Titrations An Introduction. Have a cookie… Does anyone remember my delicious cookie recipe… 1 cup flour + 24 choc. chips  3 cookies (NO SUGAR ADDED!

Slides:



Advertisements
Similar presentations
Titrations An Introduction. Have a cookie… Remember my delicious cookie recipe: 1 cup flour + 24 choc. chips 3 cookies.
Advertisements

Stoichiometry of Precipitation Reactions
Calculations involving neutralization reactions
Neutralization Reactions Reaction that occurs between an acid and a base. Example: HCl + NaOH  NaCl + H 2 O & Water Products always include: A “Salt”
Acids and Bases Titrations AP Chemistry. Neutralization Reactions and Titrations Neutralization Reactions Strong acid + Strong Base  Salt + Water HCl.
Acid-Base Stoichiometry
Unit 4: TOXINS Stoichiometry, Solution Chemistry, and Acids and Bases
Titrations Main Idea: Titrations are an application of acid-base neutralization reactions that require the use of an indicator. 1.
Chapter 4.  Definitions  Bronsted - acids are proton donors, bases are proton acceptors  Arrhenius – acids produce H + ions in water and bases produce.
Solution Stoichiometry
Unit 6 – Acids and Bases.  Indicators are dyes that change colour under varying conditions of acidity.  Although not as accurate as instruments such.
Titration Chemistry: The Molecular Nature of Matter, 6 th edition By Jesperson, Brady, & Hyslop acid–base, 198–199, 811–819 redox reactions, 239–240.
Topic 1.5 Titrations. Titrations In a titration a solution of accurately known concentration is added gradually added to another solution of unknown concentration.
Strong Acid-Base Titrations Chapter 17. Neutralization Reactions Review Generally, when solutions of an acid and a base are combined, the products are.
There are several ways to test pH – Blue litmus paper red = acid – Red litmus paper blue = basic – pH paper multi-colored – pH meter 7 is neutral, 7 base.
Strength of Acids and Bases The strength of an acid (or base) is determined by the amount of IONIZATION This is not the concentration If the acid (or base)
Chapter 16 More Work with Acids and Bases pH Self-Ionization of Water: 2H 2 O H 3 O + + OH - -Occurs in 2 per 1 billion molecules in PURE (deionized.
Titration Calculations. An example of titration problem: I have a mL sample of a strong acid at an unknown concentration. After adding mL.
Molarity by Dilution Diluting Acids How to Calculate Acids in concentrated form are diluted to the desired concentration using water. Moles of acid before.
Neutralization Reactions
ACIDS AND BASES Acid Base Titration A very accurate method to measure concentration. Acid + Base  Salt + Water H + + OH -  H 2 O Moles H + = Moles.
Updates Assignment 06 is due Mon., March 12 (in class) Midterm 2 is Thurs., March 15 and will cover Chapters 16 & 17 –Huggins 10, 7-8pm –For conflicts:
(equimolar amounts of acid and base have reacted)
Titrations Acid Base Titrations Indicators Calculations.
Section 16.3 Titrations and Buffers 1.To know how to neutralize acids and bases (titration) Learning Goal.
19.4 Neutralization Reactions > 1 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Chemists use acid-base reactions to determine.
 Brønsted-Lowry – proton donor  Arrhenius – acids produce H + ions in water  HCl  H + + Cl -  HCl, HBr, HI, H 2 SO 4, HC 2 H 3 O 2.
TITRATIONS An Introduction 1. It’s your BIRTHDAY! I’m going to make you birthday cupcakes. Every birthday cupcake has two candles in it, or: 1 cupcake.
Titrations Main Idea: Titrations are an application of acid-base neutralization reactions that require the use of an indicator.
Titration 1.
Acid Base Titrations Chemistry 12◊ Chapter 14. Titration: A titration is a technique for finding an unknown concentration of one chemical from the known.
5.3.1 Neutralization reactions Titration Reactions.
Acid - Base Titration. What is a Titration? A titration is a procedure used in chemistry to determine the concentration of an unknown acid or base. A.
Ch Acids & Bases III. Neutralization (p )  Neutralization Reaction  Titration.
Molarity, pH, and Stoichiometry of Solutions Chapter 5 part 4.
Indicators and pH Meters
III. Titration (p ) Ch. 16 – Determining pH and Titrations.
NEUTRALIZATION, INDICATORS, AND TITRATIONS. NEUTRALIZATION REACTIONS So far we have only looked at acid and base reactions with water Ka and Kb reactions.
SOLUTION STOICHIOMETRY LECTURE 3 ACIDS AND BASES.
Titrations. Standard Solution Sample Solution Burette A titration is a volumetric analysis technique used to find the [unknown] of a sample solution by.
Titrations Chapter 13.
Titration. Definition Process used to determine the strength of an unknown acid or base Can determine the unknown acid by adding to it a base of known.
Acid-Base Reactions and Titrations Chemistry. Examples of Acid-Base Rxns HNO 3 + KOH  H 2 O + KNO 3 H 2 SO NH 4 OH  (NH 4 ) 2 SO H 2 O LiOH.
Acids and Bases Notes Part 2 Acid Rain Many industrial processes produce gases such as NO, NO 2, CO 2, SO 2, and SO 3. These compounds can dissolve in.
Objectives Describe how an acid-base indicator functions. Explain how to carry out an acid-base titration. Calculate the molarity of a solution from titration.
19.4 Neutralization Reactions. Neutralization During a neutralization reaction, an acid and a base react to produce a salt and water. Salts are ionic.
Acid-Base Reactions. Neutralization acid + base salt + water HCl (aq) + NaOH (aq) NaCl (aq) + H 2 O (l) H + + Cl - + Na + + OH - Na + + Cl - + H 2 O (l)
Acid-Base Reactions. Neutralization acid + base salt + water HCl (aq) + NaOH (aq) NaCl (aq) + H 2 O H + + Cl - + Na + + OH - Na + + Cl - + H 2 O H + +
POINT > Review acid-base neutralization POINT > Identify pH indicators and how they work POINT > Describe titration process.
WARM UP 1. Write the equation for the neutralization reaction between sulfuric acid (H 2 SO 4 ) and ammonium hydroxide (NH 4 OH).
Titrations Acid-Base Part 2.
Acids & Bases Titration.
Ch. 15 & 16 - Acids & Bases III. Titration (p )
Acids & Bases III. Titration.
Titrations This is an application of solution stoichiometry
Neutralization.
Unit 13 – Acid, Bases, & Salts
Ch. 15 & 16 - Acids & Bases III. Titration (p )
Titrations.
Review cation Ion charges anion
Titrations.
Mixing Acids and Bases All your base
Chapter 4.8 Review Acid-Base Reactions.
Net Ionic Equations Balance the equation
Unit 14 – Acid, Bases, & Salts
Ch. 15 & 16 - Acids & Bases III. Titration (p )
Determining the pH and Titrations
Neutralization reactions
Unit 13 – Acid, Bases, & Salts
Acid-Base Reactions.
Presentation transcript:

