A reversible chemical reaction is said to be at DYNAMIC equilibrium when
Athe forward reaction has stopped and only the reverse reaction proceeds
Bthe rates of the forward and reverse reactions are equal, while both reactions continue
Cthe concentrations of all reactants and products are equal
Dthe temperature of the system is at absolute zero
Answer & Solution
Correct answer: B. the rates of the forward and reverse reactions are equal, while both reactions continue
1. NCERT §6.2 defines dynamic equilibrium: at equilibrium, BOTH the forward AND reverse reactions continue to occur, but their RATES are equal — so the macroscopic concentrations of all species remain constant.
2. The system is DYNAMIC because microscopic interconversion never stops; it's at equilibrium because the net rate of change is zero.
3. Option A describes the OBSOLETE static-equilibrium picture (one reaction "finishes"), which is not what is observed experimentally (NCERT's "Student's Activity" box on radioactively-labelled iodine confirms continuous interconversion).
4. Option C confuses equal RATES with equal CONCENTRATIONS — these are usually different. Option D is unrelated.
_Source: NCERT Class 11 Chemistry, Ch 6 "Equilibrium", §6.2 (Equilibrium in Chemical Processes — Dynamic Equilibrium), p. 4–5._
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