Le Chatelier's Principle: Changes in concentration and pressure in dynamic equilibrium

len Alfred Ajibola - 09th November, 2020 @ 12:38 PM

Topics in Chemistry

Gas laws in chemistry Charles's law explained Calculation questions on Charles's law Examples of Charles's law in real life Boyle's law explained Calculation questions on Boyle's law Examples of Boyle's law in real life Summary on the kinetic molecular theory of gases Postulates of kinetic theory of gases Avogadro's number explained with worked examples Mole and Avogadro's Number explained Le Chatelier's Principle: Changes in concentration and pressure in dynamic equilibrium Chemical Equilibrium: Dynamic Equilibrium in Chemistry Static and Dynamic Equilibrium explained with their differences Chemistry Scheme of Work, SS1, First Term Chemistry Scheme of Work, SS1, Second Term Chemistry Scheme of Work, SS1, Third Term Compounds in Chemistry: Characteristics of Compounds Types of Mixture: Homogenous and Heterogeneous Mixtures What are mixtures? Characteristics of mixtures

Academic Questions in Chemistry

Please click here to see all Questions and Answers

With regards to redox reactions, which of the following statement is wrong?

  • A. Redox reaction are examples of chemical change

  • B. Reduction is the gain of electron

  • C. Substances that donates election during chemical reaction are termed reductants

  • D. Oxidizing agents are always reduced in chemical reactions

  • E. Oxidation occurs at the cathode in electrolysis

  • F. Hydrogen is a reducing agent

In chemistry, physical change is associated only with the rearrangement of molecules while the internal composition of the substance remains the same.

  • A. True

  • B. False

_____ electron(s) is a term that describes the number of electron(s) in the outermost shell of an atom.

  • A. Outer

  • B. Excess

  • C. Valence

  • D. Positive

  • E. Negative

  • F. Last

_____ is the negative electrode in electrolysis.

  • A. Anode

  • B. Anion

  • C. Cathode

  • D. Cation

  • E. Ion

  • F. Electrolyte

Electrovalent Bond - Len Academy

The above diagram shows the _____ type of bond.

  • A. Covalent

  • B. Polar covalent

  • C. Coordinate covalent

  • D. Metallic

  • E. Van dear walls

  • F. Ionic

 Metals are referred to as _____ in their impure state.

  • A. Diluted

  • B. Consecrated

  • C. Coloured

  • D. Ores

  • E. Stained

  • F. Strained

Metals generally have the quality to shine, glow, sparkle, glitter, reflect light and be polished. This characteristic of metals is termed _____.

  • A. State

  • B. Ductility

  • C. Luster

  • D. Malleability

  • E. Hardness

  • F. Inflorescence

The _____ spectrometry experiment conducted on isotopic elements gave a confirmation for the existence of isotopes.

  • A. Mole

  • B. Volume

  • C. Weight

  • D. Number of moles

  • E. Mass

  • F. Amount of substance

Le Chatelier’s Principle:

A system in chemical equilibrium can be controlled or altered in an attempt to favour either the forward or backward reaction; that is, the equilibrium position. Some of these changes include a change in concentration, pressure and temperature. The dynamics of these changes will be explained in this article.

You can read on the concept of dynamic equilibrium here.

According to French chemist - Henry Louis Le Chatelier, an altered system (in terms of changing its concentration, pressure and temperature) will adjust itself by shifting equilibrium to the right or left in order to counteract or undo the change. This is the concept of Le Chatelier’s principle.

Le Chatelier’s Principle state that when a system in dynamic equilibrium is subjected to any change or alteration, the system will adjust itself in order to counteract or revert the applied change.


Factors that affect equilibrium

Below are explanations on some factors that can change or alter equilibrium:


  • A change in concentration

The equation below will be used to explain how a change in concentration affects dynamic equilibrium according to Le Chatelier’s principle:

2SO2(g) + O2(g) ⇌ 2SO3(g)

From the above equation, if the concentration of either or both reactants (2SO2(g) + O2(g)) are increased, the forward reaction will be favoured, thus shifting equilibrium to the right. As a result, more reactants are available for usability and this ultimately favours the forward reaction because more products are formed (and the amount of reactants decreases appropriately).

