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Chemical equilibrium

The concept of Dynamic Equilibrium

The equilibrium reaction is a reaction in which the reaction product (product) can react again to form the original substances (reactants). So the reaction goes both ways (reversible):

When does a back and forth reaction reach a state of equilibrium?
At the reaction rate to the right = the reaction rate to the left

How can we know that a back and forth reaction has reached equilibrium?
When equilibrium is reached the amount of the substances both reactants and products no longer changes. The amount of the substance is proportional to mole and concentration so that when the equilibrium of moles and concentrations of the substances remain.

Characteristic of equilibrium reaction:

"Substances of the left side (reactants) are never exhausted"

In the event of equilibrium, the price of equilibrium constant (Kc) can be determined. The value is determined by using the ratio of the concentrations of the substances when the equilibrium is reached.

From the form of the above equation can be concluded:
If nikai K> 1 then the result / product generated a lot
If nikai K <1 then the result / product produced a little

FACTORS AFFECTING CHEMICAL REACTIONS OF CHEMICALS

1. Factor of Concentration Change

Based on the Le Chatelier Principle, if the reaction or reaction product concentration changes, the equilibrium will drift to reduce the effect of concentration changes that occur until new equilibrium is obtained.

There are two ways to change the concentration of substances, namely:

A. Increase / decrease the concentration of reagents or reaction products

If the concentration of reagents is increased, then the equilibrium will shift to the right. Conversely, if the reagent concentration is lowered, the reagent concentration will shift to the left

If the concentration of the reaction product is increased, then the equilibrium will shift to the left. Conversely, if the concentration of the reaction product is lowered, then the equilibrium will shift to the right.

B. Dilution

Dilution (addition of a liquid solvent such as water) will decrease the concentration of reagents of the solutes in it. For the following equilibrium reaction:

AA + bB <-> cC + dD

Dilution will only shift equilibrium if:

Total mole of reagent ≠ Total mole of reaction product

2. Pressure and Volume Changes

The effect of pressure change on reaction equilibrium applies only to reaction systems involving gas. Under Le Chatelier Principle, if the pressure of a reaction system is changed, the equilibrium will shift to reduce the effect of this pressure change.

If the pressure increases, the equilibrium will shift in the direction with a total of fewer moles
If the pressure decreases, the equilibrium will shift in the direction with a total of more moles.

3. Temperature Changes

Temperature changes associated with heat release or absorption. In the equilibrium reaction, if the reaction to the right absorbs heat (the endotherm reaction), then the reaction to the left will release the heat (exothermic reaction). Vice versa. However, the writing of the termokimianya equation will refer to the reaction to the right.
By Le Chatelier Principles:

When the reaction temperature is raised, the equilibrium will shift toward a heat-absorbing reaction (an edoterm reaction)
When the reaction temperature is lowered, the equilibrium will shift toward a heat-releasing reaction (exothermic reaction)


Please check the following vidio:

https://www.youtube.com/watch?v=V0Ak5e7L90M

Lesson Plan of Classroom Learning (RPP) of Chemistry Class XII (Implementation of Curriculum 2013)

A. Identity
School Identity: Public high school 5
Subject: Chemistry
Class / Semester: XII / 1
Basic Material: Chemical Elements
Time Allocation: 2 meetings (2 x 2 x 45 Minutes)

B. Basic Competence (KD) and Indicators:
KD of KI 1:
1.1 Recognizing the existence of regularity in the colligative nature of the solution, the redox reaction, the diversity of the elemental properties, the macromolecular compounds as the form of the greatness of God YME and the knowledge of the existence of such order as the result of the creative human thought that the truth is tentative.
1.2 Being grateful for the abundance of elements of the main groups and the transitional groups in the Indonesian realm as minerals is a gift of God YME used for the prosperity of the Indonesian people.

Indicators:
• Glorify the greatness of God Almighty
• Realize that the rules set by God Almighty are the best for us.
KD of KI 2:
2.1 Demonstrate scientific behavior (curiosity, discipline, honest, objective, open, able to distinguish facts and opinions, resilient, conscientious, responsible, critical, creative, innovative, democratic, communicative) in designing and experimenting and discussing embodied In everyday attitude.
2.2 Demonstrate co-operative, courteous, tolerant, peace-loving and caring environment and cost-effective in utilizing natural resources.
2.3 Demonstrate responsive and pro-active and prudent behavior as a form of problem-solving ability and decision making.

