Chemical Articles

SOLUBILITY

 

The solubility of a substance in a solvent represents the maximum amount of a soluble substance in a solvent. A solubility is generally expressed in grams / L or mol / L.

If some of the salt of the kitchen is dissolved into water and some is insoluble, the solution is a saturated solution. If the NaCl saturated solution is added again NaCl, the added NaCl will precipitate as a NaCl solid. Thus, the concentration of the solution is equal to the solubility of NaCl in water.

 

FACTORS AFFECTING THE FIGHT

The amount of solubility of a substance is influenced by several factors, among others:

 

1. Type of solvent
Polar compounds (having poles of charge) will be readily soluble in polar compounds, such as alcohols and all acids are polar compounds so easily soluble in water which is also a polar compound. In addition to polar compounds, ionic compounds such as NaCl also readily dissolve in water and decompose into ions. Nonpolar compounds will readily dissolve in nonpolar compounds, eg fat soluble in oil. Polar compounds are generally insoluble in nonpolar compounds, such as insoluble alcohols in kerosene.
2. Temperature
The solubility of solids in water will be higher if the temperature is increased. This is due to the heat that will result in the increasing spacing between molecules in the solid. Reducing the distance between molecules in solids molecules makes the force of force between molecules become weak so easily released by the influence of gravity of water molecules. The graph below shows the effect of temperature on the solubility of some solids. 

 

 

 

 

In contrast to solids, a rise in temperature will cause the solubility of gas in water to decrease. This is because the increased temperature causes the dissolved gas in the water to be released from water.

Thus the article on solubility, may be useful ... ..

Source:

Sudarmo, U. (2013). CHEMISTRY: For SMA / MA Class XI, Mathematics and Natural Sciences. Erlangga: Jakarta 

Final Practice Explanation of Buffer

Here is my link :  https://www.youtube.com/watch?v=6w9YbU_gk7w

What is a buffer solution? 

Definition 
The buffer solution is a substance which inhibits the change in pH when a small amount of acid or base is added thereto. 

Acidic buffer solution 

The acidic buffer solution is something that has a pH of less than 7. The acidic buffer solution is usually made of a weak acid and a salt - often a sodium salt.The usual example is a mixture of ethanoic acid and sodium ethanoate in solution. In this case, if the solution contains a molar concentration comparable between acid and salt, then the mixture will have a pH of 4.76. This is not a problem in terms of concentration, as long as both have the same concentration.You can change the pH of the buffer solution by changing the acid to salt ratio, or by choosing different acids and one of its salts. 

The alkaline buffer solution 

The alkaline buffer solution has a pH above 7. The alkaline buffer solution is usually made of weak base and its salt.Often used as an example is a mixture of ammonia solution and ammonium chloride solution. If both are in a comparable molar ratio, the solution will have a pH of 9.25. Again, that is not a problem as long as your chosen concentration is the same.How does the buffer solution work?The buffer solution contains something that will remove the hydrogen ions or hydroxide ions you might add - otherwise it will change the pH. Acid and alkaline buffer solutions reach these conditions in different ways.Acidic buffer solutionWe will take a mixture of ethanoic acid and sodium ethanoate as a typical example.Ethanoic acid is a weak acid, and the equilibrium position will shift to the left:

 

The addition of sodium ethanoate to this condition adds to the excess of ethanoate ions in large quantities. Based on the Le Chatelier Principle, the equilibrium position end is then shifted to the left.
Therefore the solution will contain something important:

     Many ethanoic acid is not ionized;
     Many ethanoic ions from sodium ethanoate:
     Enough hydrogen ions to make the solution acidic.

Something else (such as water and sodium ions) is not important in explanation.
 
Addition of acid to acidic buffer solution
The buffer solution must eliminate most of the new hydrogen ions, otherwise the pH will drop considerably.
The hydrogen ions join the ethanoate ion to produce ethanoic acid. Although the reaction is reversible, because ethanoic acid is a weak acid, most of the new hydrogen ions are removed in this way.
 
Since most of the new hydrogen ions are removed, the pH will not change too much - but because the equilibrium is involved, the pH will decrease slightly.
The addition of a base to an acidic buffer solution
The alkaline solution contains hydroxide ions and the buffer solution removes the hydroxide ions.

