CAUSE AND EFFECT CHEMICAL REACTION

CAUSE AND EFFECT OF CORROSION

 

Corrosion is the destruction or degradation of metals due to a redox reaction between a metal and various substances in the environment that produce undesirable compounds. In ordinary language, corrosion is called kararatan. The most common example of corrosion is iron fi gure.

In corrosion events, the metal undergoes oxidation, while oxygen (air) is reduced. The metal rust is generally oxide or carbonate. The chemical rust formula is Fe2O3.nH2O, a solid brown-red substance.

Corrosion is an electrochemical process. In iron corrosion, certain parts of the iron act as anodes, in which iron oxidizes.

Fe (s) <-> Fe2 + (aq) + 2e

The freed electrons in the anode flow to another part of the iron which is the cathode, where the oxygen is reduced.

O2 (g) + 4H + (aq) + 4e <-> 2H2O (l)

Or

O2 (g) + 2H2O (l) + 4e <-> 4OH- (aq)

The iron ions (II) formed on the anode subsequently oxidized to form iron (III) ions which then form hydrated oxide compounds, ie rust of iron. Regarding which part of the iron is the anode and which part is the cathode, depends on various factors, such as impurities, or the density of the metal.

Corrosion can also be interpreted as an attack that destroys metal because metal or electrochemical with the environment. There is another definition that says corrosion is in terms of metal extraction from its mineral ore. For example, iron ore minerals in the wild are present in the form of iron oxide or iron sulphide, after extracting and treating, an iron will be produced which is used for the manufacture of steel or alloy steel. During use, the steel will ignite with an environment that causes corrosion (back into iron oxide compounds).

Volta series and Nernst's law will help to know the possibility of corrosion. The speed of corrosion is highly dependent on many factors, such as the presence or absence of oxide layers, because the oxide layer can be potentially different to other electrodes that will be very different when it is clean from the oxide.

A. Cause of corrosion

Corrosion on the surface of a metal can be caused by several factors, including:

1.     Direct contact metal with H2O and O2

Corrosion on metal surfaces is a process that contains redox reactions. This reaction is a mini Volta cell. For example, iron corrosion occurs when there is oxygen (O2) and water (H2O). Iron metal is not pure, but contains a mixture of carbon that spreads unevenly in the metal. Consequently, there is a difference in electrical potential between metal atoms and carbon atoms (C). The iron metal atom (Fe) acts as anode and C atom as a cathode. The oxygen from the water-soluble air will be reduced, while the water itself serves as a medium where the redox reaction in the corrosion event occurs. The more the amount of O2 and H2O are in contact with the metal surface, the faster the corrosion occurs on the metal surface. Watch the animation. Following: iron corrosion animation.

2.    The existence of impurities

Impurities on metal surfaces may cause additional reduction reactions to cause more oxidized metal atoms. For example, the presence of carbon dust from the combustion of fuel on the metal surface can accelerate the oxygen gas reduction reaction on the metal surface. Corrosion events are thus accelerated.

3.    Contact with Electrolyte

The presence of electrolytes, such as salt in seawater can accelerate the rate of corrosion by increasing the occurrence of additional reactions. While large electrolyte concentrations can perform the rate of electron flow so that corrosion increases.

Shipwrecks on the seabed that have been corroded by a high salt content.

4.    Temperature

Temperature affects the speed of the redox reaction in corrosion events. In general, the higher the temperature the faster the corrosion occurs. This is due to the increase in temperature, so the kinetic energy of the particles increases, so the possibility of effective collision in the redox reaction is greater. Thus the rate of corrosion in the metal increases.

5.    Ph

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2H + (aq) + 2e- → H2

The presence of additional reduction reactions at the cathode causes more metal atoms to oxidize so that the corrosion rate on the metal surface is greater.

6.    Metallurgy

• Metal surface
Rougher metal surfaces will give rise to potential differences and have a tendency to become corroded anodes.
• Galvanic Coupling Effect
The low purity of the metal indicates the number of other elemental atoms present in the metal, thus triggering the Galvanic Coupling effect, ie, the potential difference in the metal surface due to the difference of E ° between different metal atomic atoms and present on the surface of the metal with low purity . This effect triggers corrosion on the metal surface by increasing the oxidation reaction in the anode region.
7. Microbes
The presence of microbial colonies on metal surfaces can lead to increased corrosion in metals. This is because the microbes are able to degrade the metal through redox reactions to obtain energy for its survival. Microbes that can cause corrosion, among others: protozoa, iron bacteria manganese oxide, sulfate reduction bacteria, and sulfur-sulphide oxidation bacteria.

