Q1. Define the following terms:
Q2. mole, molar volume, Significant figures, Gay Lussac’s law, Stoichiometry, limiting reactant, simplest formula, molecular formula
Q4. Differentiate between Empirical and Molecular formula
Q3. Define Significant figures. State their rules.
Q1. State the basic postulates of Kinetic Molecular Theory.
Q2. What is the nature of R?
Calculate value of General gas constant in:
(i) S.I. System (J) (ii) Non S.I. System (atm-liter) (ii) calorie
Q3. Define Viscosity and Surface tension. Give their units. On what factors they depend? Give the importance of Viscosity.
Q4. Give reasons for following:
i)
A liquid
rises in capillary tube. (due to
capillary action to reduce its surface area to volume ratio)
ii)
Glycerine
is distilled at reduced pressure. (High boiling liquid distill at low P to avoid
decomposition)
iii)
A drop of ink spreads over a blotting paper. (due
to capillary action, fine pores acts as capillaries)
iv)
H2O forms concave meniscus while Hg form convex
meniscus. (Wetting liquids, H2O,
A > C, Hg; C > A)
v)
A freely falling drop of liquid is always spherical in
shape. (due to ST to reduce its surface area to volume ratio)
vi)
Evaporation is a cooling process. (Escape of high energy
molecules lowers AKE of remaining molecules]
vii)
Pressure cooker is used for rapid cooking. [Increased
P, increases B.P, Stored heat cook the food quickly]
viii)
FeSO4.7H2O
and ZnSO4.7H2O are isomorphous. [have same crystal
structure and EF]
ix)
Ethyl
alcohol (C2H5OH) has greater viscosity than diethyl ether
(C2H2OC2H5). [Strong HB in ethyl
alcohol]
x) Graphite is a good conductor of electricity whereas diamond is not.
Q5. Differentiate between the following Crystalline & Amorphous solid OR Differentiate between ideal and non-ideal gases. Discuss the deviation of Ideal behaviour of gases.
Q6. Define isomorphism, polymorphism, allotropy, lattice energy, unit cell
Descriptive Answer Questions
Q7. State and explain Graham’s law of diffusion of gases
Q8. Define four types of solids according to bonding. Describe any two of them.
Q9. Derive general gas equation.
Chapter 3 …… Atomic Structure
Short Answer Questions
Q1. Differentiate between:i) Orbit and Orbital
ii) Balmer Series and Lyman Series
iii) Continuous spectrum and Line Spectrum.
iv) Alpha, beta and gamma rays
Q3. Give brief answers of the
following:
a)
Write down
the Electronic Configuration of Boron and Carbon atom in ground state and
excited state.
b)
Draw shapes of orbitals for second energy level (s and
p-orbitals).
c)
Write down the four Quantum numbers
of both electrons of Helium atom.
d)
Arrange the following energy levels
in ascending order using (n+l) rule: 5d,
3s, 4f, 7s, 6p, 2p
e)
Write down the E.C. of
Cr, Cu, Ag, Mo, Br, I, Cl‒, S2‒, C4‒,
Na+, Sr2+, Mg2+, Al3+, Fe2+,
Fe3+
f)
Which rule and principle is violated in writing the
following E.C.
i) 1s2, 2s3 (Pauli’s
exclusion principle; 1s2, 2s2 2px1)
ii) 1s2, 2px2 (Aufbau principle; 1s2, 2s2)
iii) 1s2, 2s2, 2px2
2py1 (Hund’s
rule; 1s2, 2s2 2px1 2py1
2py1)
iv)1s2, 2s2 2p6, 3s2 3p6, 3d4 4s3(Pauli’s exclusion principle and Hund’s rule; 1s2, 2s2 2p6, 3s2 3p6, 3d5 4s1 )
Q4. Complete and balance the
following nuclear reactions:
Descriptive Answer Questions
Q1. Describe cathode ray experiment to show the existence of electrons with 5 properties of cathode rays.
Q. Describe Rutherford’s experiment to show the existence of nucleus with its atomic model. Also give its two defects. OR Write short notes on each of the following. i) X-rays (ii) Quantum numbers
Q. How did Bohr’s theory explain the formation of the line spectrum of hydrogen atom? Write names and formulae each series with their regions in electromagnetic spectrum.
Q. State the postulates of Bohr’s theory. Apply derive the formula for the radius and energy of nth orbit of Hydrogen atom.
Q. Bohr’s radius is 0.529. Find the radius of the 3rd orbit of hydrogen atom.
Q. What is the wavelength and wave number of radiation that is emitted when a hydrogen atom undergoes a transition from orbit 3 to orbit 1.
Chapter 4 …… Chemical Bonding
Short Answer Questions
Q1. Differentiate between the following.
