3
3 x 1 x 6.022 x 1023
48
= 6.022 x 1023
16
= 0.37 x 1023

All of them posses same number of atoms.
13. Empirical formulas and molar masses of the compounds are given
below. What will be the molecular formulas of these compounds?
Answer:


Empirical Formula Molar mass
1 NaS2O3 270.0 g/mol
2 C3H2Cl 147.0 g/mol
3 C2HCl 141.0 g/mol
4 Na2SiO3 732.0 g/mol
5 NaPO3 305.9 g/mol
Solutions: 1 NaS2O3
E.F = NaS2O3
E.F.mass = ?
M.F = ?
M.F.mass = 270 g/mole
E.F.mass = 1 x 23 + 2 x 32 + 3 x 16 = 135
We know that M.F = n x E.F
Or n = M.F.mass
E.F.mass
n = 270
135
n = 2
So M.F = 2 x (E.F)
M.F = 2 x ( NaS2O3 )
M.F = Na2S4O6 (Answer).
2 C3H2Cl
E.F = C3H2Cl
E.F.mass = ?
M.F = ?
M.F.mass = 147 g/mole
E.F.mass = 3 x 12 + 2 x 1 + 1 x 35.5 = 73.5
We know that M.F = n x E.F
Or n = M.F.mass
E.F.mass
n = 147
73.5
n = 2
So M.F = 2 x (E.F)
M.F = 2 x (C3H2Cl )
M.F = C6H4Cl2 (Answer)
3 C2HCl .

E.F = C2HCl
E.F.mass = ?
M.F = ?
M.F.mass = 141 g/mole
E.F.mass = 2 x 12 + 1 x 1 + 1 x 35.5 = 60.5
We know that M.F = n x E.F
Or n = M.F.mass
E.F.mass

n = 141
60.5
n = 2
So M.F = 2 x (E.F)
M.F = 2 x (C2HCl )
M.F = C4H2Cl2 (Answer)
4 Na2SiO3
E.F = Na2SiO3
E.F.mass = ?
M.F = ?
M.F.mass = 732 g/mole
E.F.mass = 2 x 23 + 1 x 28 + 3 x 16 = 122
We know that M.F = n x E.F
Or n = M.F.mass
E.F.mass
n = 732
122
n = 6
So M.F = 6 x (E.F)
M.F = 6 x (Na2SiO3)
M.F = Na12S6O18 (Answer).
5 NaPO3
E.F = NaPO3
E.F.mass = ?
M.F = ?
M.F.mass = 305.9 g/mole
E.F.mass = 1 x 23 + 1 x 31 + 3 x 16 = 102
We know that M.F = n x E.F
Or n = M.F.mass
E.F.mass
n = 305.9
102
n = 3
So M.F = 3 x (E.F)
M.F = 3 x (NaPO3)
M.F = Na3P3O9 (Answer).
14. Balance the following equations.
ZnS + HCl _________ ZnCl2 + H2S
HCl + Cr _________ CrCl2 + H2
Al + Fe3O4 _________ Al2O3 + Fe
NH3 + O2 ______________ NO + H2O
C2H6S + O 2 _______________ CO2 + H2O + SO2
B + SiO2 _______________ Si + B2O3
Na2SO4 + H2 __________ Na2S + H2O

Answers: ZnS + 2HCl __________ ZnCl2 + H2S
2HCl + Cr __________ CrCl2 + H2
8Al + 3 Fe3O4 __________ 4Al2O3 + 9Fe
2(2NH3 + 5/2O2 _______________ 2NO + 3H2O)
2(2C2H6S + 9/2 O 2 _______________ 2CO2 + 3H2O + SO2
4B + 3 SiO2 _______________ 3Si + 2B2O3
Na2SO4 + 4H2 __________ Na2S + 4H2O
15. Ammonia gas reacts with hydrogen chloride gas to produce white solid
Ammonium chloride. Write down a balanced equation for this reaction. Find out the mass of hydrogen chloride gas needed to react completely with 0.20 g ammonia gas.
Answer: Solution:
NH3 + HCl ________ NH4Cl
17 g of ammonia combines with = 36.5 g of HCl
So 0.20 g of ammonia will require = (x) g of HCl
By cross multiplication we will get
17 x (x) = 0.20 x 36.5
(x) = 0.20 x 36.5
17
(x) = 0.429 g (Answer)













