3 The Preparation of Buffers at Desired ph
|
|
- Robyn Houston
- 1 years ago
- Views:
Transcription
1 3 The Preparation of Buffers at Desired ph Objectives: To become familiar with operating a ph meter, and to learn how to use the Henderson-Hasselbalch equation to make buffer solutions at a desired ph value. Introduction: A buffer system is a mixture of a weak acid or a weak base and its salt (conjugate base or conjugate acid, respectively) that permits solutions to resist large changes in ph upon the addition of small amounts of hydrogen ions (H + ) or hydroxide ions (OH - ). What does this mean? It means a buffer helps maintain a near constant ph upon the addition of small amounts of H + or OH - to a solution. In the definition of a buffer system, it should be noted that reference is made to weak acids and bases. What is the distinction between a weak and a strong acid or base? Strong acids (e.g., HCl) and bases (e.g., NaOH) almost completely ionize in water: HCl H + + Cl - ; NaOH Na + + OH - Many acids and bases, however, do not undergo complete ionization in water. These compounds, then, are called weak acids and bases. Many organic acids are weak acids. Weak acids do not completely dissociate in water. The dissociation of an organic acid is described by the following reaction: HA H + + A - weak acid conjugate base Note that the unprotonated product of the acid dissociation reaction is referred to as a conjugate base. Recall the Bronsted-Lowry definition of acids and bases. An acid is defined as a proton (H + ) donor, whereas the base is the H + acceptor. In a conjugate acid/base pair such as that indicated above, the weak acid always has one more H + than its conjugate base. Likewise, a weak base will have one less H + than its conjugate acid. CH 3 O C H + O OH + CH 3 C O - weak acid conjugate base acetic acid acetate
2 - H 2 PO 4 + H + weak base dihydrogen phosphate H 3 PO 4 conjugate acid phosphoric acid One can analyze the strength of a weak acid. This means that the amount of hydrogen ion released can be determined. To do this, one can use the following expression: K a = [H+ ] [A - ] [HA] where K a is defined as the acid dissociation constant. The larger the value of K a, the stronger the acid is. Because K a values vary over a wide range, they are usually expressed using a logarithmic scale: pka = - log Ka The hydrogen ion is one of the most important ions in biological systems. The concentration of this ion affects most cellular processes. For example, the structure and function of most biological macromolecules and the rates of most biochemical reactions are strongly affected by [H + ]. The ph scale has been devised as a convenient method of expressing hydrogen ion concentration. ph has been defined as the negative logarithm of the hydrogen ion concentration: ph = - log [H + ] The Henderson-Hasselbalch equation provides a convenient way to think about buffers and ph: ph = pka + log [A - ] [HA] If one were examining the dissociation of acetic acid, the Henderson- Hasselbalch relationship, then, would be: ph = pka + log [CH 3 COO - ] [CH 3 COOH] The Henderson-Hasselbalch equation can be used to determine if an aqueous solution of a conjugate acid/base pair is functioning as a buffer. If the concentration of the weak acid is equal to that of its conjugate base, the ratio of these two components is one. When this is the case, the Henderson-Hasselbalch equation reduces to
3 because the log(1) is equal to zero. ph = pka When the ph of the solution is equal to the pka of the ionizing group, the solution is functioning at maximum buffering capacity (best buffer). An aqueous solution of a conjugate acid/base pair functions as a good buffer when the ratio of the conjugate base to weak acid ranges from 1:9 to 9:1. Substituting these ratios into the Henderson-Hasselbalch equation, one finds that this aqueous solution functions as a good buffer when the ph of the solution is within approximately one ph unit of the ionizing group s pka. ph = pka + 1 because the log (1/9) is and the log of (9/1) is Using the Henderson-Hasselbalch Equation Example A: This is a two-component buffer system meaning that the weak acid and its conjugate base are added separately. How would you prepare 10mL of a 0.01M phosphate buffer, ph 7.40, from stock solutions of 0.10M KH 2 PO 4 and 0.25M K 2 HPO 4? pka of KH 2 PO 4 = This problem is similar to Problem 1 in Experimental Procedures. The following approach may be helpful in solving this type of buffer problem in which both the conjugate acid and base are added separately. Please note that the numbers are not rounded off until the very end and are rounded based on the limits of the pipets, cylinders, etc. that are required to accurately measure the calculated volumes. 1. Use the Henderson Hasselbalch equation to find the ratio of A - to HA. ph = pka + log [A - ] / [HA] 7.40 = log [A - ] / [HA] 0.20 = log [A - ] / [HA] = [A - ] / [HA]* *Since [A - ] / [HA] = , we can say that [A - ] / [HA] = / 1. In this case [A - ] = ; [HA] = Calculate the decimal fraction (part/whole) of each buffer component. A - = / ( ) = / = HA = / = Find the molarity (M) of each component in the buffer by simply multiplying the molarity of the buffer by the decimal fraction of each component. M A - = 0.01M x = M M HA = 0.01M x = M 4. Calculate the moles of each component in the buffer. Moles = Molarity x Liters of buffer moles A - = M x 0.01L = x 10-5 moles