(i) Sigma and pi bond(ii) Bonding and anti-bonding molecular orbitals (BMO and AMO)
(iii) VBT and MOT
(iv) Ionic and Covalent compounds
(v) Polar and Non-polar compounds
Q2. Give brief answers or reasons of the following:
(i) What
is bond energy? Give its unit and applications.
(iii) CO2 is non-polar while H2O
is Polar molecule. (Zero DM of CO2 due to linear shape)
(iv) CO2
has zero dipole moment while SO2 has some Dipole moment. (SO2
has bent structure giving some DM)
(v) s-s sigma bond is weaker than s-p or
p-p sigma bond. (p-p overlap is greater due to its directional nature)
(vi) The
boiling point of water is greater than that of HF even though Fluorine has
greater electronegativity that O.
(vii) HF forms stronger bond than HI. (HF has BE due to strong ESF in the form polar bond)
Q3. Predict the shape of the
following molecules on the basis of Hybrid Orbital Model and EPRM.
(i) BeCl2 (linear, two AEP)
(ii) NH3 (pyramidal, 4 AEP, LP
shrinks BA)
(iii) H2O (angular, 4 AEP, LP shrinks BA)
Q4. What is Dipole moment? Give its unit. On what factors it depends?
Q5. Draw dot and cross structures of the following molecules; O2, N2, H3O+, NH4+, POCl3, CH3NO2, CH4, CO2, CHCl3, C2H2 , C2H4
Descriptive Answer Questions
Q1. What is Hybridization? Define its three types and explain any two of them. Explain the shape of ethene and ethyne molecules on the basis of hybrid orbital model.
Q2. What is hydrogen bond? How does the Hydrogen bond affect the physical properties of compounds?
Q3. State the main postulates of electron pair repulsion theory and explain shape of NH3 and H2O according to this theory.
Q4. Differentiate between Ionic, Covalent and Dative bond. Explain respective formation in NaCl, Cl2 and NH4+.
Chapter 5 … Energetics of Chemical Reaction
Short Answer Questions
Q1. Define:Thermodynamics, Thermochemistry , internal energy, Enthalpy, state of system, heat of formation, standard heat of formation, heat of neutralization, Heat of combustion, heat of reaction,
Q2. Differentiate between
(i) Intensive and Extensive properties
(ii) Exothermic and Endothermic reactions
Descriptive Answer Questions
Q1. State, explain and prove Hess’s law. Give mathematical prove by an example. Give its applications.
Q2. State first
law of Thermodynamics and prove that:
i) ∆H
= qp by deriving Pressure volume work
ii) ∆E = qv
Chapter 6 …… Chemical equilibrium
Short Answer QuestionsQ1. What is chemical equilibrium? What is Kp? Give relationship between Kc and Kp.
Q2. What do you meant by solubility
and solubility product? Derive an expression for Ksp. Give its units and
application. Write down the solubility product expressions for the following
sparingly soluble salts along with their units
(i) CaSO4 (ii) Mg(OH)2 (iii) Mg3(PO4)2 (iii) PbCrO4State law of mass action.
Descriptive Answer Questions
Q3. Derive Kc expression for a more general reaction. What are the applications of law of equilibrium? (How the value of Kc is used to predict the direction and extent of reaction).
Q4. State Le-Chatelier’s Principle. Describe the effect of temperature and pressure on Equilibrium. OR Explain Contact process and Haber’s process on the basis of Le-Chatelier’s principle.
Chapter 7 …… Solutions
Short Answer Questions
Q1. Differentiate between hydration and Hydrolysis.
Q2. Explain why?
i)
Aqueous
solutions of Ammonium Chloride and Copper sulphate are Acidic in nature.
ii) Aqueous solutions of Sodium acetate and potassium carbonate are Alkaline in nature.What is Electrolysis? Name two parts of Redox reactions that occurs in electrolysis of molten CuCl2 and molten sodium chloride and state where each occurs. Describe their electrolysis with electrolytic reactions.
Define molarity, molality, mole fraction, molar solution, molal solution, concentration
What is buffer and buffer mixture? Give the importance of Buffers. Give its mechanism of action.
Define pH and pOH. What is the
mathematical relationship the pH and pOH of a solution?
Descriptive Answer Questions
Write down the postulates of Arrhenius Theory of Ionization.
Define electrode potential, standard electrode potential and SHE? How is electrode potential of zinc or copper determined? What is ECS? Give its two applications.
What is oxidation number? State its rules with examples.
Define the terms oxidation,
reduction, oxidizing agent, reducing agent and redox reactions in terms of
electron transfer. Identify the oxidizing agent and reducing agent in following
equation:
Find the oxidation number of the following:
Chapter 8 … An Introduction to Chemical Kinetics
Short Answer Questions
Derive rate expression for a general chemical reaction. Why is rate of reaction expressed as dx/dt?
Differentiate between the
following:
(i) Rate
of reaction and Rate constant
(ii) Positive
catalyst and negative catalystGive reasons of the following:
(i) Milk sours more rapidly in summer
than in winter.