You can read on the differences between static and dynamic equilibrium here.

Similarly, if the concentration of the product (2SO3(g)) is increased, the backward reaction is favoured as equilibrium shifts towards the formation of reactants. This indirectly increases the amount (or concentration) of the reactants; thus consequently reverting the system into dynamic equilibrium with time.

In summary, if the concentration of the reactants (2SO2(g) + O2(g)) increases or those of the products (2SO3(g)) decreases then:

  • The formation of more products will be favoured.

  • The added reactants are converted to more SO3.

  • The reaction's equilibrium shift towards the right.

  • Forward reaction is favoured.

If the concentration of the reactant decreases or those of the product increases:

  • The formation of more reactants will be favoured.

  • The added products (S03) will be converted to SO2 and O2 respectively.

  • The reaction's equilibrium will shift towards the left.

  • Backward reaction is favoured.

In practical terms, if the cost of 2SO3(g) is high while those of the reactants are relatively cheap, then more 2SO3(g) can be economically produced by adding more of the cost friendly reactants to the reaction.

Change in Concentration - Dynamic Equilibrium - Len Academy

It is noteworthy to state that a change in the concentration of the reactants or products neither increases or decreases the equilibrium constant. It only shifts the position of equilibrium (either to the right or left). This is because the system counteracts the change by adjusting itself according to Le Chatelier’s principle. For this reason, the equilibrium value will always remain constant regardless the amount of changes made on the concentration of the reactants, products or both.

You can read on salts in chemistry here.


  • A change in pressure

A change in pressure only becomes effective when the reacting system includes at least one gaseous substance. This is true because pressure is effected when gas molecules hit the walls of their container (due to their random motion).

The more gaseous molecules we have inside a container, the higher its pressure. The less gaseous molecules, the lesser the pressure it effects inside its container.

Please read more on gases and their characteristics here.

A change in pressure will only shift the position of equilibrium, and this will depend on where the change emanates from; but eventually, the system reverts the change, thus bringing it back to a state of dynamic equilibrium in fulfillment to Le Chatelier’s principle.

Just as similar to 'change in concentration', a change in pressure does not alter the value of equilibrium constant.

Consider the equation below:

2SO2(g) + O2(g) ⇌ 2SO3(g)

If the pressure of the reactants (2SO2(g) + O2(g)) increases or those of the products (2SO3(g)) decreases, then:

  • The formation of more products will be favoured.

  • The added reactants are converted to SO3.

  • The reactions equilibrium shifts towards the right.

  • Forward reaction is favoured.

If the pressure of the reactants decreases or those of the product increases, then:

Note: Increasing the pressure on a gaseous reaction shifts the position of equilibrium towards the side with fewer molecules. Conversely, decreasing the pressure on a gaseous reaction shifts the position of equilibrium towards the side with more molecules. This is shown in the image below:

Change in pressure - Dynamic Equilibrium - Len Academy

The explanations so far on 'changes in concentration and pressure' on equilibrium is quite superficial. Le Chatelier’s principle only gives us a quick summary of the reaction procedure. The ideal explanations on equilibrium shifts (when changes are made on concentration, pressure and temperature) are explained in a mathematical expression via the equilibrium constant 'K'.

Kindly share this article via the links below:


Click here to read on Len Academy Smart School Software. Contact us for a standard website at an affordable price

Please click here to follow Len Academy on Google News.

Please Register here or Login here to contribute to this topic by commenting in the box below.

Amazing facts in Chemistry

Plastic and Glass can decompose, but not in our lifetimes. It takes an average time of 450 years for plastics to decompose. As for the decomposition of glasses, it takes about 4,000 years

The only letters that failed to appear on the periodic table are letters:

J     &     Q

Gold and copper are the only two non-silvery colored metals.