4 moles HA = M x 0.01L = x 10-5 moles 5. Calculate the volume of each stock solution required to make the buffer Liters of stock = moles of the buffer component / Molarity of the stock L A - = x 10-5 moles / 0.25 M = x 10-4 L = 245µL L HA = x 10-5 moles / 0.10 M = x 10-4 L = 387µL 6. To prepare this buffer, one would use appropriately-sized pipets to measure and transfer each component to a 10mL volumetric flask and bring the solution to volume with dh 2 O. Example B: This is a single-component buffer system. This means that one component of the conjugate acid/base pair will be generated in situ (in solution). In the following example, the conjugate base will be generated by reaction between the weak acid (acetic acid) and strong base (sodium hydroxide). How would you prepare 10mL of a 0.02M acetate buffer, ph 4.30, from stock solutions of 0.05M acetic acid (HAc) and 0.05M NaOH? pka acetic acid = This problem is similar to Problem 2 in Experimental Procedures. 1. Use the Henderson Hasselbalch equation to find the ratio of A - to HA. ph = pka + log [A - ] / [HA] 4.30 = log [A - ] / [HA] = log [A - ] / [HA] = [A - ] / [HA] 2. Calculate the decimal fraction (part/whole) of each buffer component. A - = / ( ) = / = HA = 1.00 / = Find the molarity (M) of each component in the buffer by simply multiplying the molarity of the buffer by the decimal fraction of each component. M A - = 0.02M x = = 5.15 x 10-3 M M HA = 0.02M x = = 1.49 x 10-2 M 4. Calculate the moles of each component in the buffer. Moles = Molarity x Liters of buffer moles A - = M x 0.01L = x 10-5 moles moles HA = M x 0.01L = x 10-4 moles 5. Note: Since this buffer is prepared by the reaction of a weak acid (HAc) with a strong base (NaOH), you must determine the total moles of the weak acid component needed because the conjugate base is made in situ. Total moles = 5.15 x 10-5 moles NaOH x 10-4 moles HAc = 2.00 x 10-4 moles HAc. This sum indicates that, although in the buffer one only needs 1.49 x 10-4 moles HA, an additional 5.15 x 10-5 moles is needed to generate the conjugate base in situ. 6. Calculate the volume of each stock solution required to make the buffer
5 Liters of stock = Moles of the buffer component / Molarity of the stock L A - = x 10-5 moles / 0.05 M = 1.03 x 10-3 L NaOH = 1.0mL L HA = 2.00 x 10-4 moles / 0.05 M = 4.00 x 10-3 L CH 3 COOH = 4.0mL 7. To prepare this buffer, one would use appropriately sized pipets or cylinders to measure and transfer each component to a 10 ml volumetric flask and bring the solution to volume with dh 2 O. Example C: What is the ph of a solution resulting from a mixture of 200 ml of 0.1 M NaOH and 100 ml of 0.3 M HAc? This problem is similar to Problem 3 in Experimental Procedures. It is a limiting reagent type problem. 1. Calculate the initial moles of each reactant. Moles = Molarity x Liters Moles NaOH = 0.1M x 0.2L = 0.02moles Moles HAc = 0.3M x 0.1L = 0.03moles 2. Write the balanced equation for this reaction. Note: This is a neutralization reaction. NaOH + HAc Na + Ac - + H + OH - 3. Determine the moles of each reactant remaining after the reaction. Recall: This is a limiting reagent type problem. Since NaOH is present in the least amount and, according to the balanced equation the reactants react in a 1:1 ratio, the NaOH is completely consumed (i.e., zero moles of NaOH remain). Because the reactants react in a 1:1 ratio, Moles HAc remaining = Moles HAc initial Moles HAc reacted = 0.03moles 0.02moles = 0.01moles 4. Determine the molarity of the buffer components (i.e., the conjugate acid-base pair). M HAc = moles HAc remaining / Liters solution = 0.01moles/0.3L = 0.033M The molarity of the conjugate base Ac - resulting from the dissolution of the product NaAc is: M Ac - = moles formed / Liters solution = 0.02moles / 0.3L = 0.067M 5. Use the H-H equation to calculate the ph. ph = pka + log [A - ] / [HA] = log (0.067/0.033) = log 2.02 = = 5.07 Try this one: Determine the ph of a solution resulting from a mixture of 5mL of 0.1M KOH and 30mL of 0.1M HAc.
6 Experimental Procedures: 1. Prepare 10 ml of a 0.01 M phosphate buffer, ph 7.70, from stock solutions of 0.1 M K 2 HPO 4 and 0.2 M KH 2 PO 4. (pka for the weak acid = 7.20). A. Use the Henderson-Hasselbalch equation to calculate the volume of each stock solution needed. ph = pka + log [conjugate base] / [weak acid] B. Check your calculations with other students. See the instructor if there is uncertainty. C. Make the solution and check the ph of a portion of your buffer solution using the ph meter. (Instructions are on page 33) 2. Prepare 10 ml of 0.01 M acetate buffer, ph 3.80, from stock solutions of 0.1 M acetic acid and 0.02 M sodium hydroxide. pka acetic acid = A. C. See above. D. Calculate the exact volume of the 0.01 M acetate buffer required to make 10 ml of a M acetate buffer. 1. Prepare this new buffer using the following equation to aid you in your calculations. V 1 = (V2 x M2 ) M 1 where: V 1 = the volume of the concentrated solution (liters, L) V 2 = the volume of the diluted solution (liters, L) M 1 = the molar concentration of the concentrated solution (moles/l) M 2 = the molar concentration of the diluted solution (moles/l) 2. Check the ph of this new buffer. E. Calculate the exact volume of the 0.01 M acetate buffer required to make 10 ml of a M acetate buffer. 1. Prepare this new buffer. 2. Check its ph. Does a 10-fold dilution of your original buffer (0.01M 0.001M) affect its ph. Does the 20-fold dilution affect the ph? Why?
