Taste sour Taste sour Form solution that conduct electricity Form solution that conduct electricity React with metals React with metals Turn blue litmus paper to red Turn blue litmus paper to red React with bases to form salt and water React with bases to form salt and water Ex: fruit juice, vinegar, milk Ex: fruit juice, vinegar, milk

Form solutions that conduct electricity Form solutions that conduct electricity Slippery or soapy in the skin Slippery or soapy in the skin Taste bitter Taste bitter Turn red litmus paper to blue Turn red litmus paper to blue Reacts with acids to form salt and water Reacts with acids to form salt and water Ex: soap, shampoo, cleaning agent Ex: soap, shampoo, cleaning agent

Arrhenius Theory By Svante August Arrhenius By Svante August Arrhenius Acids form hydrogen ion(H+) in aqueous solutions Acids form hydrogen ion(H+) in aqueous solutions Bases form hydroxide ion (OH-) Bases form hydroxide ion (OH-) in aqueos solution in aqueos solution Ex: HCl(g)-----> H + (aq) + Cl - (aq) Ex: HCl(g)-----> H + (aq) + Cl - (aq) KOH -----> K + + OH - (aq) KOH -----> K + + OH - (aq)

Bronsted-Lowry Denition By Johannes Bronsted and Thomas Lowry By Johannes Bronsted and Thomas Lowry Acid is a proton donor Acid is a proton donor Base is a proton acceptor Base is a proton acceptor Ex: Ex: HCl + H 2 O ---> H 3 O + Cl- HCl + H 2 O ---> H 3 O + Cl- NH 3 + H 2 O  NH 3 + H 2 O 

Bronsted-Lowry Definition The general reaction when an acid is dissolved in water is best represented by an acid donating H + to water molecule to form a new acid (conjugate acid) and a new base( conjugate base) The general reaction when an acid is dissolved in water is best represented by an acid donating H + to water molecule to form a new acid (conjugate acid) and a new base( conjugate base) acid base conjugate Conjugate. Acid base acid base conjugate Conjugate. Acid base HA (aq) + H 2 0 (l) ----> H 3 O + (aq) + A - (aq) HA (aq) + H 2 0 (l) ----> H 3 O + (aq) + A - (aq)

Ex: HCl + H 2 O ---> H 3 O + + Cl - acid base conjugate conjugate acid base conjugate conjugate acid base acid base

Identify the acid and the base in the following reactions: HSO PO > HO SO 4 2- HSO PO > HO SO 4 2- HNO 3 + H 2 O ---> H 3 O + + NO 3- HNO 3 + H 2 O ---> H 3 O + + NO 3- H 3 PO 4 + CN - ---> H 2 PO HCN H 3 PO 4 + CN - ---> H 2 PO HCN Answers Answers Acid base Acid base a) HSO 4 - PO 4 3- b) HNO 3 H 2 O c) HCN H 2 PO 4 -

Conjugate Acid-base pair Consists of two substances related to each other by donating and accepting of a single proton Consists of two substances related to each other by donating and accepting of a single proton Acid-conjugate base pair Acid-conjugate base pair Ex: HCl(aq) + H 2 O(l)  H 3 O + + Cl - Base-conjugate acid pair Base-conjugate acid pair H 3 O + --> hydronium ion H 3 O + --> hydronium ion

Which of the following represent Conjugate acid-base pair? A) HF, F - A) HF, F - B) NH 4 +, NH 3 B) NH 4 +, NH 3 C) HCl, H 2 O C) HCl, H 2 O Answer Answer A and B are conjugate acid base pair because they differ by one H+ C is not because the conjugate acid-base pair of HCl is Cl-

Writing Conjugate Bases Write the conjugate base for each of the following: Write the conjugate base for each of the following: a) HClO 4 a) HClO 4 HClO > H + ClO 4 - HClO > H + ClO 4 - conjugate base conjugate base b) H 3 PO 4 b) H 3 PO 4 H 3 PO 4  H + H 2 PO 4 H 3 PO 4  H + H 2 PO 4 conjugate base conjugate base

Practice: Classwork Which of the following represent conjugate acid-base pair? A) HClO 4, ClO 4 - B) HCl, ClO - C) H 2 PO 4 -, HPO 4 2- D) HNO 3, NO 3- Write the conjugate base for each of the ff: a) H 2 S b) NH 3 c) H 2 SO 3

Answer Which of the following represent conjugate acid-base pair? A) HClO 4, ClO 4 - B) HCl, ClO - C) H 2 PO 4 -, HPO 4 2- D) HNO 3, NO 3- Write the conjugate base for each of the ff: a) H 2 S  HS - b) NH 3  NH 2 - c) H 2 SO 3  HSO 3 -

Lewis Theory Gilbert Lewis Gilbert Lewis Chemical reactions involve the arrangement of the valence electrons of an atom. Chemical reactions involve the arrangement of the valence electrons of an atom. Acid is an electron pair acceptor Acid is an electron pair acceptor Base is an electron pair donor Base is an electron pair donor H 2 O + NH 3 H 2 O + NH 3 H H + H H + H-O-H + : N H ---> H-N-H + OH - H-O-H + : N H ---> H-N-H + OH - H H H H Lewis Acid Lewis Base

