Documents about Conjugate Base

  • 1 Pages

    8B-handout-jan16-key

    UC Davis, CHE 8B

    Excerpt: ... 8B Handout key, jan 16 Draw the conjugate base for cyclohexanol and phenol and explain which is more acidic. OH O cyclohexanol OH conjugate base O The phenol is more acidic because the conjugate base of the phenol has an anion that is more stable, delocalized with resonance stabilization. The cyclohexanol anion is not delocalized, so it is less stable, making the anion a strong base, and the alcohol a weaker acid. phenol conjugate base Practice problems: a) Which nitrogen in imidazole is the most basic? Imidazole is aromatic. Nitrogen B is the most basic because it has a lone pair that is more available to grab a proton (this nitrogen is like pyridine) Nitrogen A has a lone pair that is part of the aromatic pi system (this nitrogen is like pyrrole). b) Which nitrogen in purine is the least basic? N N N N H purine B N NH A imidazole Only one of the nitrogens has lone pair electrons that are part of the pi-system (this nitrogen is like pyrrole), this nitrogen (indicated with the arrow) is the least basic ...

  • 1 Pages

    Lecture_22

    Michigan State University, LBS 172

    Excerpt: ... Relative Strengths of Acids & Their Conjugate Base s Observations: The stronger an acid, the weaker its conjugate base . Likewise, the stronger a base, the weaker its conjugate acid. Acids that are stronger than H3O+ are strong acids in aqueous solutions, and their conjugate base s are ineffective as bases. Bases that are stronger than OH- are strong bases in aqueous solutions, and their conjugate acids are ineffective as acids. 2 LBS 172-Lecture 22 1 of 1 ...

  • 7 Pages

    review session 3

    UMass (Amherst), CHEM 112

    Excerpt: ... BE ABLE TO IDENTIFY B-L and Lewis Acids/Bases Know behavior of strong acids/bases in contrast to weak acids and bases Recognize acid/ conjugate base pairs and base/conjugate acid pairs Know the relationship between strength of an acid and its conjugate base Calculate pH, pOH, Kw, [H3O+], use all relevant equations on equations page . 5 Concepts to know: Know that a reaction always goes from the stronger acid/base to weaker. Know how to write Ka and Kb expressions Know the mathematical relationship between Ka and Kb Kw= Ka x Kb Recognize spectator ions (Table 17.4, pg 811), acids, bases and strengths. . 6 Concepts to know: Be able to use table 17.3 on pg 808. Be able to predict which reactant or product controls the pH of the solution. Table 17.5 on pg 817 Calculate pH of a solution knowing concentration and Ka or Kb Solve for equilibrium hydronium concentration . 7 Chapt 18 concepts to know: What happens when you add strong acid or base to a solution of weak ...

  • 1 Pages

    Handout8_Chapter_17

    Cornell, CHEM 2080

    Excerpt: ... Chemistry 008 Dr. Neal Abrams brought to you by the Learning Strategies Center Handout #8 Spring 2007 Chapter 17 Review Guide Lectures 3/13, 3/15, 3/26 and 3/28 I. Buffers a. Definition - Buffer solutions contain a weak acid and its conjugate base (or a weak base and its conjugate acid) and therefore resist a drastic pH change when acid or base is added. b. Appreciable amounts of both the acid and its conjugate base must be present. c. The most effective buffering occurs when the [acid] = [ conjugate base ]. d. For a good buffer, 0.1 < [A-]/[HA] < 10. e. Selecting an Appropriate Buffer - In general, the most appropriate buffer system for a solution of a desired pH is one in which the pKa of the acid is very close to the desired pH of the solution. The Henderson-Hasselbalch Equation a. The logarithmic form of the Ka expression is known as the HendersonHasselbalch equation. It can be used to calculate the pH of buffer solutions. II. A- pH = pKa + log [HA] b. This equation neglects the auto ...

  • 2 Pages

    Handout7_Chapter15_16_17

    Cornell, CHEM 2080

    Excerpt: ... nsted-Lowry definition Acids - proton (H+) donors; Bases - proton (H+) acceptors Conjugate acid-base pairs differ only by a proton - ex. HCN (acid) and CN-(base). b. Acid Strength and Base Strength Strong acids and bases almost completely dissociate in aqueous solutions; weak acids and weak bases only partially dissociate, forming an equilibrium between the undissociated acid (or base) and the ions. The conjugate base s of strong acids are very weak bases; i.e. there is a negligible tendency to protonate the base. The stronger an acid, the weaker its conjugate base and vice-versa. c. Ka is the acid ionization equilibrium constant. For the reaction: HA + H2O - + H3O+, Ka = [3O+][-]/[HA] d. Kb is the equilibrium constant for the protonation of a base. For the reaction: - + H2O + -, Kb = [HB][-]/[-] e. Problems strong acids are treated as a typical stoichiometry problem where the reaction goes to completion. Problems involving weak acids or bases need to be solved using equilibrium concepts (e.g. I ...

