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Module 5: Equilibrium and Acid Reactions
Quick questions on Static vs dynamic equilibrium explained: HSC Chemistry Module 5
7short Q&A pairs drawn directly from our worked dot-point answer. For full context and worked exam questions, read the parent dot-point page.
What is static equilibrium?Show answer
Static equilibrium is a state of balance in which no net change is occurring and no process is active at the molecular level. A pencil balanced on a table is in static equilibrium. Two unreactive gases mixed in a sealed flask sit in static equilibrium because nothing is reacting.
What is dynamic equilibrium?Show answer
Dynamic equilibrium is the state of a reversible reaction where the forward and reverse reactions occur at equal rates. Macroscopic properties (concentration, colour, pressure, mass) remain constant. At the molecular level, however, the forward and reverse reactions continue to occur.
What is reversible vs non-reversible reactions?Show answer
A non-reversible reaction proceeds to completion in one direction. Combustion of methane is non-reversible under normal conditions because the products (CO2 and H2O) do not spontaneously reform methane.
What is conditions required for dynamic equilibrium?Show answer
1. The system must be closed (no matter escapes). 2. The reaction must be reversible.
What is saying the reaction has "stopped" at equilibrium?Show answer
This loses marks immediately. The reaction continues at the molecular level. Always write that the forward and reverse rates are equal.
What is confusing dynamic equilibrium with equal concentrations?Show answer
Concentrations at equilibrium are usually not equal; what is equal is the forward and reverse rate. The position of equilibrium depends on Kc.
What is forgetting the closed system requirement?Show answer
An open beaker of evaporating water never reaches equilibrium because water vapour escapes. Always specify "closed" or "sealed."
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