To learn about two models of acids and bases Objectives To learn about two models of acids and bases To understand the relationship of conjugate acid-base pairs To understand the concept of acid strength To understand the relationship between acid strength and the strength of the conjugate base To learn about the ionization of water

HCl, HF, HBr :HydroChloric,Fluoric..acid A. Acids and Bases The Arrhenius Model Acid – produces hydrogen ions H+ in aqueous solution: H2SO4 Sulfuric Acid HNO3 Nitric Acid HCl, HF, HBr :HydroChloric,Fluoric..acid Base – produces hydroxide ions OH- in aqueous solution NaOH Sodium Hydroxide KOH Potassium Hydroxide Mg(OH)2

The Bronsted-Lowry Model A. Acids and Bases The Bronsted-Lowry Model (1923 Danish/English independent submittals) Acid – proton donor (gives H+ ) Base – proton acceptor (takes H+) The general reaction for an acid dissolving in water is

The Bronsted-Lowry Model A. Acids and Bases The Bronsted-Lowry Model Acid-base conjugate pairs consist of an acid that donates the H+ and the ion it becomes.

The Bronsted-Lowry Model A. Acids and Bases The Bronsted-Lowry Model Water acts as a base accepting a proton from the acid. (B-L Base) hydronium ion (H3O+) (Conjugate Acid)

The Arrhenius Model is limited to Aqueous A. Acids and Bases The Arrhenius Model is limited to Aqueous The Bronsted-Lowry Model can also relate to non-aqueous reactions: NH3 + HCl  NH4+ + Cl- CH3COOH + H2O  CH3COO- + H3O +

A. Acids and Bases Identify the Bronsted-Lowry acid/base conjugate pairs in the following reactions: HSO4- + OH-  SO4-2 + H2O SO3-2 + H2O  HSO3- + OH- NH3 + HNO3  NH4+ + NO3-

The general acid/base pattern is: Acid + Base  salt + water A. Acids and Bases The general acid/base pattern is: Acid + Base  salt + water H__ + __OH  ____ + H2O HCl + NaOH  NaCl + H2O ID the Arrhenius Acid/Base and B-L Pairs…

Strong acid – completely ionized or completely dissociated B. Acid Strength Strong acid – completely ionized or completely dissociated

Weak acid – low ionization of acids B. Acid Strength Weak acid – low ionization of acids

A strong acid contains a relatively weak conjugate base. B. Acid Strength A strong acid contains a relatively weak conjugate base. HCl + H2O  H3O+ + Cl- Whereas the acid will quickly donate a proton (strong acid), the conjugate base will not quickly accept a proton (weak).

Common strong acids are B. Acid Strength Common strong acids are Sulfuric acid, H2SO4 Hydrochloric acid, HCl Nitric acid, HNO3 Are weak acids the same as dilute strong acids?

Typically a weak acid (COOH) B. Acid Strength Oxyacid – acidic proton is attached to an oxygen atom Organic acid – have a carbon atom backbone and commonly contain the carboxyl group Typically a weak acid (COOH)

B. Acid Strength

C. Water as an Acid and a Base Water is amphoteric (amphiprotic) – it can behave as either an acid or as a base Amphiprotic - etymology… ambi-Ringo Starr ringo_starr.images6.com/ringo_starr.html

http://www.coolopticalillusions.com/ambigrams/funny_ambigram.htm

C. Water as an Acid and a Base (Amphiprotic) Ionization of water - ID the B-L conjugate pairs Concentration of hydronium and hydroxide are equal in pure water

C. Water as an Acid and a Base Product of [H3O+] and [OH] is always constant in all solutions. Water is equally both an acid and a base

C. Water as an Acid and a Base pH range 0.? – 7 7 – 14 7

To learn about two models of acids and bases Objectives Review To learn about two models of acids and bases To understand the relationship of conjugate acid-base pairs To understand the concept of acid strength To understand the relationship between acid strength and the strength of the conjugate base To learn about the ionization of water Work Session: Section Review Page 572 1, 3, 4, 5, 6