This time the situation is a little more complicated because there are two processes that can remove hydroxide ions.
The removal of hydroxide ions by reaction with ethanoic acid
Most of the acidic substances in which hydroxide ions collide with ethanoic acid molecules. Both will react to form ethanoic ions and water.

 

Since most of the hydroxide ions are removed, the pH does not change too large.
The removal of hydroxide ions by reaction with hydrogen ions
It should be remembered that some of the existing hydrogen ions come from ionization of aetanoic acid.
  
 
The hydroxide ion can join it to form water. As long as it happens, the equilibrium tip replaces it. This remains until most of the hydrogen ions are removed.
 
 Again, because you have the equilibrium involved, not all hydroxide ions are removed - because they are too much. The water formed becomes ionized back into a very small amount of water to provide some hydrogen ions and hydroxide ions.

The alkaline buffer solution

We will take a mixture of ammonia and ammonium chloride solutions as a typical example.
Ammonia is a weak base, and the equilibrium position moves to the left:
 

 The addition of ammonium chloride under these conditions adds excess ammonium ions in large quantities. Under the Le Chatelier Principle, it will cause the equilibrium position end to shift to the left.
Therefore the solution will contain several important things:

     Many unreacted ammonia;
     Many ammonia ions from ammonium chloride;
     Simply hydrogen ions to produce an alkaline solution.

Other things (such as water and chloride ions) are not important in explanation.
The addition of acids to an alkaline buffer solution
There are two processes that can remove the hydrogen ions you add.
Elimination of hydrogen ions by reaction with ammonia
Most of the basic substances in which hydrogen ions collide with them are ammonia molecules. Both will react to form ammonium ions.

Most, but not entirely, hydrogen ions will be removed. The ammonium ion is a slightly weak acid, and therefore the hydrohen ion will be released again.
Removal of hydrogen ions by reaction with hydroxide ions
It should be remembered that some of the existing hydroxide ions come from the reaction between ammonia and water.
 

The hydrogen ion can join the hydroxide ion to produce water. As it happens, the equilibrium tip replaces the hydroxide ion. This continues until most of the hydrogen ions are removed. 
 

 Again, because you have the equilibrium involved, not all of the hydrogen ions are removed - just the majority.
The addition of a base to an alkaline buffer solution
The hydroxide ion of the alkali is removed by a simple reaction with the ammonium ion.

Because the ammonia formed is a weak base, the ammonia will react with water - and therefore the reaction is slightly reversible. This means that, again, most (but not all) of the hydrogen ions are removed from the solution.

Dilution of buffer solution 

Why is the pH of the buffer solution unchanged if diluted? To understand this, it can be reviewed from the Henderson-Hasselbalch equation.Henderson-Hasselbalch equationThe pH value of the buffer solution is determined only by pKa and the molar concentration ratio of the conjugate acid base pair. The Ka or the pKa of the weak acid does not depend on the acid concentration, but depends on the temperature. Therefore, dilution of the buffer solution will not change the pKa value 
The dilution of the buffer solution only changes the molar concentration of the species in equilibrium, but does not alter the comparison of the speciesFigure 8.9 The dilution of the buffer solution changes only the molar concentration of the species in equilibrium, but does not alter the comparison of the species.The conjugate acid molar conjugate concentration will change if the volume of the solution changes because the concentration depends on the total volume of the solution.  

Dilution of the solution will change all the concentrations of the species present in the solution, but since the concentration changes are felt by all species then the molar concentration ratio of the acid-base conjugate pairs is unchanged. As a result, the pH of the solution has not changed. 

