unit 11: acids, bases, and salts
DESCRIPTION
Unit 11: Acids, Bases, and Salts. RB Topic 8. I. Properties of Acids and Bases. Acids. Bases. Electrolytes! high pH (7 – 14) Arrhenius definition: produce hydroxide ions as the only negative ion in solution (OH - ) Ex: NaOH Na + + OH -. - PowerPoint PPT PresentationTRANSCRIPT
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?