16. Write down a balanced chemical equation for the reaction of phosphoric acid
(H3PO4) with calcium hydroxide (Ca (OH) 2) to produce water and calcium phosphate Ca3 (PO4)2. Find out the mass of calcium hydroxide required to react completely with 30.0 g of phosphoric acid. A also find out the amount of calcium phosphate produced in this reaction.
Answer: Solution:
2H3PO4 + 3Ca (OH)2 ________ Ca3(PO4)2 + 6H2O
196 g of phosphoric acid requires = 222 g of Ca (OH)2
So 30 g of phosphoric acid will require = (x) g of Ca (OH)2
By cross multiplication we will get
196 x (x) = 30 x 222
(x) = 30 x 222
196
(x) = 34 g. (Answer)
196 g of phosphoric acid produces = 310 g of Ca3(PO4)2
So 30 g of phosphoric acid will produce = (x) of Ca3(PO4)2
By cross multiplication we will get
196 x (x) = 30 x310
(x) = 30 x310
196
(x) = 47 g (Answer)
17. The fermentation of glucose (C6H12O6) takes place according to the following
Equation:
C6H12O6 Yeast 2C2H5OH + 2CO2
How much glucose will be used to produce 500 g of ethyl alcohol (C2H5OH)?
Answer: Solution:
C6H12O6 Yeast 2C2H5OH + 2CO2
Enzyme
92 g of Ethyl Alcohol is produced by using = 180 g of Glucose
So 500g of Ethyl Alcohol will produce by using = (x) g of Glucose
By cross multiplication we will get
92 x (x) = 500 x 180
(x) = 500 x 180
92
(x) = 978.26 g
978.26g of glucose is required for producing 500 g of ethyl alcohol (C2H5OH)






CHAPTER 3
Q 1 Fill in the blanks.
1. According to Daltons Atomic theory all atoms of an element are similar.
2. The fundamental particles of an atom are electron, proton and neutron.
3. Marie Curie discovered the element Radium
4. The number of protons in different atoms of an element is same.
5. According to Bohr’s atomic theory only orbits are for which the value of angular
momentum is nh/2ח
Q 2 Label the following sentences as true or false.
1. On passing through an electric field α rays are deviated from their straight path. (T)
2. Isotopes of an element have same atomic number but different mass number. (T)
3. The increasing order of the energy of orbital is as follows 1S, 2S, 2P, 3S (T)
4. An electron carries a charge of -1.602 x 10-19 coulomb. (T)

Q 3 Encircle all the correct answers
a. Which of the following statement is wrong regarding cathode rays?
(i). when these rays hit an object, its temperature rises.
(ii). their nature does not depend upon the gas used in the discharge tube.
(iii). they carry negative charge
(iv). their mass is equal to that of a proton.

b. In Ruther Fords experiment, what happened to those α particle which were not
deflected back?
(i). they were neutralized on combining with negative electrons.
(ii). they passed through the vacant spaces in the atoms.
(iii). they were absorbed by the thin gold foil.
(iv). they made gold radioactive.


c. The mass of an atom is.
(i). Distributed uniformly all round.
(ii). Concentrated in the nucleus.
(iii). Zero as the number of protons and electron are the same.

d. According to Bohrs Atomic Theory an electron.
(i). is stationary in different orbits
(ii). has constant value of energy
(iii). Loses its energy continuously
(iv). Emits energy when it jumps from a higher energy orbit to a lower energy
orbit.


