Making molar solutions

Introduction :
The amount of substance present in unit amount of the solution is called concentration of the solution.  Generally, concentration of a solution is expressed in
(a) molarity, M     (b) molality, m  or    (c) normality, N
Molarity:
“The number of gram molecular weight of the solute present in 1000 cm³ (or 1 dm³) of the solution is called molarity”.  It is denoted by the symbol M.

Making molar solutions Case1 and 2

Case 1:
Suppose 1 mole of Oxalic acid crystals (H₂C₂O₄. 2H₂O, Molecular weight 126g) is dissolved in 1dm³ of the solution. Molarity of the solution is 1.
Molarity of the solutions can be calculated from the expression
Formula for Molarity = (mass/dm³) / molecular weight
Case 2:
Suppose ‘x’ molar solution of Oxalic acid is asked to prepare.  Then, the weight of the Oxalic acid corresponding to ‘x’ mole of Oxalic acid is used in making x molar solution.
That is weight of Oxalic acid required is = ‘x’ moles X molecular weight of Oxalic acid
                                                                        = molarity X 126g
This much of Oxalic acid should be dissolved in 1 dm³ of solvent.

Making molar solutions Case3 ,4 and relation between molarity & normality

Case 3:
For the making of  ‘x’ molar solutions of Oxalic acid of a volume, say 100ml, the weight of the oxalic acid required is found using the below relation.

Case 4:

If a liquid reagent of certain % assay and density is given in the making of certain molar solutions, then the strength of the given liquid reagent should be determined first.  This is done by using the relation.

Strength = number of moles / dm³
               = (weight in g / Molecular weight) / dm³
               = density / Molecular weight
Now, the strength of the liquid reagent given is used in the making of the solution of required strength and volume using the below relation.
M₁.V₁ = M₂ V₂
Where:
M₁, M₂ are the molarities of the given liquid reagent and solution to be prepared
V_1, V₂ are the volumes of the given liquid reagent and solution to be prepared, respectively.
Since, Equivalent weight and Molecular weight are related as:

So, there exists a relation between the molarity and normality as below:
Molarity = (mass/dm³) / Mol. Wt
               = (mass/dm³) / [Eq. wt x valence (number of electron exchange)]
Molarity = Normality / valence    or
Normality = Molarity X valence         is used in the making of N solutions from M solutions.

Mass and volume relationship

Introduction 
Mass is the measure of inertia.  Mass of an atom is composed of the mass of the protons and the mass of the neutrons.  The mass of the electrons is negligible. It is the same thing with molecules.   The mass of a particular compound is the mass of its molecules.

 Similarly, volume is also a property exhibited by any gas. It is the space occupied by a gas.  Each gas at a certain temperature has a specific volume depending upon its mass. There is a certain co-relationship between mass and the volume of the gas at a particular temperature.

Mass and molar mass definition :

In chemistry, the mass is often expressed in terms of molar mass. The molar mass is the mass of one mole of a gas.  One mole of a gas is nothing but gram equivalent of the gas.
 To illustrate, take the gas, carbon monoxide, the molar mass of carbon monoxide is 12+ 16 = 28. 

When this mass which is in atomic mass unit is expressed in grams instead of atomic mass unit it is called as one mole. 

So one mole of carbon dioxide is 28 grams. And it has been proved that there is definite relationship between the volume and molar mass of the gas.

The relationship between the molar mass and the volume is that 1 mole of the gas would occupy 22.4 liters of volume. 

In the above case where the molar mass of carbon dioxide is 28, 28 grams of carbon dioxide would occupy 22.4 liters of volume.  This relationship was developed from the equation of ideal gas i.e. PV = nRT, where 'n' is number of moles. 

At standard temperature and pressure the values of which are 273° kelvin and 1 atmosphere, the volume figure derived is 22.4 liters. 

If the mass of a gas is expressed as 'z' then it can be said that 'z' grams of a gas occupy (z/molar mass x 22.4) liters of volume.