B.  Effect of corrosion

Carcass (corrosion) is a term given to the corrosion-damaged metal. While the metal parts are damaged and brownish black on steel is called Rust. Theoretically, rust is a term given to only one type of metal that is steel, whereas in general the term rust is more accurately called corrosion. Corrosion is defined as material degradation (especially metals and alloys) or by interacting with the environment. Corrosion is an electrochemical process or reaction that is natural and takes place by itself, therefore corrosion can not be prevented or stopped completely. Corrosion can only be controlled or slowed down so that it slows down the process of destruction. Viewed from the electrochemical aspect, corrosion is the process of electron transfer from metal to its environment. The metal acts as a cell that delivers electrons (anodes) and its environment as an electron receiver (cathode). The reaction that occurs in corrosive metal is the oxidation reaction, in which metal atoms dissolve into their environment by releasing electrons in the metal. While the cathode from the reaction occurs, where the ions from the environment close to the metal and capture the electrons left on the metal. The corrosion-generated impact is remarkable.

In Indonesia, twenty years ago the costs incurred due to corrosion in the field of industry reached 5 trillion rupiah. This value gives us an idea how big the impact of corrosion and value is increasing every year because of the lack of proper corrosion control in the field of industry. Corrosion-induced impacts may include direct and indirect losses. Direct losses are in the form of damage to equipment, machinery or building structures. While the indirect losses are the cessation of production activities due to the replacement of equipment damaged by corrosion, the loss of the product resulting from damage to the container, fuel tank or piping network of clean water or crude oil, the accumulation of corrosion products on heat exchangers and piping networks will decrease Its heat transfer efficiency, and so on.

TEACHER'S DIALOGUE AND STUDENT ABOUT CHEMICAL LESSONS

TEACHER'S DIALOGUE AND STUDENT

 ABOUT CHEMICAL LESSONS                                                                       
                        (Chemistry Time Class)

Teacher    : “Good morning my students”.
Students    : “ Morning Mrs”.
Teacher    : “Okay, are you ready to study chemistry today?”
Students    : “Yes, we are ready!”
Teacher    : “Well today we will discuss the topic of Chemicals in Everyday Life. Do you    know what are the chemicals that we often encounter?”
Intan         : “I know Mrs, I think soap, detergent, and floor cleaner.”
Teacher    : “Yes it is true Intan. Soap, detergent, and floor cleaners are cleaners. Many kinds of chemicals that exist in everyday life, which include cleaning, bleach, parfum, and pesticides. These pesticides vary in their type and function. Does anyone know the types of pesticides or even anyone knows its function too?”
Nurul        : “I know bu, Insecticide, which is a pesticide used to eradicate insects, such as grasshoppers, ladybirds, and caterpillars.”
Teacher    : “ yes, good job nurul. Next?”
Bobi        : “I know Mrs. Fungicides, bactericidal, and rodenticides. But i do not know its function bu. Can you explain?”
Teacher    : “Answer at once Bobi good question. Before I explains whether anyone knows what is fungicide, bekicisida, and rodenticide?”
Mira        : “I will try to remember it Mrs, I think Bactericide, that is pesticide to eradicate bacteria or virus and Rodentisida, that is pesticide which is used to eradicate plant pest in the form of rodent, like mouse.”
Teacher    : “ yup! That's right. There again?”
Kiki        : “Mrs, I think the fungicide is a pesticide used to eradicate the weed plant (weed).”
Teacher    : “Thanks for trying to answer kiki, but not quite right. The true fungicide is a pesticide used to eradicate and prevent the growth of mold or fungus. While what you mean is called herbicide.”
Nurul        : “Mrs, I will try to conclude. So many kinds of pesticides, including insectides, fungicides, bactericides, rodenticides and herbicides. Insecticides to combat insects, fungicides to combat fungi, bactericide to eradicate bacteria and viruses, rodenticides to eradicate rodents.”
Teacher    : “Yes .. good work nurul. Exactly. Then is there any question about our material?”
Mira        : “What chemicals are contained in the perfume Mrs?”
Teacher    : “Good question mira. Anyone can answer mira question?”
Bobi        : “I think alcohol, Mrs.”
Teacher    : “Yes it is true Bobi. Fragrances sold on the market usually contain other substances, such as alcohols for liquid perfumes and alum for dense in formers. In addition to alcohol, there are still a variety of other additives that are deliberately added to the perfume so that the perfume is easily sprayed (the substance serves as propellant). Among the additives that can serve as propellants there are those that can pollute the environment.”
Kiki        : “How can propellant can contaminate bu environment? Means fragrances that we use harmful?”
Teacher    : “This kiki, certain propellants when released into the air and then into the upper atmosphere will damage the ozone layer (a layer in the upper air that protects humans from high-energy rays, such as ultraviolet light). We may use fragrances, but we should not overdo it and preferably use liquid or gel deodorizer instead of a propellant-containing spray deodorizer.”
Intan        : “Mrs, what substance is contained in bleach? Is it dangerous?”
Teacher    : “Great question diamond. Bleach solutions sold on the market usually contain sodium hypochlorite (NaOCl) active ingredients of about 5%. In general, whitening agents sold on the market are safe to use during use in accordance with the instructions. In addition to the stain, this substance can also react with the dye clothes so that it can fade the color of clothing. Therefore, the use of this bleach should be as directed.”
Intan        : “So generally the chemicals contained in the ingredients around us are safe if used as directed. So Mrs?
Teacher    : “It is exactly Intan. Well today's chemistry lesson has been completed, if anyone wants to ask again please ask at the next meeting.”
Students    : “Ok Mrs!”
Teacher    : “On this day, until here our learning.see you next week.”