7 3. What is the ph of a solution resulting from the addition of 2.5 ml of 0.02M NaOH to 5.0 ml 0.25M acetic acid? Use the Henderson-Hasselbalch equation to calculate the ph of the resulting solution, and then follow directions B and C above. pka acetic acid = Record the data in your notebook (you should have 5 ph values):
8 The Preparation of Buffer Solutions of Desired ph STUDY GUIDE 1. The hydrogen ion concentration of tomato juice (ph 4) is how many times higher than the hydrogen ion concentration of 0.01 M NaOH (ph 12)? 2. Phosphoric acid H 3 PO 4 has three dissociable protons (it is triprotic) thus three pka values; 2.12, 7.21, and 12.32). What volume of 200 mm phosphoric acid and what volume of 500 mm NaOH are required to make 100 ml of 20 mm phosphate buffer ph 12? 3. What must be done to the electrode of the ph meter before placing it into a solution to measure its ph? 4. In the phosphate buffer system containing K 2 HPO 4 and KH 2 PO 4, what is the weak acid? What is its conjugate base? 5. If the weak acid in a buffer system has pka 10.5, in what ph range is the system a most effective buffer? 6. On the laboratory shelf are 250mM solutions of both acetic acid and sodium hydroxide. How would you make a 100 ml solution of 25mM acetate buffer of ph 5.50 using these stock solutions? 7. How would you prepare a liter of 25% NaCl (w:w) aqueous solution? 8. How would you prepare a 1.5% NaBr (w:v) aqueous solution? 9. How would you prepare a 65% acetone (v:v) aqueous solution? 10. How would you prepare 500 ml of 0.12µM aqueous solution of glucose (C 6 H 12 O 6 )? 11. What is the percent conjugate acid in an acetate buffer of ph 3.80? (pka = 4.76) 12. How many µmoles are equivalent to 100 pmoles? What is the ratio of conjugate base to weak acid in a buffer when the ph drops to two units below the pka?
ph: Measurement and Uses
ph: Measurement and Uses One of the most important properties of aqueous solutions is the concentration of hydrogen ion. The concentration of H + (or H 3 O + ) affects the solubility of inorganic and organic
UNIT 14 - Acids & Bases
COMMON ACIDS NOTES lactic acetic phosphoric citric malic PROPERTIES OF ACIDS 1. 1. PROPERTIES OF BASES 2. 2. 3. 3. 4. 4. 5. 5. NAMING ACIDS NOTES Binary acids (H + one element) Practice: 1. hydro- - HF
Chapter 21 Buffers and the titration of Acids and Bases Shuffle order make 21-3 last!
Chapter 21 Buffers and the titration of Acids and Bases Shuffle order make 213 last! 211 The HendersonHasselbalch Equation What happens when you mix an acid and its own conjugate base? Using an acetic
Name period Unit 9: acid/base equilibrium
Name period Unit 9: acid/base equilibrium 1. What is the difference between the Arrhenius and the BronstedLowry definition of an acid? Arrhenious acids give H + in water BronstedLowry acids are proton
Acids, Bases, Salts, and Buffers
Acids, Bases, Salts, and Buffers GOAL AND OVERVIEW Hydrolysis of salts will be used to study the acid-base properties of dissolved ions in aqueous solutions. The approximate ph of these solutions will
CHAPTER 9. ANS: a. ANS: d. ANS: c. ANS: a. ANS: c
CHAPTER 9 1. Which one of the following is the acid in vinegar? a. acetic acid b. citric acid c. muriatic acid d. ascorbic acid 2. Which is a basic or alkaline substance? a. gastric fluid b. black coffee
Chapter 17. The best buffer choice for ph 7 is NaH 2 PO 4 /Na 2 HPO 4. 19)
Chapter 17 2) a) HCl and CH 3 COOH are both acids. A buffer must have an acid/base conjugate pair. b) NaH 2 PO 4 and Na 2 HPO 4 are an acid/base conjugate pair. They will make an excellent buffer. c) H
Note: (H 3 O + = hydronium ion = H + = proton) Example: HS - + H 2 O H 3 O + + S 2-
AcidBase Chemistry Arrhenius acid: Substance that dissolves in water and provides H + ions Arrhenius base: Substance that dissolves in water and provides OH ions Examples: HCl H + and Cl Acid NaOH Na +
Chemical equilibria Buffer solutions
Chemical equilibria Buffer solutions Definition The buffer solutions have the ability to resist changes in ph when smaller amounts of acid or base is added. Importance They are applied in the chemical
We remember that molarity (M) times volume (V) is equal to moles so this relationship is the definition of the equivalence point.
Titrations Titration - a titration is defined as the determination of the amount of an unknown reagent (analyte) through the use of a known amount of another reagent (titrant) in an essentially irreversible
An acid is a substance that produces H + (H 3 O + ) Ions in aqueous solution. A base is a substance that produces OH - ions in aqueous solution.
