intro to acids & bases. properties of acids & bases acids acids taste sour taste sour reacts...

Intro to Acids & BasesIntro to Acids & Bases

Properties of Acids & BasesProperties of Acids & Bases

AcidsAcids Taste sourTaste sour Reacts with metalsReacts with metals Turns litmus redTurns litmus red Conducts Conducts

electricityelectricity

BaseBase Taste bitterTaste bitter SlipperySlippery Turns litmus blueTurns litmus blue Conducts Conducts

electricityelectricity

Ions in SolutionIons in Solution

Acidic solutionsAcidic solutions – contain more H – contain more H++ than OHthan OH--

Basic solutionsBasic solutions – contain more OH – contain more OH-- than Hthan H++

Neutral solutionsNeutral solutions – contain equal – contain equal amounts of Hamounts of H++ and OH and OH--

Autoionization of WaterAutoionization of Water

HH22O + HO + H22O O H H33OO++ + OH + OH--

Water is the usual solvent for acids Water is the usual solvent for acids and basesand bases

It produces equal numbers of HIt produces equal numbers of H33OO++ and OHand OH--

Arrhenius Model of Acids & Arrhenius Model of Acids & BasesBases

Acid:Acid: a substance that contains H a substance that contains H and ionized to produce Hand ionized to produce H+ + when when dissolved in water. dissolved in water.

Base:Base: a substance that contains OH a substance that contains OH and ionizes to produce OHand ionizes to produce OH-- when when dissolved in water dissolved in water


HCl HCl H H++ + Cl + Cl--

HCl contains H and ionizes to form HHCl contains H and ionizes to form H++

This could be an Arrhenius acidThis could be an Arrhenius acid NaOH NaOH Na Na++ + OH + OH--

NaOH contains OH and ionized to NaOH contains OH and ionized to form OHform OH--

This could be considered an This could be considered an Arrhenius baseArrhenius base


Although the Arrhenius model is Although the Arrhenius model is useful in describing many acids and useful in describing many acids and bases, it does not describe them allbases, it does not describe them all

For example NHFor example NH33 contains no OH contains no OH-- ions, but it is a baseions, but it is a base

A model to describe all bases is A model to describe all bases is neededneeded

Bronsted-Lowry ModelBronsted-Lowry Model

Acid:Acid: proton donor proton donor Base:Base: proton acceptor proton acceptor HX + HHX + H220 0 H H33OO++ + X + X--

HX donates an HHX donates an H++ to the water to the water moleculemolecule

The water takes the H and is there The water takes the H and is there for considered the basefor considered the base

Bronsted-Lowry ModelBronsted-Lowry Model

Conjugate acidConjugate acid – the species – the species produced when a base accepts the produced when a base accepts the HH++ ion from the acid ion from the acid

Conjugate baseConjugate base – the species – the species produced when the acid gives up its produced when the acid gives up its HH++

Conjugate Acids & Conjugate Conjugate Acids & Conjugate BasesBases

Identify the acid, base, conjugate Identify the acid, base, conjugate acid, and conjugate base of the acid, and conjugate base of the following reaction…following reaction…

HX + HHX + H220 0 H H33OO++ + X + X--

A B CA CBA B CA CB Every Bronsted-Lowry interaction Every Bronsted-Lowry interaction

involves conjugate acid base pairsinvolves conjugate acid base pairs


Identify the acid, base, conjugate Identify the acid, base, conjugate acid, and conjugate base of the acid, and conjugate base of the following reaction…following reaction…

NHNH33 + H + H220 0 NH NH44++ + OH + OH--

B A CA CBB A CA CB


What did you notice that was What did you notice that was different about the previous two different about the previous two reactions?reactions?

