Video English Naration

Corrosion

Corrosion in metals occurs due to corrosive interactions between metals and the environment, the moist environment (containing moisture) and induced by the presence of O2, CO2, or H2S gases. Corrosion can also occur due to high temperatures. Corrosion in metals can also be viewed as a process of returning the metal to its original state, ie metal ore. For example, corrosion of iron to iron oxide or iron carbonate.

4Fe (s) + 3O2 (g) + 2nH2O (l)  → 2Fe2O3.nH2O (s)
Fe (s) + CO2 (g) + H2O (l)         → Fe2CO3 (s) + H2 (g)

Because corrosion can change the structure and properties of metals then corrosion is likely to be detrimental. It is estimated that about 20% of the metal is damaged due to corrosion in each year.

The corroded metal is caused because the metal is easily oxidized. According to the standard reduction potential table, in addition to the gold metal generally metals have a lower standard reduction potential of oxygen.

If half the metal reduction reaction is reversed (metal oxidation reaction) coupled with a half of the O2 gas reduction reaction it will produce a cell potential value, positive Esel. Thus, almost all metals can react with O2 gas spontaneously. Some examples of metals that can be oxidized by oxygen are shown in the following reaction equation.

4Fe (s) + O2 (g) + 2nH2O (l) → 2Fe2O3.nH2O (s) Esel = 0.95 V
Zn (s) + O2 (g) + 2H2O (l)     → Zn (OH) 4 (s)         Esel = 0.60 V

Mechanism of Corrosion in Iron

Mechanism of Corrosion in IronBecause iron is the main ingredient for various construction corrosion control becomes very important. To be able to control the corrosion would have to understand how the mechanism of corrosion in iron. Corrosion is classified as an electrochemical process, as shown in the illustration.

Iron has a non-smooth surface due to imperfect composition, also due to the difference in surface tension that poses a potential in a certain area higher than other regions.

In the anodic area (surface area in contact with water) occurs the dissolution of iron atoms with the release of electrons to form water-soluble Fe2⁺ ions.

Fe (s) → Fe2 + (aq) + 2e-

The released electrons flow through the iron, just as the electrons flow through the outer circuit of the voltaic cell to the cathodic area until there is an oxygen gas reduction from the air:

O2 (g) + 2H2O (g) + 2e- → 4OH- (aq)

The corrosion mechanism of Fe 2+ Fe2 + is dissolved in water droplets moving toward the cathodic region, as the ions pass through the salt bridge in the voltaic cell and react with the OH-ions forming Fe (OH) 2. Fe (OH) 2 formed is oxidized by oxygen to form rust.

Fe2 + (aq) + 4OH- (aq) → Fe (OH) 2 (s)
2Fe (OH) 2 (s) + O2 (g) → Fe2O3.nH2O (s)

The overall reaction to the iron corrosion is as follows (see mechanisms on the picture aside):

4Fe (s) + 3O2 (g) + n H2O (l) → 2Fe2O3.nH2O (s)                (Rust)

Due to the migration of ions and electrons, the rust often forms in the area some distance away from the corroded iron surface (holes). The color on the carat ranges from yellow to brown-red even to black. This color depends on the number of H2O molecules attached to the rust.

Corrosion can occur if there is air (especially O2 gas) and water. If there is only water or O2 gas, corrosion does not occur.

The presence of water-soluble salts will accelerate the corrosion process. This is because in salt solution there are ions that help speed up the delivery of oxidation Fe2 + ions.

Hardness of rust increases rapidly by the presence of salt because salt solubility increases the conductivity of ions by solution so as to accelerate the corrosion process. Chloride ions also form stable complex compounds with Fe3 + ions. This factor tends to increase the solubility of iron so it can accelerate corrosion.

 https://youtu.be/tlvnK_3gP9s

RPP K13 about chemistry lesson

PLANNING ANALYSIS OF LEARNING IMPLEMENTATION PLAN LEARNING IMPLEMENTATION PLAN (RPP)

School: SMAN 1 BAYUNG LENCIR
Subject: CHEMICAL
Class / Semester: X / 1
Time Allocation: 2 x 45

A.     Core Competence (KI)

KI3: Understand, apply, analyze factual knowledge, Conceptual, procedural based on his curiosity about science Knowledge, technology, art, culture, and humanities withN Insights of humanity, nationality, statehood, and civilization Related causes of phenomena and events, and apply Procedural knowledge in the appropriate field of study With his talents and interests to solve problems.

KI4: Cultivate, reason, and serve in the realm of realm and domain Abstract related to the development of what it learned in School independently, and able to use appropriate methods Scientific rules.