(ii) Food is preserved in freezers
(iii) The reaction of powdered marble is more
vigorous than that with the piece of marble
(v) The
reactions between ionic compounds are fast.
(vi) Rate of reaction is increased by increasing temperature.
Q. Briefly explain the following:
Order of reaction, catalyst, activation energy, threshold energy, chemical kinetics, slow reaction, fast reactionDefine activation energy. Give its relation with speed of reaction.
Descriptive Answer Questions
What is Instantaneous rate? How does it determine experimentally.
Describe four factors that affect on reaction rate. Name the physical methods along with the observed change in physical properties for determining the rate of reaction.
IMPORTANT NUMERICALS
IMPORTANT SCIENTIFIC REASONS
1. A liquid (water or
organic liquid) rises in capillary tube.
The rise of a liquid in a
capillary tube against the force of gravity is called Capillary Action which is
the common property of all the liquids. This property is the result of tendency
of liquid to reduce their surface area due to surface tension. The liquid
(water) decreases its surface area by rising in the tube due to surface
tension. (The liquid (water) will rise in the capillary tube until the upward
driving force due to surface tension is just balanced by the downward
gravitational pull. In wetting liquids such as water and organic liquids,
surface tension is low and adhesive forces are stronger than cohesive forces.
These liquids have tendency to climb up in the tube above the level of liquid
in surrounding surface).
2. Glycerine is distilled at
reduced pressure.
(The process of distillation
that is carried out under reduced pressure or in vacuum is called Vacuum
Distillation or Reduced Pressure Distillation. It is based on the fact that
boiling point of liquid is decreased at lower vapour pressure by decreasing
external pressure, so that they can be distilled before their decomposition.
This technique is used for the distillation of high boiling points liquids,
which decompose at their b.p In order to avoid decomposition of such liquids,
they are distilled out at lower temperature under reduced pressure before their
decomposition temperature). Glycerine is a high boiling point liquid having
high b.p of 290°C at
760 torr and it boils with decomposition. Therefore, b.p of glycerine is
lowered to 210°C by
lowering the external pressure to 50 torr, so that it can be easily distilled
without its decomposition.
3. Water forms concave
meniscus while Hg form convex meniscus OR
Some liquids (water)
form concave meniscus while certain liquids (Hg) form convex meniscus.
The shape of the surface of a
liquid in a cylindrical container is called Meniscus (Greek word meaning small
moon). The formation of meniscus or curved surfaces of a liquid is due to
surface tension and it depends upon the interaction between liquid and surface
of the vessel.
Wetting Liquids like water forms
a concave meniscus. This is because the forces of adhesion (glass-water
interaction) exceed the forces of cohesion (intermolecular attraction on the
water molecules). Thus non-wetting liquids with stronger cohesive forces than
adhesive forces show concave meniscus (downward curve).
Non-wetting Liquids like mercury
forms a convex meniscus. This is because the cohesive forces (Hg-Hg attraction)
are much stronger than the adhesive forces (Hg-glass interaction). Thus a
liquid with stronger adhesive forces than cohesive forces shows convex meniscus
(upward curve).
4. A freely falling drop of
a liquid is spherical.
Surface tension tends to reduce
the surface to volume ratio of a liquid as small as possible thereby trying to
contract it occupy the smallest surface area. As in a sphere, surface to volume
ratio is the least, therefore, a freely falling drop of a liquid tends acquire
the shape of a sphere owing to surface tension.
5. A drop of ink spreads on
blotting paper.
A drop of ink spreads on
blotting paper due to capillary action. The billions of thin pores of blotting
paper act like fine capillaries and due to capillary action ink rises in these
fine capillaries to reduce the surface area and hence it spreads on the
blotting paper.
6. Evaporation causes
cooling
Evaporation is a cooling process
because in evaporation, high energetic molecules at liquid’s surface break the
forces of attraction among molecules and escape into the air in the form of
vapours thereby decreasing the average kinetic energy of remaining liquid’s
molecules which is manifested by the fall in temperature. The average K.E. of
all molecules measures temperature of liquid. (Thus due to escaping of higher
energy molecules, the K.E. of remaining molecules decreases. Since K.E. varies
directly with absolute temperature, the temperature of remaining liquid will
also fall). Hence cooling is caused when evaporation occurs. Therefore, evaporation is a Cooling Process.
8. Pressure cooker is used
for rapid cooking.
(The basis of working pressure
cooker is that the b.p of a liquid increases with external pressure. If
external pressure is increased, the vapour pressure of liquid become equal to
increased external pressure at a certain higher temperature and b.p of a liquid
increases). in pressure cooker (which is a closed container where vapours are
not allowed to escape which are accumulated over the surface of the liquid,
developing more vapour pressure), where pressure is higher than atmospheric
pressure, the boiling point of liquid (water) is increased and energy supplied
is conserved in it which cooks the food quickly.