e. The maximum number of electrons which can accommodated in L- shell of an
atom is
(i). 6 (ii). 8 (iii). 18. (iv). 32
Q.No 3 What information about atomic structures was obtained from the cathode rays?
Answer Major achievement was that their subatomic particles and electrons was
discovered, the cathode rays were electron, the scientist with coordination
concluded that electron is present in every atom of each element.
Q.No 4 . Explain atomic spectrum?
Answer We will discuss line emission spectrum here. If a substance is heated in a
discharge tube, the atoms get excited and electron moves to higher orbits but while
coming back they emit radiation. These radiations (photons) of different wave length and
they give bright lines against dark bands on photographic plate.
Q.No 5. What are the fundamental particles of an atom? Give properties of the particles
present in the nucleus.
Answer. The fundamental particles of atom are.
Proton (Properties):
i. It posses positive charge and is equal to -1.602 x 10-19 charge/coulomb.
ii. Its mass is 1.673 x 10-27 kg. iii. its e/m ratio is +9.5 x 107


Neutron (Properties):
i. it is neutral particle and is present inside nucleus

ii. Its mass is 1.675 x 10-27 Kg
iii as it posses no charge therefore it do not have e/m ratio.

Q No 6 What do you understand by the term atomic number and mass number? An
element has atomic number 35 and mass number 85 what will be its structure.
Answer. Atomic Number
It is the fundamental property of an element and it is defined as the number of
protons present inside the nucleus of an atom. It is denoted by a capital letter Z
Example
Z of hydrogen is = 1
Z of He = 2
Mass Number .
It is defined as sum of protons and neutrons present in the nucleus given as the mass
number of a particular atom. (Under observation/case). It is denoted by capital letter A. It
is also known as nucleons number
Example
A of H (Protium). = 1
A of He = 2
Note :- General Formula is A = P+N

ii. Structure formula of element having Z= 35 A= 80
k=2 L=8 M=18 N=7

Q NO.7 what are positive rays. Which particle was discovered by the information obtained from these rays?
Answer In 1886 , gold Stein performed experiment , it was concluded that if hydrogen gas used in
the discharge tube then positive rays (H+) are rightly to be called as proton are produced
.The minimum mass of these positive particles was found equivalent to the mass of
hydrogen.
Note: In this experiment Gold stein discovered Proton.
Q No 8. Describe Ruther Fords experiment fro the discovery of nucleus. Explain his atomic
model. What are the defects in this model?
Answer a. History 1911
b. Scientists Lord Ruther ford and his coworkers
c. Requirements α Particles source (radium) , thin gold (Au) foil photographic
plate
d. Process As shown in the diagram radium (enclosed in lead block)
emitting α particles strikes the gold foil. The photographic plate was placed as
shown in the figure
e Observation made Most of the particles passed but some deflected at wide
angles
f Result/Conclusion 1. Most of the space occupied by an atom is empty.
2. The deflection at such a large angle i-e 150 degree above means that they
come across with heavier (bulky) mass i-e then named as nucleus.
g Rather fords Atomic model (According to the results he said.)


1. Atom is a neutral particle.
2. Nucleus is positively charged.
3. Electron revolves around the nucleus.
4. Size of the atom depends upon (distance from the centre of nucleus to the
valence shell)
5.The model of the atom is like our solar system.
h. Defects found in Model (presented)
1. No information about electronic configuration (Arrangement) out side the nucleus
was given.
2. According to classical Electromagnetic theory the revolving electrons should emit
energy continuously, so due to decrease in energy it would eventually fall in the
center thus will collapse the structure.
3. If electron emits energy continuously so we should get a continuous spectrum rather
line spectrum
Q No 9. Explain Bohr’s Atomic Model .In what way this Model is better than Rather fords
model. What do you under stand by the term proton number and nucleon number?