Illustration of mass and volume relationship

Find the volume occupied by 56 grams of carbon dioxide.
The molar mass of carbon dioxide is 28;
hence number of moles = 56 / 28 = 2 moles.
 Since one mole occupies 22.4 liters at STP,
2 moles of carbon dioxide would occupy 44.8 liters of volume.

Amplitude Modulation Side Band

Introduction :-

Modulation is the process of changing one or more properties like amplitude, frequency, phase of high frequency carrier wave in accordance with the Modulating wave. Here the Modulating wave is base-band signal. Example of base-band signal is speech or music signal.

what is amplitude modulation : Amplitude Modulation is the process of changing Amplitude of high frequency carrier wave in accordance with the Amplitude of Modulating wave.

Definition of Side-Band:

A group of frequencies which is having frequency fc±fm is called as Side-Band. Here fc=Carrier frequency and fm=modulating frequency. fc+fm is called as upper side-band and fc-fm is called as lower side-band.

Different types of Amplitude Modulation

Depending on side-bands we have 5 different types of Amplitude Modulation.

1. Double-Sideband Full Carrier

2. Single-Sideband Full Carrier

3. Single-Sideband Reduced Carrier

4. Vestigial-Sideband

1. Double-Sideband Full Carrier:

The technique of amplitude modulation in which along with the carrier if both upper side-band and lower side-band is transmitted then that amplitude modulation is called as Double-Sideband full carrier.

In order to increase the efficiency of transmitter we may suppress the carrier from this DSB-AM then that technique is called as Double-Sideband Suppressed carrier Amplitude Modulation Method.

This type of amplitude Modulation is also called as conventional amplitude modulation

2. Single-Sideband Full carrier:

The technique of amplitude modulation in which single side-band is transmitted is called as single-sideband Full carrier and is denoted as SSB.

This type of modulation technique is used in shortwave radio or shortwave broadcasting

3. Single-Sideband Reduced Carrier:

The technique of amplitude modulation in which carrier and single side band is suppressed then that type of amplitude modulation is called as single-sideband Reduced carrier.

This type of modulation technique is used in amateur radio.

4. Vestigial-Sideband:

The technique of amplitude modulation in which part of single side band and all other remain as it is ,then that type of amplitude modulation in called as vestigial side-band.

This type of modulating technique is used in transmission of Television i.e., Television broadcasting.

kinetic energy of a particle

In physics, energy (from the Greek ἐνέργεια - energeia, "activity, operation", from ἐνεργός - energos, "active, working" is a quantity that can be assigned to every particle, object, and system of objects as a consequence of the state of that particle, object or system of objects. Different forms of energy include kinetic, potential, thermal, gravitational, sound, elastic, light, and electromagnetic energy. The forms of energy are often named after a related force. German physicist Hermann von Helmholtz established that all forms of energy are equivalent - energy in one form can disappear but the same amount of energy will appear in another form. Energy is subject to a conservation law. Energy is a scalar physical quantity. In the International System of Units (SI), energy is measured in joules, but in some fields other units such as kilowatt-hours and kilocalories are also used.

Any form of energy can be transformed into another form. When energy is in a form other than heat, it may be transformed with good or even perfect efficiency, to any other type of energy. With thermal energy, however, there are often limits to the efficiency of the conversion to other forms of energy, due to the second law of thermodynamics. As an example, oil is reacted with oxygen, potential energy is released, since new chemical bonds are formed in the products which are more powerful than those in the oil and oxygen.

The released energy resulting from this process may be converted directly to electricity (as in a fuel cell) with good efficiency. Alternately it may be converted into thermal energy, if the oil is simply burned in order to heat the combustion gases to a certain temperature. In the latter case, however, some of the thermal energy can no longer be used to perform work at that temperature, and is said to be "degraded." As such, it exists in a form unavailable for further transformation. The remainder of the heat may be used to produce any other type of energy, such as electricity.

