Valency Vs Oxidation Number

Valency	Oxidation Number
It is the combining capacity of an atom. It is expressed as the number of hydrogen atoms or double the number of oxygen atoms with which an atom of the element combines.	It is the residual charge which an atom has or appears to have when all the atoms are removed as ions.
Since it refers to combining capacity, it is a whole number only. As such it does not carry any plus or minus sign. For example, in NH3, the valency of nitrogen is 3 and that of hydrogen is 1.	Since it refers to charge, it can be positive, negative or zero. For example, in NH3, nitrogen has oxidation number of -3 and that of hydrogen is +1.
Valency of an element cannot be zero (except for noble gases).	Oxidation number of an element can be zero. For example, oxidation number of C in CH2Cl2 is zero.
Since atoms always combine in whole numbers, valency of an element is always a whole number.	Oxidation number may have fractional values. For example, oxidation number of S in Na2S4O6 is +2.5.
In general, elements like C, N and S exhibit constant valency. Thus, valency of N in all its compounds is three.	Even the elements C, N and S exhibit variable valency. For example, the oxidation number of N (given in brackets) in its compounds vary from +5 to -3 as: N2O5(+5), NO2(+4), N2O3(+3), NO(+2), N2O(+1), N2(0), N2H4 (-2) and NH3(-3).

Electron Gain Enthalpy Vs Electronegativity

Electron Gain Enthalpy	Electronegativity
It is the tendency of an isolated gaseous atom to attract an electron.	It is the tendency of an atom in a molecule to attract the shared pair of electrons.
It is the property of isolated atoms.	It is the property of a bonded atom.
It is the absolute electron attracting power of an atom.	It is the relative attracting power of an atom.
It can be experimentally measured.	It cannot be measured experimentally. It is only a relative number.
It has units such as kJ mol-1 or eV/atom.	It has no units. There are only scales for comparison.
The electron gain enthalpy of an atom is constant.	The electronegativity of an atom is not constant. It depends upon the oxidation state of an atom, hybridization state of the atom and the nature of substituents attached to it.

Inductive Effect Vs Electromeric Effect

Inductive Effect	Electromeric Effect
It is a permanent effect which involves slight drifting of shared σ-electrons towards more electronegative atom.	It is a temporary effect which involves complete transfer of π-electrons to one of the bonded atoms.
It operates only in saturated compounds which contain at least one polar bond.	It operates in unsaturated compounds which contain at least one multiple bond which may be polar or non-polar.
It does not need any outside reagent for its operation.	It operates only in the presence of an outside reagent.
It involves a partial separation of charges without formation of ions.	It involves complete transfer of electrons from the reagent to substrate and vice versa. As a result of this effect, ions are formed.

Schottky Defect Vs Frenkel Defect

Schottky Defect	Frenkel Defect
It is produced because of missing atoms or ions from their normal crystal sites.	It is produced when some atoms or ions are displaced from their normal sites and occupy interstitial sites.
The presence of Schottky defect lowers the density of the crystal.	It does not affect the density of the crystal.
It is generally shown by ionic solids having high co-ordination number and in which cations and anions are of equal sizes e.g., NaCl, CsCl.	It is generally exhibited by ionic solids having low co-ordination number and in which anions are larger in size than cations e.g., AgCl, ZnS.

Reversible Process Vs Irreversible Process

Reversible Process	Irreversible Process
The process in which the direction may be reversed at any stage by merely a small change in a variable like temperature, pressure, etc.	A process in which the direction cannot be reversed at any stage by change in a variable like temperature, pressure, etc.
In a reversible process, the driving force is only infinitesimally greater than the opposing force at all stages.	The driving force is different than the opposing force.
It is carried out infinitesimally slowly.	It is carried out rapidly.
At any stage during the process, equilibrium is not disturbed.	Equilibrium may exist only after the completion of the process.
It is only imaginary and cannot be achieved in actual process.	All natural processes are irreversible.
Work obtained in this process is maximum.	Work obtained in this process is not the maximum.