Chapter 8 Acids and Bases Definitions Arrhenius definitions: An acid is a substance that produces H + (H 3 O + ) Ions in aqueous solution. A base is a substance that produces OH - ions in aqueous solution.
CHEM 102: Sample Test 5
CHEM 102: Sample Test 5 CHAPTER 17 1. When H 2 SO 4 is dissolved in water, which species would be found in the water at equilibrium in measurable amounts? a. H 2 SO 4 b. H 3 SO + 4 c. HSO 4 d. SO 2 4 e.
Q.1 Classify the following according to Lewis theory and Brønsted-Lowry theory.
Acid-base A4 1 Acid-base theories ACIDS & BASES - IONIC EQUILIBRIA 1. LEWIS acid electron pair acceptor H, AlCl 3 base electron pair donor NH 3, H 2 O, C 2 H 5 OH, OH e.g. H 3 N: -> BF 3 > H 3 N BF 3 see
7 Investigation of Buffer Systems
7 Investigation of Buffer Systems Name: Date: Section: Objectives Reinforce concepts of buffer, buffer range and buffer capacity Learn how to prepare acid-base buffers Learn how to calculate the of a buffer
AP Chemistry- Acids and Bases General Properties of Acids and Bases. Bases- originally defined as any substance that neutralized an acid
AP Chemistry Acids and Bases General Properties of Acids and Bases Acids Electrolyte Taste Litmus Phenolphthalein React with metals to give off H 2 gas H 2 SO 4 (aq) + Mg (s) MgSO 4 (aq) + H 2 (g) Ionize
Strong Acids (Know These) Announcements & Agenda (02/23/07) Strengths of Acids/Bases - Ionization. Last Time: Last Time: nsted-lowry Acids & Bases
Announcements & Agenda (0//07) You should be reading Ch 0 this weekend! Quiz Today! Open Review Sessions @ pm on Wed. Low attendance this week Last Time: Bronsted nsted-lowry Acids & Bases acids donate
Acids and Bases. Chapter 16
Acids and Bases Chapter 16 The Arrhenius Model An acid is any substance that produces hydrogen ions, H +, in an aqueous solution. Example: when hydrogen chloride gas is dissolved in water, the following
Chapter 19: Acids and Bases Homework Packet (50 pts) Name: Score: / 50
Chapter 19: Acids and Bases Homework Packet (50 pts) Topic pg Section 19.1 1-3 Section 19.2 3-6 Section 19.3 6-7 Section 19.4 8 Naming Acids 9 Properties of Acids/Bases 10-11 Conjugate Acid/Base Pairs
Bronsted- Lowry Acid Base Chemistry
Bronsted Lowry Acid Base Chemistry Just a few reminders What makes an acid an acid? A BronstedLowry Acid is a compound that donates a proton (a hydrogen ion with a positive charge, H + ) o Think of the
Review for Solving ph Problems:
Review for Solving ph Problems: Acid Ionization: HA H 2 O A - H 3 O CH 3 COOH H 2 O CH 3 COO - H 3 O Base Ionization: B H 2 O BH OH - 1) Strong Acid complete dissociation [H ] is equal to original [HA]
1. In which reaction is water acting only as a proton acceptor? 1) H 2 SO 4 (aq) + H 2 O ( ) HSO 4 (aq) + H 3 O + (aq)
1. In which reaction is water acting only as a proton acceptor? 1) H 2 SO 4 (aq) H 2 O ( ) HSO 4 (aq) H 3 O (aq) NH 3 (g) H 2 O ( ) NH 4 (aq) OH (aq) CH 3 COO (aq) H 2 O ( ) CH 3 COOH(aq) OH (aq) H 2 O
Q.1 Classify the following according to Lewis theory and Brønsted-Lowry theory.
Acid-base 2816 1 Acid-base theories ACIDS & BASES - IONIC EQUILIBRIA LEWIS acid electron pair acceptor H +, AlCl 3 base electron pair donor NH 3, H 2 O, C 2 H 5 OH, OH e.g. H 3 N: -> BF 3 > H 3 N + BF
Acid-Base Properties of Drugs
Acid-Base Properties of Drugs Printer-friendly 1 23456 Functional Groups in Drug Molecules Most drugs currently in the market are small organic molecules that behave in aqueous solutions as weak acids
CHAPTERS 15 FAKE TEST QUESTIONS. 1. According to the Brønsted Lowry definition, which species can function both as an acid and as a base?
You might need to know the following K values: CHAPTERS 15 FAKE TEST QUESTIONS CH 3 COOH K a = 1.8 x 10 5 Benzoic Acid K a = 6.5 x 10 5 HNO 2 K a = 4.5 x 10 4 NH 3 K b = 1.8 x 10 5 HF K a = 7.2 x 10 4
6) Which compound is manufactured in larger quantities in the U.S. than any other industrial chemical?
MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question. 1) Which statement concerning Arrhenius acid-base theory is not correct? A) Acid-base reactions must
CHEM 12 Acids and Bases 3/22/2016
Acids and Bases Name: Expected background knowledge from acids and bases introductory reading: Definitions (Arrhenius, BL) of an acid and base Definitions of conjugate acid and base pairs Properties of
p3 Recognizing Acid/Base Properties when p11 Recognizing Basic versus Nonbasic
General Chemistry II Jasperse Acid-Base Chemistry. Extra Practice Problems 1 General Types/Groups of problems: Conceptual Questions. Acids, Bases, and p1 K b and pk b, Base Strength, and using K b or p7-10
Similarities The ph of each of these solutions is the same; that is, the [H + ] is the same in both beakers (go ahead and count).