Chemistry Vocabulary

Chemistry Vocabulary 

1. Condensing = compounds are transitioning from a gas to a liquid; an act of cooling. 
2. Deposition = transition from a gas straight to a solid where the atoms move quickly to very slowly; no liquid forms; an act of cooling. 
3. Evaporating = transition from liquid to a gas where atoms move so much they leave the container; an act of warming. 
4. Gaseous = atoms are moving fast so containers do not hold them if their is no lid; no distinct volume or shape. 
5. Freezing = transition from liquid to solid where the atoms slowly move but not outside of a shape; an act of cooling.
6.  Matter = anything that has mass and volume. 
7. Melting = transition from solid to liquid where atoms start to move more so they take the shape of the container; an act of warming. 
8. Phase of Matter = speed of compounds that dictates the volume and shape of compounds (State of matter).
9. Plasma = most common state of matter in the universe but only example on Earth is lightning; state where atoms are moving so fast the electrons move from atom to atom. 
10. Sublimation = transition from a solid straight to a gas where the atoms barely move  to very quickly; no liquid forms; an act of warming. 
11. Liquid = state where compounds are moving and take the shape of their container but have an actual volume. 
12. Solid = state where compounds are slowly moving so it has a distinct shape and volume. 
13. AMU = atomic mass unit - units for subatomic particles.
14.  Atom = small particle that makes up all matter.
15.  Chemical Bond  = forces connecting atoms to fill outer electron shells      Types: covalent bonds, ionic bonds, and metallic bonds. 
16. Chemical Formula = list all elements and amounts in a compound like 2 hydrogen atoms and 1 oxygen equals H2O. 
17. Compound = multiple elements combined (bonded) like H2O (water) or NaCl (salt).
18. Covalent bond  = atoms share electrons in molecule (example: H2O).
19. Electron = negatively charged particle surrounding nucleus; mass of about 0 AMU.
20.  Electron Cloud = actual location of electrons around nucleus. 
21. Electron Shell = electrons are in shells, but certain amounts per shell, ex: 2, 8,18, 32 (also called energy levels, orbitals). 
22. Element = pure substance of matter.
23.  Family = elements with similar properties; elements that are in the same column.
24. Ion = Atom that has gained or lost electrons, therefore, atom with a charge.
25.  Ionic Bond = atoms steal electrons in compound (example NaCl)... where ions bond. 
26. Isotope = Atoms of the same elements that differ in number of neutrons, therefore, different masses.
27.  Metallic Bond = bond between metals where electrons flow freely between metals - between ionic and covalent. 
28. Molecule = multiple atoms combined (bonded) like O2 (oxygen gas), Cl2 (chlorine gas),  H2O (water) or NaCl (salt)                       * all compounds are molecules.
29.  Neutron = no charge particle in nucleus; mass of about 1 AMU. 
30. Nucleus (atom) = proton and neutron core of atom surrounded by electrons. 
31. Period = row on periodic table so elements are a proton apart. 
32. Periodic Table = organized chart of elements showing all similarities.
33. Proton = positively charged particle in nucleus; mass of about 1 AMU. 
34. Valence electron = electrons residing in shell furthest from the nucleus.
35. Acid = substance that has a low pH, taste sour, and turns litmus paper red.
36. Alloy = a solid solution of two or more elements with one being a metal. 
37. Base = substance that has a high pH, taste bitter, and turns litmus paper blue.
38. Catalyst = substance needed to help speed up a chemical reaction but is not involved in the chemical formula of the reaction. 
39. Nonmetals = Usually gasses or brittle solids at room temperature. 
40. Metals = Good conductors of heat and electricity.