Unit #4 (part 2)

Acids and Bases

Acids and Bases

• Everyday life includes contact with many acids and bases

Strong Acids:

• Strong acids ionize completely to H+

• HCl (aq) → H+ (aq) + Cl- (aq)• In a solution of 1.0 M HCl, there is 1M H+ and 1M Cl-

Weak Acids:

• Ionize only partially

HC2H3O2(aq) H+1(aq) + C2H3O2

-1(aq)

In a solution of a weak acid greater than 95% will typically remain as molecules.

Strong Bases:

• Strong bases ionize completely to OH-

• NaOH (s) → Na+ (aq) + OH- (aq)

• Ca(OH)2(s) → Ca2+ (aq) + 2 OH- (aq)

Weak Bases:

• Ionize only partially

NH3(aq) +H2O(l) NH4+1

(aq) + OH-1(aq)

Weak bases are often Nitrogen containing compounds that react with water to form hydroxide ions.

pH-potential of hydrogen

• a measure of the acidity or basicity of a substance• Scale from 0 to 14• 0-7=acid• 7=neutral• 7-14=base

pH = - log [H+1] Kw=[H+1][OH-1]=1x10-14

14 =pH+pOH

[H+1] = 10-pH *on calc. = 2nd 10x (-) pH

Strong Acid – Strong Base Reactions:

Neutralization Reaction:

Double replacement reaction, one product will always be water; best to write as H(OH)

Example:

H2SO4 + NaOH

Strong Acids and Bases:

Must be memorized:

Strong Acids:Br I Cl SO4 NO3 ClO4

Strong Bases:hydroxides of group I except the first 1(H) and group II except the first 2(Be and Mg)

Example:

Write the neutralization reaction for HI and NaOH.

Acid-Base Titrations

• Commonly used laboratory method to determine the Molarity of a solution.

Vocab:

• Indicator – chemical dye that changes color a specific pH or range of pH values

• Endpoint – the place in the titration process where the indicator changes color

• Equivalent Point – the place in the titration where moles of acid = moles of base

Titrations

A solution of known concentration is added to one of unknown concentration to determine its concentration. Molarity is used as a conversion factor.

Example:

A beaker containing 25.00mL of H2S is titrated with 1.50M NaOH. If the process requires 15.65mL of NaOH, what is the molarity of the H2S?

Bronsted-Lowry Theory

• Acid – Hydrogen ion donor• Base – hydrogen ion acceptor• Conjugate acid – product of the base• Conjugate bases – product of the acid• Amphiprotic – substance that can serve as an acid

or a base

• Examples: HCl as an acid and NH3 as a base

Properties of Acids and Bases:

Acid Base

Sour tasting; citrus fruits, vinegar, soda

Bitter tasting; soap, shampoo, drain cleaner

Waxy texture Slippery texture

pH 0-7; turns blue litmus red pH 7-14; turns red litmus blue

Neutralize bases to form salt and water

Neutralize acids to form salt and water

Acid Naming:

• No oxygens = Hydro_________ic acid

• Anion has –ate or –ite ending:• Per____________ic acid• ______________ic acid• ______________ous acid• Hypo__________ous acid