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Acids: Sour taste Turn litmus red Electrolytes- form ions in water Corrosive-cause chemical burns to skin React w/ metals to produce salt and H2 gas HX + M MX + H2(g) (S. Repl. Rxn) Acids neutralize bases to make salt + water Complete and balance each neutralization rnx: HClO3 + Mg(OH)2 KOH + H3PO4
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Acids, Bases & Salts....Oh my!
AP Chemistry, Mr. Guerrero
Acids:Sour tasteTurn litmus redElectrolytes- form ions in waterCorrosive-cause chemical burns to skinReact w/ metals to produce salt and H2 gas
HX + M MX + H2(g) (S. Repl. Rxn)Acids neutralize bases to make salt + waterComplete and balance each neutralization rnx:
HClO3 + Mg(OH)2 KOH + H3PO4
Acids-have 3 definitions
Arrhenius Acid-Any substance which release H+ ions in water.
Rxn: HA H+ + H2O A- + H3O+
(acid) (conjugate base) (hydronium ion)
Bronsted-Lowry Acid- a proton(H+) donor.Rxn: HA H+ + A-
(ACID) (Proton) (Conjugate Base)
Lewis Acid- an e- pair acceptor.(mostly in bonding)Rxn: X + :Y X--Y
Acids-covalent compounds that have H+ cations and ionize(dissociate) in water.
Monoprotic acids- dissociate only one proton.ex: HCl, HCN, HClO3
Diprotic acids- dissociate two protons.ex: H2SO4, H2CO3, H2C2O4
Triprotic acids- dissociate three protons.ex: H3PO4
Organic(carboxylic) acids: All are weak acidsRCOOH RCOO- + H+
Write the dissociation rxn for each acid:• HCN• HNO2
• H2CO3
• CH3COOH
• H3PO4
• NH4+
• HClO4
Amphoteric molecule- a subtance that can act as either an acid(donate H+) or a base(accept a H+).
• Conjugate base of a weak acid
• water
Strong Acid- any acid that has 100 % dissociation in water
There are only 6 strong acids-HCl hydrochloric acid(muriatic acid or stomach acid)HBr hydrobromic acid(mostly in scientific research)HI hydroiodic acid(illegal to possess)HClO4 perchloric acid(strongest of all)HNO3 nitric acid(fertilizers, explosives)H2SO4 sulfuric acid(battery acid, most produced
chemical world-wide)
Oxyacid strength-the more O’s the stronger the acid.
How much more acidic is lemon juice than tomato juice?
[H+] > [OH-] [H+] = [OH-] [H+] < [OH-]
pH Equations
pH = - log [H+] (14-) Kw/known
pOH = - log [OH-]
pH + pOH = 14 [H+]x[OH-] = Kw = 1 x 10-14
Find the pH of the following solutions: 0.025 M HCl
0.085M HNO3
0.045M HCl
Weak acids-molecules with usually less than 5% dissociation
Find the pH of a 0.50 M HC2H3O2(acetic acid) solution(Ka = 1.8 x 10-5)
R .IC .E (find % diss.)Write out equilibrium expression:Ka =
Find the pH of a 0.750 M HNO2 solution(Ka = 5.1 x 10-4)
Bases
Bitter tasteTurn litmus blueDissolve protein(feel slippery)Release ions in water(ions)CorrosiveNeutralize Acids
Definitions of Bases• Arrhenius Base-any substance which releases OH-
(hydroxide ions) in water.• Ex: MOH M(aq)
+ + OH-(aq)
(metal hydroxide) (metal cation) (hydroxide ion)
Bronsted-Lowry Base-a proton acceptor!!!!Ex: BHx + H+ BHX+1
This is the first time amine chemistry is finally explained!Amines: NHx + H+ NH+
x+1
Lewis Base: e- pair acceptor:X + :Y X—Y LA LB (Coordinate Cov. Bond)
8 strong(soluble) bases-They are all Arrhenius acids:
• LiOH• NaOH• KOH• RbOH• CsOH• Ca(OH)2
• Sr(OH)2
• Ba(OH)2
Find the pH of each strong Arrhenius base solution:
• 0.0044 M NaOH
• 0.075 M Ba(OH)2
• 0.010M KOH
Most bases are weak amines.
Find the pH of 0.250 M NH3 solution(Kb = 1.8 X10-5)R ICE
Kb = _________
Find the pH of 0.0500M C5H5N(pyridine)
R ICE
Kb = _________
Find the pH of a 1.20M CH3NH2, methylamine solution, Kb = 4.38 x 10-4
RICE
Kb = _________
Polyprotic acids: Find the pH of a 3.0M H3PO4 solutionKa1 = 7.5 x 10-3 Ka2 = 6.2 x 10-8 Ka3 = 4.8 x 10-13
The weaker an acid, the stronger its conjugate base:
Acid Ka Conj. Base Kb
HCN 6.2 x 10-10
HC2H3O2 1.8 x 10-5
H2C2O4 5.9 x 10-2
HNO2 5.1 x 10-4
HF 7.2 x 10-4
Soluble Salts effect on pH1) cations and anions found in strong acids or bases have no effect on pH(always spectator ions)
ex: KCl, NaNO3, KNO3, Sr(NO3)2….
