1 Writing Chemical Equations to Symbolize Chemical Reactions

2 Solid aluminum metal reacts with oxygen gas to produce solid aluminum oxide. 1.Write the formulas of the reactants and products. Al + O 2 → Al 2 O 3 2.Add symbols to indicate physical state. Al (s) + O 2(g) → Al 2 O 3(s) 3.Balance (Law of Conservation of Mass) 4Al (s) + 3O 2(g) → 2Al 2 O 3(s) 4.Synthesis Reaction

3 Electrical current through water. Electrolysis of water into its elements. 1.Write the skeleton equation H 2 O → H 2 + O 2 2.Put in physical state symbols H 2 O (L) → H 2(g) + O 2(g) 3.Balance 2 H 2 O (L) → 2 H 2(g) + O 2(g) 4.Decomposition

4 Solid iron rusts. Solid iron reacts with oxygen gas to produce iron(III) oxide. 1.Write the skeleton equation Fe + O 2 → Fe 2 O 3 2.Put in physical state symbols Fe (s) + O 2(g) → Fe 2 O 3(s) 3.Balance 4 Fe (s) + 3 O 2(g) → 2 Fe 2 O 3(s) 4.Synthesis (aka combination)

5 Ammonium Nitrate dissolves. Since we have defined dissolving as a physical change, this is NOT a chemical reaction, just a physical change. 1.Write the skeleton equation NH 4 NO 3 → NH NO 3 − 2.Put in physical state symbols NH 4 NO 3(s) → NH 4 + (aq) + NO 3 − (aq) 3.Balance Already balanced. 4.Dissolving

6 Aqueous sodium dichromate is reacted with aqueous lead(II) nitrate to produce a solid precipitate of lead(II) dichromate and aqueous sodium nitrate. 1.Write the skeleton equation Na 2 Cr 2 O 7 + Pb(NO 3 ) 2 → PbCr 2 O 7 + NaNO 3 2.Put in physical state symbols Na 2 Cr 2 O 7(aq) + Pb(NO 3 ) 2(aq) → PbCr 2 O 7(ppt) + NaNO 3(aq) 3.Balance Na 2 Cr 2 O 7(aq) + Pb(NO 3 ) 2(aq) → PbCr 2 O 7(ppt) + 2NaNO 3(aq) 4.Double Replacement

7 Solid potassium metal is reacted with water to produce aqueous potassium hydroxide and hydrogen gas. 1.Write the skeleton equation K + H 2 O → KOH + H 2 2.Put in physical state symbols K (s) + H 2 O (L) → KOH (aq) + H 2(g) 3.Balance 2K (s) + 2H 2 O (L) → 2KOH (aq) + H 2(g) 4.Single Replacement

8 Solid calcium reacted with liquid water to produce aqueous calcium hydroxide and hydrogen gas. 1.Write the skeleton equation Ca + H 2 O → Ca(OH) 2 + H 2 2.Put in physical state symbols Ca (s) + H 2 O (L) → Ca(OH) 2(aq) + H 2(g) 3.Balance Ca (s) + 2H 2 O (L) → Ca(OH) 2(aq) + H 2(g) 4.Single Replacement

9 Solid zinc reacts with aqueous hydrochloric acid to produce aqueous zinc chloride and hydrogen gas. 1.Write the skeleton equation Zn + HCl → ZnCl 2 + H 2 2.Put in physical state symbols Zn (s) + HCl (aq) → ZnCl 2(aq) + H 2(g) 3.Balance Zn (s) + 2HCl (aq) → ZnCl 2(aq) + H 2(g) 4.Single Replacement

10 Burning of methane gas, CH 4 1.Write the skeleton equation CH 4 + O 2 → H 2 O + CO 2 2.Put in physical state symbols CH 4(g) + O 2(g) → H 2 O (g) + CO 2(g) 3.Balance CH 4 (g) + 2O 2(g) → 2H 2 O (g) + CO 2(g) 4.This is the gas that comes through our Bunsen burners. 5.Combustion

11 Nylon is formed from hexamethylenedamine reacting with sebacoyl chloride to produce the nylon polymer and hydrochloric acid. 1.Nylon is a generic term to represent a particular type of polymer. C 6 H 12 N 2 H 6 + C 6 H 8 Cl 2 O 2 → C 12 H 20 O 2 N 2 H HCl 2.Balance C 6 H 12 N 2 H 6 + C 6 H 8 Cl 2 O 2 → C 12 H 20 O 2 N 2 H HCl 3.This is a typical polymerization reaction. Polymer = many mers (repeating small units) Polymerization = making polymers from monomers.

12 Polymerization - making large molecules from small units 1.You may remember that many glucose molecules hooked together make the polymer starch or cellulose