Writing Total and Net Ionic Equations

WRITING TOTAL AND NET IONIC EQUATIONS 1. Write the overall equation including the correct designations for the physical state of the substances (s, l, g, aq). Balance this equation. Most of these kinds of equations are double displacement reactions: AX + BY 6 AY + BX 2. For the total ionic equations, write strong electrolytes in solution in the form of aqueous ions. (a) Strong acids. The common strong acids and their aqueous ions are: HI HBr HCl HNO3 HClO4 H2 SO4 Hydroiodic acid Hydrobromic acid Hydrochloric acid Nitric acid Perchloric acid Sulfuric acid H+ (aq) + I-(aq) H+ (aq) + Br-(aq) H+ (aq) + Cl-(aq) H+(aq) + NO3 -(aq) H+ (aq) + ClO4 -(aq) 2 H+ (aq) + SO4 -2 (aq) (b) Strong bases. Strong bases are the hydroxides of the alkali (Group IA) and alkaline earth (Group IIA) metals ions which are sufficiently soluble. The common strong bases and their aqueous ions are: LiOH NaOH KOH Sr(OH)2 Ba(OH)2 Lithium hydroxide Sodium hydroxide Potassium hydroxide Strontium hydroxide Barium hydroxide Li+(aq) + OH-(aq) Na+ (aq) + OH-(aq) K+ (aq) + OH-(aq) Sr+2(aq) + 2 OH-(aq) Ba+2(aq) + 2 OH-(aq) (c) Soluble salts. Determinations of the solubility of a salt may be made by reference to SOLUBILITIES OF IONIC COMPOUNDS. Soluble salts are written as their aqueous ions: NaCl(aq) K2 SO4 (aq) Li2 CO3 (aq) Na3 PO4 (aq) (NH4 )2 SO4 (aq) Sodium chloride Potassium sulfate Lithium carbonate Sodium phosphate Ammonium sulfate Na+(aq) + Cl-(aq) 2 K+ (aq) + SO4 -2 (aq) 2 Li+ (aq) + CO3-2 (aq) 3 Na+ (aq) + PO4 -3 (aq) 2 NH4 + (aq) + SO4 -2 (aq) 3. For the total ionic equations, write the weak electrolytes in solution as their (predominantly) molecular form. Weak electrolytes, or un-ionized substances, include (with examples): (a) weak acids HC2 H3 O2 (aq) HCN(aq) (b) weak bases NH3 (aq) (NH4OH written as NH3(aq) + H2O(l) (c) water H2 O(l) 4. For the total ionic equations, write insoluble substances as the total compound (in their molecular form). Unstable substances are written in their decomposed forms. These substances include (with examples): (a) precipitates or insoluble reactants (b) gases (c) derived from unstable substances CaCO3 (s) CO2 (g) If NH4 OH, write NH3 (aq) + H2 O(l) Zn(OH)2 (s) SO2 (g) If H2 CO3 , write CO2 (g) + H2 O(l) Mg(OH)2 (s) SO3 (g) If H2 SO3 , write SO2 (g) + H2 O(l) Ca(OH)2(s) O2(g), N2(g) 5. For the net ionic equations, cancel any substances or ions that appear on both sides of the equation. WRITING TOTAL AND NET IONIC EQUATIONS EXAMPLES Reaction of hydrobromic acid and ammonium carbonate in aqueous solution (a) Overall equation: 2 HBr(aq) + strong acid (NH4)2CO3(aq) -----> soluble salt 2 NH4Br(aq) + H2CO3(aq) soluble unstable salt substance (b) Total ionic equation: 2 H+ (aq) + 2 Br-(aq) spectator ion + 2 NH4 + (aq) spectator ion + CO3 -2 (aq) -----> 2 NH4 + (aq) + spectator ion 2 Br-(aq) spectator ion + CO2 (g) + H2 O(l) (c) Net ionic equation: 2 H+ (aq) charge: +2 + CO32-(aq) -2 = 0 ----> CO2 (g) + 0 H2O(l) 0 Reaction of sodium sulfite with hydrochloric acid in aqueous solution (a) Overall equation: Na2 SO3 (aq) soluble salt + 2 HCl(aq) 6 strong acid Ð[H2 SO3 (aq)]Ð unstable substance H2 O(l) + SO2 (g) + 2 NaCl(aq) soluble salt (b) Total ionic equation: 2 Na+ (aq) spectator ion + SO3 -2 (aq) + 2 H+ (aq) H2 O(l) + + 2 Cl-(aq) spectator ion ----> SO2 (g) + 2 Na+ (aq) spectator ion + H2 O(l) + 0 SO2 (g) 0 (c) Net ionic equation: SO3 -2 (aq) charge: -2 + 2 H+ (aq) +2 = 0 ----> 2 Cl-(aq) spectator ion