Acids and Bases

Arrhenius Theory Acids produce H+ ions. Bases produce OH- ions. HCl g H+ + Cl- NaOH g Na+ + OH- Applies only to water solutions

Strong acids HCl (stomach acid) H2SO4 (battery acid) HNO3 (nitric acid) Weak acids H2CO3 (carbonic acid) HC2H3O2 (acetic acid) Formic acid- wasp stings

Strong bases KOH NaOH Weak bases NH4OH Mg(OH)2 (milk of magnesia)

Bronsted-Lowry Theory Acids donate protons Bases accepts protons NH3(g) + H2O(l) g NH4+(aq) + OH-(aq) conjugate acid conjugate base base acid

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 base H3O+(aq) + Cl-(aq) g HCl(g) + H2O(l) acid base Acid + base g conjugate base + conjugate acid conjugate acid conjugate base H+ 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 acid conjugate base

Acid conjugate base HCl Cl- H2SO4 HSO4- H3O+ H2O Base conjugate acid NH3 NH4+ H2O H3O+

Monoprotic- has 1 H; HCl Diprotic- has two H; H2SO4 Triprotic- has three H; H3PO4

Characteristics of acids Taste sour pH from 0-6.99 Has H+ at the beginning of the formula Produce H2h when reacting with most metals Neutralize bases Conducts electricity (electrolytes) Turns litmus paper red

Characteristics of bases Taste bitter pH between 7.01-14 Have OH- ion Feels slippery Neutralize acids Turns litmus paper blue

Naming acids anion acid name example -ide Hydro- ic HCl hydrochloric acid -ite -ous HNO2 nitrous acid -ate -ic HNO3 nitric acid

Try these H2SO4 HF H3PO4 H2SO3 sulfuric acid hydrofluoric acid phosphoric acid sulfurous acid

1 l l l l l 7 l l l l l l14 acid neutral base pH scale 1 l l l l l 7 l l l l l l14 acid neutral base

Ionization of water H2O(l) H+(aq) + OH-(aq)

[H+] means hydrogen ion concentration in moles per liter (molarity). Water at 25◦C : [H+] = 10-7moles/L [OH-] = 10-7moles/L Since [H+] = [OH-], water is neutral

[H+] ∙ [OH-] = 10-14 mole2/L2 Example: Find the [OH-] in a solution in which [H+] = 10-5. [H+] ∙ [OH-] = 10-14 mole2/L2 [OH-] = 10-9 If the concentration of either ion is known, the concentration of the other can be determined.

[H+] = 10-pH [OH-] = 10-pOH pH + pOH = 14.0 Sample problem: A 0.01 M sample of NaOH completely ionizes. What is its pH, pOH, [H+], and [OH-] ? [OH-] = 0.01 mole/L = 10-2 pOH = 2 pH = 14 – pOH = 12 [H+] = 10-12

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+] = 10-14 = 10-3 10-11

pH values of common liquids Human gastric juices 1-3 Lemon juice 2.2-2.4 Vinegar 2.4-3.4 Soda 2-4 O.J. 3-4 Coffee, black 4 Milk 6.5 Blood 7.3-7.5 Sea water 7.8-8.3 Ammonia 10.5-11.5 1M NaOH 14.0

Neutralization reactions Always form a salt and water Salt- a crystalline compound formed from an acid’s anion and a base’s cation.

Titration An 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.

Titration Standard solution- one whose concentration is known Endpoint- the point at which equivalent amounts of reactants are present. M∙V = moles MaVa=MbVb The standard solution is dropped from a buret into a measured amount of unknown solution.

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 + NaCl 15mL x 0.500M = 25.0 ml x Ma = 0.300M HCl

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).

HF(aq) D H+(aq) + F-(aq) Buffered solution is mostly HF and F-. If H+ is added: H+ + F- g HF If OH- is added: OH- + HF g F- + H2O