Compare 1 L of acetate buffer solution (0.50 mol of acetic acid and 0.50 mol sodium acetate) to 1 L of HCl solution AcO - AcO - H+ Cl - AcO - AcO - Cl - Cl - AcO - Cl - Cl - Cl - Cl - AcO - AcO - AcO -
2. Write a balanced chemical equation which corresponds to the following equilibrium constant expression. 1/2 3/ 2
Practice Problems for Chem. 1B Exam 1 F2011 These represent the concepts covered for exam 1. There may be some additional net ionic equations from chem. 1A. This is not the exact exam! Sections 16.1-16.3
Buffer Solutions. Buffer Solutions
Chapter 18 Common Ion Effect Buffers and Titration Curves A/B Titrations Salts and Solubility Product The Common Ion Effect and If a solution is made in which the same ion is produced by two different
Buffer solutions. Division of Radiooncology, Deutsches Krebsforschungszentrum, 69120 Heidelberg, Germany
Buffer solutions WOLF D. KUHLMANN, M.D. Division of Radiooncology, Deutsches Krebsforschungszentrum, 69120 Heidelberg, Germany Aqueous buffer solutions and acid-base reactions Buffer solutions have the
Lecture 6: Lec4a Chemical Reactions in solutions
Lecture 6: Lec4a Chemical Reactions in solutions Zumdahl 6 th Ed, Chapter 4 Sections 1-6. 4.1 Water, the Common Solvent 4.2 The Nature of Aqueous Solutions: Strong and Weak Electrolytes 4.3 The Composition
Chapter 9 Lecture Notes: Acids, Bases and Equilibrium
Chapter 9 Lecture Notes: Acids, Bases and Equilibrium Educational Goals 1. Given a chemical equation, write the law of mass action. 2. Given the equilibrium constant (K eq ) for a reaction, predict whether
Factors that Affect the Rate of Dissolving and Solubility
Dissolving Factors that Affect the Rate of Dissolving and Solubility One very important property of a solution is the rate of, or how quickly a solute dissolves in a solvent. When dissolving occurs, there
Chem101: General Chemistry Lecture 9 Acids and Bases
: General Chemistry Lecture 9 Acids and Bases I. Introduction A. In chemistry, and particularly biochemistry, water is the most common solvent 1. In studying acids and bases we are going to see that water
This value, called the ionic product of water, Kw, is related to the equilibrium constant of water
HYDROGEN ION CONCENTRATION - ph VALUES AND BUFFER SOLUTIONS 1. INTRODUCTION Water has a small but definite tendency to ionise. H 2 0 H + + OH - If there is nothing but water (pure water) then the concentration
Chapter 17. How are acids different from bases? Acid Physical properties. Base. Explaining the difference in properties of acids and bases
Chapter 17 Acids and Bases How are acids different from bases? Acid Physical properties Base Physical properties Tastes sour Tastes bitter Feels slippery or slimy Chemical properties Chemical properties
WEAK ACIDS AND BASES
WEAK ACIDS AND BASES [MH5; Chapter 13] Recall that a strong acid or base is one which completely ionizes in water... In contrast a weak acid or base is only partially ionized in aqueous solution... The
4. Acid Base Chemistry
4. Acid Base Chemistry 4.1. Terminology: 4.1.1. Bronsted / Lowry Acid: "An acid is a substance which can donate a hydrogen ion (H+) or a proton, while a base is a substance that accepts a proton. B + HA
Lecture 6. Classes of Chemical Reactions
Lecture 6 Classes of Chemical Reactions Lecture 6 Outline 6.1 The Role of Water as a Solvent 6.2 Precipitation Reactions 6.3 Acid-Base Reactions 1 Electron distribution in molecules of H 2 and H 2 O The
Titration Curve of a Weak Acid
Titration Curve of a Weak Acid Amina Khalifa El-Ashmawy, Ph.D. Collin College Department of Chemistry Introduction: Titration is an analytical process whereby two reactant solutions are carefully reacted
Chapter 9 Acids, Bases and Buffers in the Body Outline 9.1 Acids and Bases Definitions Acids
Lecture Presentation Chapter 9 Acids, Bases and Buffers in the Body Julie Klare Fortis College Smyrna, GA Outline 9.1 Acids and Bases Definitions 9.2 Strong Acids and Bases 9.3 Chemical Equilibrium 9.4
Notes: Acids and Bases
Name Chemistry Pre-AP Notes: Acids and Bases Period I. Describing Acids and Bases A. Properties of Acids taste ph 7 Acids change color of an (e.g. blue litmus paper turns in the presence of an acid) React
Answer the following questions on notebook paper, to be collected and graded for correctness.