  • 4 Pages

    preexam2poop

    Wisconsin, CHEM 104

    Excerpt: ... Lewis base that is not a Bronsted base. Ex. Likewise for an acid Conjugate acids and conjugate base s Ex: The conjugate acid of any molecule "X" has what formula? Ex: The conjugate base of any molecule "XHn" has what formula? Ex: Give an example of the conjugate base of a molecule "X" where X has no hydrogens. Write "phoo" if this is not possible. Ex: Give an example of the conjugate acid of a molecule that has hydrogens (e.g. CH4). Write "phoo" if this is not possible. Ex: Give two examples of a molecule that has both a conjugate acid and conjugate base . The equilibrium equation for ionization of acids. For an acid "HX" with Ka=0.0012. a) Write the equilibrium expression for its ionization. b) What is the pH of a 0.1 molar solution? c) What is the percent ionization of this solution? The equilibrium equation for hydrolysis of bases. For a strong base "B" in water. a) Write the equilibrium expression for its "hydrolysis" ? b) What is the pH of a 0.1 molar solution? c) What is the percent hydrolysis of thi ...

  • 3 Pages

    In class notes for November 9, 2007

    Vanderbilt, CHEM 102a

    Excerpt: ... General Chemistry Lecture 102a In class notes for November 9, 2007 Ch 7 OWL due today at 11:59 pm Ch 8 OWL due Thursday at 11:59pm (part of Ch 8) Exam #3 is Thursday 7-9pm 2nd part of Ch 6, Ch 7 and Ch 8 Last lecture Le Chatliers Principle Today Acid-Base Chemistry Previously Arrhenious Acid Increases amount of H+ in solution Base Increases amount of OH in solution Now Bronstead-Lowry Acid: A proton (H+) (HCl) Base: A proton acceptor (H2O) HCl (aq) + H2O (l) H3O+ (aq) + Cl-(aq) Acid Base Conj. Acid Conj. Base Conjugate base s come in to play here There is always something counteracting the acid or the base If there is an acid on one side, there will be a conjugate acid on the other side The difference between an acid and its conjugate is a proton. HCO3-(aq) + H2O(l) H2CO3 (aq) + OH-(aq) Base Acid Conj. Acid Conj. Base Be able to identify the base, acid, conjugate base , and conjugate acid HC ...

  • 6 Pages

    103B Exam 2-A

    Arizona, CHEM 103B

    Excerpt: ... Exam I master Page 1 Chemistry 103B Exam 2 Answer Key Form A 1. (2) What is [OH ] for a solution that has pH = 14.85? (a) 7.1 M (b) 2.3 x 10 M -4 - (c) 0.14 M (d) 4.4 x 10 M -9 (e) 4.3 x 10 -11 M Definitions of pOH and pH. pOH = 14.00 14.85 = -0.85 [OH ] = 10 -pOH = 10 0.85 = 7.1 mol/L Hydrobromic acid, HBr(aq), is a strong acid . The next five questions involve solutions of this acid or its conjugate base , bromide ion. 2. (2) What is the pH of a 0.0020mol/L solution of HBr(aq)? (a) 2.30 (b) 2.70 (c) -0.27 (d) 0.080 (e) -0.69 Since it is a strong acid , it is 100 % dissociated . The concentration of hydrogen ion is 0.0020 mol/L. From the study outline : "Calculation of the equilibrium concentrations of all solution species in problems involving strong acids or bases. This includes finding pH." 3. (2) What is the pH of a 0.0020mol/L solution of NaBr(aq)? (a) 0.69 (b) 0.30 (c) -0.20 (d) -0.69 (e) 7.00 Br is the conjugate base of a strong acid , and therefore ...

