Quick questions on Solubility rules and precipitation reactions (QCE Chemistry Unit 2)

9short 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 qCAA solubility rules (memorise this set)?

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QCAA data booklets sometimes include a solubility table; verify which version applies to your cohort. The rules above are the most common 2026 set.

What are writing the three equation forms?

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Once you know a precipitate forms, you can write the reaction in three equivalent ways. Each makes different information explicit.

What are limitations of solubility rules?

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"Insoluble" in the rules really means "very slightly soluble". Even AgCl has a tiny solubility (about 1.3 x 10^-5 mol/L at 25 degrees C). The solubility product Ksp formalises this at Unit 3 / 4 level.

What is molecular equation?

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Shows the formulas of the reactants and products. Always include state symbols.

What is complete ionic equation?

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All aqueous strong electrolytes (soluble ionic compounds and strong acids/bases) are written as separated ions. Insoluble solids, weak electrolytes, gases and molecular liquids stay together.

What is net ionic equation?

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Cancel the spectator ions (those that appear unchanged on both sides).

What is q1?

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Using solubility rules, predict whether a precipitate forms when

\text{BaCl}_2(aq)

is added to

\text{Na}_2 \text{SO}_4(aq)

. Write the net ionic equation. [3 marks]

What is q2?

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25.0 \, \text{mL}

0.0500 \, \text{mol L}^{-1}

\text{Pb(NO}_3)_2

is mixed with

50.0 \, \text{mL}

0.0400 \, \text{mol L}^{-1}

\text{KI}

. Identify limiting reagent and mass of precipitate. [4 marks]

What is q3?

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A student is asked to test an unknown white solid. (a) Suggest a test using

\text{AgNO}_3

. (b) Predict outcomes for chloride vs sulfate.

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