Acids And Bases

Class question Where can acids be found? –Sodas –Stomach –Vinegar –Citrus fruits Where can bases be found? –Soap –Drano –Antacid tablets –Windex –detergent

Properties of Acids Taste sour React with bases Litmus paper test – turn blue litmus paper red Electrolytic – conduct electricity

Properties of Bases Taste bitter Feels slippery React with acids Litmus paper test – turn red litmus paper blue electrolytic

Nomenclature of Acids Acids are composed of a(n) ________________ followed by a(n)_______ Hydrogen ion (H + ) anion Ex: H + + Cl 1- H + + SO 4 2- HCl H 2 SO 4

Binary Acids H + + anion H + + anion with –ide ending  acid name is __________________ HCl anion? _______ acid name ________________ Hydro _____ic acid Hydrochloric acid chloride

Binary Acids H + + anion H + + anion with –ide ending  acid name is __________________ HF anion? _______ acid name ________________ Hydro _____ic acid Hydrofluoric acid fluoride

Oxyacids H + + anion H + + anion with –ate ending  acid name is __________________ HNO 3 anion? _______ acid name ________________ _____ic acid nitric acid nitrate

Oxyacids H + + anion H + + anion with –ate ending  acid name is __________________ H 2 SO 4 anion? _______ acid name ________________ _____ic acid sulfuric acid sulfate

Oxyacids H + + anion H + + anion with –ite ending  acid name is __________________ HNO 2 anion? _______ acid name ________________ _____ous acid nitrous acid nitrite

Oxyacids H + + anion H + + anion with –ite ending  acid name is __________________ HClO 2 anion? _______ acid name ________________ _____ous acid chlorous acid chlorite

Writing acid formulas Hydrobromic acid anion? ___________ formula ______ Acetic acid anion? ___________ formula ______ Nitrous acid anion? ___________ formula ______ HBr HC 2 H 3 O 2 HNO 2 Bromide (Br 1- ) acetate(C 2 H 3 O 2 1- ) nitrite (NO 2 1- )

Nomenclature of Bases Bases are composed of a(n) _______ followed by a(n) ________________ cation hydroxide (OH 1- )

Writing Base Names Rule: name the cation and add “hydroxide” NaOH Mg(OH) 2 Fe(OH) 3 sodium hydroxide magnesium hydroxide Iron (III) hydroxide Memorize: NH 3 = ammonia

Writing base formulas potassium hydroxide cation? ______ formula ______ Calcium hydroxide cation? ______ formula ______ Aluminum hydroxide cation? ______ formula ______ KOH Ca(OH) 2 Al(OH) 3 K+K+ Ca 2+ Al 3+

Ions In Solution Why are some solutions acidic, basic, or neutral? It depends on number of H + and OH - ions present.

Ions In Solution Acidic solution – contain more H + ions than OH - ions 4000 H + and 0 OH - is acidic 1000 H + and 500 OH - is acidic 5 H + and 3 OH - is acidic

Ions In Solution Basic Solution – contain more OH - ions than H + ions 4000 OH - and 0 H + is basic 1000 OH - and 500 H + is basic 5 OH - and 3 H + is basic

Ions In Solution Neutral Solution – equal amounts of H + and OH - ions 4000 OH - and 4000 H + is neutral 1000 OH - and 1000 H + is neutral 5 OH - and 5 H + is neutral

Self Ionization of Water Proper ionization H 2 O + H 2 O  hydronium ion O HH H H O HH O HH O  + + H 3 O + + OH -

Self Ionization of Water simplified version H 2 O → H + + OH -

Types of Acids/Bases Arrhenius Model Bronsted-Lowry Model Lewis Model

Arrhenius Model of Acids and Bases Arrhenius Acids –D–Defn: contain H + and ionizes to form H + –E–Examples HCl  HNO 3  H + + Cl - H + + NO 3 - makes solution ACIDIC

Arrhenius Model of Acids and Bases Arrhenius Bases –Defn: –contain OH - and ionizes to produce OH - ions –Examples NaOH  Ca(OH) 2  Na + + OH - Ca OH - makes solution BASIC

Flaw with Arrhenius model Not all bases contain hydroxide Ex: ammonia (NH 3 ) is basic Therefore a new type of acid/base must be determined

Bronsted-Lowry Model Bronsted-Lowry Acid –Defn: proton/H + donor can give H + to another species Bronsted-Lowry Base –Defn: proton/H + acceptor can take H + from another species

Bronsted-Lowry Model REMEMBER!!!! REMEMBER!!!! acids donate, bases accept protons Abigail doesn’t buy apples.

Examples HCl + H 2 O  Cl - + H 3 O + What is happening here? Acid (donates proton) Base (accepts proton) Which is the acid? base?

Bronsted-Lowry Model Examples NH 3 + H 2 O  NH OH - What is happening here? Acid (donates proton) Base (accepts proton) Which is the acid? base?