nswer the following questions on notebook paper, to be collected and graded for correctness. 1. Name the following binary acids: a. HCl hydrochloric acid b. HF hydrofluoric acid c. H 2 S hydrosulfuric
Ionization Constants of Cysteine
Ionization Constants of Cysteine Introduction Cysteine is an important amino acid which, when protonated at low ph, has three acidic hydrogens: carbonyl ( COOH), amino ( NH 3 + ), and thiol ( SH): H HS
Acids and Bases: Definitions. Brønsted-Lowry Acids and Bases. Brønsted-Lowry Acids and Bases CHEMISTRY THE CENTRAL SCIENCE
CHEMISTRY THE CENTRAL SCIENCE Professor Angelo R. Rossi Department of Chemistry Spring Semester Acids and Bases: Definitions Arrhenius Definition of Acids and Bases Acids are substances which increase
UNIT (6) ACIDS AND BASES
UNIT (6) ACIDS AND BASES 6.1 Arrhenius Definition of Acids and Bases Definitions for acids and bases were proposed by the Swedish chemist Savante Arrhenius in 1884. Acids were defined as compounds that
A strong acid and the salt of its conjugate base don't make a good buffer. Why? (aq) + OH - (aq)
5.111 Lecture Summary #23 cid/base Equilibrium Continued From Friday s handout Topic: Titrations 23.1 cid buffer action: The weak acid,, transfers protons to O ions supplied by strong base. The conjugate
Lab Activity: Strong Acids & Strong Bases, Weak Acids & Weak Bases, and the Hydrolysis of Salts
Lab Activity: Strong Acids & Strong Bases, Weak Acids & Weak Bases, and the Hydrolysis of Salts Strong acids and strong bases completely ionize in water to make hydronium or hydroxide ions. Because the
Titrations. Acid-Base Indicators and Titration Curves. Shapes of Titration Curves. A titration curve is a graphical history of a titration
Acid-Base Indicators and Titration Curves Titrations In a titration a solution of accurately known concentration is added gradually added to another solution of unknown concentration until the chemical
Acid-Base (Proton-Transfer) Reactions
Acid-Base (Proton-Transfer) Reactions Chapter 17 An example of equilibrium: Acid base chemistry What are acids and bases? Every day descriptions Chemical description of acidic and basic solutions by Arrhenius
ACID-BASE TITRATIONS: DETERMINATION OF CARBONATE BY TITRATION WITH HYDROCHLORIC ACID BACKGROUND
#3. Acid - Base Titrations 27 EXPERIMENT 3. ACID-BASE TITRATIONS: DETERMINATION OF CARBONATE BY TITRATION WITH HYDROCHLORIC ACID BACKGROUND Carbonate Equilibria In this experiment a solution of hydrochloric
14-Jul-12 Chemsheets A
www.chemsheets.co.uk 14-Jul-12 Chemsheets A2 009 1 BRONSTED-LOWRY ACIDS & BASES Bronsted-Lowry acid = proton donor (H + = proton) Bronsted-Lowry base = proton acceptor (H + = proton) Bronsted-Lowry acid-base
Solubility Equilibria
Chapter 17: Acid-Base Equilibria and Solubility Equilibria Key topics: Common ion effect Buffers Acid-base equilibria Solubility equilibria; complex ion formation The Common Ion Effect If we have two solutes
Topic 5. Acid and Bases
Topic 5 5-1 Acid and Bases Acid and Bases 5-2 There are a number definitions for aicd and bases, depending on what is convenient to use in a particular situation: Arrhenius and Ostwald: Theory of electrolyte
Auto-ionization of Water
2H 2 O H 3 O + + OH Hydronium ion hydroxide ion Q: But how often does this happen? This is the fundamental concept of all acid-base chemistry In pure water, how much of it is water and how much is ions?
Acids, Bases and Concentrations
61 Chapter 7 Acids, Bases and Concentrations Thoughts or pictures of a shark usually evoke fear. But most sharks are not harmful to humans and shark attacks while dangerous and sometimes fatal are extremely
If we write these equations in ionic form, in each case the net ionic equation is the same; H 3 O + (aq) + OH - (aq) H 2H 2 O(l)
CHEM 1105 ACIDS AND BASES 1. Early Definitions Taste: Effect on Indicators: Neutralization: acids - sour; bases - bitter acids turn blue litmus red; bases turn red litmus blue phenolphthalein is colourless
Acid-Base Titrations Using ph Measurements
Acid-Base Titrations Using ph Measurements Introduction According to the Brønsted Lowry definition, an acid is a substance that donates a hydrogen ion and a base is a substance which will accept a hydrogen
SECTION 14 CHEMICAL EQUILIBRIUM
1-1 SECTION 1 CHEMICAL EQUILIBRIUM Many chemical reactions do not go to completion. That is to say when the reactants are mixed and the chemical reaction proceeds it only goes to a certain extent, and
Review of Basic Concepts, Molarity, Solutions, Dilutions and Beer s Law
Review of Basic Concepts, Molarity, Solutions, Dilutions and Beer s Law Aqueous Solutions In Chemistry, many reactions take place in water. This is also true for Biological processes. Reactions that take
Chapter 14 - Acids and Bases
Chapter 14 - Acids and Bases 14.1 The Nature of Acids and Bases A. Arrhenius Model 1. Acids produce hydrogen ions in aqueous solutions 2. Bases produce hydroxide ions in aqueous solutions B. Bronsted-Lowry
I. ACID-BASE NEUTRALIZATION, TITRATION
LABORATORY 3 I. ACID-BASE NEUTRALIZATION, TITRATION Acid-base neutralization is a process in which acid reacts with base to produce water and salt. The driving force of this reaction is formation of a
Volumetric Analysis. Lecture 5 Experiment 9 in Beran page 109 Prelab = Page 115
Volumetric Analysis Lecture 5 Experiment 9 in Beran page 109 Prelab = Page 115 Experimental Aims To prepare and standardize (determine concentration) a NaOH solution Using your standardized NaOH calculate
Acids and Bases: A Brief Review
Acids and : A Brief Review Acids: taste sour and cause dyes to change color. : taste bitter and feel soapy. Arrhenius: acids increase [H ] bases increase [OH ] in solution. Arrhenius: acid base salt water.
