9th Class Chemistry Important Solved Short Notes for Exam 2013

9th Class Chemistry Important Solved Short Notes For Exam 2013



The branch of science which deals with the composition and properties of matter, changes in matter and the laws or principles which govern these changes is called Chemistry.

Q1: Define Chemistry also define the branches of chemistry?

Ans: Chemistry:-The branch of science which deals with the composition and properties of matter, changes in matter and the laws or principles which govern these changes is called Chemistry.
The five branches of chemistry are as follows:
1: Organic chemistry:-Organic chemistry is the study of carbon containing substances and the synthesis of such material. many consumer products are organic in nature.
2: Inorganic chemistry: Inorganic chemistry is the chemistry of element and their compounds except those of carbon-hydrogen compounds and their derivatives.

3: Physical chemistry: Physical chemistry is the branch of chemistry which deals with the forces and principles involved in the combination of atoms and molecules.
4: Analytical chemistry: Analytical chemistry is the study of method and techniques used to determined the kind and quantity of various component in a given substance.
5: Biochemistry: Biochemistry is the chemistry of living organisms such as plants and animals.

Q2: Define mass?
Ans : Mass:-The quantity of matter contained in a body is called its mass.
its SI unit is “kilogram” and its symbol is “m”.

Q3: Define volume?
Ans : Volume:- Space occupied by a body is known as volume.
its SI unit is “m3″ and its symbol is “v”.

Q4: Define density?
Ans: Density:-It is define as ratio between mass and volume. mass per unit volume is known as density.
mathematically: d=m
Its SI unit is kg/m3. density of solid and liquid usually expressed in g/cm3 and that of gases as g/dm3.

Q5: Define temperature?
Ans: Temperature:- Temperature is a measure of the intensity of heat. it is thus a measure of the degree of hotness and coldness in a body.

Q6: Define specific gravity?
Ans: Specific gravity:- The specific gravity of a substance is the ratio of its mass to the mass of an equal volume of water at a specified temperature.
Specific gravity = mass of substance
mass of an equal volume of water
specific gravity of a substance ia a ratio between two same quantities and then fore has no unit.

Q7: Define element?
Ans: Element:- An element is defined as a substance in which all the atoms are chemically identical having same atomic number. for example: iron: silver: gold: copper: oxygen: hydrogen: etc.

Q8: Define compound?
Ans: Compound:- A compound is pure substances which consist of two or more element chemically combined in a fixed proportion by mass. compound can be broken down by chemical method.
for example: water(H2O); salt(NaCl).

Q9: Define mixture?
Ans: Mixture:-A mixture contains two or more element which can easily be separated by physical method. the component doesn’t lose its chemical properties.
for example: soil; rock; etc

Q10: Define valency?
Ans: Valency:-The chemical combining capacity of an atom or an element with another element is called valency.

Q11: Define atom?
Ans: Atom:-It is the smallest particle of an element. it does not exist freely into nature. it is the unit of an element involved in a chemical reaction.

Q12: Define molecule?
Ans: Molecule:- It is the combination of two or more atom. it can exist freely in the nature.

Q13: Define mole?
Ans: Mole:-The weight of an atom or a molecule expressed in grams is known as one mole.

Q14: Define atomic mass?
Ans: Atomic mass:-The atomic mass of an element is the average relative mass of the isotopes of that element referred to the atomic mass of carbon which is taken as 12.0000 amu.

Q15: Define molecular mass?
Ans: Molecular mass:- The molecular mass of an element when it exists in the form of molecular or of a compound is the average mass of the molecular as compound to one atom of 12C6.

Q16: Define gram atomic mass?
Ans: Gram atomic mass:- The weight of an atom expressed in gram is called gram atomic mass. it is also called gram atom.

Q17: Define gram molecular mass?
Ans: Gram molecular mass:- The weight of molecule expressed in gram is called gram molecular mass .it is also called gram molecule.

Q18: Define Avogadro’s number (n)?
Ans: Avogadro’s number:-The number of particles contained in a mole is equal to 6.023*10 power 23 is known as Avogadro number.

Q19: Define low of constant composition with examples?
Ans: Low of constant composition:-Proust formulate the low of constant composition in 1799 as that every pure sample of a particular chemical compound contain the same element combined in the same fixed proportion. it is also called the low of definite proportions.

1, He obtained several samples of copper carbonate from different sources and also prepared it through different methods in his laboratory. he found whatever source of method of preparation was used, it always had the same proportion of copper, carbon and oxygen by mass.
2, He also mixed ten grams of lead with different amount of sulphur to make the grey solid lead sulphide. he always found that the lead sulphide had the same fixed percentage of lead and sulphur.

Q20: Define heterogeneous mixture?
Ans: Heterogeneous mixture: the mixture which do not have uniform composition throughout their mass, are called heterogeneous mixture.

