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| 9th chemistry Notes |
1. Define
Organic chemistry.
Ans. Organic chemistry is defined as the covalent compounds of carbon and hydrogen (hydrocarbons) and their derivatives. Organic compounds occur naturally and are also synthesized in the laboratories. Organic compound determine the structure and properties of these naturally occurring as well as synthesized compounds. Scope of this branch covers petroleum, petrochemicals and pharmaceutical industries.
Ans. Organic chemistry is defined as the covalent compounds of carbon and hydrogen (hydrocarbons) and their derivatives. Organic compounds occur naturally and are also synthesized in the laboratories. Organic compound determine the structure and properties of these naturally occurring as well as synthesized compounds. Scope of this branch covers petroleum, petrochemicals and pharmaceutical industries.
2. Define Biochemistry.
Ans. Biochemistry
is the branch of chemistry in which we study the structure, composition and
chemical reactions of substances found in living organisms. It covers all
chemical processes taking place in living organisms, such as synthesis and
metabolism of bimolecular like carbohydrates, proteins and fats. Biochemistry
emerged as a separate discipline when scientists began to study how living
things obtain energy from food or how the fundamental biological changes occur
during a disease. Example of applications of biochemistry are in the fields of
medicine, food science and agriculture etc.
3. Define
Industrial chemistry.
Ans. The
branch of chemistry that deals with the manufacturing of chemical compounds of
commercial scale is called industrial Chemistry.
4. Explain
difference between physical chemistry and biochemistry.
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Ans.
Physical
Chemistry
|
Biochemistry
|
Physical
chemistry is defined as the branch of chemistry that deals with the
relationship between the composition and physical properties of matter along
with the changes in them.
|
Biochemistry
is the branch of chemistry in which we study the structure, composition and
chemical reaction of substance found in living organisms.
|
5. Define
Physical chemistry and Nuclear chemistry.
Or Define Physical Chemistry:
Ans. Physical Chemistry:
Physical chemistry is defined as the
branch of chemistry that deals with the relationship between the composition
and physical properties of matter, after along with the changes in them.
Nuclear Chemistry
Nuclear chemistry is the branch of
chemistry that deals with the radioactivity nuclear process and properties. The
main concern of this branch is with the atom energy and its uses in daily life.
Ans.
Environmental
Chemistry
|
Nuclear Chemistry
|
The branch of chemistry in which we
study about components of the environment and the effect of human activity on
the environment
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The Branch of chemistry that deals
with the radioactivity nuclear process and properties. The main concern of
this branch is with the atomic energy and its uses in daily life.
|
7. Define chemistry. Explain any two
branches of chemistry.
Ans. Chemistry
The branch of science which deals
with the composition, structure, properties and reaction of matter is called
chemistry.
Two branches of chemistry are as
under.
Physical Chemistry
Physical chemistry is defined as the
branch of chemistry that deals with the relationship between the composition
and physical properties of matter along with the changes in them.
Biochemistry
It
is the branch of chemistry in which the structure, composition and chemical
relation of substance found in living organism is called biochemistry.
8. Define
Inorganic Chemistry.
Ans. Inorganic
chemistry deals with the study of all elements and their compounds expect these
of compounds of carbon and hydrogen (hydrocarbons) and their derivatives.
9. Define
Industrial chemistry and Analytical Chemistry.
Ans. Industrial Chemistry
Industrial
chemistry is the branch of chemistry that deals with the manufacturing of
chemical compounds on commercial scale is called industrial chemistry.
Analytical Chemistry
Analytical
chemistry is the branch of chemistry that deals with separation and analysis of
a sample to identify its components.
10. Differentiate between Biochemistry and
Industrial Chemistry.
Ans.
Biochemistry
|
Industrial Chemistry
|
Biochemistry
is the branch of chemistry in which we study the structure, composition and
chemical reaction of substance found in living organisms.
|
Industrial
chemistry is the branch of chemistry that deals with the manufacturing of
chemical compounds on commercial scale.
|
Q. Write two applications of nuclear
chemistry.
Ans. (i)
It is applied in radiotherapy
(ii) generation of electrical power.
11. Define Environmental Chemistry.
Ans. The
branch of chemistry in which we study about components of the environment and
the effect of human activity on the environment.
12. Differentiate between Organic and Inorganic Chemistry.
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Ans.
