Knowing the meaning of chemical equilibrium – Chemical equilibrium is a subject of chemistry studied in class 11 SMA. As an IPA subject, Chemistry is usually easily forgotten. Many have sudden amnesia.
Well, especially about the chapter on balance, when studying it, many people admit to being worried. Worried about continuing to study because the mind immediately wanders.
Come on, let’s try to discuss it slowly so that worries disappear and we get enlightenment
Understanding Chemical Equilibrium
Let’s say we want to make a simple cookie dough from a quarter of flour and 2 eggs. At the time of 0 seconds, there is no intention, of course the flour and eggs have not reduced and are still intact. It hasn’t been mixed yet!
Let’s say 30 seconds later we pour the flour into the container, until the flour is reduced by half, then we break one egg. Then we start making the dough alias the dough starts to exist.
Let’s say 10 minutes later all the eggs and flour are gone because they have been mixed into a dough.
If we use flour, we liken it to an amount of A and then we mix it with eggs, let’s say B, then we liken the dough to C. Chemically, the reaction can be written like this:
A + B → C
A and B whose positions are on the left side of the back and forth arrow we call reactants. When A and B were mixed to form C, it lasted 10 minutes.
After 10 minutes A and B are no longer there because they have all formed C. The C that is on the right side of the arrow is called the product. So after 10 minutes the dough is formed.
This type of reaction is called a unidirectional reaction. Or if the result is already formed, it’s over alias the end. So the batter or the C is the ending.
Examples of this reaction are rusted iron, burnt paper and stale rice. All reactions are the reactions of 1 episode immediately ended.
Well, but there is also a chemical reaction that goes back and forth, does it mean back and forth like a courtship breaking up? Ishsh why did you go there!
Like this, let’s say that the reaction A mixed with B formed C, well if it turns out that a few seconds later, the C goes back to form A and B then this reaction is called a reversible reaction, the cool language is reversible .
So if the cake dough can separate back into flour and the dough as a whole, that means the reaction of making the cake is reversible, right? But it’s horrible if it happens!
Back and forth reaction If it is written like this, this is the form of the reaction. There is an arrow with two directions.
A + B ↔ C
After a few seconds A and B are formed, eh he goes back to C, and vice versa. Reactants become products, products become reactants.
The components on the left side of the arrow, reactants or reactants, they gradually decrease when they will form C. Speed A and B It is called the reduction speed.
Then C increases over time until the rate of reaction is called the rate of increase.
Notice, this is the graphic.
Lines A and B appear to go down, because they decrease and experience a decreasing rate, while line C appears to rise, because C increases and experiences an increasing rate.
Wait a minute, the speed of the reaction has not been explained yet ? The reaction rate for the reduction rate means the reduction of the substance in a matter of time.
Usually per second. If the rate of increase means the increase of a substance in a matter of time, do you understand?
It’s simple like this, let’s say the original A is 4 moles. Oya, the mole is a unit commonly used in chemical reactions.
Well, after 10 seconds, there are 2 moles left, which means that the reduction rate of A is all we have to reduce
Velocity A= final moles-initial moles Second
Velocity
A= 4mol-2mol
10 seconds
= 0.2 mol/second
If we talk about the rate of increase, it means that it is almost the same, we calculate the difference between the initial mole and the final mole, after that divided by time.
Velocity C= final moles-early moles Time
If it’s still difficult, the flour that was a quarter or 250 grams earlier, for example after 30 seconds there are 125 grams left, the original two eggs are left with 1.
Are the flour and eggs less? Well let’s say the rate of reduction of wheat is 125 grams per 10 seconds while eggs are 1 grain per 10 seconds
Meanwhile, if after 10 seconds there is 130 grams of dough formed, it means the rate of increase of the dough is 130 grams per second,
You can understand why A and B are called the speed of reduction while C is the speed of increase, ok smart sip everyone!
In the future, we will replace A, B and C all so that it feels more chemical.