9. Graphite is a good
conductor of electricity whereas diamond is not.
In diamond, each carbon atom is covalently bonded to four other carbon atoms at an angle of 109.5° to give crystal lattice of diamond. Since all the four valence electrons of each carbon are consumed and there is no free electron, so diamond is bad conductor of electricity.
In graphite, each carbon atom is covalently bonded to three other carbon atoms at an angle of 120°, forming layers of hexagons. Since each carbon has one unpaired electron in the form of free electron, graphite conducts electricity.
Important Definitions and Terms
Accuracy
The close reproducibility of measured result with true or accepted result is called Accuracy. It is the nearness or correctness of a result to its true value. OR Accuracy is the close agreement of measured result with true or universally accepted result. Accuracy shows how closely the measured results agree with correct value. If results are close to true value then accuracy is high and vice versa.
Amorphous Solids
The solids in which atoms, molecules or ions have a random or non-repetitive three dimensional arrangement having no definite shape are called amorphous or non-crystalline solids. Amorphous means shapeless. Amorphous solids may be regarded as super-cooled liquid because they are produced when a substance in liquid state is cooled rapidly e.g. glass, plastic, rubber
Anisotropy
It is the variation of certain physical properties in different directions and the substances possessing this property is called Anisotrope. It is the property of a crystalline substance in which its crystal shows variable intensity of physical properties (such as electrical conductivity, refractive index etc.) in different direction. Crystalline solids are usually anisotropic i.e. they have certain physical properties that vary with direction.
Antibonding Molecular
Orbital (AMO)
The molecular orbital
in which there is a minimum electron cloud density between the centres of two
nuclei and which has higher energy than the energy of the separate atomic
orbitals from which it is derived is called Antibonding Molecular Orbital
(AMO).
Artificial or Induced
Radioactivity
The phenomenon in which small sized atoms (e.g. C, B, N etc.) of non-radioactive stable elements are converted into radioactive element by bombarding them with fast moving high energy particles (a-particles), giving out very penetrating rays is called Artificial or Induced Radioactivity. OR The phenomenon in which a non-radioactive element is made radioactive by bombardment with certain high energy particles (e.g. a, b or g-rays) by giving out some sub-atomic particles is known as Artificial Radioactivity.
Atomic Mass
It is the average relative mass of the isotopes of an element compared with 1/12th mass of one atom of carbon-12. The atomic mass of an atom is approximately equal to the total mass of all its heavy subatomic particles. The sum of number of protons and neutrons gives the approximate atomic mass e.g. atomic mass of sodium is 23 a.m.u.
Atomic Mass Number
The sum of the number of protons and number of neutrons in the nucleus of an atom is called Atomic Mass Number denoted by A. It is an integer nearest to atomic mass
Atomic Mass Unit
(a.m.u.)
One twelfth of the
mass of carbon-12 is termed as atomic mass unit abbreviated as a.m.u. Generally
atomic masses, molecular masses and formula masses are expressed in a.m.u.
1
a.m.u. =
1/12th mass of C-12
1
a.m.u. =
Mass of one H atom = 1.66 x 10-24 g = 1.66
x 10-27 kg.
Auf-Bau Principle
It is assumed that in an atom all the orbitals are vacant and electrons fill these orbitals in the order of increasing orbital energy starting with 1s orbital. OR The electrons are added to orbitals by order of increasing orbital energy starting with 1s orbital i.e. orbitals of minimum energy are filled up first with electrons and only then the orbitals of higher energy are filled.
Avogadro’s Law
Equal volumes of all
gases under the same conditions of temperature and pressure contain the same
number of molecules. Thus volume of a gas is directly proportional to the
number of molecules of the gas at constant temperature and pressure.
V a n (at constant temperature and pressure) or V = Kn
Avogadro’s Number
The number of atoms, ions or molecules (particles) contained in one mole (gram atomic or gram molecular mass or gram formula mass) of a substance (element or compound) is found to be 6.02 x 1023. This number is constant and is called Avogadro’s Number.
Azimuthal Quantum
Number
It is further breaking up of principal quantum number that is why it is also called Subsidiary Quantum Number. It gives possible number of sub-energy levels along with shape of an orbital. It is denoted by letter ‘l’ and has values from O to (n – 1).
Boiling Point
Boiling point is the
temperature at which the vapour pressure of a liquid becomes equal to external
pressure applied on the liquid. Normal boiling point is the temperature at
which the vapour pressure of the liquid equals to one atmosphere (standard
atmospheric pressure). Boiling point is the criteria of purity of liquids as
pure liquids have sharp and fixed boiling point.
Bond Dissociation
Energy
The enthalpy change i.e. amount
of energy released when one mole of (i.e. Avogadro’s number) of bonds are
formed from the free constituent atoms in the gaseous state to form a molecule
is known Bond making energy. The bond formation is an exothermic process and
enthalpy change is expressed by negative sign.