Q21: Define homogenous mixture?
Ans: Homogenous mixture: mixtures having uniform composition are called homogenous mixture.

Q22: Differentiate between compound and mixture?

Compound Mixture1:it is a pure substance. 1:it is an impure substance.
2:it cannot be separated by physical methods. 2:it can be separated into its components by simple physical methods.
3:element forming compound lose their original properties-s. 3:substance making up the mixture do not lose their original properties.
4:its composition is fixed. 4:its composition is not fixed.
5:the melting point and boiling point of compound are sharp and characteristic of each compound. 5:the melting point and boiling point of a mixture are not sharp.


Q1: State law of conservation of mass (matter)? Give examples.
Ans.: During any process, mass is neither created nor destroyed this law was put forward by a French chemist, lavoiser in 1785.
This law states that:
Matter is neither created nor destroyed during a chemical reaction.
During a chemical reaction, the total mass of the product is equal to the total mass of the reactants.
Example no 1:
When a piece of iron is left in moist air its surface gradually turns brown, the object gets rusted and gains mass.
The increase in mass is just the mass of oxygen.
Example no 2
When coal burns it leaves behind ash. The ash is lighter than coal. But the mass of coal will be equal to that of ash and the liberated carbon dioxide.

Q2: state exothermic and endothermic reaction with examples?
Ans: exothermic reaction:-Reaction in which heat energy is evolved is known as exothermic reaction in such reaction the system become warmer and neat potential energy of substances decreases. The enthalpy of product is less than the enthalpy of
When unslaked calcium oxide is added to water. the water becomes warm with formation of
Slaked time . in this reaction heat energy is released.

Endothermic reaction:-Reaction in which heat energy is absorbed is known as endothermic reaction . in such reaction enthalpy of reactants is lower than those of product. Since energy
Is absorbed during reaction the temperature of reaction decreases. (example are)
Heat is absorbed in the decomposition of calcium carbonate. In this reaction heating must be continuous to decompose calcium carbonate.

Q3: What are different types of reaction? Give chemical reaction of each type?
Ans: Chemical reaction are of following types:
1: Simple decomposition :-In this reaction a single compound is decomposed into two or more simple substance.
2: Synthesis:-In this reaction two or more substance combine to from a single compound it is also known as addition reaction.
3: Displacement:-In this reaction an atom or radical displaced by another in a compound. Such reaction depend upon the electropositive or electronegative nature of an atom or radical to displaced another.
4: Double decomposition / displacement :-In this reaction the two reactants decomposed to form two new substances by exchanging their radicals.
5: Neutralization:-In this reaction , the hydrogen ion of an acid neutralized by the hydroxide ion of a base to from salt and water.
6: Hydrolysis:-In this reaction the salt of either weak acid and base dissolve in water to from acid and base.

Q4:Explain Laws of Chemical Combinations with example.

Ans: Laws of Chemical Combinations

There are four laws of chemical combinations these laws explained the general feature of chemical change. These laws are:

1. Law of Conservation of Mass

2. Law of Definite Proportions

3. Law of Multiple Proportions

4. Law Reciprocal Proportions
Antoine Lavoiser has rejected the worn out ideas about the changes that take place during a chemical reaction. He made careful quantitative measurements in chemical reactions and established that mass is neither created nor nor destroyed in a chemical change.
Law of Conservation of Mass

It is presented by Lavoiser. It is defined as:

“Mass is neither created nor destroyed during a chemical reaction but it only changes from one form to another form.”

In a chemical reaction, reactants are converted to products. But the total mass of the reactants and products remains the same. The following experiment easily proves law of conservation of mass.
Practical Verification (Landolt Experiment)

German chemist H. Landolt, studied about fifteen different chemical reactions with a great skill, to test the validity of the law of conservation of mass.

For this, he took H.shaped tube and filled the two limbs A and B, with silver nitrate (AgNO3) in limb A and Hydrochloric Acid (HCl) in limb B. The tube was sealed so that material could not escape outside. The tube was weighed initially in a vertical position so that the solution should not intermix with each other. The reactant were mixed by inverting and shaking the tube. The tube was weighed after mixing (on the formation of white precipitate of AgCl). He observed that weight remains same.

HCl + AgNO3 ———-> AgCl + NaNO3
Law of Definite Proportions

It is presented by Proust. It is defined as:

“When different elements combine to give a pure compound, the ratio between the masses of these elements will always remain the same.”

Proust proved experimentally that compound obtained from difference source will always contain same elements combined together in fixed proportions.

Water can be obtained from different sources such as river, ocean, well, canal, tube well, rain or by the chemical combination of hydrogen and oxygen. If different samples of water are analyzed, it will have two elements, hydrogen and oxygen and the ratio between their mass is 1:8.
Law of Multiple Proportions

This law is defined as:

“When two elements combine to give more than one compounds, the different masses of one element, which will combine with the fixed mass of other element, will be in simple whole number ratio.”