Chapter 4 Notes - Types of Chemical Reactions and Solution Chemistry
AP Chemistry A. Allan Chapter 4 Notes - Types of Chemical Reactions and Solution Chemistry 4.1 Water, the Common Solvent A. Structure of water 1. Oxygen's electronegativity is high (3.5) and hydrogen's
WATER, ph, ACIDS, BASES, AND BUFFERS
COURSE READINESS ASSESSMENT FOR PHYSIOLOGY WATER, ph, ACIDS, BASES, AND BUFFERS Sections in this module I. Water is a polar molecule II. Properties of water III. ph IV. Acids and bases V. Buffers I. Water
Acid Base Concepts. Arrhenius concept. Hydronium Ion. Page 1
Acid Base Concepts Page 1 The Swedish chemist, Svante Arrhenius, framed the first successful concept of acids and bases. He defined acids and bases in terms of their effect on water. According to Arrhenius,
CHM1 Review for Exam 12
Topics Solutions 1. Arrhenius Acids and bases a. An acid increases the H + concentration in b. A base increases the OH - concentration in 2. Strong acids and bases completely dissociate 3. Weak acids and
Acids and Bases. When an acid loses a proton, the resulting species is its conjugate base. For example, NH 3 + H +
Acids and Bases Definitions An acid is a proton donor, e.g. HCl. For example, consider the reaction between HCl and H 2 O. HCl + H 2 O H 3 O + + Cl - Acid In this reaction, HCl donates a proton to H 2
Topic 18 Acids and Bases. 18.1 Exercises
Topic 18 Acids and Bases 18.1 Exercises 1. Define: (a) ph The negative log of the hydrogen ion concentration in a solution. i.e. ph = log[h 3 O + ] (b) poh The negative log of hydroxide ion concentration
ph. Weak acids. A. Introduction
ph. Weak acids. A. Introduction... 1 B. Weak acids: overview... 1 C. Weak acids: an example; finding K a... 2 D. Given K a, calculate ph... 3 E. A variety of weak acids... 5 F. So where do strong acids
Spectrophotometric Determination of the pka of Bromothymol Blue
Spectrophotometric Determination of the pka of Bromothymol Blue INRODUCION cidbase indicators are compounds that are simply weak acids (or bases) that exhibit different colors depending on whether they
Chapter 15: Acids, Bases, and Salts. 15.1: Acids and Bases
Chapter 15: Acids, Bases, and Salts Name: 15.1: Acids and Bases Define an Acid: Define a Base: Ex of an acid in aqueous solution: Ex of a base in aqueous solution: List some of the properties of acids
ph of strong acid and base
ph of strong acid and base What does strong mean in terms of acids and bases? Solubility. Basically, if you say an acid or base is strong, then it dissociates 100% in water. These types of situations are
Ch 8.5 Solution Concentration Units % (m/m or w/w) = mass of solute x 100 total mass of solution mass of solution = mass solute + mass solvent
1 Ch 8.5 Solution Concentration Units % (m/m or w/w) = mass of solute x 100 total mass of solution mass of solution = mass solute + mass solvent % (v/v) = volume of solute x 100 volume of solution filled
Chapter 14: Acids and Bases
Ch 14 Page 1 Chapter 14: Acids and Bases Properties of Acids Sour taste React with some metals Turns blue litmus paper red React with bases Some Common Acids HCl, hydrochloric acid H 2 SO 4, sulfuric acid
Acids and Bases: A Brief Review, see also pp and pp Brønsted-Lowry Acids and Bases 143. The H + Ion in Water
Quiz number 5 will be given in recitation next week, Feb 26Mar 2 on the first part of Chapter 16, to be covered in lectures this week. 16.1 Acids and Bases: A Brief Review 16.2 BronstedLowry Acids and
16. What is the H 3 O + concentration of a solution that has an OH concentration of 1 10 3 M? 1) 1 10 4 M 3) 1 10 11 M
1. If the [OH ] = 1 10 4 at 298 K for a given solution, the [H + ] of the solution is equal to 1) 1 10 14 3) 1 10 6 2) 1 10 10 4) 1 10 4 2. Based on Reference Table V, which is the strongest base? 1) NO
Experiment # 6 Determining the percent composition of a mixture by acid-base
Experiment # 6 Determining the percent composition of a mixture by acid-base Objective Determine the percent composition of a mixture of sodium carbonate (Na 2 CO 3 ), sodium bicarbonate (NaHCO 3 ) and
ionic substances (separate) based on! Liquid Mixtures miscible two liquids that and form a immiscible two liquids that form a e.g.