Alternatively, the enthalpy change i.e. energy required to break a particular bond between two atoms in one mole of gaseous covalent molecule to form neutral atoms is termed as Bond Dissociation Energy or simply bond energy designated by D (stands for dissociation) and is always a positive quantity. It is a quantitative measure of the stability of a covalent molecule. It is reported in kJ/mol (i.e. energy change per 6.02 x 1023 bonds).
Bonding Molecular
Orbital
The molecular orbital in which there is a maximum electronic cloud density between the centres of two nuclei and which has lower energy than the total energy of the atomic orbitals from which it is derived is called a Bonding Molecular Orbital (BMO).
Bond Length
The average optimum distance between the centers of the nuclei of two covalently bonded in a molecule is called Bond Length. It is the equilibrium distance between the nuclei of two bonded atoms in a molecule. OR The sum of covalent radius of two bonded atoms (having very small energy difference) is called Bond Length. For example; the covalent radius of chlorine is 0.99 A°, hence bond length in Cl2 molecule would be 1.98 A°.
Boyle’s Law
Providing temperature
constant, the volume of a given mass of a gas is inversely proportional to the
pressure applied. The product of pressure and volume of a given mass of a gas
at constant temperature is always constant.
V a Þ V
= K x [Here
K =
Constant of proportionality] Þ PV =
Constant = K
Catalyst
A catalyst is a substance which is minute amount alters (increases or decreases) the rate of a chemical reaction without itself undergoing a permanent change or any quantitative loss. A catalyst can reduce or enhance the activation energy of the reacting molecules thereby making a reaction fast or slow.
Cell Parameter
The shape of unit cell is described by length of its edges, denoted by letters a, b and c and angle between the edges represented by letters a, b and g. The length and angles of a unit cell are collectively called cell dimensions or cell parameters.
Central Atom
The atom with the
least Electronegativity is the central atom. For binary compounds and
polyatomic ions, the central atom is the one that appears only once in the
formula e.g. S in SO3, Be in BeCl2. H and F atoms can
never be a central atom. O atom is not at the centre unless it is combined with
two other atoms as in H2O or OF2 or H–O–Cl. For oxyacids
the atom other than H or O is the central atom. Carbon is the central atom in
any carbon containing compounds.
Charle’s Law
Holding the pressure constant, the volume of a given mass of a gas is directly proportional to the absolute (Kelvin) temperature. In other words, the ratio of volume of a gas to its absolute temperature at constant pressure always remains constant.
Chemical Bond
The attractive forces between the atoms due to which they are held together in the form of molecule of a compound is called Chemical Bond. OR The linkage between the atoms due to which they form a stable structure called molecule is known as Chemical Bond.
Chemical Equilibrium
The state of a reversible reaction at which there is no change in the concentration of reactants and products and rate of forward reaction is exactly equal to the rate of reverse reaction is called Chemical Equilibrium. Thus at equilibrium state; Rate of forward reaction = Rate of backward reaction
Chemical Kinetics
It is the branch of chemistry which deals with the study of reaction rates, factors affecting their rates and the mechanisms by which the reactions take place.
Cleavage and cleavage
plane
The breakage of a big
crystal into small crystals of identical shape due to external pressure is
called Cleavage. The plane through which
a big crystal can be broken down into small identical crystals is called
Cleavage Planes.
Common Ion Effect
The suppression of ionization of an electrolyte in a saturated solution at a given temperature by the addition of common ion (+ive or –ive) is known as Common Ion Effect. OR It is the phenomenon of lowering the degree of ionization of a weak electrolyte (or sparingly soluble salts) by adding a common ion to decrease its solubility and for its precipitation. OR The decrease in the solubility of the salt in a solution that already contains an ion common to that salt is called Common Ion Effect.
Compressibility Factor
(z)
The ratio of PV and nRT (PV/nRT) is called Compressibility Factor (z) which is equal to 1 for ideal gas
Continuous Spectrum
It is a type of spectrum in which different colours are diffused into one another without any sharp line of demarcation between different colours obtained from the light emitted by the sun or incandescent lamp. In between red and violet colours, the other colours are orange, yellow, green, blue and indigo. Spectrum consists of red colour at one end which is least deviated and violet colour at the other end which is maximum deviated. In between red and violet colours, the other colours are orange, yellow, green, blue and indigo.
Co-Ordinate / Dative
Covalent Bond
The covalent bond in
which the shared pair of electrons between two atoms is donated by one atom
only while the other atom does not donate any electron is known as Co-ordinate
or Dative Covalent Bond. During dative bond formation, the species (atom, ion
or molecule) which provides an electron pair are called DONOR while the species
which accepts an electron pair to complete its octet is called ACCEPTOR. The
co-ordinate covalent bond is represented by an arrow mark (®)
pointing from the donor to the acceptor atom. e.g. in H3O+,
(H2O+®O), H4N+
(H3N+®H), O3 (O=O®O).