Answer. Bohr’s Atomic model
(a) History (1913)
Scientist Neil Bohr’s
Model of atom (presented)
1. Electron’s revolves around the nucleus in fixed orbits.
2. As long as it revolves in fixed orbits, energy remains constant.
3. Electrons when absorbs energy it jumps from lower orbit to higher orbit but comes back
to original position and emits energy (when false from higher to lower orbit).
4. The energy is released as quanta’s.
5. The deference of energy or change in energy can be expressed as E=E2-E1

Note: E= hv
Bye rearranging we get v= E/h
When electron comes back to the lower orbit from higher one the v= -- E/h
6. Only those orbits are permissible whose angular momentum, mvr= nh/2π
7. Maximum number of electron an orbit can accommodate is found by the formula 2n2
Reason: (Model presented by Bohrs was better than rather fords)
1. it gives formula (2n2) about the configuration of electrons as we know that all the
electrons are not in single orbit
2. It solved the problem of continuous emission of energy and said that electron release energy
in packets (quanta’s) when they fall from higher to lower orbit / energy level
Proton Number: It is also called as nuclear magnitude. It is denoted by capital letter (Z) It is the number
of protons present inside the nucleus of an atom.
Nucleon Number: It is also called as Mass number. It is denoted by capital letter (A). It is equal to sum
of protons and neutrons of an atom.
Q.NO: 10: write the electronic configuration of oxygen, nitrogen and chlorine, there atomic
numbers are 8,7,17, while there mass numbers are 16, 14, 35 respectively?
Answer:






Oxygen=16O8
Afu-bau principle, S2,P6 ,d10,f 14. S stands for Sharpe , P for principle, d
for defused, f for fundamental)

S1 Elements
belongs to I A
Electronic configuration= Is2, 2s2, 2p4

1S
2S 2P
3S 3P 3d
4S 4P 4d 4f
5S 5P 5d
6S 6P
7S
S2 Elements
belongs to II
Nitrogen=14N7
P1 Elements belongs to III P1
Elements belongs to III A
Electronic configuration=Is2, 2s2, 2p3
P2
Elements Belongs to iv-A

Chlorine=35Cl17
P3
Elements Belongs to v-A
Electronic configuration=Is2, 2s2, 2p6, 3s2,3p5
P4
Elements Belongs to VI-A
P5
Elements Belongs to VII-A
P6
Elements Belongs to VIII-A






Q.NO:11 write a detail note on radio activity? How did this phenomenon help in
understanding the atomic structure?
Ans: Radio activity
History: 1896
Scientist: Henri Becquerel (Discovered Phenomenon)
It is the phenomenon in which substances emit certain types of rays (Alpha, Beta,
and Gamma)
Radio Active Elements: Such elements are called radio active which emits spontaneous
radiations. Explanation (Natural radio activity)
Henri Becquerel (1896) discovered that uranium and its compounds emit certain type of
rays which caused fogging on photographic plate.
Note: I: In (1988) Marie curie discovered radium (Another radioactive
element)
Ii: till now forty radioactive elements have been discovered.
Example: 238U92 ____ 234Th 92 + 4He2 (Alpha particle)
234Th 92_______ 234Pa 91 + 0e-1 (Beta particle)

Natural Radioactivity is a nuclear phenomenon.
It is not affected by temperature, pressure, or physical and chemical conditions
Artificial Radioactivity:
History: (1932)
Scientists: James Chadwick
Discovered: (Neutrons)
Explanation:- When an element is made (Rendered) radioactive by bombarding with alpha-
Particles, then this phenomenon is called artificial radioactivity.

Chadwick’s Experiment:
He bombarded Beryllium with alpha-particle and got neutrons. (Neutral particle)

9Be4 + 4He2 --------- 12C6 + 1n0

Note: When molecule of Nitrogen Gas was bombarded with alpha-particles protons are
obtained.

14N7 + 4He2 ---------------- 17O 8 + 1H1

Conclusion about atom

Neutrons, Protons, and Electrons are the Fundamental particles constituting an
atom. In addition to the fundamental particles there is also presence of other
particles.







