4 Strong basesKOHNaOHWeak basesNH4OHMg(OH)2 (milk of magnesia)
5 Bronsted-Lowry Theory Acids donate protonsBases accepts protonsNH3(g) + H2O(l) g NH4+(aq) + OH-(aq)conjugate acidconjugate basebaseacid
6 Conjugate acids and bases A conjugate acid is formed when a base gains an H+ ion.A conjugate base is formed when an acid loses an H+ ion.HCl(g) + H2O(l) g H3O+(aq) + Cl-(aq)acid baseH3O+(aq) + Cl-(aq) g HCl(g) + H2O(l)acid baseAcid + base g conjugate base + conjugate acidconjugate acidconjugate baseH+ is a proton.Conjugate acid of a base is formed when the base acquires a proton.Conjugate base of an acid forms when a proton is released from an acid.conjugate acidconjugate base
16 [H+] means hydrogen ion concentration in moles per liter (molarity). Water at 25◦C : [H+] = 10-7moles/L[OH-] = 10-7moles/LSince [H+] = [OH-], water is neutral
17 [H+] ∙ [OH-] = mole2/L2Example: Find the [OH-] in a solution in which [H+] = 10-5.[H+] ∙ [OH-] = mole2/L2[OH-] = 10-9If the concentration of either ion is known, the concentration of the other can be determined.
19 [H+] = 10-pH [OH-] = 10-pOHpH + pOH = 14.0Sample problem:A 0.01 M sample of NaOH completely ionizes. What is its pH, pOH, [H+], and [OH-] ?[OH-] = 0.01 mole/L = pOH = 2pH = 14 – pOH = [H+] = 10-12
20 Sample Problem 2:A solution has a pH of 3. What is its pOH, [H+], and [OH-]?pOH = 14 – 3 = 11[OH-] = 10-11[H+] = = 10-310-11
21 pH values of common liquids Human gastric juices 1-3Lemon juiceVinegarSoda 2-4O.J. 3-4Coffee, black 4Milk 6.5BloodSea waterAmmonia1M NaOH 14.0
22 Neutralization reactions Always form a salt and waterSalt- a crystalline compound formed from an acid’s anion and a base’s cation.
23 TitrationAn unknown concentration of acid or base can be determined by measuring the amount of a known acid or base that will neutralize the other.An indicator changes color when the “endpoint”, or neutralization occurs.
24 Titration Standard solution- one whose concentration is known Endpoint- the point at which equivalent amounts of reactants are present.M∙V = molesMaVa=MbVbThe standard solution is dropped from a buret into a measured amount of unknown solution.
25 If 15. 0ml of 0. 500M NaOH is used to neutralize 25 If 15.0ml of 0.500M NaOH is used to neutralize 25.0ml HCl, what is the concentration of the acid?NaOH + HCl g H2O + NaCl15mL x 0.500M = 25.0 ml x Ma= 0.300M HCl
26 Buffers Can absorb acids and bases without changing its pH A weak acid (HA) with its salt (NaA)A weak base (MOH) with its salt (MA)They contain ions that will react with H+ (a base) and OH- ions (an acid).
27 HF(aq) D H+(aq) + F-(aq) Buffered solution is mostly HF and F-.If H+ is added: H+ + F- g HFIf OH- is added: OH- + HF g F- + H2O