Let’s Start with the Basics ... A + B → C + D 2A + B → E The ratio in which the reactants react and which the products are produced is called the STOICHIMETRY of the reaction. Balanced symbol equations tell us about the AMOUNTS of substances that react together and are produced. State symbols: (s) (l) (g) (aq) Which are the reactants and products? Why do we use an arrow? Do we ever use an “=“? What does the “2” mean? Can we add big numbers? Can we add in small numbers? Why? – use example of H2O and H2O2 not being the same thing.

Writing Balanced Equations e.g., Calcium reacting with water Step 1: Write the word equation Step 2: Add symbols Step 3: Add state symbols Step 4: Balance Calcium + water → calcium hydroxide + hydrogen Ca + H2O → Ca(OH)2 + H2 Ca (s) + H2O (l) → Ca(OH)2 (aq) + H2 (g) Ca (s) + 2H2O (l) → Ca(OH)2 (aq) + H2 (g)

Ca(s) + 2H2O(l)  Ca(OH)2(aq) + H2(g) Molecular Equations Ca(s) + 2H2O(l)  Ca(OH)2(aq) + H2(g) This is a molecular equation. The equation shows that one mole of calcium reacts with 2 moles of water to form one mole of calcium hydroxide and one mole of hydrogen gas.

Ions Using your table of common ions, work out the symbol formula for each compound. Aluminium bromide Calcium fluoride Magnesium sulphate Zinc chlorate (I) Iron (III) oxide Silver Sulphide

Ions Using your table of common ions, work out the symbol formula for each compound. Aluminium bromide AlBr3 Calcium fluoride CaF2 Magnesium sulphate MgSO4 Zinc chlorate (I) Zn(ClO3)2 Iron (III) oxide Fe2O3 Silver Sulphide Ag2S

Ionic Equations Reactions involving ionic compounds can be written as IONIC EQUATIONS They focus on the IONS that react together and ignore the ones that do NOT take part in the reaction. NB: When dealing with IONIC Equations, the TOTAL of the CHARGES on each side should be the same.

H+(aq) + Cl-(aq) + Na+(aq) + OH-(aq)→Na+(aq) + Cl-(aq) + H2O (l) Spectator Ions Full Equation: HCl (aq) + NaOH (aq) → NaCl (aq) + H2O (l) Water exists as molecules here. The other 3 are ionic compounds, made from ions. Here is the equation again, this time with all of the ions written out separately: H+(aq) + Cl-(aq) + Na+(aq) + OH-(aq)→Na+(aq) + Cl-(aq) + H2O (l) What do you notice about Na+ and Cl-? They appear on both sides of the equation. They separate in solution and DO NOT take part in the reaction. SPECTATOR IONS. They “watch” the reaction happening without reacting themselves.

H+(aq) + Cl-(aq) + Na+(aq) + OH-(aq)→Na+(aq) + Cl-(aq) + H2O (l) Spectator Ions Full Equation: HCl (aq) +NaOH (aq) → NaCl (aq) + H2O (l) Ionic Equation: H+(aq) + Cl-(aq) + Na+(aq) + OH-(aq)→Na+(aq) + Cl-(aq) + H2O (l) You can leave out the spectator ions by cancelling them from the equation: This gives: H+(aq) + OH-(aq)→H2O (l) This is an ionic equation. Note that it is simpler than the full equation. It helps to see which ions have actually taken place in the reaction. Pupils will have seen this equation at GCSE. It is the equation for any acid/alkali reaction. This is the reaction that produces the heat in a neutralisation reaction.

Using Ionic Equations Neutralisation Precipitation Displacement

Using Ionic Equations: Neutralisation Same principle as the previous example ... Sulfuric acid and ammonia solution: Full Equation: H2SO4(aq) + 2NH4OH(aq) → (NH4)2SO4(aq) + 2H2O(l) Full Ionic Equation: 2H+(aq)+SO42-(aq) + 2NH4+(aq)+2OH-(aq)→2NH4+(aq)+SO4(aq) + 2H2O(l) 2H+(aq) + 2OH-(aq)→2H2O (l) Simplifies to: H+(aq) + OH-(aq)→H2O (l)

Using Ionic Equations: Precipitation Precipitates are INSOLUBLE in water (s) e.g., silver nitrate and potassium chloride Full Equation: AgNO3(aq) + KCl(aq) → AgCl(s) + KNO3(aq) Full Ionic Equation: Ag+(aq)+NO3-(aq) + K+(aq)+Cl-(aq) → AgCl(s) + K+(aq) + NO3-(aq) Ag+(ag)+ Cl-(aq) → AgCl(s) What is a precipitate?

Using Ionic Equations: Displacement One reactant displaces another. e.g., copper displaces silver from silver nitrate solution Full Equation: Cu(s) + 2AgNO3(aq) → Cu(NO3)2(s) + 2Ag (s) Full Ionic Equation: Cu(s) + 2Ag+(aq)+2NO3-(aq) → Cu2+(aq)+ 2NO3-(aq) 2Ag(s) Cu(s) + 2Ag+(aq)→ Cu2+(aq)+ 2Ag(s) What is a precipitate?

Check Your Understanding 1. Write the balanced ionic equation corresponding to each of the following full equations: a. KOH(aq)+HCl(aq)→KCl(aq)+H2O(l) b. 2NaOH(aq)+H2SO4(aq)→Na2SO4(aq)+2H2O(l) c. BaCl2(aq)+CuSO4(aq)→BaSO4(aq)+CuCl2(aq) d. Cu(s)+2AgNO3(aq)→2Ag(s)+Cu(NO3)2(aq) 2. Balance these ionic equations: a. Mg2+(aq)+OH-(aq) →Mg(OH)2(s) b. Al3+(aq)+OH-(aq) →Al(OH)3(s) c. Fe(s) + Pb2+(aq) →Fe3+(aq)+ Pb(s)

Task Complete Task 6 from Chemsheets