Copper is the only metal that is naturally antibacterial. For this reason, some children utilize 'copper water bottles' in schools

Water freezes faster when it’s warm than when it’s cold

Most element in their pure state exists physically in different forms. For instance, pure carbon can exist as both diamond and graphite. This phenomenon is called allotropy

If you pour a handful of salt into a full glass of water, the water level will go down rather than overflowing the glass.

Similarly, if you mix half liter of water and half litre of alcohol, the total volume of the liquid will be les than one litre

Notable points in Chemistry

Periodic Table - Len Academy

The periodic table, also called periodic table of elements or Mendeleev's table, is a table that shows an organized arrangement of the 118 chemical elements according to their atomic number.

Out of the 118 elements; elements 1 - 94 are present in nature while elements 95 - 118 are synthesized artificially.

The manner at which elements are arranged on this table reveals some similarities in their electronic configurations and chemical properties.

Please read on the periodic table of elements here.

A compound composed of iron (Fe) and oxygen (O) was analyzed and found to contain 69.94% iron and 30.06% oxygen. Find the empirical formula of the compound. (Molar mass of Fe=55.85, O=16)

  • Solution:

Step 1: Identify the given parameter from the question.

  • Fe = 69.94%,   O = 30.06%.

  • Empirical formula = Fe?O?


Step 2: Convert the percentages to gram. (just attribute grams to the %).

  • 69.94% = 69.94g while 30.06% = 30.06g


Step 3: To get the mole ratio of each element, convert the gram to moles using the formula (mole = mass/molarmass). Please merorize this formula because we always work with moles in emperical formula.

  • Mole of Fe: 69.94/55.85 = 1.252mol

  • Mole of O: 30.06/16 = 1.879mol


Step 4: Divide both sides by the smallest mole ratio.

  • Iron has the smallest mole ratio in our case, therefore: 1.252/1.252 = 1,    1.879/1.252 = 1.5

  • We now have the formula = Fe1O1.5


Step 5: Multiply each of the moles by the smallest whole number that will convert each into a whole number. (In our case, the number '2' is the smallest whole number that will make '1.5' and '1' whole numbers when multiplied by it.

  • For iron (Fe), we will have 1 x 2 = 2

  • For oxygen (O), we will have 1.5 x 2 = 3


Step 6: Write the empirical formula.

  • The empirical formula= Fe2O3

  • Iron(III)tetraoxosulphate(VI)

In chemistry, hydrocarbons can be classified as either aliphatic or aromatic. Recently, both classifications of hydrocarbon were based on their structure rather than their origin.

Aliphatic hydrocarbons are put into three main groups according to the types of bonds they possess. These are:

  1. Alkanes

  2. Alkenes

  3. Alkynes

They are shown in the image below:

Alkanes, Alkenes and Alkynes - Len Academy

It's important to note the followings:

  • Alkanes have single bonds (only) in their structures.

  • Alkenes always have a carbon-carbon double bond present in their structure.

  • Alkynes always have a carbon-carbon triple bond present in their structure.


Aromatic hydrocarbons are classified into:

  • Arenes: They contain benzene ring as a structural unit. Below is the structure of a benzene ring.

Benzene Ring - Len Academy


  • Nonbenzenoid aromatic hydrocarbons: They possess special stability but lack a benzene ring as a structural unit.

Organic chemistry is the study of carbon and it's compounds.

Carbon is the focus of organic chemistry because it has a wide chemical diversity in the sense that it can combine with other carbon atoms to form a long chain of carbon molecule. This ability and process whereby carbon can form a long chain of itself is called catenation.

Please read the introduction to organic chemistry here

A major challenge encountered when calculating molecular mass is that it becomes difficult or impossible to calculate especially when the relative molecular mass of large molecules, polymers and macromolecules are involved.

Examples of large molecules (with indefinite molecular masses) include carbohydrates, cellulose and complex sugars.

The large molecules (above) have no specific chemical formula throughout their volume.

Please read more on carbohydrates and sugars here

Understand that Relative Molecular Mass prove to be useful only when we calculate substances with small and definite molecular sizes. This was proven through the modifications of Dalton's atomic theory.

Please read on Dalton's atomic theory and its modifications here.