Two different elements can combine to form more than one compound. They can do so by combining in different ratios to give different compounds.

Hydrogen and oxygen combine with one another to form water (H2O) and hydrogen peroxide (H2O2). In water and hydrogen oxide 2 g of hydrogen combine with 16g and 32g of oxygen respectively. According to law of multiple proportions, the different masses of oxygen (16g and 32g) which have reacted with fixed mass (2g) of hydrogen will have a simple ratio between each other i.e. 16:32 or 1:2. It means that hydrogen peroxide contains double the number of oxygen atoms than water. This law proves this point of Dalton’s Atomic Theory that atoms do not break in a chemical reaction.

Law of Reciprocal Proportions

This law is defined as:

“When two element A, B combine separately, with the mixed mass of the third element E, the ratio in which these elements combine with E is either the same or simple multiple of the ratio in which A and B combine with each other.”

Hydrogen and Nitrogen separately combine to form ammonia (NH3) and dinitrogen oxide (N2O), in these compounds, fixed mass of nitrogen is 14g and combines with 8 g of oxygen and 3 g of hydrogen. The ratio between the mass of oxygen and hydrogen is 8:3. Hydrogen and oxygen also combine with one another to form water (H2O). The ratio between hydrogen and oxygen in water is 16:2. These ratios are not same. Let us observe whether these ratios are simple multiple to each other or not following mathematical operation is carried out.

8:3 ::16:2

8/3 : 16/2


8/3 x 2/16


1/3 => 1:3



Q1) Define solubility what are the factors which can affect solubility?
Ans: Solubility:-“The solubility of a solute in a solvent at a particular temperature is the number of grams of solute necessary of saturate 100g of the solvent at that temperature.”
Factore of solubility
1)Temperature:-it is often observed solubility of many solute the solution generally increases in temperature for example, the solubility of potassium mitrate increases with temperatures the solubility of some solute decreases with the increase in temperature such solute generally heat when dissolved in water for example, calcium oxide is less soluble in hot water than in the cold state.
gases are also more soluble in cold solvent than in hot solvent.

2) Pressure:-Solubility of gases increases with the increase in pressure . carbon di oxide in filled in soda water bottles pressure.
3) Nature of the solute and the solvent:-The solubility of polar compound is more in polar solvent and that of non-polar solvent in non-polar solvent.

Q2) Define molarity?
Ans: Molarity:-Molarity is a measure of the concentration of solution. it is denoted by “M”.”it is define as the number of moles of solute dissolved per liter of solution(not solvent)”.
M= number of mole of solute
volume of solvent in dm3(L)

Q3) What are electrolysis and non-electrolysis also give example of strong and weak electrolysis?

Ans: Electrolysis: The substance which allow electricity to pass through their solution and are chemical decompose are called “electrolysis.”
example: acid,base,salt
Non-electrolysis:-” These substances which do not dissociate into ions when dissolved in water and do not induct electricity are known as non-electrolysis.”
Strong electrolysis:-Those electrolysis which are highly dissociated and can conduct large current are known as “strong electrolysis”.
example: HCl, NaOH
Weak electrolysis:Those electrolysis which are poorly dissociated and can conduct poor current are known as” weak electrolysis”.
example: acetic acid, mercuric chloride

Q4)Define electrolysis? explain the prosis of electrolysis of copper chloride solution?
Ans: Electrolysis: The movement of ion of an electrolyte and their deposition as neutral species at the electrodes under the influence of electric current is known as “electrolysis”.
The electrolysis of aqueous copper chloride: When aqueous copper chloride is electrolyzed between carbon electrodes copper is deposited at the cathode(negative electrode) & chlorine is given at the anode(positive electrode).
Aqueous copper chloride contain copper ion and chloride ion. The copper ion behind positively charged move towards the cathode and the chloride ion behind negatively move towards the anode. The copper ion take up electrons from the cathode and deposit copper on it.
Reaction at cathode: Cu++(aq)+2e-Cu(s)
Reaction at anode: 2Cl-(aq)Cl2 + 2e-

Q5) Define saturated, unsaturated and super saturated?
Ans: Saturated: A saturated solution is the solution which contains maximum amount of solute that it can dissolve at a particular temperature.
Unsaturated: An unsaturated solution is one which contains less amount of solute that it can held at a particular temperature.

Super saturated: A super solution is one which contains more solute that it can theorically be held by the solvent at a particular temperature

Q6) What do you mean by hard water and soft water?
Ans: Soft water:-Water which produces lather with soap easily and do not produce insoluble curdy precipitate is called soft water.
Hard water:-Water which produces insoluble curdy precipitate with soap and lather is not easily formed is called hard water.



