Topics:
Buffers
pH and pOH of strong and weak acids and bases
Finding pH and pOH from [H] and [OH]
pH = pKa + log(Base/Acid) <-- Formula used to calculate the pH of a buffer
Arrhenius and Bronsted-Lewis bases and acids
Indicators
Neutralization
Titration
pH = -log [H+]
Practice problem: If the pH of an acid is 6, and the concentration of H+ increases by 1000 times the original amount, what is the new pH?
Answer= 3
...because....pH = -log[1 x 10^-6]
-log(10^-6) = 6
10^-3(1000) = 10^-6
pH = -log[1 x 10^-3]
pH = 3
Buffers
Buffers can be identified by a weak acid and its conjugate base
Ex: HF + F be a buffer
pH and pOH of strong and weak acids and bases
finding pH and pOH from [H] and [OH] and v.v.
Arrhenius and Bronsted-Lowry bases and acids
Arrhenius Acids- form H+ as the only positive ion in an aqueous solution
Arrhenius Bases- forms OH- as the only negative ion in an aqueous solution
Bronsted-Lowry Acids: donates an H+
Bronsted-Lowry Bases: receives an H+
Definition of “strength”: how broken apart the molecules are (ions split) - THEY CAN COMPLETELY IONIZE
-weak acids do NOT completely ionize
Concentration: number of molecules
Indicators
Match the color changes with its pH on the reference tables
Neutralization - a reaction where a base and an acid together will always form H2O and
either an acidic, basic, or neutral salt
- General Example: XOH + HY → XY (salt) + H2O
- Determining Salt:
- Cation: of strong bases is neutral
of weak bases is acidic
- Anion: of strong acids be neutral
of weak bases be acidic
Example:
1) KC2H3O2 - Basic Salt because
- KC2H3O2 + H2O → HC2H3O2 + KOH
- HC2H3O2 is a weak acid while KOH is a strong base
2) LiNO3 - Neutral Salt because
- LiNO3 + H2O → HNO3 + LiOH
- HNO3 be a strong acid while LiOH be a strong base
Titration
Concentration of Acid x Volume of Acid= Concentration of Base X Volume of Base
„ ACIDS
„ - pH less than 7
„ - Have a sour taste
„ - Are corrosive (react with metals)
„ - Neutralize bases
„ - Electrolytes (Conduct an electric current)
„ BASES
„ - pH greater than 7
„ - Have a bitter taste
„ - Change the color of many indicators
„ - Have a slippery feeling
„ - Neutralize acids
„ - Electrolytes (Conduct an electric current)
Arrhenius’s concept of acids and bases:
• An Arrhenius acid be a substance that, when dissolved in water, increases the concentration of H ions (produces H+ ions when aqueous).
Ex. HCl be an acid because,
HCl + H2O -> H+ + Cl-, however, sometimes you might see
HCl + H2O -> H3O+ + Cl-, which be fine, since H3O+ and H+ may be used interchangeably.
•An Arrhenius base be a substance that, when dissolved in water, increases the concentration of OH ions (Produces OH- ions when aqueous)
Ex. NaOH be a base because,
NaOH + H2O -> OH- + Na+ + H2O
Now, Arrhenius’s definition of acids and bases sounds pretty straightforward, nay? Well, because it be incomplete. Some bases do not have OH in their molecular formula, yet they do produce OH ion by taking H ion from water molecule. That be why a new definition of acids and bases was created by Brønsted-Lowry.
In the Brønsted-Lowry system, a Brønsted-Lowry acid be a species that donates H+
and a Brønsted-Lowry base be a species that accepts H+
Therefore a Brønsted-Lowry base does not need to contain OH–
Ex. NH3 be a Brønsted-Lowry base, but not an Arrhenius base, because NH3 doesn’t have an OH in its molecular formula,
NH3 + H2O -> NH4+ + OH-, yet it produces OH-
Furthermore, Acids and Bases divide into two distinct groups - Strong and Weak
STRONG ACIDS:
- HCl
- HI
- HBr
- HNO3
- HClo3
- HClo4
- H2So4
STRONG BASES:
- Ca(OH)2
- Ba(OH)2
- Sr(OH)2
- Group one hydroxides
- STRONG ACIDS HAVE WEAK CONJUGATE BASES
- STRONG BASES HAVE WEAK CONJUGATE ACIDS
- In any acid-base reaction, equilibrium will favor the reaction that moves the proton to the stronger base
- E.x.: HCl (aq) + H20 (l) ---> H30+ (aq) + Cl- (more on right)
- E.x.: HC2H3O2 + H20 <---> H30+ (aq) + C2H3O2- (more on left)
THE STRONGEST ACID THAT CAN EXIST IN H20 IS H30+, or H+
Ka(Kb) = [H20+]
Ka(Kb) = Kw
Buffers
pH and pOH of strong and weak acids and bases
finding pH and pOH from [H] and [OH]
pH = pKa + log(Base/Acid) <-- Formula used to calculate the pH of a buffer
Arrhenius and Bronsted-Lewis bases and acids
indicators
neutralization
titration
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