Chemistry Lesson Plan based on Curriculum 2013

RPP CHEMICAL GRADE X IPA 2013 SEMESTER 1
RPP KIMIAULUM CHEMICAL 2013

 

Here's an example of the 2013 Curriculum Chemical RPP created by a group of teachers:

LESSON PLAN
(RPP)

Unit of Education: SMA
Class / Semester: X / 1
Subject: Chemistry - specialization
Topic: The Role of Chemistry in Everyday Life
Time: 3 × 45 minutes

A. Core Competence of High School X:1. To live and practice the religious teachings that he embraces2. Develop behavior (honest, disciplined, responsible, caring, polite, environmentally friendly, cooperative, cooperative, peace-loving, responsive and proactive) and demonstrate attitudes as part of the solution to various ways in environments with social and natural environments and Placing ourselves as a reflection of the nation in the association of the world3. Understand, apply, analyze factual, conceptual, procedural knowledge based on his knowledge of science, technology, art, culture, and humanities with the insights of humanity, nationality, state and civilization related to phenomena and events, and application of procedural knowledge in the field of Yang Specific in accordance with his talents and interests to solve problems.4. Cultivate, reason, present, and create in the realm of concrete and abstract realms related to the development of the self-study in the school independently, and able to use methods according to scientific rules.
B. Basic Competence1.1. Showing a happy attitude, confidence, internal motivation, attitude, honest, and confident in completing various things.2.1. Have tolerant attitude to process which problem is different and creative3.1 Understanding the essence of chemistry, scientific methods and safety in the laboratory and its role in life
C. Indicators of Competency Achievement1. Engage actively in learning to play a role in everyday life2. B Assist in group activities.3. Tolerance to the different and creative processes.4. Explain the role of science in everyday life5. Explain the essence of chemistry6. Skilled apply the concept / method of scientific and safety work dilaboratoriumD. Learning ObjectivesWith the discussion and learning activities in the learning process in everyday life is expected students actively involved in learning activities and responsible in conveying opinions, answering questions, giving suggestions and criticism, about1. The role of chemistry in everyday life.2. The nature of chemistry3. Scientific and safety methods
E. Chemical Material1. The role of chemistry in everyday life2. Chemical chemistry3. Scientific and occupational safety methodsF. Model / Method of Learning
The learning approach is the scientific (scientific) approach. Cooperative learning (cooperative learning) using problem-based discussion groups.

G.     Learning Activities

Activities	Event Description	Time Allocation
preliminary	1. The teacher provides an overview of the importance of understanding Chemistry and provides an overview of the application of Chemistry in everyday life. 2. As an apperception to encourage curiosity and critical thinking, students are invited to solve problems about the role of chemistry in everyday life, the essence of chemistry and the method of scientific and occupational safety. 3. Teachers convey the purpose of learning to be achieved is the role of chemistry in everyday life, the essence of chemistry sert scientific methods and safety work.	10 minutes
Core	1.The teacher asks about how the role of chemistry in everyday life, the essence of chemistry and the method of scientific and safety work.2. When students have not been able to answer it, the teacher gives an example that is around us.3.With the question and answer, concluded the role of chemistry in everyday life, the essence of chemistry and scientific methods and safety work.4. Next, the teacher asks the students to mention other examples related to the role and nature of chemistry.5.The teacher divides the students into 8 groups and assigns students the task of applying the scientific method in a case.6. As students work in groups, teachers pay attention to and encourage all students to engage in discussions, and direct when there are groups who stray far away from their work.7. One discussion group (not necessarily the best) was asked to present the results of the discussion to the front of the class. While other groups, responding and perfecting what was presented.8.The teacher collects all the results of each group's discussion9.With the question and answer, the teacher directs all the students to the conclusion about the application of scientific method in a case.	70 minutes
Cover	1. Students are asked to conclude about the role of chemistry in everyday life, the essence of chemistry and scientific and occupational safety methods. 2. Teachers assign tasks on scientific and occupational safety methods in other cases. 3. Teacher ends learning activity by giving message to keep learning.	10 minutes

H. Tools / Media / Learning Resources
1. Package book, Worksheet or worksheet (student)
2. Inlay materials
3. Assessment sheets
4. Video about work safety.

