1 / 17

Lecture 26

Lecture 26. Introduction to Acid-Base Chemistry J.1-J.3, 10.1-10.6 3-November Assigned HW I.18, J6, J8, 10.2, 10.6, 10.12, 10.16, 10.22, 10.26 ( note that NH 2 - is a strong base ), 10.28 Due: Monday 8-Nov. Review. Equilibrium is when the forward and reverse reaction rates are equal

yitta
Download Presentation

Lecture 26

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Lecture 26 Introduction to Acid-Base Chemistry J.1-J.3, 10.1-10.6 3-November Assigned HW I.18, J6, J8, 10.2, 10.6, 10.12, 10.16, 10.22, 10.26 (note that NH2- is a strong base), 10.28 Due: Monday 8-Nov

  2. Review • Equilibrium is when the forward and reverse reaction rates are equal • Dynamic equilibia governed by an equilibrium constant (K) • Equilibrium constants are unitless • Heterogenousequilibria – only aqueous or gas phase included in K • Reaction spontaneity can be determined by • Can be determined using pressures or concentrations • For a gas phase reaction, • To determine equilibrium concentrations from starting concentrations, use ICE tables • LeChatlier’s Principle  a stress applied to a reaction at equilibrium will result in the reaction proceeding in a direction the relieves the stress • Adding reactants  products formed • Increasing temperature  • ΔH > 0  products formed • ΔH < 0  products formed • Increasing Pressure  reaction shifts toward lowest number of gas molecules

  3. Introduction to Acids and Bases Arrhenius Formalization Acid  compound that contains hydrogen and reacts with water to form hydrogen ions (HCl, HCOOH) Base  a compound that produces hydroxide ions in water NaOH, Mg(OH)2 HXaq+ H2O(l) HXaq H+aq + X-aq H3O+aq + X-aq MOHaq M+aq + OH-aq

  4. Introduction to Acids and Bases When an acid reacts with a base, a neutralization occurs When dissolved in water, full dissociation of ions occurs – dissolution. Which intermolecular force facilitates this? H+aq+X-aq+ M+aq + OH-aq HXaq+ MOHaq H+aq+ OH-aq MOHaq HXaq MXaq M+ + X-aq H2O(l) H2O(l) + MXaq H2O(l) + M+aq + X-aq H+ + X-aq M+ + OH-aq K for these processes is VERY big – no reactants left. Spectator ions Complete ionic equation – includes ALL species Net ionic equation – does NOT include spectator ions Equilibrium constant is ONLY dependent on Net ionic equation.

  5. Introduction to Acids and Bases Bronsted-Lowry Formalism: Acid  proton donor HCl, HCOOH Base  proton acceptor NaOH, HCOONa Conjugate base  the base that results from removing a proton from an acid Deprotonation

  6. Introduction to Acids and Bases When Bronsted Acid is dissolved in water, something MUST act as a base HAaq H+aq + A-aq Is water an acid or a base in this reaction? What is the equilibrium constant?

  7. Introduction to Acids and Bases Can water be an acid? What will be the conjugate base? H2O(l)+A-aq OH-aq + HAaq What is the equilibrium constant?

  8. Strong/Weak Acids and Bases Strong acids are completely deprotonated in solution Strong bases are completely protonated in solution Very Large K H2O(l) + X-aq H2O(l) + X-aq HXaq HXaq H+ + X-aq H+ + X-aq OH- + HXaq OH- + HXaq Very Large K Weak acids are only partially deprotonated in solution Weak bases are partallyprotonated in solution Weak acids and bases consist of reactants AND products at equilibrium Strong acids and bases consist of ONLY products at equilibrium

  9. Strong/Weak Acids and Bases The conjugate base of a strong acid is a weak base If the reaction proceeds as written, HA must be a stronger acid than HB

  10. Strong/Weak Acids and Bases Factors that contribute to acid strength Bond Strength Electronegativity

  11. Polyprotic Acids HCO3-(aq) H2CO3(aq) H+aq + CO32-aq H+aq + HCO3- (aq) Can an anion be an acid? Common Polyprotic Acids H3PO4 H2SO4 H2CO3

  12. Lewis Acids and Bases Lewis Formalism: Acid  electron pair acceptor Base  electron pair donor HCl is an acid. Does the Lewis formalism apply to HCl? NaOH is a base. How does the Lewis formalism apply to NaOH? Water can be an acid or base. Verify this with Lewis Formalism

  13. Lewis Acids and Bases Given the following reaction: Identify all Bronsted Acids and Bases Identify all Lewis Acids and Bases

  14. Proton Exchange Between Water Water can be an acid or a base  amphiprotic Acid H2O(l) + H+ 2 H2O(l) H2O(l) H3O+ OH- + H+ OH- + H3O+ Base Autoprotolysis of water

  15. Proton Exchange Between Water Water can be an acid or a base  amphiprotic Acid H2O(l) + H+ 2 H2O(l) H2O(l) H3O+ OH- + H+ OH- + H3O+ Base Autoprotolysis of water In 0.1 M HCl at 25 °C, calculate the concentration of H+ and OH-.

  16. The pH Scale The acidity of a solution is usually reported in pH units Quantitative measure of acidity Calculate the pH of a 100 mM solution of HBr

  17. The pOH Scale Quantitative measure of basicity Calculate the pOH of a 0.1 mM solution of HBr

More Related