Water was an acid in one and a base Water was an acid in one and a base in the otherin the other

Amphoteric Amphoteric – substance that can – substance that can act as either an acid or a baseact as either an acid or a base


Identify the acid, base, conjugate Identify the acid, base, conjugate acid, and conjugate base of the acid, and conjugate base of the following reactions…following reactions…

NHNH44++ + OH + OH-- NH NH33 + H + H2200

A B CB CAA B CB CA

HBr + HHBr + H22O O H H33OO++ + Br + Br --

A B CA CBA B CA CB

Neutralization ReactionsNeutralization Reactions

Neutralization reactionsNeutralization reactions – acid + – acid + base base a salt + water a salt + water

Neutralization reactions are just a Neutralization reactions are just a special type of double replacement special type of double replacement reactionsreactions

Write the equations for the following Write the equations for the following neutralization reactionsneutralization reactions

Acetic acid and ammonium hydroxideAcetic acid and ammonium hydroxide HCHHCH33COO + NHCOO + NH44OH OH HOH + NH HOH + NH44CHCH33COOCOO

Nitric acid and cesium hydroxideNitric acid and cesium hydroxide HNOHNO33 + CsOH + CsOH HOH + CsNO HOH + CsNO33

Neutralization ReactionsNeutralization Reactions

The pH ScaleThe pH Scale

[H[H++] is often expressed in very small ] is often expressed in very small numbers. Chemists needed an easier numbers. Chemists needed an easier way to express [Hway to express [H++] ions] ions

pHpH is a mathematical scale in which is a mathematical scale in which the concentration of hydronium ions the concentration of hydronium ions in a solution is expressed as a in a solution is expressed as a number from 0 to 14.number from 0 to 14.

pH = -log[HpH = -log[H++]]

Interpreting the pH ScaleInterpreting the pH Scale

pH of 7 is neutral. A pH less than 7 is pH of 7 is neutral. A pH less than 7 is acidic, and a pH greater than 7 is acidic, and a pH greater than 7 is basic.basic.

pH CalculationspH Calculations

pH = -log[HpH = -log[H++]] pOH = -log[OHpOH = -log[OH--]] pH + pOH = 14pH + pOH = 14

Calculating pHCalculating pH

What is the pH of a 0.5M HCl What is the pH of a 0.5M HCl solution?solution?

0.5 mol HCl0.5 mol HCl x x 1 mol H1 mol H++ = 0.5M H = 0.5M H++

L 1 mol HClL 1 mol HCl pH = -log[HpH = -log[H++]] pH = -log[0.5]pH = -log[0.5] pH = 0.3pH = 0.3


Calculate the pH of a 0.0057M HBr Calculate the pH of a 0.0057M HBr solution. solution.

2.22.2


What if we have a base?What if we have a base? What is the pH of a 0.05M NaOH solution?What is the pH of a 0.05M NaOH solution? 0.05 mol NaOH0.05 mol NaOH x x 1 mol OH1 mol OH-- = 0.05M OH = 0.05M OH--

L 1 mol NaOHL 1 mol NaOH pOH = -log[OHpOH = -log[OH--]] pOH = -log[0.05]pOH = -log[0.05] pOH = 1.3pOH = 1.3 pH + pOH = 14pH + pOH = 14 pH = 12.7pH = 12.7


Calculate the pH of a 0.000089M Calculate the pH of a 0.000089M KOH solution.KOH solution.

9.959.95

Acid/Base StrengthAcid/Base Strength

The strength of an acid or a base The strength of an acid or a base tells you the degree of ionizationtells you the degree of ionization

Strong acids & bases break down Strong acids & bases break down into many ionsinto many ions

Weak acids & bases break down into Weak acids & bases break down into just a few ionsjust a few ions


Strong acids Weak acids

hydrochloric acid, HCl acetic acid, CH3COOH

hydrobromic acid, HBr

hydrocyanic acid, HCN

hydriodic acid, HI hydrofluoric acid, HF

nitric acid, HNO3 nitrous acid, HNO2

sulfuric acid, H2SO4 sulfurous acid, H2SO3

perchloric acid, HClO4

hypochlorous acid, HOCl

periodic acid, HIO4 phosphoric acid, H3PO4


Strong bases Weak bases

sodium hydroxide, NaOH ammonia, NH3

potassium hydroxide, KOH

sodium carbonate, Na2CO3

calcium hydroxide, Ca(OH)2

potassium carbonate, K2CO3

barium hydroxide, Ba(OH)2

aniline, C6H5NH2

sodium phosphate, Na3PO4

trimethylamine, (CH3)3N

intro to acids & bases. properties of acids & bases acids acids taste sour taste sour reacts...

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