Titrations An Introduction

Have a cookie… Does anyone remember my delicious cookie recipe… 1 cup flour + 24 choc. chips  3 cookies (NO SUGAR ADDED! )

Titrations This is the purpose of a titration: determining the thing you can’t see based on the thing you know. Usually, chemical titrations involve relating the reactants to each other rather than relating the reactants to the product (as we just did)

Back to the Cookies If I used 8 cups of flour to make these cookies, how many chocolate chips did I have? 8 cups flour * 24 choc. chips = 192 chips 1 cup flour You’re sure? Of course you are! Even though we didn’t count the chips

How many chips do you have? You know how many chips, without counting them because you know how many chips in each cookie! 2 cookies * 24 choc. chips = 16 choc chips 3 cookies

Titrations It’s all about the moles, folks! (Isn’t it always…) Suppose I have a solution of waste water and I need to know how much Compound A (like chocolate chips only toxic! ) is in it. How would you do it? Find something that reacts with Compound A in a known chemical reaction: A + 2 B → C This is a recipe, it gives an exact ratio between the moles of A and B. So if I know how much B I add to the sample to get it to all react, then I know how much A was there when I started!

Known vs. Unknown A + 2 B → C Well, if I add “B” to the sample, what will happen? If I add “B” to the sample, it should form “C” but only if… …I have “A”

A + 2 B  C B A So, I start with “5 As” in my beaker and then add B to it. What happens?