To understand pH and pOH Objectives To understand pH and pOH To learn to find pH and pOH for various solutions To use a calculator to find pH and [H+] To learn methods for measuring pH of a solution To learn to calculate the pH of strong acids   

The “p scale” is used to express small numbers. pH = log [H+] A. The pH Scale The “p scale” is used to express small numbers. pH = log [H+] What is the pH if [H+] = 1 X 10 -7? Calculator practice- do the log function? If [H+] = 2.3 X 10-5? pH = 4.64 is this acid or base?

A. The pH Scale Because the pH scale is a log scale based on 10, the pH changes by 1 for every power of 10 change in the [H+].

Calculate the pH given the following concentrations: [H+] = 1.0 X 10-5 A. The pH Scale Calculate the pH given the following concentrations: [H+] = 1.0 X 10-5 [H+] = 1.0 X 10-11 [H+] = 3.4 X 10-4 [H+] = 2.6 X 10-8 [H+] = 2.3 X 10-5 [H+] = 1.9 X 10-6

Calculate the pOH if [OH] = 1.0 X 10-6 pOH = 6 A. The pH Scale pOH scale pOH = log [OH] Calculate the pOH if [OH] = 1.0 X 10-6 pOH = 6 remember [H+] [OH] = 1.0 X 10-14 If [OH] = 1.0 X 10-6 , then [H+] = 1.0 X 10-8 If [OH] = 6 , then [H+] = 8 Since pH + pOH = 14.00 pOH = 14.00 – pH (shortcut)

Knowing the pH, determine the pOH: [H+] = 1.0 X 10-5 pH = 5, pOH = 9 A. The pH Scale Knowing the pH, determine the pOH: [H+] = 1.0 X 10-5 pH = 5, pOH = 9 [H+] = 1.0 X 10-11 pH = 11, pOH = 3 [H+] = 3.4 X 10-4 pH = 3.47, pOH = ? [H+] = 2.6 X 10-8 pH = 7.59, pOH = ? [H+] = 2.3 X 10-5 pH = 4.64, pOH = ? [H+] = 1.9 X 10-6 pH = 5.72, pOH = ?

Can you determine the [H+] from pH? If pH = 3.98, what is the [H+] ? A. The pH Scale Can you determine the [H+] from pH? If pH = 3.98, what is the [H+] ? Inverse log function….. [H+] = inverse log (-pH) [H+] = inverse log (- 3.98) [H+] = 1.05 X 10-4

Calculate the [H+] given the following pH: pH = 5 [H+] = ? A. The pH Scale Calculate the [H+] given the following pH: pH = 5 [H+] = ? pH = 7 [H+] = ? pH = 10.1 [H+] = ? pH = 4.5 [H+] = ? pH = 3.22 [H+] = ? pH = 9.54 [H+] = ?

In an acid solution the indicator will be in the HIn form. B. Measuring pH Indicators – substances that exhibit different colors in acidic and basic solutions In an acid solution the indicator will be in the HIn form. In a basic solution the indicator will be in the In form.

Phenolphthalein color change 8.0 – 9.8 B. Measuring pH Phenolphthalein color change 8.0 – 9.8                                                                                                                                                                                                                                                                                                                                                                              http://antoine.frostburg.edu/chem/senese/101/acidbase/indicators.shtml

Bromothymol Blue color change 6.0 – 7.6 B. Measuring pH Bromothymol Blue color change 6.0 – 7.6                                                                                                                                                                                                                                                                                                                                                                              http://antoine.frostburg.edu/chem/senese/101/acidbase/indicators.shtml

Thymol Blue – tri color! B. Measuring pH                                                                                                                                                                                                                                        http://antoine.frostburg.edu/chem/senese/101/acidbase/indicators.shtml