  • 39 Pages

    10-15-08

    University of Texas, CH 318M

    Excerpt: ... 318M Krische, Lecture 21: W - 10/15/08, Substitution/Elimination Today, we begin substitution and elimination. It is observed that nucleophiles (species that are electron rich) will react with aliphatic alkyl halides and other electrophiles (species that are electron deficient at carbon by virtue of a polarized carbon heteroatom bond) to give products of substitution, i.e. products whereby the halide has been displaced or substituted by the nucleophile. Such reactions are termed nucleophilic substitutions. The following reaction is an example of nucleophilic substitution: NaOH + CH3Br HOCH3 + NaBr For this reaction, NaOH is the nucleophile and CH3Br is the electrophile. The thermodynamic driving force for this reaction is easily recognized. First, we are breaking a relatively weak C-Br bond (70 Kcal/mol) and forming a relatively strong C-O bond (91 Kcal/mol). Secondly, we are exchanging NaOH, the conjugate base of a weak acid (H2O), for NaBr, the conjugate base of a strong ac ...

  • 6 Pages

    103B Exam 2-C

    Arizona, CHEM 103B

    Excerpt: ... Exam I master Page 1 Chemistry 103B Exam 2 Answer Key Form C 1. (2) What is [H3 O ] for a solution that has pOH = 14.47? (a) 8.4 M (b) 2.3 x 10 M -4 + (c) 0.39 M (d) 2.95 M (e) 4.3 x 10 -11 M Definitions of pOH and pH. pH = 14.00 pOH = -0.47 [H3 O+] = 10-pH = 100.47 = 2.95 HBrO3 (aq) is a strong acid . The next five questions involvewatersolutions of either this acid or of its conjugate base . 2. (2) What is the pH of a 0.00030mol/L solution of HBrO3 (aq)? (a) 0.30 (b) 3.52 (c) -0.20 (d) 13.97 (e) 1.52 Since it is a strong acid, it is 100% dissociated. The concentration of hydrogen ion is 0.00030 mol/L. From the study outline: "Calculation of the equilibrium concentrations of all solution species in problems involving strong acids or bases. This includes finding pH." 3. (2) What is the pH of a 0.00030mol/L solution of NaBrO3 (aq)? (a) 1.52 (b) 0.30 (c) 13.97 (d) -0.69 (e) 7.00 BrO3 - is the conjugate base of a strong acid, and therefore not a base. The solution is neutral ...

  • 6 Pages

    Problem_Set_2_Solutions

    Arizona, CHEM 241A

    Excerpt: ... e there are only hydrogens attached, we can disregard them as being the same (i.e. within 2 kJ/mol of each other). Therefore, disregarding the conformations that are the same, we only need to consider the central four bonds, giving us 34. If you are really motivated, you could go through and calculate all of the energies to see which ones are within 2 kJ/mol, but the above strategy is what Dr. Ghosh wanted you to do. The strength of an acid is relative to the stability of its conjugate base . In the examples above, the + charge on the carbon of the nitrile stabilizes the negative charge on the deprotonated carbon of the conjugate base . Having 2 or 3 nitriles increases the + charge surrounding the negative charge on the conjugate base , and therefore leads to greater stabilization. This greater stabilization of the conjugate base increases the acidity of the acid. From least acidic to most acidic: A) H3C OH O OH Cl O OH O OH Cl + pKa ~15 B) H3C O CH3 pKa ~5 OH pKa < 5 OH2 pKa < 4 pKa ~20 C) CH3 ...

  • 6 Pages

    103B Exam 2-B

    Arizona, CHEM 103B

    Excerpt: ... Exam I master Page 1 Chemistry 103B Exam 2 Answer Key Form B 1. (2) Which acid/ conjugate base pair would be best for making a buffer solution with pH = 3.00? (a) H3 PO4 / H2 PO4 - (b) HCO3 /CO3 2- (c) H2 CO3 /HCO3 - (d) HCN/CN - (e) CH3 OH/CH3 O - Essentially from the d2l practice test. Definition of pH 2. (2) Lead(II) iodide, PbI2 (s), has Ksp = 7.9e-9. What is the concentration of iodide ion, I (aq), in a saturated solution of PbI2 ? (a) 1.3e-3 M (b) 2.5e-3 M (c) 2.0e-3 M (d) 6.3e-5 M (e) 1.3e-4 M - From the study outline : "Be able to calculate the pH or hydrogen ion concentration of a buffer solution given the equilibrium concentrations of the weak acid , its conjugate base and the appropriate Ka ." 3. (2) A water solution has a pH of 0.00. This means: (a) The solution is neutral. (b) the hydrogen ion concentration is 1.00 mol/L (c) There is no hydronium ion present . (d) There is no hydroxide ion present . (e) The hydrogen ion concentration is 0.00 mol/L. 4. (2) ...

