Exothermic endothermic chemical reactions

Introduction: there are two types of reactions on the basis of heat changes involved: exothermic reaction and endothermic reactions.

Exothermic reactions:
Those reactions in which heat is evolved are known as “exothermic reactions”.

For example:
(i) when carbon burns in oxygen to form carbon-di-oxide, a lot of heat is produced in this reaction:
                    C(s)       +    O₂ (g)   -------------------------->         CO₂ (g)          +        Heat
                Carbon          oxygen                                     carbon dioxide

The burning of carbon in oxygen is an exothermic reaction because heat is evolved in this reaction. AN exothermic reactions is indicated by the writing “+Heat” or “Heat energy” or just “+Energy” on the products’ side of an equation.

(ii)Respiration is also an example of exothermic reactions because energy is produced during this process. In respiration, glucose combines with oxygen in the cells of our body to form carbon dioxide and water along with production of energy:
C₆H₁₂O₆ (aq)     +         6O₂ (g)    ------------------------------->         6CO₂ (g)       +        6H₂O (l) +    Energy
(Glucose)                    (Oxygen)                                          (Carbon dioxide)           (Water)

Exothermic Endothermic Chemical Reactions : Endothermic Reaction

Endothermic reactions:
Those reactions in which heat is absorbed are known as “endothermic reactions”.

For example:
(i) When nitrogen and oxygen are heated to a very high temperature (of about 3000^o C) they combine to form nitrogen monoxide, and a lot of heat is absorbed in this reaction:
N₂ (g)         +       O₂ (g)      +    Heat   ---------------------->   2NO (g)
(Nitrogen)          (0xygen)                                             (Nitrogen monoxide)
The reaction between nitrogen and oxygen to form nitrogen monoxide is an endothermic reaction because heat is absorbed in this reaction. An endothermic reaction is usually indicated by writing “+Heat” or “+Heat energy” or just “+Energy” on the reactants side of an equation.
(ii)  All the decomposition reactions require energy ( in the form of light , heat or electricity) to take place. For example , when calcium carbonate is heated , it decompose to form calcium oxide and carbon dioxide:
      CaCo₃ (s)                +       heat  -------------------->        CaO (s)         +       CO₂ (g)
Calcium carbonate                                                     Calcium oxide          carbon dioxide

Ethane Chemical Formula

Introduction to ethane :

Ethane is an organic compound and it is the second member of alkane. The chemical or molecular formula of ethane is  C₂H₆. Ethane is an aliphatic saturated hydrocarbon. C₂H₆, the chemical formula of ethane was created synthetically by Michael Faraday in the year 1834. It was formed by the electrolysis of potassium acetate. The name ethane is derived from tther ( diethyl ether). The molar mass of ethane is 30.07g. Ethane is a colorless, odorless, and a flammable gas at standard temperature and pressure.  The melting point and boiling point of ethane are -181.76˚ and -89˚C respectively.   The 3D structure of ethane whose chemical formula is C₂H₆ .

Bonding of Ethane

There are two carbon atoms and six hydrogen atoms present in ethane. Both the carbon atoms are sp3 hybridized, so there will be overlapping of 8 sp3 orbitals, 2 from 2 carbon atoms and 6 from 6 hydrogen atoms, so the bond between two carbon atoms is the sigma bond.
The bond length between two carbon atoms is 154pm and between hydrogen and carbon is 110pm. The bond angle is 111.17˚.

Production of ethane:
Ethane is obtained by the separation method from methane by liquefying it at cryogenic temperatures.
The fractionating column is as shown below, ethane is obtained by heating crude oil in the furnace, then it is fed to the fractionating column. In fractionating column, the substances which have lowest boiling point can be extracted first. So, the gases of hydrocarbon from C1 to C4 which contains ethane escapes out at 20˚C. Similarly,  the number of hydrocarbons can be according to their boiling point.

Chemical Reactions of Ethane:

Chemical reactions of C₂H₆:

• Halogenation of ethane:

Ethane reacts with halogens like chlorine, halogen substituted ethane will form.
H₃C-CH₃  + Cl₂ ===> CH₃-CH₂-Cl + HCl.

