2 Friday, May 6th: “A” Day Agenda Homework questions/problems/collectQuiz over section 15.2: “Acidity, Basicity, and pH”Section 15.3: “Neutralizations and Titrations”Neutralization reaction, equivalence point, titration, titrant, standard solution, transition range, end pointHomework:Sec review, pg. 556: #1-10Concept Review: “Neutralizations and Titrations”Lab Write-Up: “Titration of an Acid and a Base”
3 Section 15.2 Quiz “Acidity, Basicity, and pH” You may use your guided notes, your book, and a partner to complete the quiz.
4 H3O+(aq) + OH−(aq) 2 H2O(l) NeutralizationNeutralization reaction: the reaction of hydronium ions and hydroxide ions to form water molecules and a salt.When solutions of a strong acid and a strong base, having exactly equal amounts of H3O+(aq) and OH−(aq) ions, are mixed, almost all of the hydronium and hydroxide ions react to form water.H3O+(aq) + OH−(aq) 2 H2O(l)*correct*
5 NeutralizationSuppose that hydrochloric acid, HCl, and sodium hydroxide, NaOH are mixed.The result will be a solution of only water and the spectator ions sodium and chlorine.This is just a solution of sodium chloride.HCl + NaOH NaCl + H2OThis representation can be misleading because the only reactants are H3O+(aq) and OH−(aq) ions and the only product is H2O.
6 TitrationsIf an acidic solution is added gradually to a basic solution, at some point the neutralization reaction ends because the hydroxide ions are used up.Likewise, if a basic solution is added to an acid, eventually all of the hydronium ions will be used up.The point at which a neutralization reaction is complete is known as the equivalence point.Equivalence point: the point at which the two solutions used in a titration are present in chemically equivalent amounts.
7 TitrationsWhen a solution of a strong base is added to a solution of a strong acid, the equivalence point occurs when the amount of added hydroxide ions equals the amount of hydronium ions originally present.Titration: the gradual addition of one solution to another to reach an equivalence point.The purpose of a titration is to determine the concentration of an acid or a base.
8 TitrationIn addition to the two solutions, the equipment needed to carry out a titration usually includes two burets, a titration flask, and a suitable indicator.One buret is for the acid solution, the other is for the basic (alkaline) solution.Titrant: a solution of known concentration that is used to titrate a solution of unknown concentration.
9 TitrationTo find the concentration of the solution being titrated, you must already know the concentration of the titrant.Standard solution: a solution of known concentration.The concentration of a standard solution has usually been determined by reacting the solution with a precisely weighed mass of a solid acid or base.
10 TitrationA distinctively shaped graph, called a titration curve, results when pH is plotted against titrant volume.Because the curve is steep at the equivalence point, it is easy to locate the exact volume that corresponds to a pH of 7.00.A titration is exact only if the equivalence point can be accurately detected.
11 Equivalence PointThis graph of pH versus the volume of M NaOH added to an HCl solution indicates that the equivalence point occurred after 38.6 mL of titrant was added.
12 IndicatorsTransition range: the pH range through which an indicator changes color.End point: the point in a titration at which a marked color change takes place.If an appropriate indicator is chosen, the end point and the equivalence point will be the same.
13 Selecting an Indicator In titrations of a strong acid by a strong base, the equivalence point occurs at pH 7.When a weak acid is titrated by a strong base, the equivalence point is at a pH greater than 7.The titration of a weak base and a strong acid, the equivalence point is at a pH less than 7.
16 Titration Calculations At the equivalence point in a titration of a strong acid by a strong base, the amount of hydroxide ion added equals the initial amount of hydronium ion.C: concentration (in moles per liter)V: volume (in liters) of the solution
17 Titration Calculations An easier way to think of this:(C Acid)(V Acid) = (C Base) (V Base)C: concentration (in moles per liter)V: volume (in liters) of the solution
18 (CAcid) (VAcid) = (CBase) (VBase) Sample Problem D, pg. 555 Calculating Concentration from Titration DataA student titrates mL of an HCl solution of unknown concentration with a M NaOH solution. The volume of base solution needed to reach the equivalence point is mL. What is the concentration of the HCl solution in moles/liter?(CAcid) (VAcid) = (CBase) (VBase)
19 Sample Problem D, continued… NaOH is a strong base so:NaOH Na + + OH-M MC(acid) = ?V(acid) = mL = .04LC(base) = MV(base) = mL = L(CAcid) (VAcid) = (CBase) (VBase)C (Acid) (.04 L) =( M) ( L)C(acid) = mol/L
20 Additional PracticeIf 72.1 mL of M H2SO4 completely titrates 39.0 mL of KOH solution, what is the molarity of the KOH solution?H2SO4 is a strong acid so:H2SO H2O SO H3O +0.543 M MBecause of the 1:2 ratio, 1 mole of H2SO4 makes 2 moles of H3O +.[H3O+] = 2 [H2SO4] = 2 (0.543 M) = M
21 Additional Practice, continued… (CAcid) (VAcid) = (CBase) (VBase)C(acid) = MV(acid) = 72.1 mL = LC(base) = ?V(base) = 39.0 mL = L(1.086 M) (.0721 L) = (C Base) (.0390L)C(base) = 2.01 M
22 U of I 3D-Printing Presentation on Tuesday! Titration lab on Thursday HomeworkSection 15.3 review, pg. 556: #1-10Concept Review: “Neutralizations and Titrations”Lab Write-Up: “Titration of an Acid and a Base”Looking Ahead:U of I 3D-Printing Presentation on Tuesday!Titration lab on ThursdayNo Flip-Flops!
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