  • 33 Pages

    General Chemistry II - Assignment 4

    Logan University, UG 07120_02

    Excerpt: ... [ Print View ] General Chemistry II Assignment 4 Due at 11:00am on Wednesday, August 6, 2008 View Grading Details Adding a Strong Acid to a Buffer Learning Goal: To understand how buffers use their reserves of conjugate acid and conjugate base to ameliorate the effects of acid or base addition on pH. A buffer is a mixture of a conjugate acid-base pair. In other words, it is a solution that contains a weak acid and its conjugate base , or a weak base and its conjugate acid. For example, an acetic acid buffer consists of equimolar amounts of acetic acid, , and its conjugate base , . Because ions cannot simply be added to ). a solution, the conjugate base is added in a salt form (e.g., Buffers work because the conjugate acid-base pair work together to neutralize the addition of or ions. Thus, for example, if ions are added to the acetate buffer described above, they will be largely removed from solution by the reaction of with the conjugate base : Similarly, any added acid: ions will be neutralized ...

  • 6 Pages

    103B Exam 2-D

    Arizona, CHEM 103B

    Excerpt: ... Exam I master Page 1 Chemistry 103B Exam 2 Form D Answer Key 1. (2) Which acid/ conjugate base pair would be best for making a buffer solution with pH = 3.00? (a) H3 PO4 / H2 PO4 - (b) HCO3 /CO3 2- (c) H2 CO3 /HCO3 - (d) HCN/CN - (e) CH3 OH/CH3 O - Essentially from the d2l practice test. 2. (2) Lead(II) iodide, PbI2 (s), has Ksp = 7.9 x 10 . What is the concentration of iodide ion, I (aq), in a saturated solution of PbI2 ? (a) 1.3e-3 M (b) 2.5e-3 M (c) 2.0e-3 M (d) 6.3e-5 M (e) 1.3e-4 M -9 - From the study outline : " Computation of the equilibrium concentrations of ions in a saturated solution of an ionic compound ." 3. (2) A water solution has a pOH of 0.00. This means: (a) The solution is neutral. (b) the hydroxide ion concentration is 1.00 mol/L (c) There is no hydronium ion present . (d) There is no hydroxide ion present . (e) none of these . Definition of pOH 4. (2) What is the pH of a buffer solution that consistes of 0.10 M HCO3 (aq) and 0.95 M CO ...

  • 7 Pages

    Chemistry 103B Exam 2 answer key 2

    Arizona, CHEM 103B

    Excerpt: ... Chemistry 103B Exam 2 Answer Key Form B 1. (2) Which acid/ conjugate base pair would be best for making a buffer solution with pH = 3.00? (a) H3PO4/H2PO4(b) HCO3-/CO32(c) H2CO3/HCO3(d) HCN/CN(e) CH3OH/CH3O- Essentially from the d2l practice test. 2. (2) Lead(II) iodide, PbI2(s), has Ksp = 7.9e-9. What is the concentration of iodide ion, I (aq), in a saturated solution of PbI2 ? (a) 1.3e-3 M (b) 2.5e-3 M (c) 2.0e-3 M (d) 6.3e-5 M (e) 1.3e-4 M From the study outline: " Computation of the equilibrium concentrations of ions in a saturated solution of an ionic compound." 3. (2) A water solution has a pH of 0.00. This means: (a) The solution is neutral. (b) the hydrogen ion concentration is 1.00 mol/L (c) There is no hydronium ion present. (d) There is no hydroxide ion present. (e) The hydrogen ion concentration is 0.00 mol/L. Definition of pH 4. (2) What is [H3O+] of a buffer solution that consistes of 0.10 M HF(aq) and 0.95 M NaF(aq)? (a) 6.8e-3 M (b) 7.6e ...

  • 3 Pages

    Che 131 Notes Ch. 16

    SUNY Stony Brook, CHE 131

    Excerpt: ... rse reaction, H3O+ acts as an acid (donor), and acetate ion as a base 2. every Brnsted-Lowry acid has its conjugate base , and every base has its acid a. removing an H+ ion from the acid and making the charge of the remaining portion of the acid one unit more negative gives the conjugate base i. i.e. HF Fb. one member of a conjugate acid-base pair is always a reactant, and the other is always a product i. they are never both products or both reactants F. Relative Strengths of Acids and Bases 1. Strong acids are better H+ donors than weak acids; strong bases are better acceptors a. stronger acids have weaker conjugate base s and weaker acids have stronger conjugate base s 2. the stronger acid and the stronger base will always react to form a weaker conjugate base and a weaker conjugate acid a. find whether the forward or the reverse reaction is favored in an equilibrium i. Stronger to weaker II. 16.2 Carboxylic Acids and Amines A. Many weak acids are organic acids 1. i.e. acetic, lactic, pyruvic 2. ...