Basic Salts: [H+] < [OH-]
1) Salts that produce a basic solution:-salts w/ anions that are conj. Base of weak acids:NaC2H3O2
KNO2
NaCN
2) Basic Anhydrides- Metal oxidesNa2OCs2OSrO
Acidic Salts: [H+] > [OH-]
• 1) ammonium salts:Ex. NH4Cl
2) Acid Anhydrides: Nonmetal oxides oxyacids(NON REDOX!!!)
Ex. CO2
NO2
SO3
3) Transition metal cations-form complex ionsCu(NO3)2
FeCl3
Al(ClO4)3
Is each salt acidic, basic or neutral?KBr NaC2H3O2
NH4Cl CO2
Na2O KNO2
Cu(NO3)2 NH4NO3
N2O KNO3
NaClO4 SrOAl(ClO4)3 NaClKClO2 BaF2
BaCl2 K3PO4
Complete Neutralization Equation:NaVa = NbVb
Neutralization- Acid + Base Salt + H2ONaVa = NbVb
What volume of 0.25M HCl is needed to neutralize 15.0 ml 0.45M Ba(OH)2?
18.5 ml phosphoric acid neutralizes 50.0 ml 1.25 M sodium hydroxide
85.0 ml 0.60M acetic acid neutralizes 75.0 ml KOH. What is the conc. of the base?
Buffer Solutions-solutions that resist great changes in pH when strong acid or base are added.
• All buffers are made by dissolving:1) a weak acid(HA) and an alkali metal salt w/ it’s conjugate base as the anion(NaA) The cation acts only as a spectator.
Or2) A weak base (B) and a chloride salt with BCl as a cation. The anion acts only as a spectator
Fill in the missing part of the buffer:
HA A-
HCNNH3
HNO2
NaClO2
C5H5NNH4
+
KHCO3
Henderson-Hasselbalch eq- pH for buffers:
Henderson-Hasselbalch equation: finds pH of buffered solutions
Find the pH of a 0.150 M HC2H3O2(Ka = 1.8 x 10-5) and 0.350 M NaC2H3O2:
Find the pH of a buffer that is 0.500M HCN (Ka = 4.9 x 10-10) & 1.25M NaCN
652mL of a 1.00M HF & 1.65M NaF solution,(Ka = 7.2 x 10-4)1) Optimum pH
2) pH of the buffer
3) pH after 1.50 grams of KOH are added
pH calculations during a neutralization rxn: titration curve
Titration Curve: graph of pH of sample during titration
Titration Curve: Weak acid titrated with a strong base:
Label: x axis, y axis, equivalence pt, ½ way to equivalence pt.
.125M HC2H3O2 is titrated with .0100M NaOH.• What is the pH before titration begins?
• At equivalence pt?
• ½ way to equivalence pt.?
• 75% to equivalence pt.?
• 95% to equivalence pt.?
Weak polyprotic acid titrated with a strong base:
2.10grams NaOH neutralizes 250. ml of .350M HClO(Ka = 4.0 x 10-8). What is the pH at the equivalence pt.?
How many grams of NaC2H3O2 (Kb = 5.56 x 10-10)are needed to produce 1.25 Liters of a buffer with a pH of 5.36, that is 2.35 M HC2H3O2?
• How many moles of HCl are needed to lower the pH of the previous buffer to 4.00?
• Acids, bases, salts, buffers quiz tomorrow!!!!!
Solubility Equilibria-Rxns are written as solids dissociating into ions, Keq is Ksp(solubility product
constant)• All insoluble salts are never really completely
insoluble. • Very small amount of ionization occurs with all salts.
When the maximum amount of solute dissolves the solution is saturated.
• The maximum concentration that can dissolve is called the molar solubility(x).
Below is a picture of lead(II) Iodide ppt. The Ksp = 8.5 x 10-9. What is the molar solubility?
Solubility Equilibria-Rxns are written as solids dissociating into ions, Keq is Ksp(solubility product
constant)
ZnC2O4 has a molar solubility of 3.5 x 10-5M at 25oC. What is the maximum solubility of the solution?
What is the pH of a saturated Mg(OH)2 solution, Ksp = 5.6 x 10-12M
How many grams Ca3(PO4)2 will dissolve in 750. mL of solution at 25oC, Ksp = 1.0 x 10-26
2.0 grams Nickel(II) carbonate(Ksp = 1.3 x 10-7) are mixed with 2.50 liters of water. Is the solution saturated or unsaturated?
We need to solve for Qsp-rxn quotient for solubility.
If Qsp < Ksp solution is unsaturatedIf Qsp > Ksp solution must be saturatedIf Qsp = Ksp solution is saturated and is about to ppt.