Q1: Write down the general characteristic group of IA, VIIA and VIIIA?
Ans:Group IA(ALKALI METAL): The alkali metals lithium, sodium, potassium, rubidium, cesium and francium are light metal. They are very reactive and chemically are strongly electropositively.As the group is descending there is a gradual decrease in ionization potential with an increase in the size of the atom. They contain one electron in their outer most shell and form ionic bonds by loss of valence electron. Compound of these metal were obtained from wood ashes.
Group VIIA(HALOGEN FAMILY):-Fluorine, chlorine, bromine and iodine constitute a group or family of element called the halogen, a term which means “salt forms”. The halogen are very active non-metal and are very much a like in their chemical properties. Each of the halogen has seven valence electron. Halogen are highly electronegative element and their electro negatively decrease down the group.Flourine and chlorine are gases at ordinary temperature bromine is a liquid and iodine is a solid. all the halogen exit as diatomic molecule.
Group VIIIA(NOBLE GASES):-The element of group VIIIA are called “noble gases” or “inert gases” or “zero gases” element. They are monatomic and low boiling gases. Since the outermost shell of these element are complete therefore these element are mostly chemically unreactive.All the noble gases except radon are normally present in the atmosphere. They are mostly obtained from air by liquefaction process.

Q2) What are transition element write four properties of them?
Ans: Transition element: Element of group IB, IIB, through VIIB are known as transition element. They include the element scandium, yttrium, thanum and actinium and the two rare-earth series of element the lanthanide and actinide series.
(1) These element have incomplete inner electron shell.
(2) All transition element are metal.
(3) The bond between the atom are very strong and they have melting points.
(4) These compound are formed by coordinate covalent bond.
Q3)Define and explain Mendeleyv’s Period Table and Periodic Law also discuss the Defects in Mendeleyv’s Periodic Table
Ans: Mendeleyv’s Period Table and Periodic Law

Russian Chemist, Mendeleyv’s (186) who was working separately from Lother Mayer published a table of elements.

According to Mendeleyv’s when the element were arranged in order of their increasing atomic masses, the elements with similar properties were repeated after regular interval and were placed one above the other. A table obtained in this manner is called Periodic Table. Mendeleyv’s stated this periodicity in the form of Periodic Law.

Important Features of Mendeleyv’s Periodic Table

The important features of Mendeleyv’s Periodic table are:
Periods and Groups

The horizontal rows which run from left to right in Periodic Table are called Periods and they are twelve in number.

The vertical rows which run from top to bottom in periodic table are called groups and they are eight in number.
Vacant Spaces

Mendeleyv’s left many vacant spaces for the still unknown elements. For example, next to Calcium (40) should be Titanium (48) but it resembled silicon (28) instead of Aluminum (27). He left vacant space for element with atomic mass 44.
Discovery of New Element

Mendeleyv’s discovered new elements and also guessed their atomic mass and properties.
Atomic Mass Correction

Mendeleyv’s corrected the atomic masses of certain elements on basis of their properties and provided proper place to them in the periodic table.
Defects in Mendeleyv’s Periodic Table

The Mendeleyv’s Period Table has following defects:
Irregular Position of Some Elements

According to Mendeleyv’s Periodic Law Potassium (39) should be placed before Argon (40) but he placed Argon (40) before Potassium (39) which goes against his law.
Position of Isotopes

Mendeleyv’s periodic table gives no indication about the position of isotopes.
Structure of Atom

Mendeleyv’s Periodic table gives no idea about structure of atoms.
Position of Lanthanides and Actinides

Lanthanides and Actinides have not been given proper place in Periodic Table.
Coinage and Alkali Metals

Alkali metals and coinage metals with different properties are placed in the same group. This defect has been replaced by placing them into two sub groups.

Q4)Define the following with its unit,factors,tends or variation in groups and periods.

Atomic Radius

One half of the distance between the nucleus of two identical atoms when these are in close contact with each other is called Atomic Radius.

It is measured in angstrom unit A.
Trend in Period

The atomic radii decreases from left to right within a period in the periodic table. This is because nuclear charge increases with the increase of atomic number. But the number of shells remains same within a period.
Trend in Group

Atomic radius increases from top to bottom in a group. This is because, although nuclear charge increases from top to bottom but at the same time on new shell is also added for each successive element down the group.
Ionization Energy (I.E) or Ionization Potential (I.P)

The minimum energy needed to remove an electron from an isolated, gaseous atom in its ground state is called Ionization Energy.

It is expressed in electron volts or kilo-joules per mole.