Reader can learn chemical equilibrium as well as other grade 11 chemical materials in the SMA/MA Grade 11 Chemical Science book by Tine Maria Kuswati and Sri Rahayu Ningsih below.
Basic Concepts of Chemical Equilibrium
Let’s look again at the formation reaction of C from A and B
A + B ↔ C
When the rate of reduction of A and B is equal to the rate of increase of C, then this condition is called an equilibrium state.
Although it may only be for a moment, it seems that the reaction stops when the rate of reduction and the rate of formation are the same.
But this is the macroscopic level (to the naked eye), yes, actually the microscopic level, aka molecular reaction continues.
Reader can also learn another basic chemical concept namely the environment in the book Basic Concepts of Environmental Chemistry Edition 3 which discusses the influence of environmental factors on organisms and dead things around them.
Factors Affecting Equilibrium
If the reaction is already in equilibrium, will the reaction continue like that? can that balance be disturbed? Ariel Noah said in his song “Tak ada yang abadi”, as well as balance
Well, the one who thought this far was Henri Louis Le Chatelier (1850-1936). He has a theory that:
“When an action (action) is performed against an equilibrium, the system will have a reaction that tends to reduce the influence of the action”
The way he can slide to the left is the reactant direction or slide to the right is the product direction.
Yes, the analogy is this;
If someone has been dating/married for a long time, and they are equally compatible, suddenly someone tries to disrupt the relationship of either woman/man, then there will be an effort to restore the harmony of their relationship, right? Ga may be left, as is the equilibrium reaction.
So what are the factors that affect the shift in equilibrium?
1. Volume
If the volume is increased, then the equilibrium will shift in the direction of the reaction that has a larger coefficient.
On the other hand, if the volume is decreased, then the equilibrium shift will shift in the direction of the reaction that has a smaller amount of coefficient.
Example: Nitrogen (N2) and hydrogen (H2) react to form ammonia (NH3)
N2(g) + 3H2(g) ↔2NH3(g)
If the volume is added, then the equilibrium shift will shift towards the reaction that has a larger number of coefficients
We calculate the reaction coefficient.
The sum of the left reaction coefficients is
1 N2(g) + 3 H2(g)
N2=1 H2= 3
so total reaction coefficient= reaction coefficient N2 + reaction coefficient H2= 1+3=4
Right coefficient
2NH3
NH3= 2
Left reaction coefficient=4
Right reaction coefficient=2
Left reaction coefficient > Right reaction coefficient
Then the equilibrium will shift to the left
2. Stress
If the pressure is increased then the equilibrium shifts to a small coefficient
on the contrary If the pressure is increased then the equilibrium shifts to a large reaction coefficient
Example:
Nitrogen (N2) and hydrogen (H2) react to form ammonia (NH3)
N2(g) + 3H2(g) ↔2NH3(g)
If pressure is added, then the equilibrium shift will shift towards the reaction that has a smaller number of coefficients
We calculate the reaction coefficient
The sum of the left reaction coefficients
1 N2(g) + 3 H2(g)
N2=1 H2= 3
so total reaction coefficient= reaction coefficient N2 + reaction coefficient H2= 1+3=4
Right coefficient
2NH3
NH3= 2
Left reaction coefficient=4
Right reaction coefficient=2
Right reaction coefficient< Left reaction coefficient
Then the equilibrium will shift to the right
3. Temperature
If the temperature is increased then the equilibrium will shift towards the formation of endothermic absorbing compounds.
The characteristic of this reaction is the price of ∆H is positive (+). ∆H is the price of heat or heat change
If the temperature is lowered then the equilibrium will shift towards the formation of compounds that release exothermic heat. The characteristic of this reaction is the value of ∆H is negative (-)
To imagine the reaction like this:
N2(g) + 3H2(g) ↔2NH3(g) ∆H=-90 kJ
The formation reaction of NH3 is exothermic (∆H is negative yes)
The opposite of an exothermic reaction is an endothermic reaction. If the reaction of forming NH3 is exothermic, then the reaction of B2 and h2 is endothermic.