• Reduction of ethane:

Ethane undergoes reduction in presence of Zinc dust which acts as catalyst gives ethene.
H₃C-CH₃ ===> H₂C=CH₂
Uses of Ethane:
Ethane has wide applications, few of them are as follows

• It is used to produce ethylene gas from steam cracking.
• It is used as a fuel and also used as refrigerant.
• It is used in bath soaks and was also used in gasing whales in world war II

Learn the list of chemical formulas Online

Chemical Formula exist for both organic and inorganic compounds.  Inorganic compounds are normally compounds without carbon hydrogen bond where as organic compound contains carbon. 

The naming for organic compound has been given by the International Union of Pure and Applied Chemistry (IUPAC).

But some of the organic compounds are still known by their  common names:

Formulas List of Inorganic Compounds

Chemical formulas List:

Chemical Formula exist for both organic and inorganic compounds.  Inorganic compounds are normally compounds without carbon hydrogen bond where as organic compound contains carbon. 

The naming for organic compound has been given by the International Union of Pure and Applied Chemistry IUPAC names.

But some of the organic compounds are still known by their  common names

Inorganic compounds except for few rules they are called by common name.  Names can also be broadly classified according to the nature of bonding.  For example ionic compounds are name differently than covalent compounds.

Inorganic compound (ionic) generally follow a general convention in naming.  Except for water all other inorganic compound follow the convention.  The convention is that the cation is name the first like metal and then the anion.

Normally cation whether it is metal or nonmetal is name as such like Sodium,  Potassium, Calcium etc.

Chemical Formulas and Names

Table I:

Formula	Name
HNO3	Nitric acid
H2SO4	Sulfuric acid
NaCl	Sodium chloride
SnCl2	Tin(II) Chloride
KBr	Potassium Bromide
CsI	Cesium Iodide
CaCl2	Calcium chloride
H3PO4	Phosphoric acid
Na2Cr2O7	Sodium dichromate
PCl3	Phosphorous trichloride
IF5	Iodine hexaflouride
CO2	carbon dioxide
SO3	Sulfur trioxide
NaNO3	Sodium nitrate
ZnBr2	Zinc bromide
NaCN	Sodium cyanide
AgBr	Silver Bromide
FeCl2	Iron(II) chloride
FeCl3	Iron(III) chloride
PbSO4	Lead(II) sulfate
Hg2Cl2	Mercury(I) chloride
NaI	Sodium Iodide
HIO3	Iodic acid
XeF2	Xenondiflouri

Inorganic names may contain Roman numericals when the metal can exist in  more than one oxidation states. Some examples are
Coper(I) and Copper(II) i.e., Cu+ and Cu2+
Table II:

Formula	Name
CH3COOH	Acetic acid
CH4	Methane
CH3COCH3	Acetone
HCHO	Formaldehyde
C6H6	Benzene
C6H5NH2	Aniline
C6H5N2Cl	Benzenediazonium chloride
C2H5OC2H5	diethyl ether
HCOOH	Formic acid
C5H10	Pente

Molar Volume of a Gas

The molar volume of a gas is equal to the volume occupied by the 1 mole of a gas at given conditions of temperature and pressure. The molar volume can be obtained by dividing the molar mass by the density of the gas at given temperature.
                              Molar volume = molar mass / density
The unit of molar volume is M³ / mole or dm³/mole

Introduction to molar volume of a gas :

The volume of an ideal gas can be obtained by the ideal gas equation
                                                                 PV = nRT
V/n = RT/P plug in the values of R = 8.31 joule / mole / Kelvin, let the temperature = 273 Kelvin and the pressure as 1 Pascal = 1.01*10⁵ N/m^2. These are the STP conditions.
V_MOLAR   = (8.31*273/1.01* 10 ⁵)=22.4 liters approximately.

So the molar volume of an ideal gas at ST P is equal to 22.4 liters

 The molar volume of a real gas can be obtained by using the vanderwaal’s equation:
                                                         (P+a/V²⁾ (V-b)  = nRT  
 The a and b are the constant and different for a gas specific.