A: + B ¾¾¾¾¾® A ® B
Donor Acceptor
Covalent Bond
This type of bond is proposed by G.N. Lewis in 1916. The bond which is formed by mutual sharing of one or more pairs of electrons between two atoms is known as Covalent Bond. OR A covalent bond is the joint internuclear attractive force which is originated due to the mutual sharing of electrons between the bonded atoms.
Crystal
A crystal is a solid
with definite geometrical form in which atoms, ions or molecules have a
characteristic, regular and repetitive three dimensional arrangement and it
occurs naturally. In other words; Crystals are homogenous solids having regular
and definite geometrical shape with faces and sharp edges showing sharp melting
points. e.g. sugar, alum, metals, diamonds, salt, minerals. [The reason for formation
of regular pattern or crystal is that atoms, ions or molecules tend to arrange
themselves in position of maximum attraction or in position of minimum energy.]
Crystal Lattice
A crystal is formed by the arrangement of unit cells in a definite pattern, unit cells in turn are formed by the arrangement of atoms, ions or molecules in three dimensional space. If atoms, ions or molecules constituting a crystal are replaced by dots or points and placed at the same places as in a unit cell, then the resulting three dimensional array of points is called Crystal Lattice. The geometric framework of points which describe the arrangement of atoms, ions or molecules in a crystal is called Crystal Lattice or Space Lattice.
Crystalline Solids
The solids which have regular geometrical shape due to highly ordered three dimensional arrangement of particles are called Crystalline or True solids.
Dalton’s Law of
Partial Pressure
The total pressure exerted by a gaseous mixture of non-reacting gases is equal to the sum of the partial pressure of all the gases present in the mixture.
debye
Dipole moment is
commonly expressed in Debye (D). One debye corresponds to the dipole moment
which would be produced by a negative charge of an electron (10-10
e.s.u) separated by 10-8 cm from an equal but opposite charge.
Therefore, dipole moment is of the order of 10-18 e.s.u-cm or 10-20
e.s.u-m (10-30 C-m) which is known as Debye. Debye is related to
S.I. unit C-m as follows:
1
D =
3.34 x 10-30 C.m
Thus if the product of
charge and distance has a value of 3.34 x 10-30 C-m, the dipole
moment has a value of 1 debye.
Degenerate Orbitals
The orbitals given by a particular value of ‘l’ if n is same, have the same energy and such orbitals of equal energy are called Degenerate Orbitals. The filling of degenerate orbitals with electrons takes place according to Hund’s Rule of Maximum Multiplicity.
Empirical Formula
It is the type of formula which expresses the relative number of each kind of atoms in a molecule of a compound. It gives the simplest whole number ratio of different combining atoms present in a molecule of a compound. e.g. E.F. of benzene is CH.
Energy of Activation
The combined energy
(average K.E. + excess energy) which the reacting or colliding molecules must
possess in order to form the product is called Activation Energy. It is the
extra or excess energy supplied to the reactant molecules (having average
internal energy less than threshold energy) to attain threshold energy to
undergo chemical reaction. (The hump between the reactants and products is
termed as energy barrier. This energy barrier must be surmounted by reacting
molecules to undergo a reaction.)
Activation Energy (Ea) = Threshold energy (Eth) – Average internal energy
Enthalpy or Heat Contents
of Reaction
The total heat content of a system at constant pressure i.e. the energy possessed by a substance is called its enthalpy (meaning to warm) denoted by H. It is equivalent to sum of internal energy (E) and pressure-volume (PV) energy i.e. H = E+ PV.
Exponential Notation
The short hand expression of a very large or a very small number by means of exponents is called Exponential or Scientific Notation. The powers to the base 10 are known as exponents while integer power of 10 is called Exponential term.
Formula Mass
Formula mass is the sum of atomic (ionic) masses of all ions in formula unit shown by its simplest or empirical formula.
Gay-Lussac’s Law
Gases combine or form
in chemical reactions in the ratio of simple whole numbers by volumes provided
at same temperature and pressure. i.e. Under similar conditions of temperature
and pressure, the gases react in simple ratio of their volumes. (The ratio of
the volumes of gases is same as the ratios of their moles in a balanced
equation.)
Graham’s Law of
Diffusion
The rate of diffusion of any gas is inversely proportional to the square root of the density of that gas under the same conditions of temperature and pressure. Graham also studied the comparative rates of diffusion of two gases. Therefore, the law is also stated as, the relative rates of diffusion (effusion) of two gases, under the same conditions of temperature and pressure, are inversely proportional to the square roots of their densities or molecular weights.
