Le Chatelier's Principle and the Effect of Variables:

Henry Le Chatelier, a French Chemist, in 1884 studied the effect of variables like concentration, temperature and pressure on the large number of systems in equilibrium.At the end, he summed up his conclusions in the form of generalizations, known as Le-Chatelier Principle.It is sometimes also called as principle of equilibrium.

Definition:

According to Le Chatelier principle,"when a system in equilibrium is disturbed by changing variables like temperature pressure or concentration, then the system will tend to adjust itself in such a way that it minimizes the effect of that change as far as possible."

For example, if the temperature of a system is increased, the system will shift in the endothermic direction to absorb the excess heat.

This principle has common applications in the field of physical chemistry and chemical equilibria. Some of the most common applications of the principal are as follows:

1. Production of Ammonia:

Production of ammonia has significant importance both in industry and agriculture.

Massive amount of ammonia is used for the production of fertilizers such as urea and ammonia nitrate etc.

Their reactions are explained below.👇

Synthesis of ammonia is performed by Haber's process by taking a mixture of nitrogen and hydrogen in 1:3 ratio by the volume passed through iron coil lined by the finely divided iron to maintain it at fixed temperature(450°C).

That's an exothermic reaction.

N2(g) + 3H2(g) ⇌ 2NH3(g)

And the its value of Kc can be determined by a simple derivation as shown in picture below.👇

(a) Effect of Pressure:

In equilibrium position, the effect of the change in pressure on reaction mixture is almost negligible in solids and liquids. However, in the case of gasses, a small change in pressure has significant effect on the state of equilibrium.

In Haber's process in ammonia, the forward reaction is increased by decrease in volume in equilibrium. If the pressure of system increases then the volume increases, therefore according to Le Chatelier's principle, the reaction will try to move in the direction that favours the decreases in volume. In short, the formation of ammonia will be favoured in high pressure or low volume.For this reason the pressure of a gas in Haber's process is kept as 200-600atm.

(b) Effect of Temperature:

The temperature change in a system is also notable factor its equilib state. In this reaction ilaaj about of heat is produced, so it will be an exothermic reaction.

N2(g) + 3H2(g) ⇌ 2NH3(g)

When the temperature is increased then reaction moves in receiver direction because higher temperature promote the degeneration of ammonia. Therefore,in order to get the high yield of a ammonia,t reaction is performed at lower temperature i.e. 450°C - 500°C.

And the pressure is kept between 200 to 600 atm.

In this way, we can get the higher yield of ammonia.

(c) Effect of Change in Concentration:

Besides pressure and temperature, the concentration of components is also a major factor in maintaining equilibrium state.

Now if the concentration of one component is increased then according to Le Chatelier principle the system will try to adjust is self as forest that change of concentration.

Similarly, a decrease in the concentration of a component would give rise the production of more of that substances.

To illustrate it, we suppose that N2 or H2 is added to the equilibrium mixture than more of ammonia is formed, according to the principle.

The reason behind the fact is that the addition of N2 or H2 shifts the equilibrium in that way which proceeds with a decrease in the number of these components. Ultimately, the addition of N2 and H2 will result in the more yield of ammonia.

2. Formation of Sulphur Trioxide

When SO2 reacts with oxygen then according to equation

2SO2(ᵍ) + O2(ᵍ) ⇌ 2SO3(ᵍ)

Where ∆H=-189KJ/mol

It takes place with the decreasing volume and also it is the exothermic reaction.

An increase in the concentration of either reactant promotes SO3 formation.

In the same way the increase in pressure also promotes the formation of SO3 but an increasing temperature can decrease the in formation of SO3 because of dissociation of SO3 at higher temperature.

Thus the SO3 formation vis promoted by

(i) high concentration of O2 and SO2

(i) low temperature, and

(i) high pressure

3. Formation of Nitric Oxide

Suppose that NO is formed by in the reaction of N2 and O2 by Birkland-Eyde process

N2 + O2 ⇌ 2NO ∆H=180KJ/mol

no change in volume occurs to information of nitric oxide from N2 and O2. And it is an exothermic reaction.

Therefore, there will be no change pressure as well. Since the reaction is exothermic thereby, with the rise in temperature, the equilibrium will shift in the direction in which heat is absorbed.

Consequently, the yield of NO will become higher by increasing the temperature.

Besides this, it is also interesting to know that the increase in the concentration of either of the component of this reaction will favour the formation of NO.

Frequently Asked Questions-FAQs

1. Explain what is Le Chatelier's principle?

According to Le Chatelier's principal,"when a reaction at equilibrium is disturbed by changing the variables like temperature, pressure and concentration of components, then the direction will tend adjust itself in such a way to nulify or minimize the effect of that change as far as possible.

2. What are the three main variables in Le Chatelier's principle?

The three main variables which affect in Le Chatelier's principle include pressure, temperature and concentration of components. Besides this, the catalyst employed in a reaction also plays a vital role in the equilibrium mixture.

3. How Le Chatelier's principle used in our daily lives?

The process of breathing in our bodies is its common example of Le Chatelier's principle.To maintain a delicate balance of gases in the bloodstream, this principle helps to explain how this balance is maintained. When we inhale, we take in oxygen, which reacts with hemoglobin in our red blood cells to form oxyhemoglobin. As the oxygen concentration in the bloodstream increases, Le Chatelier's Principle tells us that the equilibrium position will shift in the opposite direction, favoring the release of oxygen from oxyhemoglobin to the tissues.

Le Chatelier's Principle and the Effect of Variables

Le Chatelier's Principle and the Effect of Variables:

Definition: