1 / 24

Acids and Bases

Acids and Bases. Types of Acids and Bases. Describing Acids and Bases. Properties of Acids and Bases Acids Produce H + ions when dissolved in water Sour taste Solutions are electrolytes (some strong, some weak) React with metals to produce H 2 React with a base to form water and salt

roza
Télécharger la présentation

Acids and Bases

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. Acids and Bases

  2. Types ofAcids and Bases

  3. Describing Acids and Bases • Properties of Acids and Bases • Acids • Produce H+ ions when dissolved in water • Sour taste • Solutions are electrolytes (some strong, some weak) • React with metals to produce H2 • React with a base to form water and salt • Turn litmus paper red

  4. Describing Acids and Bases • Bases • Produce OH- ions when dissolved in water • Bitter taste • Feel slippery • Solutions are electrolytes (strong and weak) • React with acids to form water and a salt • Turn litmus paper blue

  5. Arrhenius Definition • The simplest definition is that an acid is a substance that increases the concentration of H+ ions when dissolved in water. • HCl and H3PO4 are acids according to Arrhenius. HCl H+ + Cl- H2O

  6. Arrhenius Definition • A base is a substance increases the concentration of hydroxide ions, OH–, when dissolved in water. • Ca(OH)2 and NaOH are Arrhenius bases. • NH3, ammonia, is a base, but does not fit the definition of an Arrhenius base.

  7. Monoprotic Acids • Monoprotic acids have only one ionizable hydrogen.

  8. Polyprotic Acids • Some acids have more than one ionizable hydrogen.

  9. Bronsted-Lowry Definitions • The Arrhenius definition of acids and bases has limitations • The Bronsted-Lowry definition is more general • A Bronsted-Lowry concept is based on the donation of H+ions. • The H+ ion is simply a proton with no valence electrons.

  10. Brønsted-Lowry Definitions • When a Brønsted-Lowry acid dissolves in water it gives its proton (H+) to water. • HCl (g) + H2O (l) H3O+ + Cl- • A hydronium ion, H3O+, consists of a hydrogen ion attached to a water molecule

  11. Brønsted-Lowry Definitions • A Brønsted-Lowry base is a proton acceptor. • B + H2O BH+ + OH- • ABrønsted-Lowry base does not need to contain OH-. • NH3 + H2O NH4+ + OH-

  12. Brønsted-Lowry Consider • HCl(aq) + H2O(l)  H3O+(aq) + Cl-(aq) HCl donates a proton to water. Therefore, HCl is an acid. H2O accepts a proton from HCl. Therefore, H2O is a base.

  13. Brønsted-Lowry • Consider: NH3 + H2O NH4+ + OH- NH3 accepts a proton and is a base. H2O donates a proton and acts as an acid. A substance capable of acting as both an acid and a base is amphoteric.

  14. Example • Identify the acid and base in the following reaction. acid base

  15. Problem • Identify the acid and base in the following reaction. NH3 + H2SO4 NH4+ + HSO4- acid base

  16. Strength of Acids and Bases

  17. Strong Bases • The strength of a base is based on the percent of units dissociated, not the number of OH– ions produced. • The strength of a base does NOT depend on the molarity. • 1A and 2A hydroxides, excluding Be, are strong bases.

  18. Strong Bases • Some bases, such as Mg(OH)2, are not very soluble in water, and they don’t produce a large number of OH– ions. • However, they are still considered to be strong bases because all of the base that does dissolve completely dissociates.

  19. Strong Acids • The strength of an acid is based on the percent of units dissociated, not the number of H+ ions produced. • The strength of an acid does NOT depend on the molarity. • There are 6 strong acids: HCl, HBr, HI, HClO4, HNO3, and H2SO4.

  20. Strength • Strong acids and bases are strong electrolytes because they dissociate completely. • Electrolytes conduct electricity. • Weak acids and bases don’t completely ionize.

  21. Strength • The terms weak and strong are used to compare the strengths of acids and bases, dilute and concentrated are terms used to describe the concentration of solutions.

  22. Hydrogen Ions and Acidity • The pH concept • Expressing concentration in molarity is inefficient, so we use a pH scale • The scale ranges from 0 to 14 • 0 is very acidic, 7 is neutral, and 14 is very basic • The pH of a solution is the negative logarithm of the hydrogen-ion concentration • pH = -log [H+], [H+] = 2nd log (-) pH

  23. Hydrogen Ions and Acidity • The pH concept • The pOH of a solution equals the negative logarithm of the hydroxide-ion concentration • pOH = -log[OH-], [OH-] = 2nd log (-) pOH • pH + pOH = 14

More Related