Sigma Bond Vs Pi Bond

Sigma (σ) Bond	Pi (π) Bond
A sigma bond is formed by the end to end filled atomic orbitals along the internuclear axis. The overlapping involves two s-orbitals, one s and p-orbital or two p-orbitals.	A pi-bond is formed by the sidewise overlap of two half-filled p-orbitals.
In this case, the overlapping can take place to a larger extent and therefore, the bond formed is a strong bond.	In the formation of π-bond the overlapping occurs to a lesser extent and therefore, the bond is weak.
The molecular orbital is symmetrical about the internuclear axis.	The molecular orbital is discontinuous and consists of two charged clouds above and below the plane of atoms.
There can be free rotation of atoms around the σ-bond.	Because of overlapping of the electron clouds above and below the plane of the atoms, free rotation of atoms around π-bond is not possible.
The bond may be present between two atoms either alone or along with π-bond.	The bond is always present between two atoms in addition to sigma bond.
In the formation of sigma bond, s-orbitals can participate.	s-orbitals cannot participate in the formation of pi-bond.

Compounds Vs Mixtures

Compounds	Mixtures
In a compound, two or more elements are combined chemically.	In a mixture, two or more elements or compounds just mix together.
These contain two or more elements in a fixed ratio by mass. Its composition is always fixed.	The components of a mixture may be present in any ratio. Its composition is variable.
These have a definite formula.	These do not always have a definite formula.
These are always homogeneous i.e., have the same composition throughout.	These may be homogeneous or heterogeneous.
A chemical reaction takes place and therefore, the formation of a compound takes place with absorption or evolution of energy.	No chemical reaction takes place and therefore, the formation of mixture is not accompanied by any energy change.
The properties of a compound are entirely different from those of its constituents.	These show the properties of its constituents.
These cannot be separated into their constituents by ordinary physical methods. These can be separated by chemical or electrochemical reactions.	These can be separated into its constituents by physical methods (like filtration, evaporation, distillation, sublimation, mechanical separation etc).
These have fixed melting point, boiling point, etc.	These do not have a fixed melting point, boiling point etc.

Electrochemical Cell Vs Electrolytic Cell

Electrochemical Cell	Electrolytic Cell
It is a device which converts chemical energy into electrical energy.	It is a device which converts electrical energy into chemical energy.
The redox reaction is spontaneous and is responsible for the production of electrical energy.	The redox reaction is non-spontaneous and electrical energy is supplied to make the reaction to occur (i.e., chemical change to take place).
The two half cells are set up in different containers and are connected through salt bridge or porous partition.	Both the electrodes are placed in the solution or molten electrolyte in the same container.
In electrochemical cell, anode is negative and cathode is positive electrode.	In electrolytic cell, anode is positive and cathode is negative electrode.
The electrons move from anode to cathode in external circuit.	The electrons are supplied by the external battery and enter through cathode and come out through anode.

Ideal Solution Vs Non-Ideal Solution

Ideal Solution	Non-Ideal Solution
The interactions between the components are similar to those in the pure components.	The interaction between the components are different from those of the pure components.
There is no enthalpy change on mixing (ΔmixingH = 0).	There is enthalpy change on mixing (ΔmixingH ≠ 0).
There is no volume change on mixing (ΔmixingV = 0).	There is volume change on mixing (ΔmixingV ≠ 0).
Each component obeys Raoult’s law at all temperatures and concentrations, i.e. pA = pA° × xA and pB = pB° × xB where pA and pB are the vapour pressures of the components in the solution.	Their components do not obey Raoult’s law. They show positive and negative deviations from Raoult’s law, i.e. pA ≠ pA° × xA and pB ≠ pB° × xB where pA° is the vapour pressure of the pure component A and pB° is the vapour pressure of pure component B at the same temperature.

Natural Rubber Vs Vulcanized Rubber

Natural Rubber	Vulcanized Rubber
Natural rubber is soft and sticky.	Vulcanized rubber is hard and non-sticky.
It has low tensile strength.	It has high tensile strength.
It has low elasticity.	It has high elasticity.
It can be used over a narrow range of temperature (from 10℃ to 60℃).	It can be used over a wide range of temperature (-40℃ to 100℃).
It has low wear and tear resistance.	It has high wear and tear resistance.
It is soluble in solvents like ether, carbon tetrachloride, petrol etc.	It is insoluble in all the common solvents.