By approximation and Avogadro’s’ law the volume of 1 mole of a gas at STP is 22.4 liter invariably with the nature and type of a gas. Then applying the gas equation we can find the volume of the gas at any temperature.

Molar Volume of a Gas Ilustration

Example: find the molar volume of CO2 at 2 atm pressure and 27 degree C.
 SOLUTION:
   The molar volume of CO2 at STP is 22.4 liters therefore applying the followings
   P₁=1 atm             P₂ =2 atm
     V₁= 22.4L           V₂=??
      T₁= 273 K          T₂= (27+273) = 300 K
APPLYING THE EQAUITON
      P1V1/T1 =P2V2/T2
      V2  =  P1T2V1/P2T1
       =  1*300*22.4 /(2*273) = 12.30 liters

Fuel Cell Electrochemistry

Introduction :
What is fuel cell in electrochemistry:

Fuel cells are galvanic cells in which chemical energy of fuels is directly converted into electrical energy.(In the conventional electricity generators, the fuel is burn and the heat energy produced is used to boil water. The steam produced is made to spin the turbines connected with the electricity generators)
Hydrogen - oxygen fuel cell is a common type of fuel cell based on the combustion of hydrogen to form water.
                    2H₂(g) + O₂(g)  `rarr` 2H₂O(l)

Construction of Fuel Cell of Electrochemistry:

It consists of two porous  graphite electrodes impregnated with a catalyst namely silver, platinum or a metal oxide. The electrodes are kept in an electrolyte ie an aqueous solution of NaOH or KOH. Oxygen  and hydrogen are continuously fed into the cell under a pressure of about 50 atmospheres and the cell is maintained at a temperature above 100⁰C. The gases as well as the electrolyte diffuse into the pores of the electrodes.

Working and Uses of Fuel Cell Electrochemistry:

The following electrode reactions taking place in fuel cell electrochemistry:

• Oxidation electrode reaction:

            2H₂(g) + 4OH^-(aq) `rarr` 4H₂O(l) + 4e^-

• Reduction electrode reaction:

   O₂(g) +2H₂O(l) +4e^- `rarr` 4OH^-

The overall fuel cell reaction is the sum of the above two equations .
              2H₂(g) + O₂(g) `rarr` 2H₂O (l)
The emf of the cell is found to be 1 Volt. Since the temperature of the cell is more than 100⁰C, water produced vaporizes and leaves the cell along with the unused hydrogen
Advantages of fuel cell electrochemistry:

• When compared with the conventional electical energy generators the fuel cells are more efficient.The efficiency is about 75%.

• Since the product of combustion of the two fuel gases is water, it proves to be pollution-free source of power.


• The fuel cell can be made a perennial source of electrical energy by maintaining a continuous supply of fuel.


• The fuel cells are employed in spacecrafts.


• They seem to be the promising substitute for the internal combustion engines in automobiles in the very near future, reducing pollution and enhancing efficiency. Unlike the heavy lead-acid batteries used in vehicles at present , the fuel cells are very light in weight and so many individual cells can be arranged in series connection to generate very high voltages.

Periodic Table Properties

Introduction :

According to modern periodic law, the properties of the elements are the periodic functions of elements.

The properties of the elements which are dependent of the electronic configuration of elements are called the periodic properties.  These are called periodic because these are repeated as the element of similar electronic configuration is turn up.  The physical properties of the elements can be divided in to two categories:

properties in the Periodic table of which are characteristics of an individual atom are written with their general trends across a period and down the group respectively

Electro negativity: Increase across the period and decreases down the group.

Ionization Potential: Increases across the period and decreases down the group.

Electron Affinity: Increase across the period and decreases down the group.

Atomic Radius: decrease across a period and increases down a group

Ionic Radius: decrease across a period and increases down a group. 

Effective Nuclear Charge : Increase across the period and remains almost same in the subgroup of normal elements down the group.

Valency: Valency of the atom with respect to oxygen increases increase fromm1 to 7 across a period. Down a group it remains almost same

Screening Effect: Increase across the period and increases down the group. Electropositive or Metallic: character decrease across a period and increases down a group.
Electronegative or non metallic character: Increase across the period and decreases down the group.

