Chapter 9Acids and Bases1
Learning Objectives•Identify acids and bases and describe their characteristics•Write equations for acid-base reactions•Acids and bases strength and effect on the reactions•Define the acid dissociation K and its relation to acid strength•Define the concept of the ion-product of water
Learning Objectives•Calculate pH•Determine whether a salt solution is acidic, basic or neutral•Titration of an acid or base•Describe the basic principles of a buffer•Understand the importance of a buffers in maintaining pH in the body3
4Acids & Bases•Acids•Sour taste•React with “active” metals–Zn + 2 HCl ZnCl2+ H2•React with carbonates, producing CO2–CaCO3+ 2 HCl CaCl2+ CO2+ H2O•React with bases to form ionic salts •Bases•Known As Alkalis,•Taste bitter, •Feel slippery•React with acids to form ionic salts
5Introduction to Acids and BasesThe earliest definition was given by Arrhenius:•An acid contains a hydrogen atom and dissolvesin water to form a hydrogen ion, H+.•A base contains hydroxide and dissolves in waterto form −OH.HCl(g)acidH+(aq) + Cl−(aq) NaOH(s)baseNa+(aq) + −OH(aq)
6Introduction to Acids and Bases•The Arrhenius definition correctly predicts the behavior of many acids and bases.•However, this definition is limited and sometimesinaccurate.•For example, H+does not exist in water. Instead, it reacts with water to form the hydronium ion, H3O+.H3O+(aq) H+(aq) + H2O(l) hydrogen ion:does not really exist in solutionhydronium ion:actually present inaqueous solution
7Introduction to Acids and BasesThe Brønsted–Lowry definition is more widely used:•A Brønsted–Lowry acid is a proton (H+) donor. •A Brønsted–Lowry base is a proton (H+) acceptor.H3O+(aq) + Cl−(aq)HCl(g) + H2O(l)This proton is donated.•HCl is a Brønsted–Lowry acid because it donatesa proton to the solvent water.•H2O is a Brønsted–Lowry base because it acceptsa proton from HCl.
8According to the Brønsted-Lowry theory,•Acids are hydrogen ion (H+) donors. •Bases are hydrogen ion (H+) acceptors.donor acceptor hydronium ionHCl + H2O H3O++ Cl-+ -++Bronsted-Lowry Acids and Bases
9•When NH3dissolves in water, a few NH3molecules react with water to form ammonium ion NH4+and a hydroxide ion.NH3+ H2O NH4+(aq) + OH-(aq)acceptor donor+-++NH3, A Bronsted-Lowry Base
10Introduction to Acids and BasesBrønsted–Lowry Acids•A Brønsted–Lowry acid must contain a hydrogen atom.•Common Brønsted–Lowry acids (HA): HClhydrochloric acidHBrhydrobromic acidCHHHCOOHacidic H atomacetic acidH2SO4sulfuric acidHNO3nitric acid
11Introduction to Acids and BasesBrønsted–Lowry Acids•A monoprotic acid contains one acidic proton.
Want to read all 77 pages?
Want to read all 77 pages?