Corrosion

As the metals like steel, ceremic, iron etc are greatly affected by environmental chemical reaction or by natural process, this cause the degrdation of metals or metal destruction. This degradation is known as corrosion. The corrosion of metals result destroys metals and their properties.

Corrosion Materials are the main reason for this degradation process and they are toxic in nature. They can easily attack on metal surface and alter their strength. For example the corrosion of steel is done by seawater. Similar rusting of iron is also due to corrosion because in this degradation process, the iron gets oxidized into ferric oxide Fe2O3 and the color of iron surface changes from black to yellow to orange. The process of rusting of iron takes place in some steps. First the iron gets oxidized into ferrous ions and then these ferrous ions again undergo loss of electrons and oxidize into ferric ions [Fe (III)]. This oxidation occurs due to the presence of water and oxygen. The ferric ions then react with oxygen atom and produce ferric oxide which again reacts with water and hydration reaction takes place. The whole process can be represented by a simple chemical reaction that is mentioned below;
4Fe+2 (aq) + 3O2 (g) + 2 H2O  ?  2Fe2O3.H2O

The rusting process is greatly affected by some salts and also enhanced with moisture environment. The rate of the degradation increases with increasing the moisture level.

So if we discuss that what is Corrosion then we can easily explained this process by taking the above example of iron rusting. The corrosion is classified in various categories that depend on the environmental conditions of metals, the chemical changes, and also with material type. It can be like uniform, galvanic, pitting corrosion, stress corrosion, fatigue, inter-granular corrosion, crevice corrosion, fili-form corrosion, erosion corrosion, fretting corrosion etc.

The methods that are used to control the corrosion are known as corrosion control process. For controlling this process some methods like cathodic protection in which impressed current and sacrificial anode are used. Similar Corrosion inhibitors are used to control corrosion. These are chemicals that are used to control environmental conditions and thus reduce the corrosives. Some chemicals like hexylamine, sodium benzoate, oxidising agents like chromate, lead, nitrite, amines, and thio-urea are worked as corrosion inhibitors. Today’s the manufacturing process is done in such a way to increase the inherent capacity of any material for preventing the harmful effect of corrosion. All of the other methods of corrosion control should be considered in the design process. Protective coating on materials is also used to prevent corrosion.

Atomic mass unit

The analysis of water shows that a water molecule contains 11.19% of hydrogen and 88.89% of oxygen. So the ratio of both components masses is 11.19:88.89 or 1:8. Or we can say that the ratio of both hydrogen and oxygen is 2:1. Mass of oxygen is 16 times the mass of an atom of hydrogen. Therefore relative mass of an atom of oxygen is 16 units if we take mass of an atom of hydrogen as one unit. 

Similarly relative atomic mass of other elements is determined by taking hydrogen atom mass as standard. But that is old approach. Then it was preferred to take oxygen atomic mass as standard. But the international union of chemist selected the most stable isotope of carbon and that is C-12 isotope. This is taken as standard for comparison of atomic mass of various elements. 

The mass of C-12 isotope was taken as 12 atomic mass units.

So the definition of atomic mass of any element can be defined as the average relative atomic mass of an atom of element as compared with the mass of an atom of carbon isotope C-12 as 12 unit. A scale is used to express the relative atomic mass unit. So the Atomic mass unit definition can be stated as the unit which is used to express the relative atomic mass is known as atomic mass unit. It is denoted as a.m.u. It can also defined as atomic mass unit or as unified mass as 1/12th of the actual mass of an atom of carbon isotope C-12. The atomic mass of any element shows that how many times as atom of the element is heavier than 1/12 of an atom of carbon isotope C-12.
So the Atomic Mass Formula can be written as;

Atomic mass= mass of an atom of an element / 1/12 x mass of an atom of carbon isotope C-12

This formula is useful in calculating Atomic Mass. For example, atomic mass of magnesium is 24 u. This shows that an atom of magnesium is 24 times heaviour than 1/12 of an atom of carbon isotope C-12.

But there are many cases when different atoms of the same elements possess different relative masses. Such atoms of the same elements are called isotopes. So in these cases, atomic mass of the elements is calculated as average atomic mass.

