# Exambusters Study Cards 16 Acids and Bases

 Ionization Constant
 Kw = 1 X 10-14 at 25 °C
 pH
 pH = -log[H+]
 For what pH values is a solution acidic?
 < 7
 For what pH values is a solution neutral?
 = 7
 For what pH values is a solution basic?
 > 7
 pOH
 pOH = -log[OH–]
 For what pOH values is a solution acidic?
 > 7
 For what pOH values is a solution neutral?
 = 7
 For what pOH values is a solution basic?
 < 7
 How are pH and pOH of a solution related?
 The sum of the two values = 14 pH + pOH = 14
 How are the concentrations of [H+] and [OH–] related in a solution?
 The product of the concentrations = 1 x 10-14 [H+][OH–] = 1 x 10-14
 Match pH value to distilled water. a.) pH=2 b.) pH=7 c.) pH=12
 b.) pH = 7
 Match pH value to lye. a.) pH=2 b.) pH=7 c.) pH=12
 c.) pH= 12
 Match pH value to stomach juice. a.) pH=2 b.) pH=7 c.) pH=12
 a.) pH=2
 For a solution with a pH of 3, find pOH
 pOH = 11
 For a solution with a pH of 3, find [H+]
 [H+] = 1 x 10-3
 For a solution with a pH of 3, find [OH–]
 [OH–] = 1 x 10-11
 Solubility Product Constant – Ksp
 An equilibrium exists in a saturated solution between dissolved and undissolved solute. “Ksp” is the equilibrium constant for this reaction.
 Write the solubility product expression for AgCl double arrow Ag+ = Cl–
 Ksp = [Ag+][Cl–]
 In a saturated solution of BaSO4, [Ba2+] = 2 x 10-5. Find Ksp.
 Each molecule of BaSO4 that ionizes produces equal concentrations of ions; therefore; [Ba2+] = [SO42-] Ksp = [Ba2+][SO42-] Ksp=[2 x 10-5][2 x 10-5] Ksp = 4 x 10-10
 Common Ion Effect
 When an ionization reaction is at equilibrium, and additional ion is added, the reverse reaction rate increases to consume the added ion.
 NaCl ↔ Na+ = Cl– What happens when Cl– is added to this system at equilibrium?
 According to the common ion effect, the reverse reaction will speed up, consuming Na+ and Cl–, and more NaCl will be formed.
 Six common characteristics of ACIDS
 form H2O solutions conduct electricity react with active metals turn blue litmus red neutralize bases sour taste
 Seven common characteristics of BASES
 form H2O solutions conduct electricity turn red litmus blue feel slippery caustic neutralize acids bases + fats form soap
 Strong Acids
 nitric hydrochloric sulfuric hydriodic hydrobromic perchloric
 Weak Acids
 hydrofluoric acetic carbonic and most others
 Moderately Strong Acids
 oxalic phosphoric sulfurous
 Strong Bases
 hydroxides of: potassium sodium barium s trontium calcium   also: KOH NaOH
 Hydronium ion
 H3O+ ion found in water solutions of acids. Water molecule with a proton attached.
 Neutralization Reaction
 acid + base → salt + water
 Write the equation for hydrochloric acid and sodium hydroxide.
 HCl + NaOH → NaCl + H2O
 Arrhenius Theory
 An acid yields protons in solution. (H+ ions) A base yields hydroxide ions in solution. (OH– ions)
 Bronsted-Lowry Theory
 An acid is a proton donor. A base is a proton acceptor.
 Lewis Theory
 An acid is an electron pair acceptor. A base is an electron pair donor.
 Conjugate Base: Write conjugate base of HCl.
 When a Bronsted acid donates a proton, it becomes its conjugate base. Conjugate base of HCl is Cl–.
 Conjugate Acid: Write conjugate acid of I–
 When a Bronsted base accepts a proton, it becomes its conjugate acid. Conjugate acid of I– is HI.
 Indicator
 A substance which changes color along the pH scale. e.g. litmus, phenolphthalein, methyl orange, bromthymol blue
 Titration
 A process of finding the unknown concentration of a solution by allowing it to react with another solution of known volume and concentration.
 Endpoint
 The point during a titration at which the acid reacts completely with the base. The indicator changes color.
 Write the equation to calculate concentrations and volumes in titration reactions.
 MA X VA = MB x VB   molarity = M volume = V acid = A base = B
 Calculate the volume of 10 M NaOH needed to titrate 5L of 2M HCl
 MA X VA = MB X VB 2M X 5L = 10M X VB 1L = volume of base
 Buffer Solutions
 Equilibrium systems which resist changes in pH upon the introduction of acids or bases (due to the common ion effect). e.g. a weak acid (acetic acid) and its salt (sodium acetate)
 Electrolysis
 The passage of a direct electric current through an ionic solution, producing chemical changes at the electrodes.