CB’s (anions of weak acids) - react like Kw =[OH-] [H+] = 10-14 nonhydroxide bases in water: pKw = 14 NaF strong base weak acid salt anion is a CB: F- + H2O ÅÆ HF + OH- CA’s (cations of weak bases) - react like acids in water: NH4Cl weak base strong acid salt cation is a CB: NH4+ + H2O ÅÆ H3O+ + NH3 % Dissociation Summary of Buffer Reactions: Weak Acid and Conjugate Base Buffer: Buffer Reactions: HA + H2O H + A- (weak acid controls pH) XA 3O+ X+ + A- (conjugate base A-) Neutralization Reactions: Strong acid to buffer Strong base added to buffer HCl + A- HA + Cl- NaOH + H Na+ + A- + H O 2 acid + base base + acid Weak Base and Conjugate Acid Buffer Buffer Reactions: M +H2O ÅÆ MH+ + OH- (weak base controls pH) MHX MH+ + X- (conjugate acid MH+) Neutralization Reactions: Strong acid to buffer Strong base added to buffer HCl + M MH+ + Cl- NaOH + MH+ M + Na+ + H O 2 acid + base base + acid %RICE AFTER STRONG ACID OR BASE IS ADDED TO A BUFFER: CHECK% When a strong acid is added to buffer subtract M of strong acid from the base and add to the acid When strong base is added subtract the M of strong base from the acid and add to the base: TITRATION pH = pKa at ½ equivalence point Titration: If an ACID & BASE are reacting write a neutralization reaction: (both strong) do Stoichiometry to find molarity of substance of interest; AT equivalence pt 7/ (one of them weak) SCAM then RICE TABLE, AT equivalence pt a non neutral salt will be CA or CB problem Kw = Ka ⋅Kb
CB’s (anions of weak acids) - react like nonhydroxide bases in water: NaF strong base weak acid salt anion is a CB: F- + H2O ÅÆ HF + OH- CA’s (cations of weak bases) - react like acids in water: NH4Cl weak base strong acid salt cation is a CB: NH4+ + H2O ÅÆ H3O+ + NH3 Kw =[OH-] [H+] = 10-14 pKw = 14 % Dissociation Summary of Buffer Reactions: Weak Acid and Conjugate Base Buffer: Buffer Reactions: HA + H2O H 3O+ + A- (weak acid controls pH) XA X+ + A- (conjugate base A-) Neutralization Reactions: Strong acid to buffer Strong base added to buffer HCl + A- HA + Cl- NaOH + H Na+ + A- + H O 2 acid + base base + acid Weak Base and Conjugate Acid Buffer Buffer Reactions: M +H2O ÅÆ MH+ + OH- (weak base controls pH) MHX MH+ + X- (conjugate acid MH+) Neutralization Reactions: Strong acid to buffer Strong base added to buffer HCl + M MH+ + Cl- NaOH + MH+ M + Na+ + H O 2 acid + base base + acid %RICE AFTER STRONG ACID OR BASE IS ADDED TO A BUFFER: CHECK% When a strong acid is added to buffer subtract M of strong acid from the base and add to the acid When strong base is added subtract the M of strong base from the acid and add to the base: TITRATION pH = pKa at ½ equivalence point Titration: If an ACID & BASE are reacting write a neutralization reaction: (both strong) do Stoichiometry to find molarity of substance of interest; AT equivalence pt 7/ (one of them weak) SCAM then RICE TABLE, AT equivalence pt a non neutral salt will be CA or CB problem Kw = Ka ⋅Kb