A + 2 B  C B A After I add 2 Bs, I get one C…

A + 2 B  C B A After I add 4 Bs, I get two Cs…

A + 2 B  C B A After I add 6 Bs, I get 3 Cs…

A + 2 B  C B A After I add 8 Bs, I get 4 Cs…

Watching A: B A After I add 10 Bs, I get 5 Cs…

A + 2 B  C B A After I add 1,000,000 Bs, I get 5 Cs. As soon as I ran out of A, the amount of B becomes irrelevant! I can’t make C without both A and B!

Completion of the Reaction A + 2 B → C So, if I think A is there, I can add known amounts of B. If I form C, then there was A there. If I gradually add more known amounts of B until I stop forming C, then I’ll know how much A was originally there. How much?

Equivalence Point A + 2 B → C I stop making C when Moles of B added = 2x moles of A original there! This is called the equivalence point!

Titrations ALL titrations work the same way: You have an unknown amount of one compound (call it A). You have a known amount of a different compound (call it B). You know a chemical reaction that occurs between A and B. Add B until no more reaction occurs. The amount of A is stoichiometrically equivalent to B!

The “tough part”: How do I know the reaction has stopped? 1. I get no new C. 2. I have no B left. 3. I have extra A left over.

Watch A: B A 5 A

Watch A: B A 4 A

Watch A: B A 3 A

Watch A: B A 2 A

Watch A: B A 1 A

Watch A: B A 0 A! I’m DONE!

Or you could watch B

Watch B: B A 0 B

Watch B: B A 0 B

Watch B: B A 0 B

Watch B: B A 0 B

Watch B: B A 0 B

Watch B: B A 0 B

Watch B: B A 1 B! There it is! I’m DONE!

Or you could watch C

Watch C: B A 0 C

Watch C: B A 1 C

Watch C: B A 2 C

Watch C: B A 3 C

Watch C: B A 4 C

Watch C: B A 5 C

Watch C: B A Still 5 C! I’m DONE!

A and B are easier to watch… …it’s more obvious if there is none vs. some.

Acid/Base Titrations How does this work for an acid/base titration? What is the first thing we need to know? EXACTLY! The Chemical Reaction

Acid-base Reaction In an acid/base titration, the generic reaction is: H + + OH - → H 2 O H 3 O + + OH - → 2 H 2 O An acid is a proton donor (H + ) A base is a proton acceptor, is it always an OH - ? Does it matter?

H + + OH - → H 2 O As I make water, by adding OH - to H + (or H + to OH - ), the pH changes. How do I know that I’m done adding…? When I reach “equivalence” (I’m “done”), the pH should be… 7 (for strong acids/bases)

Indicators of the endpoint You can use a pH meter to monitor pH. You can use chemical indicators to monitor pH. Some dyes change color when the pH changes. If you add a little bit of one of these dyes that changes color around pH = 7, then it will change color when you reach equivalence.

Watch B: pH is low

Watch B: B A pH is getting higher

Watch B: B A pH is even higher

Watch B: B A pH is even higher

Watch B: B A pH is near 7

Watch B: B A pH is 7

Watch B: B A pH is over 7

pH vs. mL Base added pH mL OH- added 7

An example of titration. I have a mL sample of an acid of unknown concentration. After addition of mL of a M NaOH solution, equivalence was reached. What was the concentration of acid in the original wastewater sample? Where do I start?

Chemical Reaction: H + + OH - → H 2 O At equivalence…? Moles of H + = Moles of OH - added

An example of titration. I have a mL sample of an acid of unknown concentration. After addition of mL of a M NaOH solution, equivalence was reached. What was the concentration of acid in the original wastewater sample? What do I need to determine? Moles of OH - added! How do I figure that out? Molarity combined with volume!

The solution mL NaOH 1 L = L NaOH added 1000 mL M NaOH = moles NaOH 1 L solution moles NaOH * L = 1.308x10 -3 moles NaOH 1 L solution What does that number tell us? How many moles of H + were originally there! 1.308x10 -3 moles NaOH added = 1.308x10 -3 moles H + in original sample

An example of titration. I have a mL sample of an acid of unknown concentration. After addition of mL of a M NaOH solution, equivalence was reached. What was the concentration of acid in the original wastewater sample? 1.308x10 -3 moles H + in original sample Am I done? Not quite. We need the concentration of acid: How do I calculate that? Molarity = moles/L

An example of titration. I have a mL sample of an acid of unknown concentration. After addition of mL of a M NaOH solution, equivalence was reached. What was the concentration of acid in the original wastewater sample? 1.308x10 -3 moles H + in original sample = M H L original sample`