Indicators:
• Curiosity
• Honest in using experimental data (using the data as is and results according to experimental data)
• Thorough in processing and analyzing data
• Resilient in search of a source of knowledge that supports problem solving (can solve problems in a trace from beginning to end with the correct steps).
KD of KI 3:
3.1 Analyze abundance, trends in physical properties and chemical properties of major group elements (noble gases, halogens, alkalis and alkalis, period 3) and transition elements (period 4).

Indicators:
• Identify the presence of elements that exist in Indonesia, especially Indonesia.
• Identify products that contain these elements.
• Identify the physical properties of the main elements and transition elements (boiling point, melting point, hardness, color, solubility and specific properties of each element).
• Identify the chemical properties of key elements and transition elements (reactivity to other elements).

C. Learning Objectives
• By observing demonstration or experiment activities, students can independently identify the abundance of elements in nature and the properties of the elements.
• Provided experimental data, independently students can make experimental reports about the physical properties and chemical properties of alkaline element elements, earth-algae, noble gases, halogens, third period elements as well as elements of the fourth period.
• Through exercises and discussions, students can analyze the abundance of elements in Nature, especially in Indonesia, as well as the physical and chemical properties of elements of the alkaline, earth-algae, noble, halogen, third-period elements and fourth-period elements.
• Develop curiosity, thoroughness, perseverance, and mutual respect through group discussion, question and answer, and individual assignments.
• Growing self-awareness of God's majesty and awareness of God's ordinance YME is the best provision for human life through demonstration activities, watching video or animation, and imaginative group / individual exercises.

D. Learning Materials
Abundance of Elements in Nature
Physical properties and chemical properties of the elements

E. Learning Approach and Method
Approach: scientific
Model: Cooperative Learning TPS type (Think Pair and Share), Discovery Learning
Methods: Discussion, guided discovery, question and answer, practice questions
 
F. Media and Learning Resources
• LCD projector
• Media Power Point
• Student Discussion Sheet
• High School Chemistry Class X Books

G. Learning Steps

1. Meeting 1

Activities	Event Description	Time Allocation
preliminary	· The teacher creates a religious class atmosphere by greeting the opening, praying with the students prior to the lesson, and checking the attendance of the students.                   Ø  Apperception §  The teacher explains the learning objectives / basic competencies that must be achieved by the students communicative.                   Ø  Motivation §  The teacher asks motivational questions to the students.	10 minutes
Core	Ø  Observing §  Observe the literature about the abundance of elements in nature especially in Indonesia.                 Ø  Ask §  The teacher asks the students, "What is the meaning of the element? How is the abundance in nature? "                 Ø  Data collection §  Teachers divided their students into groups to discuss the abundance of elements / compounds in nature, especially in Indonesia. §  The teacher gives some practice questions to be done by the students through discussion.                 Ø  Associate §  Aware of the regularity in the properties of the elements obtained thanks to the creative discovery of the experts. §  Grateful for the abundance of elements in nature as a gift of God Almighty.                 Ø  Communicate §  Some students come forward to do the exercises on the board. §  Teachers provide feedback and reviews on student work on the board. §  The teacher discusses the exercises together with the students and answers the students' questions.	70 minutes
Cover	· The teacher guides the students in concluding what has been discussed. · The teacher provides homework in the form of exercise questions. · The teacher tells the student the material to be discussed at the next meeting. · The teacher closes the learning activities by saying hello.	10 minutes

2. Meeting 2

Activities	Event Description	Time Allocation
preliminary	·                      The teacher creates a religious class atmosphere by greeting the opening, praying with the students before the lesson, and checking the attendance of the students.                  Ø  Apperception §  Teachers together with students discuss homework provided by teachers at previous meetings. §  The teacher explains the purpose of learning / basic competencies that must be achieved by students communicatively.                  Ø  Motivation §  Ask questions to students about the nature of the elements.	10 minutes
Core	Ø  Observe §  Observe the modern periodic table.                  Ø  Ask §  Ask questions to students about material. §  The teacher asks the students if there is material that has not been understood.                  Ø  Data collection §  Teachers introduce students about what is the physical nature and chemical properties of the elements. The teacher explains the material on the physical properties and chemical properties of elements of the alkaline, alkaline, halogen, noble, third element, and fourth period elements. §  The teacher gives some practice related questions that the material has been taught to be done by the students.                  Ø  Associate §  Summing up the existence of elements in nature, in the periodic system based on physical and chemical properties possessed.                  Ø  Communicate §  Some students come forward to do the exercises on the board. §  Teachers provide feedback and reviews on student work on the board. §  The teacher discusses the exercises together with the students and answers the students' questions.	70 minutes
Cover	· The teacher guides the students in concluding what has been discussed. ·   The teacher provides homework in the form of exercise questions. · The teacher tells the student the material to be discussed at the next meeting. · The teacher closes the learning activities by saying hello.	10 minutes

H. Assessment of Learning Outcomes

1. Test the learning outcomes (mastery of the concept) using a chemical peskoran (each question is         given a score of 1 if the answer is correct, and the score is zero if wrong).

