Acid and Base Chemistry

Review• Acids• pH less than 7• Turns litmus from blue to red• Sour taste

• Bases• pH greater than 7• Turns litmus from red to blue• “slippery” feeling

Definitions• Arrhenius• Acids produce H+ ions, bases produce OH- ions in

aqueous solutions• Limits the number of reactions considered Acid-Base

• Bronsted-Lowry• Acid is an H+ donor• Base is an H+ acceptor

• Lewis• Acid Accepts an electron pair• Base donates an electron pair

Properties of acids1. Sour taste

citric, malic, tartaric are well known food additives

Properties of Acids

2. Contain the hydrogen ion (H+ ), react with active metals to give off H2 gas

Properties of Acids3. Change the color of indicators

Low pH

Properties of acids

4. React with bases to produce salts and water

Base + Acid → Water + Salt2NaOH + H2SO4 → 2H2O + Na2SO4

Properties of Acids5. Acids are electrolytes

Break apart and form ionscan conduct electricity

Common acids• HCl – hydrochloric acid• H2SO4 – sulfuric acid• HC2H3O2 – acetic acid - vinegar• HNO3 – nitric acid• H3PO4 – phosphoric acid• H2CO3 – carbonic acid

Hydrochloric Acid (Muriatic Acid)• Produced in the stomach and aids in digestion• Industrial Cleaning Agent

Sulfuric Acid• #1 industrial chemical• Fertilizers, petroleum refining, metallurgy• Production of metal, paper, paint, detergents• Used as a measure of a country’s economy

Acetic Acid• Dilute acetic acid is vinegar• Used in making plastics• Raw material necessary in the production of food

supplements

Nitric Acid• Explosive making uses nitric acid, due to its

instability• Used in the rubber and plastics industry• Dyes and drug production also utilize nitric acid

Phosphoric Acid• Manufacture of fertilizers and animal feed• Detergents and ceramics also utilize phosphoric

acid• Carbonated beverage production

Carbonic Acid• Made from dissolving carbon dioxide (CO2) in

water• Sodas, or any carbonated beverage.

Monoprotic Acid vs Diprotic acid• Monoprotic Acids donate 1 proton (H+) • Ie HCl

• Diprotic Acids donate (2) protons (H+) per molecule• Ie: H2SO4

Triprotic acids• Donates (3) protons• Example: H3PO4

Strong vs Weak Acids and Bases• Does not mean dangerous vs safe• Strong Acids ionize completely• Every available H+ ion is separated from anion in aqueous

solution• If 0.1 mol of HCl is added to water, then 0.1 mol of H+,

and 0.1 mol of Cl- are fromed• Table 4.1

• Weak Acids do not ionize completely• We use a reversible reaction (double) arrow to represent

not complete ionization

Bases

Properties of bases1. Bitter taste

Properties of Bases

2. Feel slippery to the skin

3. Change color of indicatorsHigh pH

Properties of Bases

4. React with acids to produce water and salts

2NaOH + H2SO4 → 2H2O + Na2SO4

5. Bases are electrolytes

Common bases

Sodium hydroxide

• (NaOH), also known as lye or caustic soda, is a caustic metallic base. It is widely used in many industries, mostly as a strong chemical base in the manufacture of pulp and paper, textiles, drinking water, soaps and detergents. Worldwide production in 1998 was around 45 million tons.

Ammonium hydroxide• (NH4)(OH)• Common household cleaner

pH scale

pH Equation• - log [H+]• If [H+] = 1 x 10-8 M• Then –log[1 x 10-8] = pH pH = 8

pH Equation• Notice pH can be estimated by the exponent • -log(1.0 x 10-5) = pH of 5• -log(1.0 x 10-9) = pH of 9• -log(1.0 x 10-13) = pH of 13

If [H+] = 3.4 x 10-5 find pH = -[(log 3.4 x 10-5)]

= -[(log 3.4 + log 10-5)] = -[(0.53) + (-5)] = -(0.53 – 5) = 4.47

Reactions• Neutralization of Acids / Base• When acid and base react to an equivalence point• Where all H+ ions have reacted with all OH- ions to

produce _________?

“Spectator Ions” – Ions that do not actually take part in the reaction.

Often times, the other ion in the acid or base, that gets separated from the H+ or OH- doesn’t really take part in the reaction.

If [H+] = 3.4 x 10-5 find pH = -[(log 3.4 x 10-5)]

= -[(log 3.4 + log 10-5)] = -[(0.53) + (-5)] = -(0.53 – 5) = 4.47

Neutralization reactions• React an Acid and a Base together to form water,

bring pH to neutral• Reaction of hydronium ions (H3O+) and hydroxide

(OH-) ions to form water• Hydronium is sometimes simplified to H+

H3O+ + OH- 2H2OorH+ + OH- H2O or H+OH-

Titration

• Controlled addition & measurement of an amount of solution of a known concentration, that is required to react completely with a measured amount of solution of unknown concentration.

• Example: HCl + NaOH NaCl + H2OA 100.0 mL sample of HCl is titrated to a stoichiometric endpoint with 76.8 mL of a 1.17 M NaOH. What is the molarity of the HCl?

Acid-Base Titrations• Reaction to an equivalence point (pH 7)

• Used to determine the concentration of an unknown solution.

• If you find how much volume of a known concentration (standard) you need to add to a known volume of an unknown concentration……

• If I have 25.0 mL of a .316 M solution of H2SO4, What volume of NaOH do I need to neutralize it?

Graph of titration typical titration curve