Lewis Model Lewis acid –an atom, ion, or molecule that accepts an electron pair to form a covalent bond Lewis base –An atom, ion, or molecule that donates an electron pair to form a covalent bond

Lewis Model Lewis acid-base reaction –The formation of one or more covalent bonds between an electron-pair donor and an electron-pair acceptor

Conjugate Acid/Base Pairs Conjugate acid – new species produced when base gains H + ion Conjugate base – new species produced when acid donates H + ion

Conjugate Acid/Base Pairs general Bronsted-Lowry reaction acid + base  conj. acid + conj. base conj. acid/base pair Every acid has a conjugate base. Every base has a conjugate acid.

Conjugate Acid/Base Pairs Examples HNO 3 + H 2 O  H 3 O + + NO 3 - What is the acid? base? acidbase What is the conjugate acid/base? C.A.C.B. conj. acid/base pair

Conjugate Acid/Base Pairs Examples NH 3 + H 2 O  NH OH - What is the acid? base? acidbase What is the conjugate acid/base? C.B.C.A. conj. acid/base pair

Conjugate acid-base pairs What is the conjugate base of: H 2 SO 4 _________ H 3 O + ________ What is the conjugate acid of: HPO 4 2- _________ OH 1- ________ HSO 4 1- H 2 PO 4 1- H2OH2O H2OH2O How can H 2 O be both acid and base?

What is the conjugate base? AcidConjugate Base H 2 SO 4 HPO 4 2- NH 4 1+ H 3 O 1+ H 2 O HSO 4 1- PO 4 3- NH 3 H 2 O OH - How can H 2 O be both acid and base?

Amphoteric Defn – substance that can act as both acids and bases HNO 3 + H 2 O  H 3 O + + NO 3 - NH 3 + H 2 O  NH OH - base acid Water is amphoteric b/c it is acts as a base in one reaction and acts as an acid in the second Is H 2 O a base or acid? Is H 2 O a base or acid?

Mono-, Di-, Triprotic Acids Defns –monoprotic (HA) – one ionizable proton ex: HF, HCl, HBr (= normality is 1) –diprotic (H 2 A) – two ionizable protons ex: H 2 SO 4, H 2 CO 3 (= normality is 2) –triprotic (H 3 A) – three ionizable protons ex: H 3 PO 4, H 3 BO 3 (= normality is 3)

Polyprotic Acid Ionization Always forms ONE H + H 3 PO 4  H 2 PO 4 1-  HPO 4 2-  H 2 PO H + HPO H + PO H +

Strong Acid/Base Defn – acid or base that completely ionizes HA H + + A - XOH X + + OH - 100% ionization  every single HA molecule ionizes into H+ and A- 100% ionization

Strong Acid Illustration H A H A H A H A H A H A All break into ions + + +

Strength of Acids and Bases Acid/base strength is based on  the degree to which they ionize 1) strong (  ) 2) weak (  )

6 Strong Acids HCl – hydrochloric acid HBr – hydrobromic acid HI – hydroiodic acid HClO 4 – perchloric acid H 2 SO 4 – sulfuric acid HNO 3 – nitric acid

Strong Bases Group I and II metal hydroxides LiOH NaOH KOH RbOH Mg(OH) 2 Ca(OH) 2 Sr(OH) 2 Ba(OH) 2 No need to memorize exact ones

Weak Acid/Base Defn – acid or base that partially ionizes HA H + + A - XOH X + + OH - partial ionization Únot all will ionize; the weaker it is the less it ionizes

Weak Acid Illustration H A H A H A H A H A H A + - Only some break into ions +

What are the weak acids and bases? The ones that are NOT strong

Strong or weak, concentrated or diluted For acids and bases, it is important to distinguish between concentrated and dilute from strong and weak. The words _________ and __________ have different meanings. Similarly, ___________ and ___________ are not the same either. strong weak concentrated dilute

Strong or weak, concentrated or diluted Strong and weak refer to ____________________________ Concentrated and dilute refer to ____________________________ how much substance ionizes how much solute is present

Example 1 M HCl 12 M HCl 1 M H 2 CO 3 12 M H 2 CO 3 Strong and dilute Strong and concentrated weak and dilute weak and concentrated

Ion Product Constant for Water (K w ) Defn: equilibrium value for self ionization of water (H 2 O  H + + OH - ) Formula K w = [H + ][OH - ] = 1 x ALWAYS

Ion Product Constant for Water (K w ) in pure water  [H + ] = [OH - ] = 1 x M in non pure water  (acidic/basic conditions), value of [H + ] and [OH - ] differ Remember pure water is neutral But still [H + ][OH - ] = 1 x