2. Assessment Attitude (behavior) using the rubric of behavior assessment

3. Assessment of data processing skills of experimental results using performance rubric.

Behavioral Observations

No.	Rated aspect	Score			Information
		1	2	3
1.	Curiosity
2.	Accuracy in using experimental data and perform data processing
3.	Perseverance / tenacity in learning both in groups and individuals in solving problems that exist in the LKS.
4.	Honesty in processing data to identify carbon compounds and in solving problems in LKS

Behavioral assessment rubric

No.	Rated aspect	Rubric
1.	Showing my curiosity	3: showing great curiosity, enthusiasm, active in both group and individual activities
		2: show curiosity, but not very enthusiastic, and only actively involved in group activities when asked or less enthusiastic in solving individual problems.
		1: do not show enthusiasm in observation, it is difficult to be actively involved in group or individual activities even though they have been encouraged to be involved.
2.	Accuracy in using data obtained from experimental results in calculating and analyzing data	3: observe the video / animation and process the experimental data according to the procedure, and perform the calculation appropriately
		2: observing the video / animation and processing the experimental results data according to the procedure, but the calculation is less precise.
		1: watch the video / animation and process the experimental data according to procedure, but the calculation is not right, or vice versa.
3.	Persistence / tenacity of students in learning both in groups and individuals viewed from the players solve existing problems in the LKS.	3: diligent / resilient in completing tasks with the best results that can be done, work on time.
		2: work on time to complete the task, but has not shown his best efforts.
		1: does not make a serious effort to complete the task, and the task is not finished.
4.	Honesty in processing the results of lab data	3: show its honesty in using experiment data (data as it is)
		2: shows his honesty in using experimental data (data as it is) to prove basic chemical law, but shows less independence in solving problems (still trying to solicit reply / cheat) especially on individual activities
		1: does not show honesty in using experiment data and seeks answers from other friends by cheating to complete individual tasks.

Chemical articles : CORROSION

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 an 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 anode, in which iron undergoes oxidation.

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

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

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

or

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

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

Corrosion can also be interpreted as an attack that damages the metal because the metal reacts chemically or electrochemically with the environment. There is another definition that corrosion is the opposite of a metal extraction process of its mineral ore. For example, iron ore minerals in the wild are present in the form of iron oxide or iron sulphide compounds, after extracting and treating, an iron will be produced for the manufacture of steel or alloy steel. During use, the steel will react with the environment causing corrosion (back to the iron oxide compound).

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 the oxide layer, since the oxide layer can block the potential difference against the other electrode which will be very different when it is still clean from the oxide

Iron corrosion prevention techniques

1. Painting
2. Wrapped in plastic
3. Coating with chrome (Cromium plating)
4. Coating with tin (Tin plating)
5. Zinc coating (Galvanization)
6. Anode sacrifice (Sacrificial Anode)

USING ENGLISH TO PREDICT RENDEMENT OF PRODUCT A REACTION

Rendement refers to the amount of reaction product produced in the chemical reaction. Rendement is actually a term in the field of chemistry studies. The yield represents the inaccuracy of the reaction result, which results always lower than the mathematical calculation. 

The formula for calculating the following rendamen:

for example :

If the reaction between 6.0 grams of ethane, C2H6 (Mr = 30) with 7.1 grams of Cl2 (Mr = 71) yields 5.16 grams of C2H5Cl (Mr. 64.5), then the percentage of ethyl chloride rendement is ....

Discussion:

_{C2H6 + Cl2 → C2H5Cl + HCl}

_{C2H6 = 6/30 = 0.2 mol}

_{Cl2 = 7.1 / 71 = 0.1mol (discharged)}

_{C2H5Cl (theoretical) = 1/1 x 0.1 mol = 0.1 mol}

                                   _{= 0.1 x 64.5 g = 6.45 g}

_{% Rendemen = 5.16 / 6.45 x 100% = 80%.}