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VICChemistryQuick questions
Unit 2: How do chemical reactions shape the natural world?
Quick questions on Writing ionic and net ionic equations for aqueous reactions: VCE Chemistry Unit 2
13short 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 which species split, which stay together?Show answer
In the ionic equation, only strong electrolytes in solution are written as separated ions. Everything else stays intact.
What is the three-step procedure?Show answer
1. Write the full balanced equation with state symbols. Use solubility rules to decide whether a product is $(aq)$ or $(s)$. 2.
What is three common reaction types in VCE Unit 2?Show answer
Precipitation. Two soluble salts are mixed and an insoluble product forms. Swap the partners and check solubility rules. Example: $Pb(NO_3)_2(aq) + 2KI(aq) \to PbI_2(s) + 2KNO_3(aq)$ gives the net ionic equation $Pb^{2+}(aq) + 2I^-(aq) \to PbI_2(s)$.
What is checking your work?Show answer
Two checks for every net ionic equation:
What is precipitation?Show answer
Two soluble salts are mixed and an insoluble product forms. Swap the partners and check solubility rules. Example: $Pb(NO_3)_2(aq) + 2KI(aq) \to PbI_2(s) + 2KNO_3(aq)$ gives the net ionic equation $Pb^{2+}(aq) + 2I^-(aq) \to PbI_2(s)$.
What is acid-base neutralisation?Show answer
A strong acid plus a strong base in stoichiometric amount gives a salt and water. The net ionic equation collapses to:
What is metal displacement?Show answer
A more reactive metal displaces a less reactive one from its salt. Net ionic equations show only the metal and the ion that changes:
What is splitting weak acids in an ionic equation?Show answer
$CH_3COOH$ stays as $CH_3COOH(aq)$, not $H^+ + CH_3COO^-$. Only strong acids fully ionise.
What is splitting solids?Show answer
$CaCO_3(s)$ stays intact even when it is reacting. Only $(aq)$ ionic species split.
What is forgetting to balance charges before cancelling spectators?Show answer
$H^+ + 2OH^- \to H_2O$ is wrong: the charge is $-1$ on the left and $0$ on the right.
What is cancelling species that have changed in number?Show answer
If $K^+$ appears as 2 on the left and 2 on the right, both cancel. If it appears as 2 on the left and 1 on the right, only 1 cancels and the leftover stays.
What is writing the same equation for every neutralisation?Show answer
Strong acid plus strong base does collapse to $H^+ + OH^- \to H_2O$, but a strong acid plus a weak base (or vice versa) does not. The weak species stays molecular.
What is wrong state symbols on the precipitate?Show answer
$AgCl$, $PbI_2$ and $BaSO_4$ are insoluble; mark them $(s)$. $NaNO_3$, $KCl$ and most other group 1 salts are $(aq)$.