Chapter 20Chapter 20

DefinitionsDefinitionsAcid:Acid: any substance that produces H+

in solutione.g.: HCl(g) H+

(aq) Cl-(aq)

(H2SO4, vinegar, lemon juice)

Base:Base:any substance that produces OH- in solution

e.g.: NaOH(s) Na+(aq) OH-

(aq)

(KOH, detergents, oven cleaner)

CharacteristicsCharacteristics

AcidsAcids BasesBases

taste sourtaste sour taste bittertaste bitterreact with metals producing Hreact with metals producing H22

gasgas feel slipperyfeel slippery

produce Hproduce H++ produce OHproduce OH--

conduct electricityconduct electricity conduct electricityconduct electricity

Neutralization ReactionsNeutralization Reactionswhenever an acid reacts with a base,

a neutralization reaction takes place.

e.g.:

HCl(aq) H2O(l) NaCl(aq)

net ionic equation:

H2O(l)H+(aq)OH-

(aq)

NaOH(aq)NaOH(aq) HCl(aq)

base acid water salt

Acid / Base TitrationsAcid / Base Titrationsa solution of base (NaOH) with known concentration

is used to determine the concentration of acid (HCl) in another solution.

e.g.:

HCl(aq) H2O(l) NaCl(aq)NaOH(aq)

standard unknown

Acid / Base Titrations Acid / Base Titrations continuedcontinued

an acid / base indicator (or pH meter) is used to identify when all of the acid in an unknown sample has been neutralized by the base.

the number of moles of OH- equals the number of moles of H+ when the pH = 7 (neutral)

Problem:

It takes 35.0 mL of 6.0 M NaOH to neutralize the acid in a 750 mL HCl solution of unknown concentration.

What is the concentration of the HCl solution?

Titration Problem Titration Problem SolutionSolution

HCl(aq) H2O(l) NaCl(aq)NaOH(aq)

= 0.21 molmoles NaOH = 0.0350 L 6.0 M

moles of OH- equal moles of H+ when neutral

moles OH- = 0.21 mol

therefore, moles H+ = 0.21 mol

NaOH(aq) Na+(aq) OH-

(aq)

HCl(aq) H+(aq) Cl-

(aq)

= moles HCl

[HCl] = 0.21 mol

0.750 L= 0.28 M

AssignmentAssignment In Class:In Class:

Page 595Page 595Questions 1-5Questions 1-5

Homework:Homework:Read Experiment 13C (pp. 195-199)Read Experiment 13C (pp. 195-199)There will be a There will be a Pre-Lab QuizPre-Lab QuizOnline Titration Tutorial Online Titration Tutorial AssignmentAssignment