Organic
Chemistry
|
Inorganic
Chemistry
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The study of
covalent compounds of carbon and hydrogen. (Hydrocarbon) and their
derivatives is called organic chemistry.
|
The study of
all elements and their compounds expect those of compounds of carbon and
hydrogen (Hydrocarbons) and their derivatives is called inorganic chemistry.
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13. Define matter and give two example.
Ans. Matter
Matter is defined as anything that
has mass and occupies space. For example, gas, water, wood etc.
Examples: Water, petrol,
wood etc.
14. Name
the elements represented by the following symbols W, Ba, Hg and Na.
Ans. W Tungstan Ba Barium Hg Mercury Na
Sodium
15. Write the percentage by weight of oxygen
in atmosphere and oceans.
Ans. In atmosphere oxygen is 21% while in oceans
it is 86%.
16. Define
symbol and valency with example.
Ans. Symbol
The representation of any element
with one or two English letters is called symbol.
Example: Sodium (Na),
Calcium (Ca).
Valency: Combining capacity
of an element with other elements is called valency.
Example: Sodium Na+1
, Chlorine CI-1
17. What is difference between compound and mixture?
Ans. Difference between compound and mixture.
Compound
|
Mixture
|
|||
1
|
It is formed
by a chemical composition of atoms of the element.
|
1
|
It is formed
by the simple mixing up of the substances.
|
|
2
|
Its components
lose their own properties and produce new substance that has entirely
different properties.
|
2
|
Its component
retains own chemical identities and properties.
|
|
Ans. Matter: Anything that has mass and
occupies space is called matter. Matter exists in three physical states. Solid,
liquid, gas.
Mixtures: Impure matter is
called a mixture. It can be homogeneous or heterogeneous in its composition.
Examples: Air, ice-cream
etc.
19. Write difference between physical and
chemical properties.
Ans.
Chemical Properties
|
Physical Properties
|
Chemical properties depend upon the
composition of the substance. When a substance undergoes a chemical change,
its composition changes and a new substance is formed. e.g. when hydrogen
react with oxygen, it forms water, is chemical change.
|
The properties that are concerned
with the physical state of matter are called physical properties e.g. colour,
smell, taste, hardness, shape of crystal, solubility, melting and boiling
point etc.
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20. What
is the valency of the following?
(a) Barium (b) Nitrogen
(c) Sodium (d) Sulphur
Ans. Elements Valency
(a)
|
Barium
|
2
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(b)
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Nitrogen
|
3
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(c)
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Sodium
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1
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(d)
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Sulphur
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2
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21. What is valency, on which factor its
depends?
Ans. Valency: Combining
capacity of an element with other elements called valency.
Factor: Valency
depends on number of valence electrons.
Example: Sodium (Na+1
) Chlorine (Cl-1
)
22. What is meant by element? Explain with example.
Ans. Element
A substance made up of same type of atoms,
having same atomic number and cannot be decomposed into simple substances by
ordinary chemical means is called an element.
At present more than
118 elements have been discovered out of which 92 occur naturally. Elements may
be solids, liquids or gases. On the basis of their properties, elements are
divided into metals, non-metals metalloids and gases.
Examples: Na, Ag, Cu, Fe, Hg, S, etc
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Ans. When two or more elements or compounds
mix-up physically without any ratio they form a mixture.
Example:
Air is a mixture of
nitrogen, oxygen, carbon dioxide, noble gases and water vapours. Sand, clay,
mineral salts, water and air.
24. Define
atomic numbers and atomic mass.
Or Write difference between atomic number
and mass number.
Ans.
Atomic
Mass
|
Atomic
Number
|
The sum of
number of protons and neutrons present in the nucleus of an atom is called
atomic mass. It is represented by "A".
|
The number of
protons present in the nucleus of an atom is called atomic number. It is represented
by "Z"
|
26. Differentiate
between molecular mass and formula mass.
Ans.
Formula
Mass
|
Molecule
Mass
|
The sum of
atomic masses of all the atoms present in one formula unit of a substance is
called formula mass e.g.
NaCI = 23 + 365
= 58.5 amu
|
The sum of
atomic masses of all the atoms present in one molecule of a molecular
compound is called molecular mass e.g.
(H2O) = 2(1) + 16
= 2 + 16 = 18 a.m.u
|
27. What
is meant by element? Explain with example.
Ans. Elements: Element is substance which made up
of same types of atoms, having same atomic number and it cannot be decomposed
into simple substance by ordinary chemical means.
Examples: Sodium (Na),
Oxygen (O), etc.