I. Assessment of Learning Outcomes
 1. Assessment Technique: observation, written test
 2. Assessment Procedure:

No	Rated aspect	Assessment Technique	Assessment Time
1.	Attitude A. Engage actively in chemistry learning. B. Cooperate in group activities. C. Tolerable to different and creative problem-solving processes.	Observation	During learning and during discussion
2.	Knowledge A. Explain again the role of chemistry in everyday life B. Redefining the scientific and occupational safety methods. .	Observations and tests	Completion of individual and group tasks
3.	Skills Skillfully apply the concept / principle of scientific method and work safety in laboratory.	Observation	Completion of tasks (both individual and group) and during discussion

J. Assessment Instrument Learning outcomes
 
Written test
1. Explain the role of chemistry in everyday life.
2. Explain the essence of chemistry in everyday life.

3. Make a case study and solve it scientifically.

Predict Rendement of Product a Reaction

Steps to Predicting the Products of Chemical Reactions

TYPES OF REACTIONS REVIEW

2 NaNO3 + PbO . Pb(NO3)2 + Na2O

 Double Displacement

 C2H4O2 + 2 O2  2 CO2 + 2 H2O

 Combustion

ZnSO4 + Li2CO3  ZnCO3 + Li2SO4

Double Displacement

V2O5 + 5 CaS  5 CaO + V2S5

DOuble Displacement

S8 + 8 O2  8 SO2

Synthesis

Organize Your Thoughts 

 

PREDICTING THE PRODUCTS

 We want to be able to predict the products for the following reaction types :

• Combustion
• Single Displacement
• Double Displacement 

RULES FOR PREDICTING PRODUCTS

OF CHEMICAL REACTIONS

’ Here are a few important things to remember when predicting products:

’ The compounds form must be neutral ionic compounds (which means you’ll be paying attention to their charges)

’ You do NOT carry subscripts from the reactants to the products.

’ You always balance your equation LAST

PREDICTING REACTION PRODUCTS:

COMBUSTION REACTIONS

’ A hydrocarbon and oxygen (O2) indicate a combustion reaction

’ If it is combustion, then just write H2O and CO2 as products

’ Then, balance the equation (can be tricky)

’ Examples: 

 

PREDICTING REACTION PRODUCTS:

REPLACEMENT REACTIONS

’ A metal will not always replace a metal in a compound dissolved in water because of differing reactivities

’ An activity series can be used to predict if reactions will occur

’ To replace a metal, the other metal must be MORE REACTIVE

’ Same applies for halogens

 

PREDICTING REACTION PRODUCTS:

SINGLE REPLACEMENT REACTIONS

´ To predict the products: Replace the single element with the corresponding element in the compound
´ A metal will replace the cation in the compound
´ A non-metal will replace the anion in the compound
´ If the element is more reactive than the one it attempts to replace, then the reaction will be spontaneous and exothermic
´ Otherwise, it will not be spontaneous and will be endothermic (NO REACTION)

  PREDICT IF THESE REACTIONS WILL OCCUR
 
PREDICTING REACTION PRODUCTS:
SINGLE REPLACEMENT REACTIONS
 

PREDICTING REACTION PRODUCTS:
DOUBLE REPLACEMENT REACTIONS
´ If it is double replacement, then the cation
and anions switch places
´ It is helpful to separate each compound
into their cation and anionic parts with their
charges
´ Then switch places, and criss cross the new
compounds to make sure they are the
correct neutral compound formulas

PREDICTING REACTION PRODUCTS:
DOUBLE REPLACEMENT REACTIONS
´ AB and CD are both ionic compounds
´ Separate each compound & write their
charges
´ Switch places and re-write new compounds
´ Example:
 ´ Balance at the end!!

PREDICTING REACTION PRODUCTS:
DOUBLE REPLACEMENT REACTIONS
´ Not all double replacement reactions will occur
´ In order for a double replacement reaction to
take place:
´ Both of the reactants must be soluble in water
´ If a compound contains at least one of the ions
that is proven soluble, then the compound will be
at least moderately soluble
´ One product must be soluble and one
product must be insoluble
´ The insoluble product is the precipitate that
forms when the reaction takes place
´ Usually a precipitate is a solid, but it doesn't
have to be

SOLUBILITY TABLE



PREDICTING REACTION PRODUCTS:
DOUBLE REPLACEMENT REACTIONS
Predict if a reaction will occur when you combine aqueous solutions
of iron (II) chloride with aqueous sodium carbonate solution.
If the reaction does occur, write a balanced chemical equation showing it.