Properties of Acids
• Taste sour (don't taste them!)... the word 'acid' comes from the Latin acere, which means 'sour'
• acids change litmus (a blue vegetable dye) from blue to red
• their aqueous (water) solutions conduct electric current (are electrolytes)
• react with bases to form salts and water
• evolve hydrogen gas (H2) upon reaction with an active metal (such as alkali metals, alkaline earth metals, zinc, aluminum)
Properties of Bases
• taste bitter (don't taste them!)
• feel slippery or soapy (don't arbitrarily touch them!)
• bases don't change the color of litmus; they can turn red (acidified) litmus back to blue
• their aqueous (water) solutions conduct and electric current (are electrolytes)
• react with acids to form salts and water
Examples of Common Acids
• citric acid (from certain fruits and veggies, notably citrus fruits)
• ascorbic acid (vitamin C, as from certain fruits)
• vinegar (5% acetic acid)
• carbonic acid (for carbonation of soft drinks)
• lactic acid (in buttermilk)
Examples of Common Bases
• detergents
• soap
• lye (NaOH)
• household ammonia (aqueous)
Strong Acids
A strong acid is an acid which is fully (almost 100%) ionised in solution.
Strong Acids The Formulae
Sulphuric acid
Hydrochloric acid
Nitric acid
Perchloric acid H2SO4
HCl
HNO3
HClO4
Weak Acids
A weak acid is an acid which is only partially (nearly 1%) ionised in solution. Examples are- CH3COOH, HCOOH, etc.
Strong Bases
A strong base is one which is fully ionised in solution.
Strong Bases The Formulae
Lithium hydroxide
Sodium hydroxide
Potassium hydroxide
Barium hydroxide
Calcium hydroxide LiOH
NaOH
KOH
Ba(OH)2
Ca(OH)2
Weak Bases
A weak base is a base which is only partially ionised in solution. Examples are- NH4OH, Mg(OH)2, Al(OH)3, etc.
Amphiprotic substances: Molecule or ions that behave both as Bronsted acid and base. For example, H2O.
Basic Principles of the Various Theories of Acids & Bases
Traditional approach Substance that have certain properties Acid: sour taste, turns litmus red; Base: bitter taste, turns litmus to blue
Arrhenius Acid : give H+ in aqueous solution
Base : give OH- in aqueous solution
At neutrality: [H+] = [OH-]
Bronsted-Lowry Acid : H+ donor
Base : H+ acceptor
Conjugate acid-base pairs
No concept of neutrality
Lewis Acid : a potential electron-pair acceptor
Base : a potential electron-pair donor