Metallic Conduction Vs Electrolytic Conduction

Metallic Conduction	Electrolytic Conduction
Metallic conduction is carried by the movement of electrons.	Electrolytic conduction is carried by the movement of ions.
It involves no change in the chemical properties of the conductor.	It involves the decomposition of the electrolyte as a result of the chemical reaction.
It does not involve the transfer of any matter.	It involves the transfer of matter as ions.
Metallic conduction decreases with increase in temperature.	Electrolytic conduction increases with increase in temperature.

Hierarchical Data Model Vs Network Data Model Vs Relational Data Model

Hierarchical Data Mode	Network Data Model	Relational Data Model
Relationship between records is of parent-child type.	Relationship between records is expressed in the form of pointers or links.	A relation that contains a key for each record involved in the relationship represents relationship between records.
Many to many relationships cannot be expressed in this model.	Many to many relationships can be implemented.	Many to many relationships can be easily implemented.
It is a simple, straightforward and natural method of implementing record relationships.	Record relationship implementation is quite complex due to the use of pointers.	Relationship implementation is very easy through the use of a key or composite key field.
This type of model is useful only when there is some hierarchical character in the database.	Network model is useful for representing such records, which have many to many relationships.	Relational model is useful for representing most of the real-world objects and relationships among them.
In order to represent links among records, pointers are used. Thus, relations among records are physical.	In order to represent links among records, pointers are used. Thus, relations among records are physical.	Relational model does not maintain physical connection among records. Data is organized logically in the form of rows and columns and stored in the table.
Searching for a record is very difficult since one can retrieve a child only after going through its parent record.	Searching for a record is easy since there are multiple access paths to a data element.	A unique, indexed key field is used to search for a data element.
During updating or deletion process, chances of data inconsistency is involved.	No problem of inconsistency exists in network model because a data element is physically located at just one place.	Data integrity maintaining methods like normalization process, etc. are adopted for consistency.

Tranportation Model Vs Assignment Model

Transportation Model	Assignment Model
The transportation problem contains specific demand and supply in columns and rows.	In assignment problem the demand and supply in each column and row is one.
The cost matrix is not necessarily a square matrix.	The cost matrix is a square matrix.
We use three methods to solve transportation problem: VAM, NWCR and LCM.	We use two methods to solve assignment problem: Completer Enumeration method and Hungarian method.
The problem is unbalanced if total supply is not equal to total demand.	The problem is unbalanced if the cost matrix is not a square matrix i.e., number of rows is not equal to number of columns.
There is no restriction in the number of allocations.	Only one allocation can be made in particular row and column.

Lyophilic Colloids Vs Lyophobic Colloids

Lyophilic Colloids	Lyophobic Colloids
The colloidal solutions in which the particles of the dispersed phase have a great affinity for the dispersion medium are called lyophilic colloids.	The colloidal solutions in which there is no affinity between particles of the dispersed phase and the dispersion medium are called lyophobic colloids.
These are easily formed by direct mixing.	These are formed only by special methods.
The particles of colloids are true molecules and are of big size.	The particles are aggregates of many molecules.
The particles are not easily visible even under ultra-microscope.	The particles are easily detected under ultra-microscope.
These are very stable.	These are unstable and requires traces of stabilizers.
They are not easily precipitated by small amount of electrolytes. Very large quantities of electrolytes are required to cause coagulation.	They are easily precipitated by the addition of small amount of suitable electrolytes.
These are reversible in nature i.e., once precipitated can reform the colloidal sol by simply remixing with the dispersion medium.	These are irreversible in nature i.e., once precipitated cannot form the colloidal sol by simply addition of the dispersion medium.
These particles do not carry any charge. The particles may migrate in any direction or even not under the influence of an electric field.	These particles move in a specific direction i.e., either towards anode or cathode depending upon their charge.
The particles of colloids are heavily hydrated due to the attraction for the solvent.	The particles of colloids are not appreciably hydrated due to the hatred for the solvent.
The viscosity of the sols is much higher than that of the dispersion medium.	The viscosity is nearly the same as that of the dispersion medium.
The surface tension is usually lower than that of the dispersion medium.	The surface tension is almost the same as that of the dispersion medium.
They do not show Tyndall effect.	They show Tyndall effect.