Is solution acidic, basic, or neutral? Acidic Basic neutral [H + ] > [OH - ] [H + ] < [OH - ] [H + ] = [OH - ]

pH and pOH pH a)Defn: pH = -log [H + ] b)Scale: range from 0 to ACIDICBASIC (neutral) pH

c)change one pH unit  represents a ten fold change in strength - ex: pH = 3 vs pH = 4 pH 3 is 10 1 or 10 times more acidic - ex: pH = 7 vs pH = 10 pH 7 is 10 3 or 1000 times more acidic

pOH Formula: -log [OH - ]

Relation of pH and pOH pH + pOH = 14 If given one variable, subtract to find the other

Overall Relationship pHpOH [H + ][OH - ]

Sample problem #1 Calculate the pH of a solution with [H + ] = 3.0 x M. pH = -log [H + ] = - log [3.0 x ] = 5.52

Sample problem #2 Calculate the pH of a solution with [OH - ] = 8.2 x pOH= -log[OH - ] = -log [8.2 x ] = 5.09

Sample problem #2 pH + pOH = 14 pH = 14 pH = 8.91

Sample problem #2 Calculate the pH of a solution with [OH - ] = 8.2 x [H + ][OH - ] = 1 x [H + ][8.2 x ] = 1 x [H + ] = 1.22 x pH = -log[1.22 x ] = 8.91

Sample problem #3 What is the [H + ] of a solution with pH = 2? pH = -log[H + ] [H + ] = 10 -pH = = 0.01 M

Sample problem #4 (i) What is the [OH-] of a solution with pOH = 3.7? [OH - ] = 10 -pOH [OH - ] = = x M = 2.0 x M

Sample problem #4 (ii) What is the pH? pH + pOH = 14.0 pH = 14.0 pH = 10.3

Sample problem #4 (iii) What is the [H + ] ? [H + ] = 10 -pH = = 5.01 x M

Reaction between acids and bases Neutralization (defn) – reaction of acid and base to form a salt and water –The reaction is a double replacement Salt (defn) – ionic compound made of cation from base and anion from acid

Reaction between acids and bases Ex reaction Mg(OH) 2 + HCl  MgCl 2 + H 2 O baseacidsalt water Mg 2+ + OH - H + + Cl - Mg 2+ - cation from base Cl - - anion from acid

Ex problems i) What is the salt formed from sulfuric acid (H 2 SO 4 ) and potassium hydroxide (KOH)? base cation? acid anion? K + SO 4 2- What is salt?K 2 SO 4

ii) What is the salt formed when Al(OH) 3 and HBr react? base cation? acid anion? Al 3+ Br - What is salt?AlBr 3

Is salt solution acidic, basic, or neutral? a)strong acid + strong base  b)strong acid + weak base  c) weak acid + strong base  Neutral salt acidic salt basic salt

Ex problem Determine if salt solution is acidic, basic, or neutral. a)LiBr acid? base? HBr LiOH (strong acid) (strong base) Salt is ____________ NEUTRAL  Li + + Br -

Ex problem Determine if salt solution is acidic, basic, or neutral. b)Fe(NO 3 ) 3 acid? base? HNO 3 Fe(OH) 3 (strong acid) (weak base) Salt is ____________ ACIDIC  Fe 3+ + NO 3 -

Acid-Base Indicator A compound that will change color as the pH changes –Phenolphthalein changes between clear and pink –Hydrangeas grow pink or blue depending on the pH of their soil

How does an indicator work? Indicators are weak acids or weak bases. In the acid form they have one color. When they switch to the base form they have a different color.

Titration The controlled addition and measurement of the amount of a solution of known concentration required to react completely with a measured amount of a solution of unknown concentration.

Why do we use titrations? To experimentally determine the concentration of a solution –The bottle wasn’t labeled –The label faded –Your chemistry teacher is evil

How do we conduct a titration? 1.Measure a volume of the solution of unknown concentration into a flask. 2.Add 3 to 5 drops of indicator. 3.While stirring slowly add a measured volume of the solution of known concentration to the flask. 4.Use math to find the concentration you don’t know. Read pages 500 – 501 for a more detailed explanation, including pictures showing this process.

Equivalence point: Moles of hydrogen ions = moles of hydroxide ions M H+ V H+ = M OH- V OH-

End Point When the indicator changes color This is when you stop adding the known into the unknown Use the volume at the end point for your calculations

Sample Problem In a titration, 25.0 mL of M Ba(OH) 2 neutralizes 16.5 mL of HCl solution. What is the molarity of the HCl solution?

Sample Problem In a titration, 25.0 mL of M Ba(OH) 2 neutralizes 16.5 mL of HCl solution. What is the molarity of the HCl solution? N b = * 2 = (2 hydroxides in each one)

Sample Problem In a titration, 25.0 mL of M Ba(OH) 2 neutralizes 16.5 mL of HCl solution. What is the molarity of the HCl solution? N b = * 2 =

Sample Problem In a titration, 25.0 mL of M Ba(OH) 2 neutralizes 16.5 mL of HCl solution. What is the molarity of the HCl solution? N b = * 2 =