Chemical Equilibrium Definition

Steps:

• Examine the reaction at equilibrium: forward and reverse processes occur but net change is zero.
• Apply equilibrium principle: concentrations stabilize when reaction rates balance.
• Evaluate options against rate equality and reaction properties.
• Confirm B matches the core equilibrium condition.

Why B is correct:

• Dynamic equilibrium requires forward and reverse rates to be equal, per Le Châtelier's principle and rate law definitions.

Why the others are wrong:

• A: Equilibrium concentrations do not change with time; they remain constant.
• C: Positive ΔH (+170 kJ/mol) means forward reaction is endothermic, absorbing heat.
• D: Both sides have two molecules (N₂ + O₂ = 2; 2NO = 2), so equal.

Final answer: B