Dynamic equilibrium
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All 12 Flashcards — Dynamic equilibrium
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Question
What is a reversible reaction?
Answer
A reaction that can go in **both directions** — reactants can form products and products can re-form reactants. Shown with the **⇌** symbol.
Question
Define dynamic equilibrium.
Answer
The state, in a **closed system**, where the **forward and reverse reactions occur at equal rates**, so the **concentrations of reactants and products stay constant**.
Question
Why is equilibrium called 'dynamic'?
Answer
Because **both** the forward and reverse reactions are **still happening** — the reaction has **not** stopped; the opposite changes simply cancel out.
Question
At equilibrium, are the concentrations equal?
Answer
**No** — they are **constant** (unchanging), but generally **not equal** to one another.
Question
What is true about the rates at equilibrium?
Answer
The **rate of the forward reaction = the rate of the reverse reaction**.
Question
Why must the system be closed for equilibrium?
Answer
So that **nothing is added or escapes** (no reactant/product/heat leaves); an open system could never settle to constant concentrations.
Question
Name three macroscopic properties that stay constant at equilibrium.
Answer
**Colour (absorbance)**, **pressure** (for gases) and **pH** — all remain constant because the concentrations are constant.
Question
What does 'equilibrium position' mean?
Answer
**How far** a reaction has gone — the **relative amounts** of reactants and products. To the **right** = mostly products; to the **left** = mostly reactants.
Question
How could you tell experimentally that equilibrium has been reached?
Answer
Measure a **macroscopic property** over time (e.g. colour intensity); when it **levels off to a constant value**, equilibrium has been reached.
Question
Most common misconception about equilibrium?
Answer
That the reaction has **stopped** — in fact both reactions continue (it is **dynamic**); the concentrations are merely constant.
Question
On a rate–time graph, what happens to the forward and reverse rates?
Answer
The **forward rate falls** and the **reverse rate rises** until they **meet (become equal)** — that point is equilibrium.
Question
On a concentration–time graph, how do you spot equilibrium?
Answer
Both the reactant and product curves **level off** (become flat) and stay constant — at **different** values.
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Topic 5.3 hub
How far? The extent of chemical change
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