Unit 11: Acids, Bases, and Salts

• RB Topic 8

I. Properties of Acids and Bases

Acids• Electrolyes! (conduct

electricity in solution)• low pH (1 to 7)• Arrhenius definition:

– produce hydrogen ions/hydronium ions as the only positive ion in solution(H+

or H3O+)

Ex:HCl + H2O H3O+ + Cl-

Bases• Electrolytes!

• high pH (7 – 14)• Arrhenius definition:

– produce hydroxide ions as the only negative ion in solution(OH-)

Ex:NaOH Na+

+ OH-H2O

Acids• “Alternate definition”

– donate protons (H+)

• more H+ than OH-

• Table K• Examples:

Bases• “Alternate definition”

– accept protons (H+)

• more OH- than H+

• Table L• Examples:

Ex: NH3 + H2O NH4+ + OH-

Acids• General formula:

HHnonmetal(s)

CxHyCOOHCOOH

Bases• General formula:

metalOHOH

*NH3 is an exception

Which of the following are bases?

CH3COOH NH3 HCl

HC2H3O2 Ca(OH)2 KCl

NaF CH3CH2OH

II. The pH Scale

• measures the H+ or H3O+ concentration in a solution

• write concentration (molarity) as [H+]

• “pH” stands for “potential to ATTRACT Hydrogen ions”– Acids have a LOW pH (release/DONATE H+)– Bases have a HIGH pH (grab up H+)

• pH scale is logarithmic, which means that a change of ONE pH unit ONE pH unit will change the concentration of HH++ by a factor of TEN by a factor of TEN

[H+] = 1 x 10-pH

0 147

strong acid

weak acid neutral

weak base

strong base

[H+] = 1 x 100 M = 1 M

[H+] = 1 x 10-7 M = 0.0000001 M

[H+] = 1 x 10-14 M

[H+] > [OH-] [H+] = [OH-] [H+] < [OH-]

Q: What is the relationship between pH value and hydrogen ion concentration?

III. Changes in pH

Add in… Acid BasepH ↓ ↑

[H+] ↑ ↓Solution

becomes…more acidic more basic

(alkaline)

• if pH changes by 1 unit, [H+] changes by a factor of 101 (10, “tenfold”)

• if pH changes by 2 units, [H+] changes by a factor of 102 (100, “a hundredfold”)

• if pH changes by 3 units, [H+] changes by a factor of 103 (1000, “a thousandfold”)

Ex: Describe what happens to the concentration of hydrogen ions in a solution if the pH is changed from 7 to 5

Ex: Describe what happens to the concentration of hydrogen ions in a solution if the pH is changed from 5 to 8

IV. How to measure pH• Use Table M!

If pH is below the first #, solution will be first colorIf pH is above the second #, solution will be second

colorIf pH is between the #s, solution will be a mix of

colors

V. Reactions of Acids with Metals• Use Table J!

acid + more active metal H2(g) + a salt

*Cu, Au, and Ag (below H2 on Table J) do NOT react with acids

VI. Neutralization Reactions

acid + base water + a salt

Ex: HCl (aq) + NaOH (aq) H2O (l) + NaCl (aq)

*Write the products and balance the following:

___ H2SO4 + ___ LiOH

___ HBr + ___ Ca(OH)2

VII. Titrations

• procedures used to determine the concentration (molarity) of an acid or a base

Titration setup

If an acid and base are mixed…it’s a TITRATION!!!Use Reference Table T equation:

MA = molarity of H+ VA = volume of acid

MB = molarity of OH– VB = volume of base

MAVA = MBVB

Ex 1: A 16.0-milliliter sample of HNO3 (aq) is neutralized by 24.7 milliliters of 0.230 M KOH (aq). What is the concentration of the acid?

Ex 2: How many milliliters of 0.275 M NaOH are needed to neutralize 110. mL of 0.120 M HCl?