28. Define formula mass and give example.
Formula
Mass
The sum of atomic
masses of all the atoms present in one formula unit is called formula mass.
Example Sodium chloride NaCI
= NaCI = 23 + 365 = 58.5amu
29. An
element with A=39,Z=19. Calculate the number of electrons and proton in one
atom of this element.
Ans. Atomic mass of element = A = 39
Atomic
number of element = Z = 19
Proton
and electron always equal in any atom, that's why,
Number
of proton = 19
Number
of Electron = 19
30. Draw dot end across formula of Methane.
Ans. CH4
Ans. The relationship between molecular and
empirical formula is given.
Molecular
formula = (Empirical formula) x n
When
n = 1,2,3 and so on.
Example: Molecular formula benzene = C6H6.
Which is derived from the empirical
formula CH when value of n = 6.
32. What
is difference between element and compound?
OR What are the compounds? Explain with
examples?
Ans.
Compound
|
Element
|
Compound is a
substance made up of two or more element chemically combined together in a
fixed ratio by mass. (For example water H2O).
Example: Water (H2O)
|
Element is the substance made up
of same type of atom, having same atomic no and cannot decomposed into simple
substance by chemical was.
Example: Sodium (Na), Copper (Cu).
|
33. For an element Z = 92, A = 238 calculate the
number of electron and proton in it.
Ans. Number of protons Z = 92 , Atomic Mass A = 238
Number
of neutrons n
= A -
Z
=
238-
92 = 146
34. How
does Homogenous mixture differ from Heterogeneous?
OR
Define Homogeneous mixture and give
example.
Ans. Homogeneous mixture
Mixture that have uniform composition throughout are
called homogeneous mixture.
Example: Air, gasoline, ice-cream.
Heterogeneous
mixture:
The mixture which does not have uniform
composition is called heterogeneous mixture.
Example: Rock, soil and wood etc.
35. Define relative atomic mass on the base
of C-12.
Ans. Relative atomic mass of an element is the
average masses of an atom of that element as compared to 1/12th the mass of an
atom of carbon -12 isotopes.
36. Define atomic mass unit.
Ans. The unit for relative atomic masses is
called atomic mass unit. With symbol amu, one atomic mass unit is 1/12th mass
of one atom of carbon 12th.
37. Write four examples of mixture.
Ans.
(i) Air is a mixture of nitrogen, carbon
dioxide, noble gases and water vapours.
(ii) Soil is a mixture of sand, clay, mineral
salts, water and air.
(iii) Milk is a mixture of water, sugar, fat
proteins, mineral salts and vitamins.
(iv) Brass is a mixture of copper and zinc metals.
38. Write name of any two elements found in
gaseous state.
Ans. Nitrogen (N2) and oxygen (O2)
both found in gaseous state.
39. Write name of any two elements found in
the liquid state at room temperature.
Ans. Mercury (Hg) and bromine (Br) are two
elements which found in liquid state at room temperature.
40. What is the significance of the symbol of an element?
Ans. Symbol is the identification, used for the
chemical name of an element. In chemical equation whole name of an element is
difficult to write, because the formula or chemical equation becomes too
lengthy. Thus symbol makes an easy representation and understanding in this
case.
41. Soft drink is mixture while water is
compound. Give the reason.
Ans. Water
Water
forms by the chemical reaction of hydrogen and oxygen. That's way it is called
compound.
Soft
drink
Soft drink form by physical
composition water, sugar. The raw material in it maintains their components
chemical reaction.
42. Write two significance of chemical
formula
Ans. (i) It
represents the name of elements present in it.
(ii) It represents mole ratio.
43. Calculate the formula mass of potassium
sulphate.
Ans. Formula mass of potassium sulphate (K2SO4)
K2SO4
= 2(39)+(32)+4(16)
=
78 + 32 + 64
=
174 amu
44. Calculate
molecular mass of NH3.
Ans. Molecular Mass = 14 + 1 x 3
Molecular
Mass = 17 amu
45. Write down the chemical formula of
silicon dioxide and calcium chloride.
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Ans. CaCl2 , SiO2.
46. Define
molecular formula and give example.
Ans. Molecular formula that show actual number of
atoms of each element present in a molecular of that compound.
Example: Molecular formula of benzene is C6H6.
47. Calculate
the molecular mass of sulphuric acid H2SO4.