In all such energy transformation processes, the total energy remains the same. Energy may not be created nor destroyed. This principle, the conservation of energy equation, was first postulated in the early 19th century, and applies to any isolated system. According to Noether's theorem, the conservation of energy is a consequence of the fact that the laws of physics do not change over time.

Although the total energy of a system does not change with time, its value may depend on the frame of reference. For example, a seated passenger in a moving airplane has zero kinetic energy relative to the airplane, but non-zero kinetic energy (and higher total energy) relative to the Earth.

Kinetic Energy of Gasses

Introduction :
Let us see about the kinetic energy of gases. In continuous motion, molecules also exert strong electric forces on one another when they are close together. The forces are both attractive and repulsive. The former hold molecules together and the latter cause matter to resist compression. The kinetic theory can explain the existence of the solid, liquid and gaseous states.

Two ways of measuring kinetic Energy:

The energy produced by a body by virtue of its motion is called kinetic energy. A moving body gives kinetic energy. For example bullet shot forms a rifle, flossing water of a river, blowing wind have kinetic energy. A moving body can do work due to its kinetic energy. For example the kinetic energy of a hammer is used to drive a nail in wooden block; the kinetic energy of air may be used to run wind mills, the kinetic energy of a bullet fired from a gun can pierce a target.
The kinetic energy of a body may be measure in two ways.

• By calculating the work required by an external agent to set the body into motion from the state or rest.
• By calculating the work done by the moving body against dissipative force before it comes to rest.

Kinetic Energy of Gases:

The molecules in gases are much farther apart than in solids or liquids and so gases are much less dense and can be squeezed into a smaller space. The molecules dash around at very high speed about 500m/s in all the space available. It is only during the brief spells when they collide with other molecules or with the walls of the container that the molecular forces act.

A model of a gas is shown in figure. The faster the vibrator works the more often the ball-bearings have collisions with the lid, the tube and with each other, representing a gas at a higher temperature. Adding more ball-bearing is like pumping more air into a tyre. If a polystyrene ball is dropped into the tube its irregular motion represents Brownian motion.

Benzene molecular formula

Introduction :
Carbon has valency of 4.Hydrogen has valency of 1.Untill the discovery of benzene,no compound with find empirical formula C_nH_n was discovered.As such benzene with same empirical formula posed a great challenge.It was predicted that the molecule would invariably contain unsaturation.

Progressive attempts on benzene molecular formula

Since it was first isolated and identified in 1825,the knowledge of structure of eluded the chemists for many decades

The existence of double bond in ethene was discovered by Scottish chemist Alexander Brown in 1864.However the discovery of the probable structure of C6H6 continued to dodge the chemists.It was so because never before was any structure derived for a compound with the empirical  formula C_nH_n.
The chemists were confused as to how all the valencies of carbon would stand satisfied in such a compound.

Kekule's contribution in benzene molecular formula

Simultaneously attempts were also made by Adolph Carl Ludwig Clause ,Henry Armstrong etc. to propose certain structures.However they failed.

It was only in 1865 that Kekule could make a breakthrough in devising this structure.He devised the structure with hexagonal ring. He said that he had discovered the ring shape of the benzene molecule after having  day-dream of a snake seizing its own tail .

This structure  met with lot of criticism in the beginning and was further refined.In 1872 he put forth that the atoms are oscillating and were in reverse and forward collision with the neighbouring carbon atoms.

pi bonds in benzene

Kekule put forth the correct structure in 1865.According to it ,benzene has aromatic structure. He revealed that he had discovered the ring shape of the benzene molecule after having  day-dream of a snake seizing its own tail .This structure  met with lot of criticism in the beginning and was further refined.
The only way in which this could be explained is pi bonds in the aromatic ring.

Unconventional pi bonds

It means it consists of a conjugated planar ring system with delocalized pi electron clouds.These electtrons which form the double pi bond keep on 'hopping' between subsequent bonds.This also can be expressed in following sentence.

