CHEMICAL EQUATIONS There are three basic types of chemical equations: Molecular, Ionic, & Net ionic. MOLECULAR EQUATIONS – written as if all substances were molecular, even though some substances may exist as ions. HCl (aq) + NaOH (aq)  NaCl (aq) + H 2 O (l) IONIC EQUATIONS – have the substances which exist as ions written in ionic form. H + (aq) + Cl - (aq) + Na + (aq) + OH - (aq)  Na + (aq) + Cl - (aq) + H 2 O (l) NET IONIC EQUATIONS – ionic equations with the Spectator ions removed. H + (aq) + OH - (aq)  H 2 O (l) SPECTATOR IONS do not participate in a reaction (that is they do not react to form a new substance). Common Spectator ions are Group I, many Group II, and NO 3 - (nitrate) and C 2 H 3 O 2 - (acetate) ions.

DOUBLE REPLACEMENT All double replacement reactions must have a driving force to allow for it to go to completion. This driving force is the removal of at least one pair of ions from solution… 1. Formation of a Precipitate  learn the solubility rules 2. Formation of a Gas  know common substances that exist as gases  know that some substances break up into gases H 2 CO 3  CO 2 (g) + H 2 O H 2 SO 3  SO 2 (g) + H 2 O NH 4 OH  NH 3 (g) + H 2 O HNO 2  NO(g) + NO 2 (g) + H 2 O

3. Formation of a Weak Electrolyte -only break up into ions “a little” in solution  Water, weak acids, NH 4 OH  know strong acids so you can recognize a weak acid  HCl, HBr, HI, HNO 3, H 2 SO 4, HClO 3, HClO 4, HIO 4

Workshop on Double Displacement Reactions: Write the formulas to show the reactants and products for the following laboratory situations described below. Assume that solutions are aqueous unless otherwise indicated. Write NR if no reaction occurs. 1. Silver nitrate combines with potassium chromate. 2. Ammonium chloride combines with cobalt(II) sulfate. 3. Lithium hydroxide reacts with sodium chromate. 4. Zinc acetate is mixed with cesium hydroxide. 5. Ammonium sulfide reacts with lead(II) nitrate. 6. Iron(III) sulfate combines with barium iodide. 7. Chromium(III) bromide reacts with sodium nitrate. 8. Rubidium phosphate mixes with titanium(IV) nitrate. 9. Ammonium carbonate combines with nickel(II) chloride. 10. Tin(IV) nitrate reacts with potassium sulfite.

Formation of a Gas Common gases formed in metathesis reaction are listed below: H 2 S Any sulfide (salt of S 2- ) plus any acid form H 2 S(g) and a salt. Solid iron(II) sulfide is mixed with hydrochloric acid. CO 2 Any carbonate (salt of CO 3 2- ) plus any acid form CO 2 (g), H 2 O, and a salt. Potassium carbonate is reacted with nitric acid. SO 2 Any sulfite (salt of SO 3 2- ) plus any acid form SO 2 (g), H 2 O, and a salt. Sodium sulfite is combined with hydrochloric acid. NH 3 Any ammonium salt (salt of NH 4 + ) plus any soluble strong hydroxide react upon heating to form NH 3 (g), H 2 O, and a salt. Ammonium chloride is mixed with sodium hydroxide.