1 ev = 96.49kj
Factors Affecting Ionization Energy

The ionization energy of elements depends upon the following factors:
1. Effect of Nuclear Charge on I.E

The greater the nuclear charge the higher is the ionization energy.
2. Effect of Atomic Size

The larger the size of atom the lower is the ionization energy.
Trend of I.E in Period

Ionization energy increases from left to right in a period due to increase in nuclear change and decrease in atomic size.
Trend of I.E in Group

I.E decreases from top to bottom in a group due to increase in atomic size.
Electro negativity

The tendency of each atom in a covalent molecule to attract a shared pair of electrons towards itself is known as its electro negativity.
Factors Affecting Electro negativity

Electro negativity depends upon the following factors:
Atomic size
Atomic Number
Electron Affinity
Ionization Energy
Trend or Variation in the Period

Electro negativity increases from left to right within a period due to increase in nuclear charge and decrease in atomic size.
Trend or Variation in the Group

Electro negativity values decreases from top to bottom within a group due to increase in atomic size.
Electron Affinity

The energy change that occurs when an electron is gained by an atom in the gaseous state is known as Electron Affinity.

Electron Affinity for the addition of first electron is negative i.e. energy is released but for further addition of electrons it is positive because energy has to be added to over come repulsion between negative ion and electron.

It is measured in KJ/mol or in e.v per atom.
Factors Affecting Electron Affinity
Atomic Size
Nuclear Charge
Tend or Variation of Electron Affinity in Group

Down the group in the periodic table, electron affinity decreases because the addition of a new shell to each atom decreases its force of attraction.
Trend or Variation of Electron Affinity in Period

In a period, the electron affinity increases from left to right because the incoming successive atoms have higher nuclear charge and attract electron more towards itself.


Q1) Describe the postulates of Dalton atomic theory? What are the draw backs in this theory?
Ans:Dalton atomic theory:-The fundamental postulates of Dalton atomic theory are stated below:
1) Matter is composed of extremely tiny invisible particles called atom.
2) Atom can neither be created or destroyed.
3) Atom of a particular element are identical in size shape mass and all other properties & differ from atom of other element in these properties.
4) Chemical combination takes place between small whole number of atom.
According to the latest research on the structure of atom &matter neutral particle following defeat are observed in Dalton atomic model.
Drawbacks of dalton atomic theory:-
1) Atom consist of charged particle called proton and electron & neutral particle called neutron.
2) The atom of the same element may differ in their atomic mass and such atom of an element are called isotopes.
3) The ratio between atom of various element in many molecules of the organic compound is not simple.
4) Matter can be converted into energy by Einstein equation E=mc2

Q2) How was electron discovered? describe in detail the experiment performed for the discovery of electron?
Ans: Discovery of electron:-Electron is the smallest particle of atom. the most convising evidence for the existence of electron came from the experiment performed by crooker, faraday, and JJ Thomson. A high voltage electric current was pass through gases at a very low pressure(1mm of hg) in a dis charge tube. When high voltage is applied across the two metallic electrode sealed in a discharge tube the rays begin ti originate from cathode which are called cathode ray. These rays travel in straight line towards the anode. If an electric field is applied , these rays bend towards the positive pole which show their negative nature.
Properties of cathode rays:-
1) Cathode rays travel in straight line away from the cathode.
2) Cathode rays are negatively charged as they bend towards the positive pole of the magnetic field.
3) The rays upon striking glass or certain other material cause these material to glow.
4) The charge to mass ratio (e/m) of those particle was found equal to that of electron.
e/m = 1.76 * 10 power8 coulomb per gram
5) The mass of each negative particle was found equal to 1/1837 of the lightest hydrogen atom.
On the basic of those properties it was concluded that cathode rays are negatively charged particle called electron.

Q3) Discuss bohrs atomic model &describe its significance in atomic structure?
Ans: Bohrs atomic model:- Neil bohr proposed a new model for the structure of the atom in 1913.The salient features of this model are that.
1) Electron revolve around the nucleus in fixed circular paths which he called orbit or energy level.
2) As long as an electron revolve in a particular energy level it does not emit or absorb energy.
3) When an electron absorb energy it moves to a higher energy level further away from the nucleus. When it lose energy it return to lower energy level closer to the nucleus & the energy is emitted as light.
4) The electron loses a definite quantity of energy called quantum of energy when it jump down from an orbit of higher energy level to a lower energy level. The energy is emitted in the form of radiation. The frequency of the energy emitted is directly proportional to the difference in energy between the two level.
5) The angular momentum (mvr)of an electron in any orbit is integral multiple of h/2x
mvr = nh/2x

Q4) Name the fundamental particle of an atom write the characteristic of each particle?
Ans: fundamental particles of atom:- fundamental particle of an atom are:
1: It is a negatively charged particle.
2: Its mass is equal to 9.11*10 power-31 kg
3: The charge on electron is unit negatively or 1.6022*10power -19 coulomb
4: Electron are present around the nucleus of an atom.
2) Proton:
1: It is a positively charged particle.
2: Its mass is equal to 1.6726*10 power-27 kg
3: The charge on proton is equal to that of electron.
4: Proton are present in the nucleus of an atom.
3) Neutron:
1: Neutron has no charge.
2: Its mass is equal to 1.67492*10 power-27 kg
3: It is 1842 times beaver than an electron.
4: Neutron are also present in the nucleus of an atom.
Q5) Describe the Rutherford Experiment and Discovery of Nucleus

?What are the draw backs Rutherford Model?