The electrons for C–C bonding are distributed equally between each of the six carbon atoms.
Average length between the C-C and C=C is at 0.139 nm. This is called as 'resonance'. Resonance adds to the energy of the structure. As a result benzene is more stable by 150 kJ mol^-1than predicted by Kekule because of resonance.

Each carbon atom is attached to one hydrogen atom in addition to two carbon atoms.The electrons of the pi bonds keep on oscillating forth and back.In this way an the valencies of the atoms stand satisfied,albeit in a unconventional way.Thus in order to facilitate this,the structure would be planar and not three dimensional.This enhanced stability is the fundamental property of aromatic molecules that differentiates them from non-aromatic molecules.

Because of these pi bonds, benzene undergoes nucleophilic as well as electrophilic addition reactions at one end of any double bond.

Structure with respect to moleculr formula

The structure of benzene has aromatic nature.
It means it consists of a conjugated planar ring system with delocalized pi electron clouds.The electrons for C–C bonding are distributed equally between each of the six carbon atoms. Each carbon atom is attached to one hydrogen atom.The electrons of the pi bonds keep on oscillating forth and back.In this way an the valencies of the atoms stand satisfied,albeit in a unconventional way.Thus in order to facilitate this,the structure would be planar and not three dimensional.This enhanced stability is the fundamental property of aromatic molecules that differentiates them from non-aromatic molecules .

The discovery of ring structure of benzene has led to vast field of aromatic compounds in organic chemistry. Many important chemicals are derived from benzene by replacing one or more of its hydrogen atoms with another functional groups.e.g toluene,phenol etc.The ring structure is also the basic unit of many biochemicals like hormones.

Atomic structure of phosphorus

Introduction
Phosphorus is an element of Group 15 and period 3. Its symbol is P having atomic number 15 and mass number 31. It belongs to p- block elements. It is a non- metal. Its electronic configuration is
[Ne]3S² 3P³

It generally exists in two forms, white phosphorus and red phosphorus. It is very reactive so it is not found in Free State in nature. White phosphorus emits light or glows when exposed to air or oxygen.

Atomic structure of phosphorus

Atomic number of phosphorus is 15 and thus its electronic configuration is 2,8,5. So it has following atomic structure.It has 2 electrons in K shell, 8 in L and 5 in M shell.

Image of phosphorus and its structure

Properties of phosphorus

Luminsecence is the main property of phosphorus. This property can be defined as the ability to emit light or glow in dark. Allotropes.

Phosphorus has two common allotropes called white phosphorus and red phosphorus. Red phosphorus is an intermediate phase between white and violet phosphorus. White phosphorus is most reactive and least stable form of all allotropes of phosphorus. It is insoluble in water. Two radioactive isotopes of phosphorus have half-lives that make them useful for scientific experiments. ³²P has a half-life of 14.262 days and ³³P has a half-life of 25.34 days. Phosphorus can expand its valence electron to make penta- and hexavalent compounds eg phosphorus chloride molecule.

Most common Oxidation states of Phosphorus are 5, 4, 3, 2, 1 , -1, -2, -3

The first, second and third Ionization energies of phosphorus are as follows
1011.8 kJ·mol⁻¹, 1907 kJ·mol⁻¹ and 2914.1 kJ·mol⁻¹.As per Pauling scale the Electronegativity of phosphorus is 2.19.

Preparation of phosphorus by Brand’s process

Phosphorus is not found in the native state in nature as it is reactive. So it can be prepared by Brand's process by using sand in the reaction

4 NaPO₃ + 2 SiO₂ + 10 C → 2 Na₂SiO₃ + 10 CO + P₄

Phosphate rock is the main source of phosphorus. It is made up of tri-calcium phosphate mineral called apatite.

Conclusion for the atomic structure of phosphorus

From the discussion, we conclude that phosphorus is a non metal having atomic number 15 and is reactive. It has 5 valence electrons in its outermost shell so it needs 3 more electrons to complete the octet. So it is reactive.