Ex: reaction between BCl 3 and NH 3 Cl H Cl H Cl – B + : N –H ---> Cl –B – N –H Cl H Cl H Lewis Lewis Lewis acid-base acid base adduct Adduct is the term used for the product of the Lewis Acid-base reaction

Strong Acids Bronsted-Lowry definition is useful in describing the strength of an acid Bronsted-Lowry definition is useful in describing the strength of an acid Strong acid is one that dissociates or ionizes completely in water Strong acid is one that dissociates or ionizes completely in water Ex:HCl + H 2 O  H 3 O + + Cl - Ex:HCl + H 2 O  H 3 O + + Cl -  Forward reaction predominates which indicates ionization is complete  Strong acid contains a weak conjugate base weaker than water

Weak Acid It does not completely dissociate or ionize. It does not completely dissociate or ionize. Ex: Acetic Acid( CH 3 COOH) Ex: Acetic Acid( CH 3 COOH) CH 3 COOH + H 2 O H CH 3 COO - CH 3 COOH + H 2 O H CH 3 COO - acetate ion acetate ion  The two arrows indicate that the ionization is not complete  The reverse reaction predominates that means only few ions are dissociated  Weak acid contains relatively strong conjugate base

Strong Bases Common strong bases are those that contain the hydroxide ion Common strong bases are those that contain the hydroxide ion Ex:,NaOH,KOH Mg(OH) 2, Ca(OH)2 Ex:,NaOH,KOH Mg(OH) 2, Ca(OH)2 Ba(OH) 2 Ba(OH) 2 Very soluble in water Very soluble in water

Weak Bases The strengths of bases that do not have OH - are described in the same way that the strengths of the acids were described The strengths of bases that do not have OH - are described in the same way that the strengths of the acids were described Weak base does not completely dissociate in water Weak base does not completely dissociate in water Ex: NH 3 + H 2 O NH OH- Ex: NH 3 + H 2 O NH OH- reverse reaction predominates reverse reaction predominates

Show the ionization of H 2 SO 4 and NaOH H2O H2O H 2 SO 4 (l) ----> H + (aq) + SO 4 2- (aq) 2H + (aq) + SO 4 2- (aq) 2H + (aq) + SO 4 2- (aq) H2O H2O NaOH > Na + + OH -

Acid Strength StrongAcidStrongBase Moderate Acid WeakAcid Weak Base HClO 4 Perchloric acid NaOH H 3 PO 4 Phosphoric acid CH 3 COOH NH3 HClO 3 Chloric Acid KOHModerateBase H 2 CO 3 HCO3- HIMg(OH)2 CO 3 2- H 3 BO 3 CH3COO- HBrHydrobromicCa(OH)2 CH 3 COOH SO 4 2- H 2 SO 4 Sulfuric acid Ba(OH)2 Very Weak Acid Base Base HClHydrochloric H2OH2OH2OH2O H2OH2OH2OH2O HNO 3 Nitric Acid

Water as an acid and a base Amphoteric substance Amphoteric substance  A substance that can behave either as an acid or a base Ionizaton of water Ionizaton of water H 2 O(l) + H 2 O(l) ---> H 3 O + (aq) + OH - (aq) H 2 O(l) + H 2 O(l) ---> H 3 O + (aq) + OH - (aq) The forward reaction is not great The forward reaction is not great In pure water only a tiny amount of H 3 O + and OH - is present. In pure water only a tiny amount of H 3 O + and OH - is present. [H 3 O + ] = [OH - ] = 1.0x10 -7 M [H 3 O + ] = [OH - ] = 1.0x10 -7 M

The product of the H 3 O + and OH - concentrations is always constant at 25 0 C The product of the H 3 O + and OH - concentrations is always constant at 25 0 C [H 3 O] [OH - ] = 1x (1x ) ( 1 x ) = 1 x This is called the ion product constant of water ( Kw)  Note the product of H 3 O and OH - in any aqueous is constant which means when [OH - ] goes up the [H3O] must go down  Acidic solution  [H + ] > [OH - ]  Basic solution  [ H + ] < [OH - ]  Neutral solution  [H + ] = [OH - ]

Ex : calculate [H + ] or [OH - ] as required for each of the following at 25 0 C and state whether the solution is acidic, basic and neutral A) 1.0x10 -5 M OH - A) 1.0x10 -5 M OH - Given: [OH - ] = 1x10 -5 Given: [OH - ] = 1x10 -5 Find: H + Solution: [H + ] [OH - ] = 1x [H + ] = 1x [H + ] = 1x [OH - ] [OH - ] [H + ] = 1 x [H + ] = 1 x [ 1x10 -5 ] [ 1x10 -5 ] = 1x M = 1x M Since OH - = 1x10 -5 M H+ = 1x10 -9 M H+ = 1x10 -9 M The solution is basic since OH - > H +

b) 10.0M H + Find: OH - Find: OH - Solution: [H + ][OH - ] = 1 x [OH - ] = 1x [OH - ] = 1x M 10.0M = 1x 10-15M = 1x 10-15M [OH - ] = 1x [OH - ] = 1x [H + ] = 1x 10 1 M [H + ] = 1x 10 1 M [H + ] > [OH - ] = the solution is acidic