Q. no12 . what are isotopes? Explain with examples.


Answer. Isotopes:

Atoms of the same element having same atomic number (Z) but different mass number (A) are called isotopes.
Note: The difference in mass number is due to the difference in number of Neutrons.
Example: Hydrogen element has three isotopes i-e Protium, Deuterium, Tritium

1 Protium (Ordinary hydrogen)
A=1
Z =1

2. Deuterium (Heavy hydrogen)

A=2
Z=1
3. Tritium (In Trace amount)

A=3
Z=1




Chapter no 4
Q no 1 Fill in the blanks

1 In Mendeleev periodic table, the elements are arranged in increasing order of their atomic masses.
2 VI A group elements can have valances 2 or 6
3 Elements showing properties of both metals and non metals are called metalloid
4. Oxides of metals are basic where as oxides of non metals are acidic in nature.
5. F block elements in the modern periodic table are called lanthanides and actinides.

Q. No 2 choose the correct answer.

1. Number of periods in Mendeleev periodic table were
a. three√ b. ten. c. Twelve d. thirty two e. twenty one
2. Number of elements In fourth period of the moderns periodic table is
a. Eighteen√ b. ten. c. Eight d. twenty one e. twenty two
3. The Nobel gases which react to give a few compounds is a. helium b. neon c. argon. d. krypton. E. xenon√.

4. The number of elements present in zero group is a. Three. B. Nine c. Seven d. Six√ e. Eight

5. The most reactive non metal is a. Chlorine b. Oxygen. c. Phosphorus d. fluorine√ e. Hydrogen

Q. No 3 Atom of an element M has three electronic shells and the outer most shell contains six electrons
(i). in which group and period the will the element the M be placed in the modern periodic table.
(ii). Write the electronic configuration of its outer most shell.
(iii). Element M belongs to which Block of the periodic table.
(iv). is the element M a metal or a non metal.
(v). Write a symbol, name, and atomic number of the element M.
Answers.
(i). as it has three electronic shells so it belongs to third period and it is in group Six A (A is written because third period contains S and P block elements/Normal elements only) as it has Six electrons in the valence shell.
(ii). Electronic configuration of M = third shell, it is 3S2, 3P4(P four indicates it belongs to VI A group.
(iii). It belongs to P Block elements.
(iv). It is a non metal.
(v). a. Symbol is ‘S’ b. It is Sulphur
c. Atomic number or Z number is 16

Q, No 4. Why helium and Neon are called Nobel gases?

Answer. Because their outer most shell is complete and they do not take part in chemical reactions.

Q, No 5. Atomic mass of argon is more then that of Potassium in the fourth period what will happen if their present positions in the modern periodic table are exchanged?

Answer. Modern periodic table is made by considering atomic number as the fundamental property. Exchanging the positions is not wise able because noble gas argon has completely filled outer most shell but potassium is highly reactive monovalent alkali so element will not posses periodicity.

Q, No 6. How will the modern periodic table be disturbed if isotopes of an element are discovered now?

Answer. No effect because periodic table is based on Z = proton number and the isotopic concept is just difference in number of neutron.

Q, No 7. Keeping in view the answers of 5 & 6 , is it advisable to arrange the elements in the increasing order of their atomic masses.?

Answer. No it is not fair because we will not observe any periodicity then.

Q, No 8. How many vertical rows of elements are there in d-block and f-block?
ii How many electrons can be accommodated in d-orbital and f-orbital.?

Answer. There are ten and fourteen vertical rows in D and F blocks respectively.
ii. The D orbital can have maximum ten electrons while the F orbital can have maximum fourteen electrons.
Q, No 9. If a new element is discovered which resembles noble gases what would be its possible atomic number?

Answer. Its (Z) number would be 118

Q, No 10. What is the name and atomic number of an element present in VI period and group IV B.?

Answer. It is hafnium and its atomic number is 72.

Q, No 11. If an element having atomic number 120 is discovered where will be it be placed in the periodic table? How many electrons will it have in its outer most shell?

Answer. i. It should be placed in 2A, below radium.
ii. It will be divalent i-e having two electrons in the outer most shell.
Q, No 12. Uranium is an important element for generating nuclear energy see table 4.5 (Periodic table) then answers the following questions?
i. In which period and which block is uranium present?
ii. What is the name of the series of elements containing uranium and other similar elements? How many elements are there in this series?
iii. Is uranium a metal or a non metal?
iv. Is it dangerous to hold U235 in hand? Explain your answer.

