Question: Write the ionic equation, with state symbols, for the reaction of solid calcium carbonate with dilute hydrochloric acid.Step 1: write the balanced full equation.CaCO3(s) + 2HCl(aq) → CaCl2(aq) + H2O(l) + CO2(g) Step 2: split only the aqueous ionic substances. Calcium carbonate is an insoluble solid, so it is not split into ions, even though it is ionic. Water and carbon dioxide are covalent, so they are not split either.CaCO3(s) + 2H+(aq) + 2Cl-(aq) → Ca2+(aq) + 2Cl-(aq) + H2O(l) + CO2(g) Step 3: cancel the spectator ions. The only spectator ions are the chloride ions.CaCO3(s) + 2H+(aq) → Ca2+(aq) + H2O(l) + CO2(g) Step 4: check. Atoms: 1 Ca, 1 C, 3 O and 2 H on each side. Charge: 2+ on the left and 2+ on the right.Compare this with sodium carbonate solution. Sodium carbonate is soluble, so it is split into Na+(aq) and CO32-(aq). Now Na+ and Cl- are both spectators and the ionic equation is:CO32-(aq) + 2H+(aq) → H2O(l) + CO2(g) The key point: always use the state symbols to decide what to split. Only (aq) ionic substances are written as separate ions.
Ionic Equations - Question3
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Specification: Edexcel Chemistry (8CH0), AS-level, Topic 5: Formulae, Equations and Amounts of Substance. Topic: Amount of Substance and Calculations.
Key terms in this lesson
- spectator ion
- An ion present in a reaction mixture that appears unchanged on both sides of the equation and takes no part in it.
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