Clicker Question Does that make sense? A. Move on B. Go Back C. Drop dead

Another little problem A mL sample of waste water is titrated to its phenolphthalein endpoint by addition of mL of M NaOH. What is the pH of the original waste water sample? mL * M = mL * X M X = M

pH = - log [H + ] Does the [H+] = [acid]? What if it’s a polyprotic acid? M of what? Of [H + ] – we reacted the waste water with OH -, all we know is the equivalent amount of H + - which is all we need to know to get the pH

pH = - log [H + ] pH = - log ( M) pH = 0.56

Another Little Problem Titration of mL of an unknown sulfuric acid solution required mL of M NaOH to reach equivalence. What is the concentration of the sulfuric acid? What do you need to notice about this problem? Sulfuric Acid (H 2 SO 4 ) is a diprotic acid.

If it helps… …write the balanced equation (a chemist would). H 2 SO 4 (aq) + 2 NaOH (aq) → Na 2 SO 4 (aq) + 2 H 2 O (l) This is sometimes written as a “net ionic equation”: H + (aq) + OH - (aq) → H 2 O (l)

Stoichiometry ALWAYS Matters 1*43.57 mL* M = 2*25.00 mL * X M X = M H 2 SO 4 If you wanted to calculate the pH…? You need to again consider stoichiometry: each H 2 SO 4 gives 2 protons

2 [H 2 SO 4 ] = [H+] 2* M = M H + pH = - log (0.3408) = 0.47

Acid-base Reaction Acid + Base  H 2 O + salt HA + MB  H-B + MA An acid is a proton donor (H + ) A base is any proton acceptor – where’d the OH - come from?

Acid-base Reaction It could come from the base: HCl + NaOH  H 2 O + NaCl But, not all bases have an OH: HCl + NH 3  ??? NH 3 + H 2 O  NH 4 OH HCl + NH 4 OH  H 2 O + NH 4 Cl You can always generate OH - in water, because water can always act as an acid.

A little bitty problem… A mL sample of waste water is titrated to its phenolphthalein endpoint by addition of mL of M NaOH. What is the pH of the original waste water sample? (This is just another way to phrase the question.)

Solution A mL sample of waste water is titrated to its phenolphthalein endpoint by addition of mL of M NaOH. What is the pH of the original waste water sample? mL * M = mL * X M X = M

pH = - log [H + ] Does the [H+] = [acid]? What if it’s a polyprotic acid? M of what? Of [H + ] – we reacted the waste water with OH -, all we know is the equivalent amount of H + - which is all we need to know to get the pH

pH = - log [H + ] pH = - log ( M) pH = 0.56

A Little Clicker Problem Titration of mL of an unknown sulfuric acid solution required mL of M NaOH to reach equivalence. What is the concentration of the sulfuric acid? A M B M C M D M E M

If it helps… …write the balanced equation (a chemist would). H 2 SO 4 (aq) + 2 NaOH (aq) → Na 2 SO 4 (aq) + 2 H 2 O (l) This is sometimes written as a “net ionic equation”: H + (aq) + OH - (aq) → H 2 O (l)

Stoichiometry ALWAYS Matters 1*21.78 mL* M = 2*25.00 mL * X M X = M H 2 SO 4 If you wanted to calculate the pH…? You need to again consider stoichiometry: each H 2 SO 4 gives 2 protons

Another Little Problem Titration of mL of an unknown sulfuric acid solution required mL of M NaOH to reach equivalence. What is the concentration of the sulfuric acid? What do you need to notice about this problem? Sulfuric Acid (H 2 SO 4 ) is a diprotic acid.

If it helps… …write the balanced equation (a chemist would). H 2 SO 4 (aq) + 2 NaOH (aq) → Na 2 SO 4 (aq) + 2 H 2 O (l) This is sometimes written as a “net ionic equation”: H + (aq) + OH - (aq) → H 2 O (l)

Stoichiometry ALWAYS Matters 1*43.57 mL* M = 2*25.00 mL * X M X = M H 2 SO 4 If you wanted to calculate the pH…? You need to again consider stoichiometry: each H 2 SO 4 gives 2 protons

2 [H 2 SO 4 ] = [H+] 2* M = M H + pH = - log (0.3408) = 0.47