Answer. i. It is a member of F block elements, it belongs to 7th period
ii. It is actinide series having 14 members (Elements) including uranium.
iii. It is a metal
iv. Yes it is dangerous to hold U235 in hand. Because it is radioactive (emits radiations) which harm us.

Q, No 13, An unreactive gas is filled in red tube lights used for advertisements. What is the name of that gas and to which group does it belongs?
Answer. It is Neon and it belongs to group (8A).Nobel gases

Q, No 14. Sodium is a highly reactive metal, which readily reacts with air at room temperature, Element of which group may be mixed with it for its safe use?
Answer. As we know that Nobel gases are not reactive so better it would be to place the highly reactive electropositive metal sodium in a gas jar having noble gas.
Q, No 15. Hydrogen gas is passed through hot vegetable oil to make banaspati ghee. Nickel (Ni) is used as a catalyst in this reaction, see the periodic table and answer the following questions?
i. Can helium gas be used instead of hydrogen in this reaction?
ii. Which other metal can be used as catalyst instead of Ni in this reaction? Will those metals will give a better or poor result then Nickel

Answer. i. No because for saturation of unsaturated compounds we do hydrogenation (add hydrogen) in the presence of Nickel, also we can’t get the product (saturated) If we use helium (uncreative gas)
ii. Platinum and Palladium are tested and found better then Nickel.

Q,No 16. Which element has larger atomic size in the following Paris? Give reasons for your answers
a. Al or P b. Cu or Ag c. Fe or Ni
Answer. Aluminum will posses larger radius because moving along the period (Row) the radius decreases (left to right)
Reason. It is due to increase of nuclear magnitude (influence) and entrance of electron in the same shell so cause shrinkage in atomic radius.

b.. Cu will have smaller radius

Reason. Going down the group radius increases because shell after shell is added

c. Fe will posses more radius
Reason. we know that both come in the same period but going left to right radius decreases because of increase of nuclear influence.

Q,No 17. Which particle out of the following pair are larger in size explain your answer?
a. Na and Na+ b. Mg and Mg+2 c. Cl and Cl-

Answer. a. Na is larger in size

Reason. Na is having no charge i.e normal atom but in case of Na+ (Monovalent catain) the [M] shell is not there secondly increase of nuclear influence occurs because now it has (nucleus) to cover less electro therefore decrease of radius occurs.

b. Mg is larger in size

Reason Mg is having no charge i.e. a normal atom but in case of Mg+2 (divalent catain) the [M] shell is not there secondly increase of nuclear influence occurs because now it has (nucleus) to cover less electron therefore decrease of radius occurs

c. Chlorine is having smaller radius/size

Reason It is due to reason that in case of chloride ion [Cl-] the extra electron which comes in the valence shell decreases the nuclear pull/ influence and inter electron repulsion also comes which causes increase of radius, also size of atom increases.
Q. No 18. Write down the formula of three acidic oxides , three basic oxides and three amphoteric oxides?

Answer. Acidic Oxides. 1. CO2 2. SO2 3. NO2
Basic Oxides 1. Na2O 2. CaO 3. MgO
Amphoteric Oxides. 1. Al2O3 2. ZnO 3. PbO

Q. No 19. Explain which oxides will be more acidic in the following pairs
a. SeO2 and SO2 b. Al2O3 and SiO2

Answer. a. SO2 is more acidic
Reason. S is more electronegative and having less size as compared to Se.
b. SiO2 is acidic

Reason Al2O3 is amphoteric oxides [behaves both as acidic as well as basic].

Q.No.20 State Mendeleev periodic law. What was defect in it, how the periodic law is modified to remove this defect.
Answer. Mendeleev periodic law Properties of elements are a periodic function of their atomic masses.
Defect. It emphasized that the periodicity in properties is due to atomic mass but practically found incorrect.