B.     Basic Competencies and Indicators

Basic competencies

Indicator

3.3 Understand how to write electron configurations and outer electron configuration patterns for each class in the periodic table 4.3 Determining the location of an element in the periodic table and its properties based on the electron configuration

3.3.1 Identify quantum numbers 3.3.2 Determining quantum numbers (possible electrons are) 3.3.3 Describes skin and sub skin and its relation to quantum numbers 3.3.4 Write down electron configurations based on stinking principles and rules 3.3.5 Connect the electron electron configuration to the location of elements in the elemental periodic system 4.3.1 Determining the location of an element in the periodic table based on the electron configuration 4.3.2 Describe the relationship between properties of elements with electron configurations

C.   Learning Materials

No	Knowledge	Learning materials
1 2 3 4	Factual Concept Principle Procedural	·         The atomic constituents are protons, electrons and neutrons. ·         Atomic number, mass number ·         Electron consists of skin, sub skin ·         Isotopes, Isobars, Isotons ·         Quantum Numbers ·         The principle of auf smell ·         Hund Rules ·         Properties - Properties Elements in groups ·         Configuration of electrons

D.     Learning Activities
1. First Meeting: (2 JP)
Indicator:
1. Identify Quantum Numbers
2. Determining quantum numbers (possible electrons are)
3. Describes skin and sub skin and its relation to quantum numbers

a. Activity Introduction
1. Master greets.
2. Ask students to lead prayers.
3. Asking readiness to learn.
4. Apersespi asks some atomic models.

b. Core activities
Sintak learning       Description of learning activities         Time Allocation
Stimulation                        Problem stateman (Problem identification)

Collecting data.

Data processing,Verification,Generalization

Presents some images of the atomic skin sequence

Figure 1

Figure 2

Learners discuss the link between the two images and their relation

to the position of an atom. Collect data on skin and sub skin

relationships with electron position. By dividing the group into

several topics.

Topic 1: Major kuamtum numbers

Topic 2: Quantum azimuth number

Topic 3: Magnetic Quantum Numbers

Topic 4: Spin quantum number

Students compare the results of the discussion in groups with the

results of other groups through visits to each other group.

Through class discussions each group presented the results of the

group discussion.The teacher reinforces and straightens the results of

class discussions on quantum number determination.

Learners exercise about the quantum number determination with the

game Rolling stick

c. Closing Activity
1. Learners conclude about quantum numbers
2. Learners meferleksi learning activities

E.      Assessment technique
1. Knowledge: Test Write, Test Write.
2. Attitude: Observation of Discussion activities

F.      Media / tools, Materials, and Learning Resources
1. Media / tools: Images, Charts, Game cards about, LCD.
2. Material: -
3. Learning Resources: Textbooks, Internet

Attachments:
1. Learning Materials Meeting 1
2. Assessment Instruments Meeting 1

Assessment of Attitude

NO	ASPECT ATTITUDE	WRITTEN INDICATORS	SCORING SCORES
1 2 3.	To be responsible Discipline Appreciate	1.      Complete the tasks according to the given assignment of tasks 2.      Submitting performance results according to the time set 3.       Appreciate peers in discussions	0          1          2

Information :
Score 0 = Less In accordance with the indicator
Score 1 = Adequate In accordance with the indicator
Score 2 = Very in accordance with the indicator

Reflection:
There are still many difficulties to determine the relationship between syntax and learning activities.

Dialogue about corrosion

Neng :  What is an electrochemical cell?

An expert :The place where chemical energy is converted into electrical energy, or electric energy is converted into chemical energy. Electrochemical cells are divided into voltaic cells [galvani cells] and electrolysis cells.

Neng : What is corrosion? 

An expert :Metal corrosion is a spontaneous redox reaction that is quite complex and can be understood with the concept of electrochemical cells.

Neng: Is corrosion always harmful?

An expert : Basically corrosion is the destruction of the metal, but the oxide layer that is formed is not always detrimental. For example in corrosion of aluminum metal, the formed oxide layer is strong and solid, thus protecting Al metal from further corrosion.

Neng: Corrosion is also referred to as electrochemical cells in nature. Based on the statement, then on the corroded metal there is anode and cathode. Explain the anode and cathode parts on a corroded piece of iron!

 An expert : In moist air, the iron tends to corrodate, especially in areas that are scratched or bent. Such an area is called anode while the other regions on iron serve as cathode.

Neng: Explain the factors that can cause corrosion!

An expert : The content of H2O and O2, pH, temperature, the presence of impurities, electrolyte and concentration, galvanic coupling, and metallurgical factors.

Neng: Describe methods that can protect the material against corrosion!

An expert :Use a protective coating to prevent direct contact with H2O and O2 B) Using cathode protection C) Using anode protection