B. Measuring pH Other methods Indicator paper pH meter Cabbage juice

To understand pH and pOH Objectives Review To understand pH and pOH To learn to find pH and pOH for various solutions To use a calculator to find pH and [H+] To learn methods for measuring pH of a solution To learn to calculate the pH of strong acids    Work Session: Review Page 581 1, 2, 3, 4

To learn about acid-base titrations Objectives To learn about acid-base titrations To demonstrate calculations and techniques for titration lab To understand the general characteristics of buffered solutions

A. Acid-Base Titrations Titration – delivering a measured volume of a solution of known concentration into the solution being analyzed Titrant – a standard solution Buret – device used for accurate measurement of the delivery of a liquid Stoichiometric point (equivalence point) – when just enough titrant has been added to react with all of the solution being analyzed

A. Acid-Base Titrations Titration curve (pH curve) – plot of the data (pH vs volume) for a titration

A. Acid-Base Titrations HCl + NaOH  NaCl + H2O Stoichiometrically, there is a 1 to 1 ratio of H+ to OH- ions between HCl and NaOH For this reason, we can use the dilution equation in the form MacidVacid = MbaseVbase to determine the amount of one Molarity solution to completely neutralize a given amount of another Molarity solution

A. Acid-Base Titrations HCl + NaOH  NaCl + H2O What volume of 1 M HCl would be required to completely neutralize 20 ml of 2 M NaOH? MacidVacid = MbaseVbase Macid = Vacid = Mbase= Vbase=

A. Acid-Base Titrations HCl + NaOH  NaCl + H2O What volume of 1 M HCl would be required to completely neutralize 20 ml of 2 M NaOH? MacidVacid = MbaseVbase Macid = 1 M Vacid = ? Mbase= 2M Vbase= 20 ml

A. Acid-Base Titrations HCl + NaOH  NaCl + H2O What volume of 1 M HCl would be required to completely neutralize 20 ml of 2 M NaOH? MacidVacid = MbaseVbase Vacid = MbaseVbase Macid Vacid = (2M)(20 ml) = 40 ml (1 M)

A. Acid-Base Titrations HCl + KOH  KCl + H2O Calculate the volume of 0.30 M HCl needed to titrate 75.0 ml of 0.150 M KOH. MacidVacid = MbaseVbase Macid = Vacid = Mbase= Vbase=

A. Acid-Base Titrations HCl + KOH  KCl + H2O Calculate the volume of 0.30 M HCl needed to titrate 75.0 ml of 0.150 M KOH. MacidVacid = MbaseVbase Macid = 0.30 M Vacid = ? Mbase= 0.150 M Vbase= 75.0 ml

A. Acid-Base Titrations HCl + KOH  KCl + H2O Calculate the volume of 0.30 M HCl needed to titrate 75.0 ml of 0.150 M KOH. MacidVacid = MbaseVbase Vacid = MbaseVbase Macid Vacid = (0.150M)(75 ml) = 37.5 ml HCl (0.30 M)

A. Acid-Base Titrations (Lab Prep) HCl + NaOH  NaCl + H2O Using (MacidVacid = MbaseVbase), calculate the volume of 1.0 M HCl required to titrate 20.0 ml of 0.5 M, 1.0 M, and 2.0 M NaOH to the equivalence point. Show the calculations and record the HCl volumes in Table 1.

Presence of a weak acid and its conjugate base buffers the solution B. Buffered Solutions Buffered solution – resists a change in its pH when either an acid or a base has been added Presence of a weak acid and its conjugate base buffers the solution

B. Buffered Solutions

C. Lab Techniques Buret Filling Buret Clearing Buret Reading Carol

To learn about acid-base titrations Objectives Review To learn about acid-base titrations To demonstrate calculations and techniques for titration lab To understand the general characteristics of buffered solutions Work Session: Review Page 586 1, 3, 4

A. The pH Scale

A. The pH Scale

C. Calculating the pH of Strong Acid Solutions Determine the [H+]. pH = log[H+]