1. Which is greater [OH-] or [H+], if [H+]= 2.8x 10-5M an aqueous solution at 25 0 C? [H+]= 2.8x 10-5M an aqueous solution at 25 0 C? 2. How many times greater is [OH-] than [H+] if [H+] = 1.0x 10-9 M in aqueous solution at 250C? 3. Calculate the [H+] or [OH-] as required for each of the following at 250C and state whether the solution is neutral, acidic or basic. a) [H+] = 3.4 x M b) [H+] = 2.6x M c) [OH-] = 6.2 x M

The pH Scale  Was proposed by Soren Sorensen  Was proposed by Soren Sorensen ( Danish biochemist) ( Danish biochemist) pH means power of hydrogen pH means power of hydrogen Has a range from 0 to 14 and is logarithmic Has a range from 0 to 14 and is logarithmic which means that each step is ten times the previous which means that each step is ten times the previous Ex: pH of 5 is ten times more acid than 6 What about pH 5 and 7 What about pH 5 and 7 ---> pH 5 is 100times more acid than 7 What about pH 5 and 8?  1000 times acidic

pH scale 0-most acidic and 14 is most basic 0-most acidic and 14 is most basic At pH-7, water has equal amount of H + and OH - ions At pH-7, water has equal amount of H + and OH - ions [H+] = [OH-]  neutral [H+] > [OH-]  acidic [H+] < [OH-]  basic

pH of a solution Defined is the negative of the logarithm of the hydronium ion concentration, [H 3 O + ] Defined is the negative of the logarithm of the hydronium ion concentration, [H 3 O + ] pH = - log [H 3 O+] pH = - log [H 3 O+] Ex: Pure water has [H 3 O + ]= 1x10 -7 M. Find pH pH = -log[H 3 O + ] pH = -log[H 3 O + ] pH = -log[ 1x10 -7 M] pH = -log[ 1x10 -7 M] pH = - (-7) pH = - (-7) pH = 7 pH = 7

In Basic solution, In Basic solution, [OH-] can be expressed as pOH [OH-] can be expressed as pOH pOH = -log [OH - ] pOH = -log [OH - ] Recall that [H 3 O + ] [OH - ] = 1 x Using the definition of pH and pOH the equation can be translated as Using the definition of pH and pOH the equation can be translated as pH + pOH = 14 pH + pOH = 14 In summary, pH= -log[H 3 O + ] pOH = -log [OH - ] [H 3 O + ][OH - ] = 1x pH + pOH = 14

In Pure water, the concentrations of H 3 O + and OH - are equal [H3O + ] = [OH-] = 1x10 -7 M thus [H3O + ] = [OH-] = 1x10 -7 M thus pH and pOH are also equal pH and pOH are also equal pH = pOH = 7 pH + pOH = = 14

Ex: Find the pH and pOH of 0.001MHCl solution Find the pH and pOH of 0.001MHCl solution Given: [H 3 O + ] = 0.001M Given: [H 3 O + ] = 0.001M Find a) pH b) pOH Find a) pH b) pOH Solution Solution A) pH = -log [H 3 O + ] A) pH = -log [H 3 O + ] = -log [ 1x10 -3 ] = -(-3) = -log [ 1x10 -3 ] = -(-3) = 3 = 3 B) pH + pOH = 14 B) pH + pOH = 14 pOH = 14 - pH pOH = 14 - pH = =

Ex2: If the OH- is equal to M, Find the pH If the OH- is equal to M, Find the pH Solution: Get the pOH first pOH=-log[OH-] = -log(10 -5 M) = -log(10 -5 M) = -(-5) = -(-5) pOH = 5 Get the pH pH +pOH = 14 pH = 14 – pOH = 14 – 5 = 14 – 5 pH = 9

Class work A solution has a H 3 O+ concentration equal to 5.5x M. What is the pH of the solution? A solution has a H 3 O+ concentration equal to 5.5x M. What is the pH of the solution? The pH of rainwater in a locality is 3. What is the [H 3 O + ]? The pH of rainwater in a locality is 3. What is the [H 3 O + ]? What is the [H + ] of a solution with a pH of 4.2? What is the [H + ] of a solution with a pH of 4.2? The pOH of blood is 6.6. What is the pH of the blood? The pOH of blood is 6.6. What is the pH of the blood? Calculate the pH and pOH for each of the ff. Calculate the pH and pOH for each of the ff. A) a solution in which[H+] = 3.6 x M A) a solution in which[H+] = 3.6 x M B)[OH-] = 9.2 x 10-2M B)[OH-] = 9.2 x 10-2M The pH of the solution is What is the pOH of the solution? The pH of the solution is What is the pOH of the solution?