Ans. Molecular mass of Sulphuric acid H2SO4
:
= 2 (1) + (32) + 4
(16)
=
2 + 32 + 64 = 98 amu
48. Calculate the formula mass of the sodium
sulphate.
Ans. Sodium Sulphate (Na2SO4)
Formula
mass of sodium sulphate:
Na2SO4
= 2 (23) + (32) +4(16)
= 46 + 32 + 64
= 142 amu
49. Calculate the mass of nitric acid.
Ans. Formula mass of nitric acid HNO3
HNO3 = 1 + 14 + 48
=
63 amu
50. Define relative atomic mass.
Ans. Relative atomic mass of an element is the
average masses of an atom of that element as compared to 1/2th the mass of an
atom of carbon -12 isotopes.
51. Calculate the molecular mass of carbon
dioxide.
Ans. CO2 = 12+ 2 (16)
=
12 + 32 = 44 amu
52. Define empirical formula and give an
example.
Ans. Empirical Formula
Empirical formula is a formula
which represents simplest whole number ratio of atoms of elements present in a
compound.
Example: Empirical formula
of glucose (C6H12O6) is CH2O.
53. Write chemical formula of aluminum
sulphate and calcium phosphate. (LHR-G1)-15
Ans. Aluminum phosphate Al2(SO4)2
Calcium
phosphate Ca3(PO4)2
54. What is the empirical
formula of the acetic acid? Calculate its molecular mass.
Ans. Empirical formula of the acetic acid is CH2O
Molecular
mass of acetic acid = 24 + 4 + 32
CH3
COOH = 2(12) + 4(1) + 16(2)
=
24 + 4 + 32
=
60 a.m.u
=
2(12) + 4(1) + 16(2)
CH3 COOH = 24 + 4 + 32
=
60 a.m.u
55. Which gases present in Air? Write their
names.
Ans. Oxygen, Nitrogen, Carbon dioxide and Argon
are major gases present in air.
56. Write chemical formulas of caustic
soda and washing soda.
Ans. Caustic Soda NaOH
Washing
Soda (Na2 CO3 .10H2O)
57. Write down the chemical formula of
ammonia and sugar.
Ans. Ammonia
(NH3 )
Sugar
(C12H22O11)
58. Write
down two difference between molecule and molecular Ion.
Ans.
Molecule
|
Molecular Ion
|
||
(i) It is the smallest particle of
an element or compound which can exist independently and shows all the
properties of that compound.
|
It is formed by gain or loss of
electrons by a molecule.
|
||
(i) It is always neutral.
|
It can have negative or positive
charge.
|
||
(iii) It is formed by the
combination of atoms.
|
It is formed by the ionization of a
molecule.
|
||
(iv) It is a stable unit.
|
It is a reactive specie.
|
||
Example: CO2,CH4
etc.
|
Example: CO+,CH+4,He+
etc.
|
||
59. Write difference between homoatomic and
heteroatomic molecules.
Ans.
Homoatomic Molecule
|
Heteroatomic Molecules
|
The molecules consisting of same types of atoms is
called homoatomic molecule.
Example: H2,O2,O3,S8,P4
etc.
|
The molecules consisting of
different types of atoms are called hetroatomic molecules.
Example: H2O,HCI,H2SO4,SiO2.
|
60. What is meant by molecular ion? Give
example.
Ans. When a molecule loses or gains on electron,
it forms a molecular ion. For example He+,CH+4
etc.
61. Write two differences between atom and
ion.
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Ans.
Atom
|
Ion
|
(i) It is the
smallest particle of an element.
(ii) It had no
net charge, it is electrically neutral.
|
(i) It is the
smallest unit of an ionic compound.
(ii) It has
net charge either negative or positive on it.
|
62. How free radical is formed?
Ans. Free radicals are formed by the hemolytic
(equal) breakage of bond between two atoms when they absorb heat or light
energy.
63. What is meant by ion? Give example.
Ans. Ion is an atom or group of atoms having a
charge on it. For example, Na+, K+ sodium and potassium
both are ions.
64. Define diatomic molecule and give
example.
Ans. If a molecule is consists of two atoms
called diatomic molecule. For example hydrogen gas (H2) oxygen gas
(O2) etc.
65. What
is meant by cation?
Ans. An atom or group of atoms having positive
charge on it is called cation.
For
example. Na+,K+ are cations of sodium (Na) and Potassium
(K) respectively.
66. What
is meant by anion? Give example.
Ans. An atom or group of atoms that has a negative
charge on it is called anion.
