DOUBLE REPLACEMENT METATHESIS REACTIONS

The driving force: All double replacement reactions must have a “driving force” or reason why the reaction will go to completion. This is the removal of at least one pair of ions from solution Driving forces: Gas Formation (learn common ones) Electrolytes (formation of weak/non-electrolytes) Precipitation (learn solubility rules)

Common Gases Look for trends, memorize! H2S: Any sulfide (salt of S -2 ) plus and acid form H2S (g) and a salt. CO2: Any carbonate (salt of CO3 2- ) plus any acid form CO2 (g), water and salt. SO2: Any sufite (salt of SO3 -2 )plus any acid form SO2 (g), water and salt. NH3: Any ammonium salt plus any soluble strong hydroxide react upon heating to form NH3 (g), water and salt.

Examples A solution of sodium sulfide is combined with sulfuric acid: Na 2 S (aq) + H 2 SO 4 (aq)  Na 2 SO 4 (aq) + H 2 S (g) S -2 + H +  H2S Solid calcium carbonate is added to hydrochloric acid: CaCO 3 (s) + HCl (aq)  CaCl 2 (aq) + CO 2 (g) + H 2 O (l) CaCO 3 + H +  Ca +2 + CO 2 + H 2 O Sodium bicarbonate solution is mixed with hydrobromic acid NaHCO 3 (aq) + HBr (aq)  NaBr (aq) + CO 2 (g) + H 2 O (l) HCO H +  CO 2 + H 2 O Solid strontium sulfite is combined with hydroiodic acid: SrSO 3 (s) + 2 HI (aq)  SrI 2 (aq) + SO 2 (g) + H 2 O (l) SrSO 3 + H +  Sr +2 + SO 2 + H 2 O

Electrolytes A strong electrolyte dissociates completely when dissolved in water. A weak electrolyte only dissociates partially when dissolved in water.

Acids There are only seven strong acids: Hydrochloric (HCl) Hydrobromic (HBr) Hydroiodic (HI) Nitric (HNO 3 ) Sulfuric (H 2 SO 4 ) Chloric (HClO 3 ) Perchloric (HClO 4 )

Bases: Substances that increase the concentration of OH − when dissolved in water (Arrhenius). Proton acceptors (Brønsted–Lowry).

Bases The strong bases are the soluble salts of hydroxide ion: Alkali metals Calcium Strontium Barium

Acid-Base Reactions In an acid-base reaction, the acid donates a proton (H + ) to the base.

Neutralization Reactions Generally, when solutions of an acid and a base are combined, the products are a salt and water. HCl (aq) + NaOH (aq)  NaCl (aq) + H 2 O (l)

Neutralization Reactions When a strong acid reacts with a strong base, the net ionic equation is… HCl (aq) + NaOH (aq)  NaCl (aq) + H 2 O (l) H + ( aq ) + Cl - ( aq ) + Na + ( aq ) + OH - ( aq )  Na + ( aq ) + Cl - ( aq ) + H 2 O ( l )

Neutralization Reactions When a strong acid reacts with a strong base, the net ionic equation is… HCl (aq) + NaOH (aq)  NaCl (aq) + H 2 O (l) H + ( aq ) + Cl - ( aq ) + Na + ( aq ) + OH - ( aq )  Na + ( aq ) + Cl - ( aq ) + H 2 O ( l ) H + ( aq ) + Cl - (aq) + Na + ( aq ) + OH - ( aq )  Na + ( aq ) + Cl - ( aq ) + H 2 O ( l )

Solubility Rules Always soluble: alkali metal ions, ammonium, nitrate, chlorate, chlorite, acetate ions Generally soluble: Ions of Cl, Br, I, F> except with Ag +, Pb 2+, Hg2 2+ (AP/H) F– Soluble except Ca 2+, Sr 2+, Ba 2+, Pb 2+, Mg 2+ (CBS-PMS Sulfate ions> Soluble except Ca 2+, Sr 2+, Ba 2+, Pb 2+ (CBS/PBS) Generally insoluble: Oxide & hydroxide ions>Insoluble except and alkali metals, and NH4 +,Ca 2+, Sr 2+, Ba 2+ (CBS) somewhat soluble CO3 2–, PO4 3–, S 2–, SO3 2–, C2O4 2– CrO4 2– Insoluble except alkali metals and NH4 +

Examples: A solution of lead (II) nitrate is added to a sodium iodide solution Ammonium phosphate solution with aqueous sodium hydroxide Hydrochloric acid is mixed with calcium acetate solution