Modification. We should consider atomic number as the fundamental property and then we would observe periodicity in the periodic table.

Q.No21. When an electron enters in the outermost shell of a gaseous fluorine atom, it simultaneously faces two opposing forces. One of these forces dominates and thus fluoride ion (F-) is formed. Explain these two opposing forces?

Answer. 1. The Electron – Electron repulsion force i.e. between the incoming electron and the host.
2. The attraction force of nucleus to get incoming electron
Result. The attraction force dominates thus fluorine atom takes up the electron and gets converted into fluoride ion.



Chapter no 5
Q. NO:1 Fill in the blanks

1 Energy is evolved new a new compound is found.
2 ionic compounds are soluble in water but not in non aqueous solvents
3 Covalent bond is formed by the mutual sharing of an electron pair.
4. HCL is a polar molecule.
5. NH3 and F3 react together to form a co-ordinate covalent bond.
Q. No: 2 Label the following statements as true or false.
1. An ionic is generally weaker then a covalent bond. (F)
2. Ionic compounds are overall neutral in nature. (T)
3. Noble gases contain 2 or 8 electrons in their outermost shells. (T)
4. A coordinate covalent bond is present in H3O+. (T)
Q. No:3 Choose the correct answer.
` (I) which one of the following pairs of atoms form a pure covalent bond?
a. Sodium and Chlorine b. Hydrogen and Chlorine
c. `Hydrogen and Oxygen d. Chlorine and Chlorine. √
(ii) What kind of bond will be formed between two atoms of oxygen?
a. ionic bond b. Covalent bond√
c. Coordinate covalent bond d. Polar bond.
e. Metallic bond
(iii) Which of the molecules given below has the highest polarity between atoms?
a. HCl b. CO2
d. H2 d. H2O √
(vi) Which one of the following statement is incorrect about the structure of NH4Cl?
a. An ionic bond is present in it. √
b. A coordinate covalent bond is present in it.
c. A covalent bond is present in it.
d. A hydrogen bond is present in it.
(v) `Which of the following statement is incorrect about the formation of a covalent bond?
a. The shared electrons bring about the attraction between the nuclei of two atoms.
b. The bond is not directional in nature. √
c. The bond is formed by mutual sharing of electrons.
Q. NO:4 How are ionic compounds formed? Give their properties?
Answer: Ionic compounds :
Compounds having ionic bond (electro valent bond) are called ionic compounds .The bond is formed by transfer of electron.
Example:
The bond formed between NaCl. In this compound Na (sodium) Atom loses
Its valance electron (transforms into catain), which accepted by
(Non metal atom) Chlorine (get converts into anion). Thus two oppositely
Charged particles attract each other and will result in the formation of an
Electrovalent bond.
Properties of ionic compounds:
1: Compounds are neutral.
2: Soluble in water but not in aqueous solvent.
3: In aqueous solution or in molten state they becomes electrolyte
4: Have high melting and boiling point
5: Solid states and are crystalline e.g. NaCl
Q. NO: 5 How a covalent bond is formed? Explain giving an example. Write down the properties of
Covalent compounds?
Answer: Covalent bond:
A covalent bond is found by sharing of electron.
Example:
H2 or H-H
Properties:
(1) Covalent compounds posses low melting and boiling points as compared to ionic compounds.
(2) Some has low molecular masses; some exists as gases while some exists as low boiling liquids.
(3) More soluble in solvents other than water.
(4) Usually non conductor of electricity.

