Acids and Bases

proton (H+​) donator

proton (H+​) acceptor

HA + B –> A- + BH+ • conjugate acid-base pair • conjugate acid-base pair differ by one proton

• substance that can act as both a proton donator and a proton acceptor • must have a lone pair of electrons and hydrogen that can be released as H+​

bases that dissolve in water to form the hydroxide ion

• ionic compound formed when the hydrogen of an acid is replaced by a metal or another positive ion

e.g. NaCl derived from acid HCl and base NaOH

salt + hydrogen

• salt + water + carbon dioxide • effervescence

salt + water

• reaction that occurs when an acid and base react together to form salt and water • exothermic

enthalpy change that occurs when an acid and a base react together to form one mole of water

gas given off so visibly produces bubbles

change color reversibly according to concentration of H+ ions in the solution

• indicators are weak acids or bases whose conjugates have different colors • color change identifies pH of substance • usually aqueous or absorbed on test paper

gives distinct or sharp color change at equivalence point

• best known acid-base indicator • dye derived from lichens • pink in presence of acid; blue in presence of alkalis

• several indicators mixed together • changes color many times across range of acids/alkalis • can be used to measure [H+] on pH scale

• reacting together a carefully measured volume of one of solutions, and adding the other solution gradually • until reach equivalence point

where an acid and base exactly neutralize each other

• pH = -log10[H+] • [H+] = 10-pH

• pH numbers usually positive • have no units • pH inversely related to [H+] • change of one pH unit represents a 10-fold change in [H+]

• probe that directly reads [H+] through an electrode • have accuracy to several decimal points • must be calibrated before each use with buffer solution • must be standardized for temperature