So if the temperature is raised, the reaction will shift towards N2 and H2 because they are endothermic
4. Concentration
If the concentration of elements/compounds in one of the sections is increased, then the equilibrium will shift in the opposite direction
For example: N2(g) + 3H2(g) ↔ 2NH3(g)
If N2 or H2 is added, then the equilibrium will shift towards NH3 (right/ product)
On the other hand if NH3 is added, then the equilibrium will shift towards N2 or H2 reactant (left)
N2(g) + 3H2(g) ↔ 2NH3(g)
If the concentration of an element/compound in one of the segments is reduced, then the equilibrium will shift towards itself
For example, if
we reduce N2 or H2, then the equilibrium will shift towards N2 and H2 (left)
On the other hand, if NH3 is reduced, then the equilibrium will shift towards NH3 (right)
Quantities and Chemical Equilibrium Formulas
Because the equilibrium reaction applies to a back and forth reaction that never ends, there is a constant value K or the equilibrium setting that will be obtained from the equilibrium reaction. K is obtained by comparing the condition of the arrow with the product.
K = Reactant products
There are two values of K calculated for the equilibrium reaction, namely the concentration setting (Kc)
and the pressure setting (Kp)
Kc
The price of Kc is only affected by compounds in the form of solution (aq) or gas (g) only.
The formula for calculating Kc is as follows:
Suppose there is a reaction:
2A(g) + 3B(s) ↔ A2B3(aq)
Because B is in the form of a solid alias solid, then B is not included in the K equation
Kp
The price of Kp is only affected by compounds/elements with gaseous form.
Formulation of the Kp equation:
For example:
observe the following reaction
2A(g) + 3B(aq) ↔ AB3(g)
So for the Kp equation, B will not enter the equation because of the (aq) solution.
So the Kp equation is like this:
Examples of Chemical Equilibrium Questions
Various other high school chemistry questions can be found by Reader in the book Sma/Ma/Smk Kls.X-Xi-Xii Smart Answering Chemistry Questions which are very accurate to be used as a reference that you can get on Sinaumedia.
Well, after we have read in theory, let’s learn to calculate the equilibrium setting yes:
Kc
Example Question 1:
at a volume of 1 liter
2A(g) + 3B(aq) ↔ A2B3(aq)
If at equilibrium there are 2 moles of A reacting with 2 moles of B to produce 2 moles of A2B3 determine the price of KC!
Well, for equilibrium in the reaction, we write down the initial condition that we call m (first), then we also add the condition r (reaction) and the condition at equilibrium (s)
For the example of the question above, it is known that the reaction is already in equilibrium, so we can directly write in the condition s, then we calculate the concentration and after that it can be entered into the Kc formula.
Here is the discussion of the question:
Let’s try another question
Example question 2:
If 3 moles of Nitrogen is reacted with 5 moles of Hydrogen then at equilibrium 2 moles of Ammonia is obtained according to the equation:
N2(g) + 3H2(g) ↔ 2NH3(g)
Determine the price of Kc
Discussion:
We write the reaction and set the initial conditions, reaction, and equilibrium.
Then we fill in the moles of N2, H2 according to the known question. Filled at the beginning or row m N2 by 3 mol and H2 by 5 mol. Then NH3 is filled with the equilibrium moment condition or s which is known in the problem 2 mol.
The moles of NH3 when the condition is in equilibrium and the reaction is the same, because NH3 (please, remember the batter earlier) initially NH3 is not there.
Remember NH3 as a product undergoes an increase!
