Svante Arrhenius
- acids produce H+ ions in aqueous solutions
- bases produce OH- ions in aqueous solutions
- water required, so only allows for aqueous solutions
- only protic acids are allowed; required to produce hydrogen ions
- only hydroxide bases are allowed
Johannes Nicolaus Brønsted - Thomas Martin Lowry
- acids are proton donors
- bases are proton acceptors
- aqueous solutions are permissible
- bases besides hydroxides are permissible
- only protic acids are allowed
Gilbert Newton Lewis
- acids are electron pair acceptors
- bases are electron pair donors
- least restrictive of acid-base definitions
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)
