Acids, Bases & Salts....Oh my! AP Chemistry, Mr. Guerrero

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 

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 acids RCOOH  RCOO- + H+

Write the dissociation rxn for each acid: HCN HNO2 H2CO3 CH3COOH H3PO4 NH4+ HClO4

Conjugate base of a weak acid 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 . I C . 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 taste Turn litmus blue Dissolve protein(feel slippery) Release ions in water(ions) Corrosive Neutralize Acids

Definitions of Bases X + :Y  X—Y 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 I C E Kb = _________

Find the pH of 0.0500M C5H5N(pyridine) R I C E Kb = _________

Find the pH of a 1.20M CH3NH2, methylamine solution, Kb = 4.38 x 10-4 R I C E Kb = _________

Polyprotic acids: Find the pH of a 3.0M H3PO4 solution Ka1 = 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 pH 1) 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 oxides Na2O Cs2O SrO

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 ions Cu(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 SrO Al(ClO4)3 NaCl KClO2 BaF2 BaCl2 K3PO4

Complete Neutralization Equation: NaVa = NbVb

Neutralization- Acid + Base  Salt + H2O NaVa = 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?

All buffers are made by dissolving: 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. Or 2) 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- HCN NH3 HNO2 NaClO2 C5H5N NH4+ 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 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) 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) 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 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 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 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 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 unsaturated If Qsp > Ksp solution must be saturated If Qsp = Ksp solution is saturated and is about to ppt.