Unit 7 Solutions, Acids & Bases Solution mixture + solvent - substance present in the amount solute - in the solvent solvent molecules solute particles ionic substances (separate) based on! Liquid Mixtures
1. Identify the Bronsted-Lowry acids and bases and the conjugate acid base pairs in the following reactions.
Exercise #1 Brønsted-Lowry s and Bases 1. Identify the Bronsted-Lowry acids and bases and the conjugate acid base pairs in the following reactions. (a) HCl(aq) + H 2 O(l) H 3 O + (aq) + Cl (aq) (b) H 2
All Solutions: the ph will lie between 0 and 14
1 Do p in Your ead Every aqueous solution has a degree of acidity or of basicity; that is, every aqueous solution has a p. There are two factors that will determine the p of a solution. These are the acidic
CHAPTER 16: ACIDS AND BASES
CHAPTER 16: ACIDS AND BASES Active Learning: 4, 6, 14; End-of-Chapter Problems: 2-25, 27-58, 66-68, 70, 75-77, 83, 90-91, 93-104 Chapter 15 End-of-Chapter Problems: 69-74, 125, 129, 133 16.1 ACIDS AND
Chapter 7 Mixtures of Acids and Bases
Chapter 7 Mixtures of Acids and Bases Introduction In Chapter 6, we examined the equilibrium concentrations in solutions of acids and solutions of bases. In this chapter, we continue our discussion of
Experiment 6 Titration II Acid Dissociation Constant
6-1 Experiment 6 Titration II Acid Dissociation Constant Introduction: An acid/base titration can be monitored with an indicator or with a ph meter. In either case, the goal is to determine the equivalence
ph Measurement and its Applications
ph Measurement and its Applications Objectives: To measure the ph of various solutions using ph indicators and meter. To determine the value of K a for an unknown acid. To perform a ph titration (OPTIONAL,
Tutorial 4 SOLUTION STOICHIOMETRY. Solution stoichiometry calculations involve chemical reactions taking place in solution.
T-27 Tutorial 4 SOLUTION STOICHIOMETRY Solution stoichiometry calculations involve chemical reactions taking place in solution. Of the various methods of expressing solution concentration the most convenient
TOPIC 11: Acids and Bases
TOPIC 11: Acids and Bases ELECTROLYTES are substances that when dissolves in water conduct electricity. They conduct electricity because they will break apart into Ex. NaCl(s)! Na + (aq) + Cl - (aq), and
Q1: What is the ph Scale? Q6: As acids become more acidic, their ph values
Q1: What is the ph Scale? Q6: As acids become more acidic, their ph values increase or decrease? Q2: The range of values of the ph scale is: Q7: As bases become more alkaline, their ph values increase
QUESTION (2012:3) (a) (i) Complete the table below showing the conjugate acids and bases. CO 3 H 2 O OH HCN CN -
QUESTION (2012:3) (i) Complete the table below showing the conjugate acids and bases. Conjugate acid Conjugate base - HCO 3 2 CO 3 H 2 O OH HCN CN - (ii) HPO 4 2 (aq) Write equations for the reactions
AMHS AP Chemistry Multiple Choice questions
1 Aqueous Equilibria: Buffers & Titrations AMHS AP Chemistry Multiple Choice questions Name Common-Ion Effect 1) The ph of a solution that contains 0.818 M acetic acid (K a = 1.77x10-5 ) and 0.172 M sodium
Acids and Bases. Basic Definitions & Concepts
Acids and Bases CHEM 102! T. Hughbanks! Basic Definitions & Concepts Most basic concepts are given clearly in your text - these notes will only list these as topics discussed, so there will be less detail.!
How many ml of 0.250M potassium permangenate are needed to react with 3.36 g of iron(ii) sulfate?
How many ml of 0.250M potassium permangenate are needed to react with 3.36 g of iron(ii) sulfate? 1 - Change the mass of iron(ii) sulfate to moles using the formula weight.of iron(ii) sulfate 2 - Change
Acid-Base Titrations. Setup for a Typical Titration. Titration 1
Titration 1 Acid-Base Titrations Molarities of acidic and basic solutions can be used to convert back and forth between moles of solutes and volumes of their solutions, but how are the molarities of these
Chemistry 201. Practical aspects of buffers. NC State University. Lecture 15
Chemistry 201 Lecture 15 Practical aspects of buffers NC State University The everyday ph scale To review what ph means in practice, we consider the ph of everyday substances that we know from experience.
CHEMISTRY 101 EXAM 3 (FORM B) DR. SIMON NORTH
1. Is H 3 O + polar or non-polar? (1 point) a) Polar b) Non-polar CHEMISTRY 101 EXAM 3 (FORM B) DR. SIMON NORTH 2. The bond strength is considerably greater in HF than in the other three hydrogen halides
CHEM 101/105 Aqueous Solutions (continued) Lect-07
CHEM 101/105 Aqueous Solutions (continued) Lect-07 aqueous acid/base reactions a. a little bit more about water Water is a polar substance. This means water is able to "solvate" ions rather well. Another
n molarity = M = N.B.: n = litres (solution)
1. CONCENTRATION UNITS A solution is a homogeneous mixture of two or more chemical substances. If we have a solution made from a solid and a liquid, we say that the solid is dissolved in the liquid and
Standardization of NaOH
EXPERIMENT 18 Prepared by Edward L. Brown, Lee University The student will become familiar with the techniques of titration and the use of a primary standard, Potassium Hydrogen Phthalate (KHP). Buret