AS 91392 · 5 credits · External
Equilibrium principles
Demonstrate understanding of equilibrium principles in aqueous systems
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In plain EnglishAI study guide · check the NZQA standard
This standard asks you to understand how chemical equilibrium works in water-based (aqueous) systems. You'll need to predict whether substances will dissolve or form precipitates, explain how buffer solutions work and why pH matters, and interpret titration curves—all by applying equilibrium principles like solubility products and ion concentrations.
What to do, grades and common mistakes
What you actually do
- ·Write and use equilibrium expressions (like Ksp) to calculate solubility products and predict whether a precipitate will form when solutions are mixed
- ·Explain how adding acids, bases, or complex ions shifts equilibrium and affects the solubility of sparingly soluble substances
- ·Demonstrate how buffer solutions work and be able to calculate what mass of chemical is needed to prepare a buffer at a specific pH
- ·Calculate the pH at different points during a titration and explain why certain indicators are suitable for detecting the equivalence point
- ·Interpret titration curves and explain differences in conductivity and pH throughout the titration process
AAchieved
You write equilibrium equations and Ksp expressions correctly, calculate solubility products and predict precipitation by comparing Qc to Ksp, describe how buffers function, and calculate buffer component masses using the correct process.
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