Chemistry · Grades 10–12
Dynamic chemical equilibrium
Do not confuse equal rates with equal amounts.
Learn the idea
Dynamic
At equilibrium the forward and reverse rates are equal, while both directions continue.
Concentrations
Macroscopic concentrations remain constant under unchanged conditions, but need not be equal to one another.
Constant
For a specified reaction, the equilibrium constant depends on temperature.
Expression
Write the appropriate activities; simple school concentration expressions often omit pure solids and liquids.
Worked examples
At dynamic equilibrium, what is equal?
Equal opposing rates maintain constant macroscopic composition.
The forward and reverse rates.
Do molecules stop reacting at equilibrium?
The equilibrium is dynamic.
No; both reaction directions continue.
Check your understanding
For A ⇌ B with Kc = [B]/[A], [B] = 0.60 and [A] = 0.20 mol/L. Calculate Kc.
What changes the equilibrium constant of a specified reaction in the usual school model?
- Changing the ink color of the equation.
- Changing temperature.
- Adding a catalyst at the same temperature.
Why is constant concentration not the same as no reaction?
Answers and marking notes
Answers and marking notes
- 3
0.60/0.20 = 3 for this idealized expression.
- Changing temperature.
Temperature affects the equilibrium constant.
- Equal opposing reaction rates can maintain a constant net amount.
A macroscopic steady value can hide ongoing molecular events.
Further reading and review references
These are reference links, not copied exercises, institutional endorsement or proof of independent review.
Independent educational review required. Grade bands are approximate; these are not officially aligned curricula.