Acids and Bases

L’histoire

• The mediterranean / Greeks • Alkali – from the arabic for ash ….

Swedish chemist, Svante August Arrhenius (1859-1927)

• …..had the insolence to propose in his doctoral thesis that certain substances remain ionised in solution. In 1884, this constituted an act of scientific heresy. Of course, everybody thought Arrhenius was a weirdo. He was scornfully awarded a fourth class degree, and was obviously left feeling very hurt. Years later, in 1903, he was proven right: he got his revenge and the Nobel Prize !

Arrhenius

• Acids donate a proton

• Bases donate Hydroxide ion

Bronsted ( Danish ) –Lowry (UK)

• Refined Arrhenius to :-

– Acids are proton DONORS

– Bases are proton ACCEPTORS

Lewis ( America )

• Positive charges are acid and negative charges are bases.

• Or an acid is an electron pair ACCEPTOR and a base is an electron pair DONOR.

Definitions

• Bronsted-Lowry

• Conjugate acids and bases

• Amphiprotic

• Lewis

• Bases and Alkalis

• Arrhenius

Equilibrium Constant

• The higher the value the stronger the acid.

• The lower the value the stronger the base.

Acid and Base Strength

• Position of Equilibirum

• Examples

Reactions

• Hydroxides

• Metal Oxides

• Ammonia

• Reactive Metals

• Carbonates

Sums

• pH = -log10 [H+]

• 1. pH 5 = a H+ ion concentration of ?

• 2. pH + pOH = ?

• 3. If H+ is 1 x 10-11 what is pOH ?

HL

Water Equilibrium :-

Strong Acids and Bases

• What is pHof

– 1. 0.1 M HCl

– 2. 0.2M H2SO4

– 3. 1.00 x 10-3 NaOH

U Teach

• Calcs weak acids bases

• Buffers

• Indicators