Osmosis Vs Diffusion

Osmosis	Diffusion
The process of osmosis takes place through a semi-permeable membrane.	No semi-permeable membrane is needed for the diffusion process.
It involves the movement of the solvent molecules only.	In this, both the solute and the solvent molecules can move.
The molecules of solvent move from a region of lower concentration of solution into a region of higher concentration.	The molecules move from a region of higher concentration into the region of lower concentration.
It is limited to solutions only.	It is common in gases as well as in liquids.
It can be stopped or reversed by applying additional pressure on the higher concentration side.	It cannot be stopped or reversed.

CPM Vs PERT

CPM	PERT
CPM stands for Critical Path Method.	PERT stands for Programme or Project Evaluation and Review Technique.
It is a deterministic model.	It is a probabilistic model.
It deals with the activities of precise well-known time.	It deals with the activities of uncertain time.
It is activity oriented.	It is event oriented.
It is used for projects which are repetitive in nature.	It is used for projects which are non-repetitive in nature.
It is based on single time estimates.	It is based on three time estimates i.e., optimistic time, pessimistic time, and most likely time.
CPM can control both time and cost when planning.	It is a tool for planning and control of time.
It is used for construction projects.	It is used in research and development projects.

Step Index Fibre Vs Graded Index Fibre

Step Index Fibre	Graded Index Fibre
The refractive index of the core is uniform and step or abrupt change in refractive index takes place at the interface of core and cladding in step index fibres.	The refractive index of core is non-uniform, the refractive index of core decreases parabolically from the axis of the fibre to its surface.
The light rays propagate in zig-zag manner inside the core. The rays travel in the fibre as meridional rays and they cross the fibre axis for every reflection.	The light rays propagate in the form of skew rays or helical rays. They will not cross the fibre axis.
The index profile formed is in the shape of a step.	The index profile formed is in the shape of parabola (in core) and straight line (in clad).
The refractive index of the core is constant throughout the core.	The refractive index of the core is maximum at center and then it decreases towards core-clad interface.
Rays suffer from multiple total internal reflections (T.I.R’s).	Rays suffer from both multiple total internal reflections as well as multiple total internal refractions (T.I.R’s).
There is a straight line between two successive total internal reflections.	There is a no straight line between two successive total internal reflections.
There is transient time dispersion or inter modal dispersion because different modes of light entering with different angles takes different time to travel through the length of optical fibre.	No transient time dispersion or inter modal dispersion because refractive index is inversely proportional to speed.
T.I.R. take place at core clad interface.	T.I.R. can take place before core-clad interface.
It is of two types: mono mode fibre and multi mode fibre.	It is of only one type i.e. multi mode fibre.
Number of modes for step index fibre, MS = V2/2. V <= 2.405 for single mode fibre and V > 2.405 for multi mode fibre.	Number of modes for graded index fibre, MG = V2/4.

Plasma Display Vs LCD

Plasma Display	LCD
It is based on fluorescent light bulb and uses mixture of gases sandwiched between two glass panels.	It uses liquid crystal material that can block or transmit polarized light.
They are fairly heavy.	They weigh less as compared to plasma displays.
Plasma panels are more susceptible to burn-in of static images.	They do not suffer from this problem.
Life-span is shorter around 20,000 to 60,000 hours.	Life-span is longer around 50,000 to 1,00,000 hours.
These are cheaper.	These are expensive.
Plasma TVs look the same from almost any angle.	The viewing angle is up to 165°, picture suffers from the side.
It consumes more power than LCDs.	It consumes less power than plasma panels.
They do not work well at high altitudes due to pressure differential between the gases inside the screen and the air pressure at altitudes.	They have no effect of altitudes.
It has higher contrast ratio up to 3000:1. It has more ability to render deeper blacks.	It has lower contrast ratio i.e. 350-450:1. It has less ability to render deeper blacks.
There is little or no motion lag in fast moving images.	The fast moving objects may exhibit lag artifacts.
They are not as bright as LCD. Therefore it is better for use in a dimly-lite or darkened room.	They have increased image brightness. This makes LCD better for viewing in brightly lit rooms.
Plasma TVs generate more heat because of need to light phosphors to create images.	LCD produces less heat than plasma TVs.
Screen surface is more reflective than LCDs. Therefore, it is more susceptible to glare i.e. screen surface reflects ambient light sources.	Screen surface on most LCDs is less reflective making it less susceptible to screen glare.