Properties of Acids and Bases

1. Properties of Acids and Bases

2. Acids • Taste sour • Reach with certain metals (Zn, Fe, etc.) to produce hydrogen gas • cause certain organic dyes to change color • react with limestone (CaCO3) to produce carbon dioxide • React with bases to form salts and water

3. Bases • Taste bitter • feel slippery or soapy • react with oils and grease • cause certain organic dyes to change color • react with acids to form salts and water

4. Similarities • Taste sour • Reacts with each other to form salts and waters • Causes certain organic dyes to change colors

5. Definitions of acids • A substance that produces Protons, H+

6. Definitions of bases • A substance that produces Hydroxide ions, OH-

7. Reactions of acids and bases with water • Acids and bases form ions in solution:HCl(aq) ® H+(aq) + Cl-(aq) • H3O+ - hydronium ion H+ and H3O+ are equivalent in aq. solution • When we look at the reactions of acids - can be generalized using hydrogen ion • Reaction with zinc yields hydrogen gas • Reaction with limestone - produce CO2(g) • Acids react with bases to produce a salt • Similarly for bases, produce hydroxide ions

8. Neutralization and salts • Neutralization - one type of double replacement reaction • Acid + Base ® Salt + water • Net ionic equation shows what drives the neutralization reaction • example: • Molecular: HCl(aq) + NaOH(aq) ® NaCl(aq) + H2O(l) • Total Ionic: H+(aq) + Cl-(aq) + Na+(aq) + OH-(aq) ® Na+(aq) + Cl-(aq) + H2O(l) • Net Ionic: H+(aq) + OH-(aq) ® H2O(l) • SALT - a salt is formed from the anion of the acid and the cation of the base - usually present as spectator ions. - not always NaCl

9. Types of acids • Monoprotic - a solution that produces one mole of H+ ions per mole of acidHCl , HNO3 • Diprotic - a solution that produces two moles of H+ ions per mole of acidH2SO4 • Triprotic - a solution that produces three moles of H+ ions per mole of acidH3PO4 • Polyprotic - two ore more H+ per mole of acid • V. Polyprotic acids: • can be Partially neutralized • acid salt - an ionic compound containing the anion with one or more hydrogens that can be neutralized with a base

10. Strengths of Acids and Bases • STRONG ACIDS • Acids that are essentially 100% ionized in aqueous solutions • ex: HCl, HNO3, HClO4 • produce the maximum concentration of H+ • [acid] = [H+] • WEAK ACIDS • Acids that are partially ionized ( usually less than 5%) in equilibrium. • HF + H2O(l) H3O+(aq) + F-(aq) • The forward and the reverse reaction are occurring simultaneously most found as HF. • STRONG BASES • those compounds that completely ionize in water to produce OH- ions • NaOH(s) ® Na+(aq) + OH-(aq) • Concentration of base = concentration of hydroxide ions • WEAK BASES • NH3(aq) + H2O(l) NH4+(aq) + OH-(aq) • equilibrium lies far to the left (mostly reactants present)

11. Equilibrium of Water • H2O(l) + H2O(l) H3O+(aq) + OH-(aq) • Autoionization- produces positive and negative ions from the dissociation of the molecules of a liquid. • Experimentally, found concentration of ions = 1.0 x 10-7 M at 25 C • [H3O+][OH-] = Kw • At 25 C (1.0 x 10-7)(1.0 x 10-7) = 1.0 x 10-14 • Kw = ION PRODUCT - gives us the concentrations of hydronium and hydroxide ions in pure water and acidic and basic solutions • Neutral [H3O+] = [OH-] = 1.0 x 10-7 M • Acidic [H3O+] > 1.0 x 10-7, [OH-] <1.0 x 10-7 • Basic [H3O+] < 1.0 x 10-7, [OH-] >1.0 x 10-7

12. Brønsted-Lowry Acids and Bases • acid - a proton (H+) donor • base - a proton (H+) acceptor • NH3(aq) + H2O(aq)  NH4+(aq) + OH- (aq) • NH3 and NH4+ are conjugate acid-base pairs • H2O and OH- are conjugate acid-base pairs • Amphiprotic- a compound or ion that can either donate or accept H+ ions. • H2O, HSO4- , HPO42-, HSO3- etc.

13. Acidic and Basic Salt solutions • Hydrolysis - the reaction of an anion with water to produce OH- or the reaction of a cation to produce H3O+ • Neutral solutions of salts: Cation does not undergo hydrolysis • Anion does not undergo hydrolysis • Basic solutions of salts: Cation same as above • Anion undergoes some hydrolysis • Acidic solutions of salts: Cation undergoes some hydrolysis • Anion does not • Complex solutions: Cation and anion undergoes hydrolysis • Then you need to know the relative strength of each.

14. . Predicating acid base reactions in water • Acid-Base reactions always yield conj. acid-base • Strong Acid : weak conj. base • Strong Base : weak conj. acid • Weak Acid : strong conj. base • Weak Base : strong conj. acid • The strength of the reactant compared to the strength in the product determines which direction the equilibrium lies. • Three predictions can be made: • The reactant may Not react at all, leaving essentially all reactants (negligible) • The reactants may Slightly react, leaving mostly reactants (limited) • The reactants may react (essentially) completely, leaving little or no reactants (favorable)

15. Buffer solutions • Buffer solution - resists changes in pH caused by the addition of limited amounts of a strong acid or a strong base. • A buffer solution must contain: • A weak acid + its conjugate base • or A weak base + its conjugate acid

16. Citation PAge • "Chapter 12 - Acids and Bases." Modesto Junior College. N.p.. Web. 16 Nov 2012. <http://virtual.yosemite.cc.ca.us/lmaki/Chem142/chap_outlines/chapter12.htm>.