Q. NO: 6 what is a coordinate covalent bond? How this bond is different from a covalent
Bond? Explain the formation of
H3N8+_______BF38-
Answerp;
Coordinate co-valent bond:
It is the type of bond in which an atom donates a pair of electron to another atom or electron pair is shared by only one atom.
Difference from covalent bond:
Electron shared are donated by only one atom .In Coordinate
Covalent-Bond while in covalent bonding electrons are shared by both
Atoms equally
Reaction:
Formation of H3N8+_______BF38-

H F F H F F
H_____ N: → B → H______N→ B

H F H F
As shown from above reaction nitrogen has donated an electron pair which is accepted by boron and the formation of coordinate covalent bond occurred.
Q. NO:7 What do you understand by the term electro negativity. How does it affect the molecular
structure? Which of the following molecules are polar?
CH4, HBr, H2O Br2, H2 , O2
Answer: Electro negativity:
It is the force with which an atom attracts shared pair of electron to words itself
OR
It is the ability of an atom (in competing to attract shared electron pair in a covalent bond) with another atom to which it is bonded.
Effect of electro negativity on molecular structures:
If the bonded atoms are different, there will come difference of electro negativity and more the difference more will be the dipole movement because partial (S+) and partial negative poles will develop more effectively.
Difference of electro negativity can cause different types of molecular structures like Angular / Tetra gonal / Bi pyramidal structure.
If bond is between similar bonded atoms
Than their would be no polarity/ dipole movement and compound would posses a linear geometry and
Is a pure covalent compound.

Polar compounds/ Molecules
Non polar compounds/ Molecules
H2O/HBr
CH4/Br2/H2/O2



Q. NO:8 Briefly explain the following:

(i) The melting point of sodium chloride is very high i.e. 80 1oC.
(ii) Electron structure of ammonium ion and carbon monoxide.
(iii) Carbon tetrachloride exists in liquid form at room temperature.
Answer: (i) Both Na and Cl atoms are held together due to strong electrostatic force of attraction. Therefore
large amount of energy is required, so having such high melting point.

(ii) H. H.
.
H.___: N: + H+ H. ____N ____H (Ammonium ion)

H. H.

. ..
. C . + :O: _____ :C: :O (Carbon monoxide)
. __

(iii) Dipole dipole direction is week but enough to gain liquid state only.
Q. NO:9 Which of the following compounds are ionic and which are covalent? Calcium
Fluoride, carbon dioxide, sulphur dioxide, sodium oxide, potassium chloride, nitrogen dioxide.
Answer:

Covalent
Ionic
CO2
CaF2
SO2
Na2O
NO2
KCl


Q. NO:10 Explain why?
(i) Metals are good conductor of electricity.
(ii) High pressure changes the shapes of metal.
(iii) The melting and boiling points of metals are usually very high?
Answer: (i) Because of presence of free electrons and have ability to donate.
(ii) The atoms are arranged in regular manner and by applying pressure the rows slips over one another thus turns into sheets and wires.
(iii) Because metallic bond exists which is strongest bond.


Q. NO:11 Write down the formulas of the compounds formed by the reactions of carbon with
hydrogen and carbon with chlorine. Explain their electronic structures.
Answer: (i)We would get (C2H2) Ethyne by reacting carbon and hydrogen.

.__ .
. __.
Electronic structure H X_____.C.__. C.__ XH




(ii) We would get Carbon tetra Chloride (CCl4) by reacting carbon and Chlorine.


Cl
X
.
Electronic structure Cl x__. C . __xCl
.
x
Cl



Q. NO:12 Explain why lonic compounds do not exist in the form of molecules?
Answer: Ionic compound exists as crystals because each ion is surrounded by opposite changed practical from
all sides, therefore they can only exists as aggregate particles or as discrete crystal units.
Q. NO:13 Why Aluminium is a better conductor of electricity than sodium? Give reason?
Answer: Reason:
The more free electrons, the better the conductor is. We know Aluminium can lose three electron while sodium can lose one, So Aluminium is a better conductor.

Q. NO:14 Explain the formation of ammonia (NH3) and water (H2O) molecules.
Answer: Reaction:
. .H H
.
:N: + .H _______ .N.__.H
.
.H H
Explanation:
As shown from the above reaction three electrons of nitrogen out of five valence electrons are shared. While each of the three Hydrogen atoms share one electron per atom.
Reaction:
..
: O :
. . . . .
:O: + 2H______ H H


Explanation:

As shown above oxygen contributes two electrons for making covalent bonds and Hydrogen atoms shares one electrons per atom.

















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