The Average atomic mass formula = Σ (mass of isotope × relative abundance)
For example, chlorine has two isotopes having relative masses 35u and 37u with relative abundance in nature is 3:1. Thus the atomic masses chlorine is the average of these different relative masses as mentioned below;

Atomic mass of chlorine = 35x 3 + 37x1 / 4 = 35.5 u.

List of Chemical Compounds

A pure chemical substance consisting of two or more different chemical elements which can be separated into simpler substances by chemical reactions is called chemical compound. They exhibit a unique and defined chemical structure. Chemical compounds may be molecular compounds which are held together by covalent bonds, salts by ionic bonds, intermetallic compounds by metallic bonds, or complexes by coordinate covalent bonds. Pure chemical elements are not referred as chemical compounds if they contain molecules which have multiple atoms of a single element like H2, S8.

Introduction:

Elements turn into compounds and become more stable. When compounds have the maximum number of possible electrons in their outermost energy level, which is normally two or eight valence electrons, they become stable. For this reason only noble gases do not react very fast as they have eight valence electrons.

List of Compounds

Compounds are classified into the following three lists:

1) List of inorganic compounds: These compounds are without a C-H bond

2) List of organic compounds: These compounds are with a C-H bond

3) List of biomolecules.

List for Chemical Compounds

Acetic acid

Acetylcholine

Agar

Amylase

Ascorbic acid (vitamin C)

Asparagines

Aspartic acid

Auxin

Bilirubin 

Biotin (Vitamin H)

Caffeine

Calciferol (Vitamin D)

calcitonin

Cannabinol

Casein

Cellulose

Chlorophyll

Cholecystokinin (CCK)

Cholesterol

Choline

Citric acid

Citrulline

Cobalamin (vitamin B12)

Coenzyme

Colchicine

Collagen

Cysteine

Cystine

Cytidine

Cytochalasin

Deoxyribose

Deoxyribose nucleic acid (DNA)

Dopamine

Enzyme

Ephedrine

Epinephrine – C9H13NO3

Fatty acid

Fibrin

Folic acid (Vitamin M)

Follicle stimulating hormone (FSH)

Formaldehyde

Formic acid

Fructose

Galactose

Gastrin

Gelatin

Globulin

Glucagon 

Glucose – C6H12O6

Glucose oxidase

Glycine

Glycogen

Glycolic acid

Glycoprotein

Gonadotropin-releasing hormone (GnRH)

Growth hormone

GTPase

Guanine

Guanosine

Guanosine triphosphate (+GTP)

Hemocyanin

Hemoglobin

Histamine

Histidine

Histone

Histone methyltransferase

Hormone

Human growth hormone

Inositol

Insulin

Integral membrane protein

Integrase

Interferon

Isoleucine

Keratin

Kinase

Lactase

Lactic acid

Lactose

Leucine

Linoleic acid

Linolenic acid

Lipase

Lipid

Luteinizing hormone (LH)

Lysine

Lysozyme

Malic acid

Maltose

Melatonin

Membrane protein

Metalloprotein

Myoglobin

Myosin

Nucleic Acid

Oestrogens

Ornithine

Oxalic acid

Oxidase

Paclitaxel

Palmitic acid

Pantothenic acid (vitamin B5)

parathyroid hormone (PTH)

Penicillin

Pepsin

Peripheral membrane protein

phosphatase

Phospholipid

Phenylalanine

Polysaccharide

Porphyrin

Progesterone

Prolactin (PRL)

Proline

Propionic acid

Protamine

Protease

Protein

Proteinoid

Pyruvic acid

Quinone

Raffinose

RNA - Ribonucleic acid

RuBisCO

Sucrose (sugar)

Sugars (in general)

Tartaric acid 

Topoisomerase

Tyrosine

Uracil

Urea

Urease

Uric acid – C5H4N4O3

Uridine

Valine

Vasopressin

Vitamins (in general)

Water

Xylose

Check my best blog Oxidaton.

Oxidaton

Oxidation is a process in which Oxygen is added to a element or when hydrogen is removed from the molecule or electrons are removed from the atom.