Properties which are the characteristics of group of atoms are like:-     

• Melting point : the  melting point of  the element first increase and becomes somewhat maximum at the middle and then decreases ,  down the group the melting point there is regular change but it is different for different groups, for example in case of the Alkali metals the melting points decrease down the groups in case of Halogen it increases

• Boiling point: the  melting point of  the element first increase and becomes somewhat maximum at the middle and then decreases ,  down the group the melting point there is regular change but it is different for different groups, for example in case of Alkali metals the melting points decrease down the groups in case of Halogen it increases

Let us see some properties of periodic table.

Properties of Periodic Table

Similarly there is periodicity in the following properties of the groups of the atoms of the elements.
Heat of fusion, Heat of vaporization, Density,  Atomic volume, Nature of oxide .Nature of hydride. 
Since electronic configuration of the elements is the periodic table functions of atomic number of the elements therefore these atomic properties are also the periodic functions of atomic numbers of the elements and hence they are called the periodic properties. The general trends of some of the some periodic properties are as:-
Atomic and ionic radii  decrease in a period from left to right and increases in a group from top to bottom.
Electron gain enthalpy increases from left to right and decreases from top to bottom in a group.
Ionization potential increases from left to right in a period and decreases from top to bottom in a group.
Nature of oxide the acidic character of oxide increases from left to right in a period. 
Electro negativity increases from left to right in a periodic table and decreases from top to bottom in a group.

Periodic Table Nitrogen

Nitrogen belongs to the p-block of the periodic table. It comes under group 15 and the second period.

Introduction to periodic table nitrogen

It is represented as N. Its atomic number is 7 and its mass number is 14. It comes under the main group of elements otherwise known as representative elements or the normal elements of the periodic table. Nitrogen is the first member of the nitrogen family. Its electronic configuration is 2, 5. It is one of the most electro negative elements of the periodic table. It was discovered by Rutherford in 1772. It exists as a diatomic gas (N2) in the elemental state, therefore, it is also called dinitrogen. 

Anomalous properties of nitrogen:

1)       it is highly electro negative

2)       it exists in both liquid and gaseous forms

3)       it forms electrovalent as well as covalent compounds with non metals

4)       It is not metallic in nature

5)       It is a poor conductor of heat and electricity

6)       Exceptionally small atomic size

7)      Absence of d-orbitals in its valence shell

Some important properties of Nitrogen

1)      N2 molecules are held together by weak van der Waals forces of attraction which can be easily broken by the collisions of the molecules at room temperature. Therefore, N2 is a gas at room temperature.

2)      Catenation: Nitrogen can form chains containing upto 3 N atoms. Example, hydrazoic acid (N3H) or azide ion, N3^- ion.

3)      nitrogen forms a triple bond between its two atoms.

4)      Nitrogen cannot expand its covalency beyond 4. So, it does not form pentahalides

5)      The hydride of nitrogen (NH3) is stable while the hydrides of other elements are not stable. 

6)      Nitrogen forms five oxides - N2O, NO, N2O3, NO2 or N2O4 and N2O5 which are monomeric

7)    It has two stable isotopses N14 and N15. 

8)    it is neutral towards litmus

9)     it is neither combustible nor a supporter of combustion.

10)   when a mixture of dinitrogen and dihydrogen is heated to about 700K under a pressure of 200 atms., in the presence of iron catalyst and molybdenum as promoter, ammonia is formed.  

         N2 + 3H2 (g) ----------- 2NH3 (g)                reversible reaction

11)   N2 + O2 --------------2 NO (nitric oxide)       reversible reaction

Periodic Table Nitrogen: Uses

1)    it is used in the manufacture of nitric acid, ammonia, calcium cyanamide, etc.

2)    it acts as an inert diluent in reactive chemicals

3)    it is used in filling electric bulbs to reduce the rate of volatilisation of the tungsten filament

4)     nitrogen gas -filled thermometers are used for measuring high temperatures

5)     liquid nitrogen is used as a refrigerant to preserve biological materials, food items and in cryosurgery