Answer questions a-c about the Bronsted acid-base reaction below using the ident
ID: 891186 • Letter: A
Question
Answer questions a-c about the Bronsted acid-base reaction below using the identifying letters A-D below each structure. The pKa's for the acids of interest are: hydrogen cyanide (pKa = 9.3), and benzoic acid (pKa = 4.2). The pKa's for the acids of interest are: ammonium ion (pKa=9.3), and acetic acid (pKa=4.8).
HCN CN + hydrogen cyanide benzoate benzoic acid a) The stronger base is b) Its conjugate acid is c) The species that predominate at equilibrium are (two letters, e.g. ac) NH4 CH ammonium acetate ammonia acetic acid a) The stronger acid is b) Its conjugate base is c) The species that predominate at equilibrium are (two letters, e.g. ac) CH3 CH3 H- C ethylamine hydrogen chloride ethylammonium chlride a) The weaker acid is b) Its conjugate base is c) The species that predominate at equilibrium are (two letters, e.g. AC)Explanation / Answer
If the acid has greater pKa, it is weak acid and the acid with smaller pKa is strong acid.
The conjugate base of weak acid is strong base and the conjugate base of strong caid is weak base.
1. Between HCN and benzoic acid benzoic acid is stronger acid as it has lower pKa value and its conjugate base is weak base when compare with conjugate base of HCN.
a) The stronger base : C (cyanide ion CN-)
b) Its conjugate acid : A (Hydrogen cyanide, HCN)
c) The species that are predominate at equilibrium are : A and B (Hydrogen Cyanide and Benzoate)
2. Between acetic acid and ammonium ion acetic acid is stronger acid as it has lower pKa value.
a) The stronger acid : D (Acetic acid CH3COOH)
b) Its conjugate base : B (Acetate ion, CH3COO-)
c) The species that are predominate at equilibrium are : A and B (Ammonium ion and acetate ion)
3. Between HCl and ethylammonium ion HCl is very stronger acid as it can be dissociated completed when dissolved in water. Hence
a) The weaker acid : C (ethyl ammonium)
b) Its conjugate base : A (Ethyl amine)
c) The species that are predominate at equilibrium are : C and D (ethyl ammonium and Chloride)