Introduction:

For example:

2H₂(g)  + O_2(g)  ------> 2H₂O(g)
2Mg(s)  + O_2(g)  -----> 2MgO(s)

Here hydrogen is oxidized because oxygen is added to Hydrogen. Magnesium is also oxidized by oxygen.
2H₂S(g)   + O2(g)    ----> 2S(s)  + 2H2O(l)

In the above reaction H₂S is oxidized since Hydrogen is removed from H₂S
Zn (s)--------> Zn²⁺ (aq) + 2e-

In the above example the Zinc is oxidized into Zn²⁺. Zinc looses two electron to form the ion. Since it looses electron it is oxidation. Oxidation is a part of redox reaction. In this type of reaction reduction and oxidation takes place simultaneously.

Addition of other electronegative elements are also considered as oxidation.For example
Mg(s) +  F₂(g)  -----> MgF₂(s)
2K(s)  + Cl₂(g)  ----> 2KCl(s)

In the above example Magnesium is oxidized to Mg²⁺ by flourine and  potassium is oxidized to K⁺ by the chlorine. 

Examples of Oxidaton Reaction

Combustion of methane is an example of oxidation reaction.  For example methane is oxidized to carbon dioxide and water when ignited
CH₄  +2 O₂  ----->  CO₂  + 2H₂O
Iron article is oxidized to Fe₃O₄ when exposed to air and water. Oxidation is unwanted in the case of iron and to prevent it normally painting is done on the Iron.  Galvanization of Iron is another method to prevent the oxidation of Iron which is called as corrosion.   Chrome plating of Iron is another method in which Iron is coated with Chromium so that the iron is not oxidized.
Oxidation process finds many application.  Redox reaction which involves oxidation and reduction is used for volumetric determination of unknown amount of substance from the known amount of the compound.

Molecular Orbital Energy

Introduction

A molecular orbital energy level diagram is a qualitative descriptive tool explaining chemical bonding in molecules in terms of molecular orbital theory in general and the Linear combination of atomic orbitals molecular orbital method in particular.

Molecular Orbital Energy

Molecular orbital energy depends upon the two factors:

(i) The energies of the atomic orbitals gets combine to form molecular orbitals.

(ii) The overlapping between the atomic orbitals.

Greater the overlapping, more the bonding orbital is lowered and the antibonding orbital is raised in energy relative to atomic orbitals. For e.g; the extent of overlapping in case of s - orbital is greater than that in p - orbital. Consequently, the energy of a s2p_z is lesser than the energy of bonding p2p_x or p2p_y MOs.

Now, 1s atomic orbitals of two atoms form two molecular orbitals named as s1s and s*1s. The 2s and 2p orbitals form four bonding molecular orbitals and four antibonding molecular orbitals as:

Bonding molecular orbitals:

s2s, s2p_z , p2p_x , p2p_y

Antibonding molecular orbitals:

s*2s, s *2p_z, p*2p_x, p*2p_y

The energy levels of these molecular orbitals have been examined experimentally by spectroscopic methods. The order of increasing molecular orbital’s energy is obtained by the combination of 1s, 2s and 2p orbitals of two atoms is:

s1s, s*1s, s2s, s*2s, s2p_z, p2P_x = p2p_y, p*2p_x = p*2p_y, s*2p_z

Here the energy of molecular orbitals increases from s1s to s*2p_z.

However, experimental proofs for some diatomic molecules have shown that above sequence of energy levels of MOs is not correct for all molecules. For e.g., for homonuclear diatomic molecules of second row elements in periodic table such as B₂, C₂, N₂, the s*2p_z molecular orbital is higher in energy than p2p_x andp 2p_y MOs. The order of MOs for such type of molecules is:

s1s, s *1s, s 2s, s 2s, p2P_x = p 2p_y, s *2p_z, p *2p_x = p *2p_y,

 s *2p_z.

Here the energy of molecular orbitals increases from s1s to s*2p_z.

But for molecules O₂ onwards (O₂, F₂), the first order of energies of molecular orbital is correct. Thus, for diatomic molecules of second period, there are two types of energy level diagram of Mos.

