Calculations Involving Acidic and Basic Solutions Chapter 8.4 and 8.5

Some Common Acids and Bases Strong Acids: Sulfuric acid, H2SO4 Hydrochloric acid, HCl Nitric acid, HNO3 Perchloric acid, HClO4 Weak Acids: Phosphoric acid, H3PO4 Acetic acid, CH3COOH Strong Bases: Sodium hydroxide, NaOH Calcium hydroxide, Ca(OH)2 Magnesium hydroxide, Mg(OH)2 Weak Bases: Ammonia, NH3

Strong Acids and Bases Since strong acids and bases almost completely ionize in water, we can assume: the concentration of the [H+] ions is equal to the concentration of the acid The concentration of the [OH-] ions is equal to the concentration of the base

Ex 1: Calculations with Strong Acids A scientist dilutes a commercial solution of nitric acid, HNO3(aq) by adding water. The final solution has 0.25 mol HNO2(l) in a total volume of 1.00 L. Determine the concentration of hydrogen ions and hydroxide ions, and the pH and pOH of the final solution at SATP.

Ex 2: Calculations with Strong Bases A solution of calcium hydroxide has a concentration of 0.05 mol/L. Calculate the [H+], [OH-] and the pH of the solution.

Percent Ionization for Weak Acids and Bases Only a small fraction of molecules will ionize/dissociate to form ions for weak acids and bases Percentage ionization is the percentage of a solute that ionizes when it is dissolved in a solvent

Ex 3: Calculate Ka from percentage ionization Calculate Ka of hydrofluoric acid, HF(aq), if a 0.100mol/L solution at equilibrium has a percentage ionization of 7.8%.

Ex 4: Using Ka to find pH (weak acid) Calculate the pH of a 0 Ex 4: Using Ka to find pH (weak acid) Calculate the pH of a 0.10mol /L acetic acid solution. Ka for acetic acid is 1.8 x 10-5.

Ex 5: Using pH to find Ka (weak acid) A student prepares a 0 Ex 5: Using pH to find Ka (weak acid) A student prepares a 0.20mol/L aqueous solution of ascorbic acid, and measures its pH as 2.40. Based on this evidence, what is the Ka of ascorbic acid?

Polyprotic Acids A monoprotic acid is an acid that possesses only one ionizable (acidic) hydrogen atom A polyprotic acid is an acid that possesses more than one ionizable (acidic) hydrogen atom Notice that the value of: Ka1 > Ka2 > Ka3

Examples of Polyprotic Acids

**Ex 6: Calculating pH of a polyprotic acid solution A student prepares a 0.20mol/L aqueous solution of ascorbic acid, and measures its pH as 2.40. Based on this evidence, what is the Ka of ascorbic acid?

Ex 7: Calculating Kb from pH (weak base) A solution of aniline, C6H5NH2 , has a concentration of 5.0g/L and the pH of the solution is 8.68. Calculate the Kb for analine.

Ex 8: Calculating [OH-] and pH from Kb (weak base) Quinine, C20H24N2O2 , has a Kb of 3.3x10-6 . What are the hydroxide ion concentration and pH of a 3.6x10-3 mol/L solution of quinine?

Homework Section 8.4: p. 525 #1ac, 2ac, 3b, 4, 6, 7, 8 Section 8.5: p. 530 #1ac, 2ac, 3b, 4b, 6a, 7, 9