For example CI-
and O-2
are anions.
67. What is difference between ion and free
radicals?
Ans.
Ions
|
Free
Radicals
|
|
(i)
|
These are the
atoms which bear some charge.
|
(i) These
are the atoms that have odd number of electrons.
|
(ii)
|
They exist in
solution or in crystal lattice.
|
(ii) They can exist in solution as well in
air.
|
(iii)
|
Their
formation is not affected by the presence of light.
|
(iii) They may form in the presence of light.
|
Ans. Triatomic molecules:
The
molecules consist of three atoms is called triatomic molecules. For example H2O,CO2.
Polyatomic
molecules:
The molecules
consist of many atoms is called polyatomic molecules. For example C6H12O14
glucose N2 H4 hydrozine.
69. Define triatomic and heteroatomic
molecule and give one example to each.
Ans. Triatomic
molecule
If
it consists of three atoms, it is called triatomic. For example H2O
and CO2.
Heteroatomic
Molecule
When a molecule
consists of different kinds of atoms, it is called heteratomic molecule. For
example CO2,H2O and NH3.
70. Define cation and
anion and give one example of each.
Ans. Cation: An atom or group of atoms having positive
charge on it is called cation like Na+,K+ etc.
Anion: An atom
or a group of atoms that has a negative charge on it is called anion, like
CI-,O-2 etc.
CI-,O-2 etc.
71. Define gram ion.
Ans. Ion mass expressed in grams is called gram
ion.
72. Differentiate between gram atom mass and
gram molecular mass.
Ans.
Gram
Atomic Mass
|
Gram
Molecular Mass
|
The atomic mass of an element
expressed in grams is called gram atomic mass or gram atom. It is also called
a mole.
1 gram atom of
hydrogen
= 2.008 g
= 1 mole of hydrogen
|
The molecular
mass of an element or a compound expressed in grams is called gram molecular
mass or gram molecule. It is also called a mole.
1 gram
molecule of H2
= 2.0 g
= 1mol of hydrogen
|
73. Define gram formula? Give example.
Ans. The formula mass expressed in grams is
called gram formula mass.
1
gram formed NaCl = 58.5 g
74. Define mole and give example.
Ans. Atomic mass, molecular mass or formula
mass of a substance expressed in grams is called a mole.
Example: One mole of carbon
= 12 g.
75. Define Avogadro's Number?
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Ans. Avogardo's Number is a collection of 6.02 ´ 1023
particles. It is represented by symbol 'NA' Hence the 6.02 ´ 1023
number of atoms, molecules or formula units is called Avogadro's number that is
equivalent to one mole of respective substance.
76. How many atoms of hydrogen present in one
mole of water?
Ans. One molecule of water is made up of 2
atoms of hydrogen and 1 atom of hydrogen, hence
2 ´ 6.02 ´ 1023 atom of hydrogen and 6.02 ´ 1023 atoms of oxygen constitute one mole of
water.
2 ´ 6.02 ´ 1023 atom of hydrogen and 6.02 ´ 1023 atoms of oxygen constitute one mole of
water.
77. If
16g of oxygen contains 1 mole of oxygen atom, calculate the mass of one atom of
oxygen in grams.
Ans. No of atoms in one mole = 6.02 ´ 1023
The
mass of 6.02 ´
1023 atoms =16 g
The
mass of one atom is =
=
2.657 ´
10-
25
Ans. C = 84 gm
C = 12 gm
Moles =
=
7 moles
79. What would be the number of moles in 9.0
gram carbon?
Ans. mass = 9
Moles
mass of carbon = 12
=
No.
of moles = 0.75 mol
80. How many moles are in 14g of nitrogen?
Ans. No. of Moles =
No.
of Moles =
=
1 mole
81. Calculate the gram molecules in 40g of
phosphoric acid.
Ans. Molar mass of phosphoric acid H3PO4 = 3 + 31 + 64
Number
of molecules = 98
Number
of Moles = = 0.408
Number
of molecules = 6.02 ´ 1023
´
0.408
=
2.45616 ´
1023
82. Describe the number of molecules in 9g
water.
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Ans. Volume of water = 9g
Number of moles in water 9
=
=
0.5 mol
9 = 0.5 ´ 6.02 ´ 1023
Number of molecules in water = 3.01 ´ 1023 molecules
Ans.
NH3
|
Ammonia
|
H2SO4
|
Sulphuric acid
|
Sugar
|
C6H12O6
|
