The number of correct statement/s involving equilibria in physical processes from the following is ________
(A) Equilibrium is possible only in a closed system at a given temperature.
(B) Both the opposing processes occur at the same rate.
(C) When equilibrium is attained at a given temperature, the value of all its parameters became equal.
(D) For dissolution of solids in liquids, the solubility is constant at a given temperature.

Solution

Chemistry ma’am · 2 steps

At equilibrium, the measurable properties stop changing. They do not become equal to each other.

1. What equilibrium means. In a physical equilibrium, two opposite processes, such as evaporation and condensation, keep running at the same rate. Nothing looks like it is changing, but the processes have not stopped.

   Statement	Verdict	Reason
   (A) Only in a closed system at a given temperature	Correct	In an open system vapour escapes, so the reverse process cannot keep pace.
   (B) Opposing processes at the same rate	Correct	This equal rate is what makes the equilibrium dynamic.
   (C) All parameters become equal	Wrong	Parameters such as vapour pressure and concentration become constant, not equal to one another.
   (D) Solubility constant at a given temperature	Correct	A saturated solution is in equilibrium with the undissolved solid, so solubility is fixed at that temperature.

2. So. Statements (A), (B) and (D) are correct, so the number of correct statements is 3.

The common slip: 4. Reading statement (C) as correct gives 4. At equilibrium the parameters become constant, not equal to each other.

The idea to keep. At equilibrium, look for the word constant, not equal. Rates of the two opposing processes are equal. Amounts, pressures and concentrations only stop changing.

Answer from the NTA final answer key. Solution by PrepWiser.