Rutherford Experiment and Discovery of Nucleus

Lord Rutherford (1911) and his coworkers performed an experiment. They bombarded a very thin, gold fail with Alpha particles from a radioactive source. They observed that most of the particles passed straight through the foil undeflected. But a few particles were deflected at different angles. One out of 4000 Alpha particles was deflected at an angle greater than 150.


Following conclusions were drawn from the Rutherford’s Alpha Particles scattering experiment.

1. The fact that majority of the particles went through the foil undeflected shows that most of the space occupied by an atom is empty.

2. The deflection of a few particles over a wide angle of 150 degrees shows that these particles strike with heavy body having positive charge.

3. The heavy positively charged central part of the atom is called nucleus.

4. Nearly all of the mass of atom is concentrated in the nucleus.

5. The size of the nucleus is very small as compared with the size of atom.
Defects of Rutherford Model

Rutherford model of an atom resembles our solar system. It has following defects:

1. According to classical electromagnetic theory, electron being charged body will emit energy continuously. Thus the orbit of the revolving electron becomes smaller and smaller until it would fall into the nucleus and atomic structure would collapse.

2. If revolving electron emits energy continuously then there should be a continuous spectrum but a line spectrum is obtained.


Q6)Define the following:
Atomic Number

The number of protons present in the nucleus of an atom is called atomic number or proton number. It is denoted by z. The proton in the nucleus of an atom is equal to number of electrons revolving around its nucleus.
Mass Number

The total number of the protons and neutrons present in the nucleus of an atom is called mass number. The protons and neutrons together are called nucleon. Hence it is also known as nucleon number. It is denoted by A. the number of neutrons present in the nucleus of an atom is represented by N.

Mass Number = No of Protons + No of neutrons

A = Z + N

The atoms of same elements which have same atomic number but different mass number are called Isotopes. The number of protons present in the nucleus of an atom remains the same but number of neutrons may differ.
Isotopes of Different Elements
Isotopes of Hydrogen

Hydrogen has three isotopes:

1. Ordinary Hydrogen or Protium, H.

2. Heavy Hydrogen or Deuterium, D.

3. Radioactive Hydrogen or Tritium, T.

Ordinary naturally occurring hydrogen contains the largest percentage of protium. It is denoted by symbol H. It has one proton in its nucleus and one electron revolve around the nucleus.
Number of Protons = 1
Number of Electrons = 1
Number of Neutrons = 0
Atomic Number = 1
Mass Number = 1

Deuterium is called heavy hydrogen. The percentage of deuterium in naturally occurring hydrogen is about 0.0015%. It has one proton and one neutron in its nucleus. It has one electron revolving around its nucleus. It is denoted by symbol D.
Number of Proton = 1
Number of Electron = 1
Number of Neutrons = 1
Atomic Number = 1
Mass Number = 2

Radioactive hydrogen is called tritium. It is denoted by symbol T. The number of tritium isotope is one in ten millions. It has one proton and 2 neutrons in its nucleus. It has one electron revolving around its nucleus.
Number of Proton = 1
Number of Electron = 1
Number of Neutron = 2
Atomic Number = 1
Mass Number = 3


Q1) Explain ionic bond and covalent bound with any one example?
Ans: Ionic bond:- It is a bond formed by the complete transfer of electrons from one atom to the other atom.
the atom which lose electron acquire positive charge and the one which again which acquire negative charge. for example 1
Consider the formation of NaCl:- In formation of NaCL molecules one electron is transferred from an atom to CL atom their by the octet of each atom is completed.
Covalent bond :-It is the bond formed by the mutal sharing of electron between the tow bonded atoms. example.
Formation of molecule:-Considered two hydrogen atoms. each has one electron in its outer most shell. thus the two atoms contribute there two electron to form a shared pair electron. the pair of shared electron is known as covalent bond. it is donated by H-H.

Q2) Describe the types of covalent bond?
Ans: Types of covalent bonds
Single covalent bond:-A covalent bond formed by the mutual sharing of one electron pair is called a covalent and is denoted by single short straight line.

For example in H-Cl, H-H etc
Double covalent bond:-A covalent bond formed by sharing of two electron pair is denoted by two short line. for example in O2, C2 etc
Triple covalent bond:-A three electron pair bond is called a triple covalent bond and is donated by three short line. In nitrogen there is a triple covalent bond.

