ACID-BASE REACTIONS

Aqueous Solutions How do we know ions are present in aqueous solutions? The solutions conduct electricity! They are called ELECTROLYTES Strong Acids and Strong Bases are strong electrolytes. They dissociate completely (or nearly so) into ions.

Aqueous Solutions CH3CO2H(aq) <---> CH3CO2-(aq) + H+(aq) Acetic acid ionizes only to a small extent, so it is a weak electrolyte. CH3CO2H(aq) <---> CH3CO2-(aq) + H+(aq) Most of the acid in solution exists as the UN-IONIZED MOLECULE. The Double Arrow is used to indicate that the reaction DOES NOT RUN COMPLETELY TO PRODUCTS. Weak acids and weak bases are weak electrolytes.

Acids ---> H+ in water HCl(aq) ---> H+(aq) + Cl-(aq) Arrhenius definition of an acid: Any substance that produces hydrogen ions in water Other strong acids include: HI, HBr, HNO3, HCl, H2SO4, HClO4, HClO3 HCl is a strong acid

ACIDS Nonmetal oxides can produce acids CO2(aq) + H2O ---> H2CO3(aq) SO3(aq) + H2O ---> H2SO4(aq) and can come from burning coal and oil. *You need to know this reaction!

What are the properties of acids and bases? pH – Low <7 Taste – Sour Litmus color – Red Phenolphthalein color - Colorless BASES: pH – High, >7 Taste - Bitter Litmus color - Blue Feel – Slippery Phenolphthalein color - Pink Litmus is an extract from lichens that is used as a pH indicator

Base ---> OH- in water BASES Base ---> OH- in water NaOH(aq) ---> Na+(aq) + OH-(aq) Arrhenius definition of a base: Any substance that produces hydroxide ions in water Other strong bases include: LiOH, KOH, NaOH, RbOH, Cs(OH)2, Ba(OH)2, Sr(OH)2 NaOH is a strong base

Ammonia, NH3 An Important Weak Base Even though ammonia does not have hydroxide ion in its formula, it is a base because it interacts with water to produce hydroxide ions! Because it is a WEAK base, ammoniua does NOT produce MANY OH- in water. The Double Arrows indicate that this reaction does NOT run completely to products.

BASES Metal oxides can produce bases in water: CaO(s) + H2O --> Ca(OH)2(aq) *You need to know this reaction. CaO in water. Indicator shows solution is basic.

Acid-Base Reactions The “driving force” is the formation of water. NaOH(aq) + HCl(aq)  NaCl(aq) + H2O(liq) Net ionic equation OH-(aq) + H+(aq)---> H2O(liq) This applies to ALL reactions of STRONG acids and bases. WATER will NOT split back up into IONS* What are the SPECTATOR IONS in this reaction?? A DRIVING FORCE of a reaction is a PRODUCT the does NOT ALLOW the reaction to run back toward REACTANTS. It FORCES the reaction FORWARD to PRODUCTS!

Acid-Base Reactions Acid-Base reactions are sometimes called NEUTRALIZATION Reactions because the solution is neither acidic nor basic at the end. The other product of the Acid-Base reaction is a SALT and water. HCl + NaOH ---> NaCl + H2O This is one way to make compounds!

Gas-Forming Reactions There are four important gas-forming reactions to learn. Make a list of gases formed in these reactions. The formation of a GAS is the DRIVING FORCE in these reactions! Once the GASES leave the reaction vessel, the reaction CANNOT turn back into REACTANTS. Gas formation drives the reaction to PRODUCTS.