Conclusion for Molecular Orbital Energy

The main difference between the two types of sequences is that for molecules O₂, F₂ and Ne₂ the s2p_z, molecular orbital has lower energy than p2p_x and p2p_y MOs while in the case of molecules Li₂, Be₂, B₂, C₂ and N₂, s2p_z, molecular orbital is higher in energy than p2p_x and p2p_y MOs.

Electrochemical Impulses

Introduction:

Electrochemical impulses also called nerve impulses or action potential are conducted by specialized cells called neurons. All neurons conduct impulses along hair like cytoplasmic extensions, the nerve fibers or axons outside the central nervous system. A short-lasting event, in which the electrical membrane potential of a cell rises rapidly and falls, is known as an action potential.

In several types of animal cells, action potential occurs. These cells are called excitable cells which include neurons, muscle cells, and endocrine cells.

Function of Electrochemical Impulses:

In neurons, cell-to-cell communication is the major role of action potential. In other types of cells, activation of intracellular processes is their major function.

Mechanism of Electrochemical Impulses:

An action potential is the first step in the chain of events leading to contraction in muscle cells. They provoke release of insulin in beta cells of the pancreas. Special types of voltage gated ion-channels embedded in a cell's plasma membrane are responsible for generation of Action potential. When the membrane potential is near the resting potential of the cell, these channels are shut but they rapidly begin to open if the membrane potential increases to a precisely defined threshold value.

When the channels open, an inward flow of sodium ions is allowed, which changes the electrochemical gradient, which in turn produces a further rise in the membrane potential. This causes more channels to open, producing a greater electrical current. Until the entire ion channels are open, the process proceeds explosively leading to a large upswing in the membrane potential. The polarity of the plasma membrane gets reversed and the ion channels then rapidly inactivate because of the rapid influx of sodium ions.

As the sodium channels closes, it does not allow entry of sodium ions and they are actively transported out the plasma membrane. There is an outward current of potassium ions as potassium channels channels are activated, which returns the electrochemical gradient to the resting state.

Potassium Chloride Crystals

Introduction :

Potassium chloride crystals are the inorganic chemical compound, which is represented by the molecular formula KCl and the molar mass is 74.55g. Potassium chloride crystals is the salt of metal halide. Potassium chloride crystals are odorless and it is white in color and it is a crystalline solid.  The boiling and melting point of potassium chloride crystals are 1420°C and 770°C respectively. Potassium chloride crystals are soluble in water. Potassium chloride crystals have face centered cubic structure. Rarely potassium chloride crystals are known as muriate of potash.   It is toxic in excess if we intake orally.  It is hygroscopic in nature.  Potassium chloride crystal was discovered by Sir Humphrey Davy in 1807.

The appearance potassium chloride crystals is shown below,

              

Preparation and Structure of Potassium Chloride Crystals:

Preparation of Potassium chloride:
Potassium chloride crystals naturally occurs as sylvite, so potassium chloride is easily extracted from sylvinite.  It is obtained as a by-product in the preparation of nitric acid from hydrochloric acid and potassium nitrate. i.e.
KNO3 + HCl ===> HNO3 + KCl

Chemical properties of Potassium chloride crystals:

Potassium chloride crystals can react with silver nitrate to give silver chloride.
KCl + AgNO3 ==> AgCl + KNo3
Since potassium is more electropositive than sodium, so it is reduced to potassium metal
KCl (l) + Na (l) ⇌ NaCl (l) + K (g).

Structure of Potassium chloride crystal:
The structure o potassium chloride is face centered cubic.  The lattice constants are equal at 630 picometers .The potassium and the chloride ions are bonded through ionic bond.

Applications of Potassium Chloride Crystals:

Potassium chloride crystals have many applications; few of them are as below,

• Solution of potassium chloride crystals are used as strong electrolytes.
• They are used as good conductors of heat and electricity.
• In infrared and FTIR spectrophotometers, potassium chloride is commonly used as infrared transmission crystal windows in liquid and gaseous sample.
• It is used in preparation of fertilizers.
• It is also used in the manufacture of potassium metal and potassium hydroxide and also used as medicine.
• It is used as fire extinguishing agent.
• Like sodium chloride, it is used as flux for the gas welding of aluminium