For N2 and H2 in the reaction conditions, moles can be found as follows:
Mole N2 = reaction coefficient N2 x mol NH3
Reaction coefficient NH3
= 1 x 2 mol
2
Mole N2 = reaction coefficient H2 x mol NH3
Reaction coefficient NH3
= 3 x 2 mol
2
= 3 moles
After that, the content of the equilibrium condition for N2 and H2 is
(initial moles – moles during the reaction)
Here is the presentation:
Because for Kc what is needed is molarity, where to find Molarity we have to divide moles by liters
M = mol
Liters
Then we calculate M for N2,H2 and NH3
After that we can find Kc:
Kp
Example question
on a volume of 1 liter
2A(g) + 3B(aq) ↔ A2B3(aq)
If at equilibrium there are 2 moles of A reacting with 2 moles of B to produce 2mol A2B3, determine the value of Kp if the total pressure is 12 atm
The work to find Kp is almost the same as Kc in the first few steps, namely,
First we write the reaction and pair the initial conditions, reaction, and equilibrium
Then we fill in the moles of N2, H2 according to the known question. Filled in the first condition or line (m). N2 by 3 moles and H2 by 5 moles.
Then because NH3 is known at equilibrium then we fill in the condition at equilibrium (s) as much as 2 moles.
Moles of NH3 at equilibrium and the reaction is the same, because NH3 is initially absent. For N2 and H2, how to find moles is as follows:
Mole N2 = reaction coefficient N2 x mole NH3
reaction coefficient NH3
= 1 x 2 mol
2
Mole N2 = reaction coefficient H2 x mole NH3
reaction coefficient N2
= 3 x 2 mol
2
= 3 mol
After that, fill in the equilibrium conditions for N2, H2 and NH3
To calculate Kp, the next step is to calculate the total moles at equilibrium.
After getting the total mole we find the partial P or P of each gas.
The trick is to compare the desired reaction coefficient with the known reaction coefficient and then multiply the total moles.
Here’s how it works:
If the respective P prices have been obtained, we can calculate Kp.
Examples of Chemical Equilibrium in Everyday Life
What equilibrium reactions exist in everyday life? Of course there is, what is it?
1. Blood pH regulator
In the body, the blood pH should be maintained around 7.4. What will protect it is the buffer solution, which is carbonic acid H2CO3.
Blood plasma has carbon dioxide gas CO2. CO2 gas forms a conjugate acid-base pair between carbonic acid (H2CO3) and hydrogen ions (H+) to maintain pH.
C02(g) + H2O(ℓ) ↔ H2C03(aq)
If the blood is alkaline, the amount of H+ ions will decrease due to the binding of alkaline OH- ions, resulting in the balance shifting to the right.
But if the blood is acidic, the equilibrium shifts to the left because the H+ ions from the acid add to the concentration of H+ ions in H2CO3
So if the pH of the blood is slightly disturbed, it can be dangerous for the body because it interferes with the binding of oxygen
2. Oxygen cycle in the body
In the body, Oxygen is transported and bound by hemoglobin in the blood. This process takes place in this equilibrium reaction:
Hb(aq) + O2(aq) ↔ HbO2(aq)
Oxygen is transported by the blood to the lungs. Over time, the amount of oxygen in the blood increases.
Well, in the lungs the balance shifts to the right. The equilibrium will shift to the left if oxygen is present in the network.
The balance to the left releases oxygen that is used for the combustion process.
3. Photosynthesis Process
As we know, plants get food from the process of photosynthesis.
The reaction:
6CO₂ + 6H2O ↔ C6H12O6 + 6O2.
Photosynthesis in green plants, the breathing process (respiration) in animals and humans is also an equilibrium reaction.
The equilibrium reaction pointing to the right is the photosynthesis reaction.
When the equilibrium shifts to the right of the reaction, the amount of oxygen will increase.
This oxygen will be used by humans and animals to breathe or the respiration process.
When the equilibrium shifts to the left, the respiration process will take place quickly, releasing CO2 gas. CO2 gas is further used by plants for the photosynthesis process.
This process continues continuously forming a cycle until in nature there is an equilibrium between O2 gas and CO2 gas.
Well that was a discussion about chemical equilibrium. Hope this explanation can make you understand