The effect of addition of helium gas to the following reaction in equilibrium state, is : \(PCl _5( g ) \rightleftharpoons PCl _3( g )+ Cl _2( g )\)
The effect of addition of helium gas to the following reaction in equilibrium state, is : \(PCl _5( g ) \rightleftharpoons PCl _3( g )+ Cl _2( g )\)
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Adding an inert gas at constant volume doesn’t affect the equilibrium. At constant pressure, the equilibrium shifts towards the side with more gas molecules.
- addition of helium will not affect the equilibrium.
the equilibrium will shift in the forward direction and more of\(Cl _2\) and \(PCl _3\) gases will be produced.
the equilibrium will go backward due to suppression of dissociation of \(PCl _5\)
helium will deactivate \(PCl _5\) and reaction will stop.
The Correct Option is B
Solution and Explanation
Adding an inert gas like helium at constant volume does not affect the equilibrium position. This is because the partial pressures of the reactants and products remain unchanged. However, if helium is added at constant pressure, the volume of the system will increase. This decrease in concentration affects all gaseous products equally and therefore it shifts the equilibrium towards the side with more gas molecules, according to Le Chatelier’s principle. In this case, that is the forward direction, producing more Cl2 and PCl3.
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Concepts Used:
Equilibrium
An equilibrium represents a state in a process when the observable properties such as color, temperature, pressure, concentration etc do not show any change.
The word equilibrium means ‘balance’ which indicates that a chemical reaction represents a balance between the reactants and products taking part in the reaction. The equilibrium state is also noticed in certain physical processes such as the melting point of ice at 0℃, both ice and water are present at equilibrium.
In the case of physical processes such as the melting of solid, dissolution of salt in water etc., the equilibrium is called physical equilibrium while the equilibrium associated with chemical reaction is known as chemical equilibrium.
Equilibrium in Chemical changes
The chemical equilibrium in a reversible reaction is the state at which both forward and backward reactions occur at the same speed.
The stage of the reversible reaction at which the concentration of the reactants and products do not change with time is called the equilibrium state.
Read More: Calculating Equilibrium Concentration
Types of Chemical Equilibrium
There are two types of chemical equilibrium:
- Homogeneous Equilibrium
- Heterogeneous Equilibrium
Homogenous Chemical Equilibrium
In this type, the reactants and the products of chemical equilibrium are all in the same phase. Homogenous equilibrium can be further divided into two types: Reactions in which the number of molecules of the products is equal to the number of molecules of the reactants. For example,
- H2 (g) + I2 (g) ⇌ 2HI (g)
- N2 (g) + O2 (g) ⇌ 2NO (g)
Reactions in which the number of molecules of the products is not equal to the total number of reactant molecules. For example,
- 2SO2 (g) + O2 (g) ⇌ 2SO3 (g)
- COCl2 (g) ⇌ CO (g) + Cl2 (g)
Heterogeneous Chemical Equilibrium
In this type, the reactants and the products of chemical equilibrium are present in different phases. A few examples of heterogeneous equilibrium are listed below.
- CO2 (g) + C (s) ⇌ 2CO (g)
- CaCO3 (s) ⇌ CaO (s) + CO2 (g)
Thus, the different types of chemical equilibrium are based on the phase of the reactants and products.
Check Out: Equilibrium Important Questions