Q3) Differentiate between ionic and covalent bond?
Ans: Ionic bond Covalent bond1: It is formed by the complete transfer of electron. 1: It is formed by the mutual sharing of electron.
2: In this bond one atom acquire negative charge. 2: No charges are developed on the two bonded atoms.
3: Ionic bond are strong. 3: Covalent bond are weak.

Q4) Differentiate between ionic and covalent compound?

Ans: Ionic compound Covalent compound1: Ionic compound do not contain molecules. 1: Covalent compound contain molecules.
2: Ionic compound are mostly inorganic compound. 2: Covalent compound are mostly organic compound.
3: They are usually soluble in water. 3:They are usually insoluble in water.
4: They can conduct electricity. 4: They cannot conduct electricity.
5: They are non volatile in nature. 5: They are volatile in nature.

Q5) What is chemical bond ?
Ans: Chemical bond: The attractive force which bonds atoms together is called chemical bond.
Formation of chemical bond: When element react to from a compound, the chemical bond are formed between atom. all chemical bond between atoms are formed by utilizing the electron of outer most shell generally the atoms combine with are another in there way.

1) By using electron.
2)By gaining the electron.
3)By sharing the electron.
When the compound undergoes chemical reaction the bond b/w the atoms are rearranged.


Q:1) How hydrogen is prepared commercially and give its properties?
Ans) Commercial hydrogen is relatively less pure and can be prepared by following methods.
1) Passing steam over red hot coke:- By passing steam over red hot coke we get.
carbon monoxide can be separate from the gaseous mixture by liquefying at a temperature of -200c.

2) By the electrolysis of water:- The purest but expensive hydrogen is obtained by the electrolysis of water in the presence of little acid.
3) By thermal decomposition:- Hydrogen is prepared by thermal decomposition of natural gas.
4) Pure and relatively in expensive hydrogen is prepared by passing steam aver red hot ion.
3Fe+4H2O Fe3O4+4H2
5) By heating a mixture of natural gas steam the presence of a suitable catalyst nickel.
Properties of hydrogen:
a) Physical properties:-
1) Hydrogen has got three isotopic forms known as protium ,deuterium and tritium.
2) At room temperature hydrogen is a colorless, tasteless and odorless gas.
3) Molecular hydrogen is the lightest of all gases.
b) Chemical properties:-
1) Reducing agent: Hydrogen is a very reducing agent it can reduce metallic oxides to metal easily ,e.g.

2)Reaction with non metal: Hydrogen react with non metal like oxygen and nitrogen on heating.
3) Reaction with halogen: Hydrogen immediately react with halogen to give halides.

Q:2) How aluminum is extracted from its ore. give its physical and chemical properties?
Ans) Preparation:- It is prepared industrially by a process called the hall beroult process.
purification of ore:- naturally occurring bauxite contain impurities like silica and oxides of iron. the first step is obtained aluminum therefore involves the purification of the mineral. the natural bauxite is reacted with a hot concentrated solution of sodium hydroxide and form soluble sodium aluminates .the impurities remain undissolved and ore removed by filtration. aluminum hydroxide is then precipitate from the solution and is heated to regenerate pure aluminum oxide..
electrolysis of aluminum:- the pure aluminum oxide obtained by the above process is dissolved in a molten mixture of cryolite and calcium fluoride at 950c. this molten mixture is electrolyzed in a specially designed cell with carbon anode. the final result can be represented by the following simplified electrode reaction.
aluminum is liberated at the cathode and oxygen is liberated at the anode however the atomic oxygen released at the carbon anode reacts with anode itself to produce carbon dioxide gas.
thus the carbon anodes constantly consumed during the process and they must be replaced at suitable intervals.
1)Aluminum has a silvery white lustrous shine.
2)It is a good reflector of heat and light.
3)It is a good conductor of heat and electricity.
4)It has a melting point 66C
ACTION OF AIR :-Dry has no action .but in most air when aluminum powder is strongly heated it forms aluminum oxide.
ACTION OF WATER :-Cold water has no effect on pure aluminum. but aluminum powder decompose water at 100C liberating and forms.
REACTION WITH ALKALIS :-Aluminum react vigorously with strong alkalis eg to form aluminates along with hydrogen .

Q3) What are isotopes? describe the isotopes of hydrogen?
Ans) Isotopes are atom of same element with same atomic number but different mass number.
Isotopes of hydrogen: There are three isotopes of hydrogen i.e.
1)Protium or ordinary hydrogen
1) Protium(ordinary hydrogen):- It most frequently occur in nature. it is represented by 1H1. it has one electron in the nucleus and one electron in the k shell. it occur to 99.98%.
2) Deuterium(heavy hydrogen):- It occur to very little extent. ordinary hydrogen contain about 1 part of deuterium in 7000 part of it. it is represented by 1H2 or D. it has one electron and one neutron in the nucleus and one electron revolves in the k shell. it is usually present in the form of D2O (heavy water) in ordinary water is small amount.
3) Tritium:- It is the heaviest isotopes of hydrogen and very varely occur in nature. it is represented by 1H3 or T . it has one proton and two neutron in the nucleus and one electron revolve in the k shell. it has radio active form of hydrogen.

Q4) How is sodium hydroxide manufactured electrolytically. Give its important application.
A) sodium hydroxide commonly known as caustic soda is commonly manufactured by the electrolysis of solution sodium chloride which is commonly known as brine.
in this electrolytic process nelson cell is used. in this cell anode consist of graphite rod and a u shaped perforated steel cathode used. brine is added in the u tube which on electrolysis gives chloride anode and sodium at cathode sodium react with water to form sodium hydroxide(caustic soda).
application of sodium hydroxide:
1)It is an important laboratory reagent.
2) It is used in paper industry.
3) It is used in the refining of petroleum and oils.


Q1) How is iron manufacture by blast furnace?

A)extraction of iron: iron metal is gradually extracted from its oxide ores by reducing them with carbon in the from of coal and coke.
the charge, consisting of roasted ores, coke and limestone is fed into the top of the furnace. a preheated blast of air at about 1500c is blown into the furnace under pressure near to the bottom. the blast oxidizes the coke to carbon dioxide.
the reaction is highly exothermic considerable heats librated which raises the temperature about 1900c in this region as the carbon dioxide passes upwards it react with more coke to form carbon monoxide.
the formation of carbon monoxide is an endothermic process and the temperature in this region falls to about 1100c .the carbon monoxide thus produced serves as the main reducing agent in the upper region of the furnace.

the liquid iron runs downward to the bottom of the furnace and is with drawn through a tap hole.
the lime stone which was added to the charged is known as flux. it decomposes to form CaO and carbon dioxide.CaO react with the gangue(mostly silica and some alumina)to form their respective salts. they are known as slag.
the slag floats as the molten iron and is run off which molten iron is seen into sand moulds where it cools down to solid blocks called pig iron.

Q2) what is rusting?
ans) rusting of iron:- when an iron is exposed to air and moisture its surface is gradually corroded and converted into a brown mass. this brown mass is known as rust.

Q3)how is rusting controlled by the catholic protection and electroplating?
ans)cathodic protection:-to protect theironobject from corrosion by this method the object is connected to a block of metal such as gene or aluminum which is comparatively more reaction than iron when corrosion starts an electrochemical reaction takes place and only the more reaction prevented from rusting.
electroplating:-electroplating is used to cover iron object chromium, nickel or other less easily corroded metals. this process used to prevent decorative as well as protective coatings.
alloying:-rusting is often prevented by converting the iron into an alloy such as stainless steel.
painting:- paint is generally used for coating large object such as ship, bridges and soon.
grease and oil:- grease and oil is used for coating the moving parts of machinery.

Q4) how copper is extracted?
ans)extraction of copper:- the extraction of copper from its ore involved concentration roasting,melting,reducing and electrical refining.

1) concentration:-the ore is concentrated by a process known as froth floation.in froth floation the mixture of the mineral and impurities are mixed with water and oil. pure oil or creosote oil are usually used. air is blown into the mixture and the oil forms a froth which floats to the surface. the ore particles tend to get coated with oil and are carried to the surface with it. the froth along with the mineral particles is skim men off from the top to get the concentrated.
2) roasting:- the concentrated ore is roasted in a furnace. part of the sulphur is converted to sulphur dioxide and other impurities such as arsenic which are burnt off.
3) smelting:-in the smelting process the roasted ore is mixed with sand and heated strongly until it melts. the remaining impurities react with the silica to form a slag of molten silicates. this is removed from the top of the molten mass which remain is called matte and consist of mixture of CuS2 and FeS.
4) reduction:-reduction of the matte is carried out in a converter where air is blown through. the molten material and molten material and molten copper is obtained. more sand is added as a flux to remove the iron in the form of an iron silicate slag.
5) refining:- blistered copper is refined by electrolysis. blistered copper, in the anode and a plate of pure copper is made cathode. a solution of copper sulphate act as the electrolyte. the impure copper dissolves at the anode and is deposited in the form of pure copper at the cathode.

Q5) write 3 chemical properties of copper?
ans) chemical properties:-
1) copper react with oxygen, sulphur and halogens under suitable condition to from the corresponding compound.
2) it react with acid which contain oxygen, such as dilute nitric acid and concerned sulphuric acid.
3) copper displace less reaction metal, such as silver another precious metals like give and iron.


9th Class Chemistry Important Solved Short Notes For Exam 2013

19 thoughts on “9th Class Chemistry Important Solved Short Notes for Exam 2013”

Leave a Reply

Your email address will not be published. Required fields are marked *