Heisenberg’s Uncertainty
Principle
It is impossible to determine exactly and precisely the momentum and position of an electron simultaneously. In other words the more accurately the position of an electron is defined, the less accurately is its velocity known and vice versa. OR It is impossible to measure simultaneously both the position and momentum of a microscopic moving particle like an electron with absolute accuracy or certainty.
Hund’s Rule
Electrons are distributed among the orbitals of a sub-shell in such a way as to give the maximum number of unpaired electrons with same spin.
Hybridization
The word Hybridization means mixing or blending. The blending or mixing of different atomic orbitals (belonging to an atom) having small energy differences to give a set of new equivalent orbitals of same shape, size and energy is called Hybridization and the new equivalent orbitals are called Hybrid Orbitals. The number of Hybridized orbitals produced is equal to the number of hybridizing atomic orbitals (which are being hybridized). Hybrid orbitals are also atomic orbitals.
Hydrogen Bond
The attractive forces which bind the electropositive hydrogen atom of polarized molecule (e.g. HF, H2O, NH3) with the electronegative atom (like F, O, N) of the other molecule of the same substance is called as Hydrogen Bond. OR It is the intermolecular electrostatic force of attraction which arises between hydrogen atoms bonded to small highly electronegative atoms [such as N, O and F (as in NH3, H2O and HF respectively)] and the lone electron pair of a neighbouring electronegative atom. It is an unexceptionally strong dipole-dipole interaction. It is a type of secondary bond. e.g. Hd+–Fd¯ ..... Hd+–Fd¯ ..... Hd+–Fd¯. Its bond energy is 20-40 kJ/mol (3-10 kcal/mol).
Ideal or Perfect Gas
It is an imaginary gas whose behaviour can be predicted precisely on the basis of kinetic molecular theory and gas laws. It is a hypothetical gas which strictly obeys gas laws for all conditions of temperature and pressure and does not show deviation from gas laws. It is a model gas for which ratio of PV/nRT called Compressibility Factor (z) is equal to 1. It is a gas for which graph between P on x-axis and PV/nRT (z) on y-axis would be a horizontal line parallel to x-axis.
Ionization Potential
The minimum amount of energy required to pull out (remove) the least strongly bound electron from the outermost orbit of a neutral gaseous atom, ion or molecule thereby giving positively charged ion (cation) is called Ionization Potential (I.P) or Ionization Energy.
Isoelectric Ions
Those ions which have same electronic configuration are called Iso-Electronic Ions. e.g. Na+, Mg2+ and Al3+ are considered to be iso-electronic ions because they possess same electronic configuration i.e. 1s2, 2s2 2p6, although their atomic numbers are different i.e. 11, 12 and 13. In iso-electronic ions, the ionic radii decrease with the increase in nuclear charge.
Isomorphism
The phenomenon in which two different substances are found in the same crystalline forms is called Isomorphism. Two substances that have the same crystal structures are said to be Isomorphous or Isomorphs. CaCO3 is isomorphous with NaNO3, both are trigonal. [1 : 1 : 3]
Latent Heat of Fusion
The amount of heat energy required to completely melt 1 gram of a pure solid at its melting point is called Latent Heat of Fusion. 334 joules of heat is required to covert 1 gram ice to 1 g liquid at 0°C. Thus latent heat of fusion of ice is 334 Joules/g (6 kJ/mol).
Latent Heat of
Vaporization
The amount of heat energy required to vapourize one gram of a liquid at its boiling point, without any change in temperature is called Latent Heat of Vaporization. The heat of vaporization of water is 2.26 x 103 joule/g. OR The amount of heat energy required to vaporize one mole of liquid at its boiling point, without change in temperature is called Molar Heat of Vaporization (DHvap). Molar heat of vaporization of water and CH4 is 40.7 kJ/mole and 9.2 kJ/mole respectively.
Lattice Energy
The amount of energy required to break one mole of a crystalline ionic solid into its ions is called Lattice Energy. It is represented by positive sign.
Limiting Reactant
The reactant producing smallest yield or least amount of product is called Limiting Reactant OR A reactant which produces least quantity of products if it is completely consumed during a chemical reaction is called Limiting Reactant.
Mean Free Path
The gas molecules are in continuous state of hap hazard motion travelling in straight path between collisions, but in random directions. The average distance travelled by a molecule between one collision and the next is called Mean Free Path (MFP).
Melting Point
The temperature at which there is an equilibrium between solid and liquid phases of a solid is called melting point. OR Melting point is the temperature at which both liquid and solid phases coexist at equilibrium. Melting point is the criteria of purity of solids as pure substances have sharp M.P.
Molar Volume
According to
Avogadro’s Law, 22.4 dm3 of any gas at STP (273 K and 1 atm)
constitutes one mole of that gas. The volume occupied by one mole of any gas at
STP is called Molar Gas Volume. 22.4 dm3
(Litre) or 0.0224 m3 or 22400 cm3 at STP is referred to
as Molar Volume. i.e. 1 mole of a gas = 22.4 dm3 at STP. Molar volume
is independent of the nature of the gas. Molar volume depends on temperature
and pressure.
