Question

A mixture of three gases P (density 0.90), Q (density 0.178) and R (density 0.42) is enclosed in a vessel at the constant temperature. When equilibrium is established:
(A) The gas P will be at the top of the vessel.
(B) The gas Q will be at the top of the vessel.
(C) The gas R will be at the top of the vessel.
(D) The gases will mix homogeneously throughout the vessel.

Answer 1

Hint: To answer this we must know that equilibrium is the state where no change is taking place between the reactants or the products. When we mix gases in a closed vessel, equilibrium can be reached and no reaction is taking place between them. The mixture will take up the volume of the closed vessel.

Complete step by step solution:
To answer this, firstly let us discuss what equilibrium is.
Equilibrium is a state where no change is taking place. There are certain factors that affect the equilibrium of gases.
The first factor is temperature. Increasing or decreasing temperature affects equilibrium by increasing the kinetic energy of the gas molecules.
The next factor is pressure. When we increase the pressure, the equilibrium is shifted towards the side with a lesser number of molecules of gases and when we decrease the pressure, the equilibrium is shifted towards the side with a higher number of gas molecules.
Equilibrium is also affected by the concentration of the reactants and products formed.
Now let us see the question given to us.
Here we have three gases with different densities. The vessel is closed i.e. it is a closed system and the temperature is also constant. The gases will take up the volume of the vessel.
So, when equilibrium is established, the gases will be mixed homogeneously throughout the vessel irrespective of their densities.

Therefore, the correct answer is option (D) the gases will mix homogeneously throughout the vessel.

Note: We often use the term equilibrium for chemical reactions where the reactants and the products stay at a constant state. It is not necessary for the reactant to be equal to the product in order for it to be at equilibrium. We can obtain equilibrium by carrying out a reaction in a closed container where neither the reactant nor the product is lost.