Mole
Mole is the S.I. unit for amount of substance. A mole is the gram atomic mass or gram molecular mass or gram formula mass of any substance (element or compound) which contains 6.02 x 1023 particles (Atoms, molecules or ions)”. OR “The amount of substance that contains as many numbers of particles as there are atoms contained in 12 g (0.012 kg) of pure carbon is called a Mole”.
Mole Fraction
The ratio of the number of moles of any component divided by the total number of moles present in solution is called Mole Fraction denoted by X. The sum of the mole fractions of the components in a solution is always unity i.e. Xa + Xb = 1.
Molecular Formula
It is the type of formula which expresses the actual number of atoms of each element present in a molecule of a substance. Molecular formula gives actual atomic ratio in a molecule of a compound. Molecular formula is same as empirical formula or it may be an integral multiple of empirical formula. e.g. M.F. of benzene is C6H6.
Molecular Mass
The average mass of a molecule of a substance (element or compound) numerically equal to sum of atomic masses of all atoms present in its molecule as compared with one atom of C-12 is known as Molecular Mass.
(n + l) Rule
According to this
rule, the electron will always enter into that sub-shell first whose n + l value is lowest and when n + l values
of two sub-shells are the same then the electron will enter into that sub-shell
whose n
value is lower.
Nodal Plane
Nodal Plane is the
place where the probability of finding electron is zero. OR The point where the
two lobes join each other is referred as Nodal Plane along which the
probability of finding electron is zero.
Octet Rule
Noble gases or Inert Gases like Ne, Ar, Kr, Xe etc. have 8-electrons in their outermost orbit (Valence Shell). They are regarded as more stable and non-reactive. According to Octet Rule, the outermost orbit of an atom can have at maximum 8 electrons.
Orbitals
The three dimensional regions in space around the nucleus of an atom where the chances of finding electrons is maximum having a certain amount of energy is called an Orbital. Thus orbitals are certain regions of space around the nucleus in which an electron with a specific energy is most probably located. “An orbital cannot have more than two electrons”.
Pauli’s Exclusion
Principle
According to this principle, no two electrons in an atom can have the same set of four quantum numbers. Thus an orbital can contain a maximum of two electrons with opposite spins.
Polymorphism
The phenomenon in which a single compound crystallizes into two or more different crystalline forms under different conditions is called Polymorphism. The substance which can exist in more than one crystalline form is called Polymorphous or Polymorphs. e.g. calcium carbonate [Calcite (trigonal) and Aragonite (Orthorhombic)].
Precision
The close reproducibility of several results of measurement is called Precision. OR Precision is the close agreement of several results of measurements. The close agreement among the values when the same quantity is measured several times is called Precision.
Principle of Maximum
Overlap
The extent of overlapping in sigma bond is sufficient. This results in a strong bond between two atoms. The relative strength of s sigma is related to the overlap of atomic orbitals. This is known as the Principle of Maximum Overlap. The relative bond strength is p – p > s – p > s – s.
Radioactivity
The phenomenon in which there is a spontaneous and continuous emission of nuclear radiations from atom whose atomic number is greater than 83 due to the splitting of atomic nuclei is called Radioactivity. The elements which emit these radiations are called Radioactive Elements. OR The phenomenon in which nuclei of unstable heavy elements emit invisible radiations and change into nuclei of stable elements is called Radioactivity.
Random Errors
Random errors are caused by the uncertainty in every physical measurement. Thus random errors are unavoidable as the cause of such errors cannot be eliminated. A random error may be positive or negative. That is why the average of several replicate measurements is taken which is more reliable than any individual measurement.
Rounding Off Data
To round off means to reduce a number to the desired significant figures. It is the procedure of dropping non-significant digits in a calculation and adjusting the last digit reported. Thus dropping off last insignificant digit of a data to reduce a number to the required significant digit is called Rounding Off Data.
Significant Figures
The reliable digits known with certainty in a given number are called Significant Figures. The number of significant figures refers to the precision of measured quantity. Thus significant figures are directly related to the accuracy of measurements that are made in scientific work. The certain digits of a measured quantity plus one uncertain last digit are called Significant Figures.
Stoichiometry
Stoichiometry is the study of quantitative relationships between the amounts of reactants and products in chemical reactions as given by balanced chemical equations”.
Systematic Errors
Systematic errors are caused by the defect in the analytical method or by the improper functioning of instrument. Systematic errors are avoidable because the cause of error may be eliminated or corrected
Unit Cell
A crystal is formed by
a large number of repetitions of basic pattern of atoms, ions or molecules in
space. The basic structural unit of a crystal possessing a definite geometric
shape, containing number of atoms, ions or molecules and showing all the
characteristics of actual crystal is called Unit Cell (unit crystal).
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