ACIDS AND BASES

ACIDS AND BASES

ACIDS

• It comes from the Latin word "acidus", which means "sharp" or "sour". 
•  A solution that has an excess of H+ ions. 
•  It loses its acidity when they are combined with alkalies.
•  Strong Acids are dangerous and can burn your skin.
•  It changes the colour of LITMUS :

                         Blue ---> Red 

Examples of Acids:

1. Vinegar 

3. Citrus Fruits 

2. Stomach Acid (HCl)

Strong Acid:

The pH value is below 3.

A strong acid is one which is virtually 100% ionised in solution.

Weak Acid: 

An acid that only partially ionizes in an aqueous solution. This means that not every molecule breaks apart. Weak acids usually have a pH close to 7 (3-6). 

BASES

• A solution that has an excess of OH- ions. 
• Another word for base is "alkali".
• It feels slippery.
• It become less alkaline when they are combined with acids.
• It changes the colour of litmus:

                            Red --- >  Blue

Examples of Bases:

1. Sodium hydroxide(NaOH, strong base)

2. Ammonia

Strong Base: 

The pH value is above 10.

Weak Base: 

A base that only partially ionizes in an aqueous solution. This means that not every molecule breaks apart. Weak bases usually have a pH close to 7 (8-10). 

Common Acids

Acetic acid                                   : vinegar, acetate

Acetylsalicylic acid                     : aspirin

Ascorbic acid                              : vitamin C

Carbonic acid                             : soft drinks, seltzer water

Citric acid                                   : citrus fruits, artificial flavorings

Hydrochloric acid (HCl)           : stomach acid

Nitric acid                                   : fertilizer, explosives

Sulfuric acid                               : car batteries

Common Bases

Aluminum hydroxide              : antacids, deodorants

Ammonium hydroxide            : glass cleaner

Calcium hydroxide                  : caustic lime, mortar, plaster

Magnesium hydroxide             : laxatives, antacids

Sodium bicarbonate/sodium hydrogen carbonate : baking soda

Sodium carbonate                   : dish detergent

Sodium hydroxide                   : lye, oven and drain cleaner

Sodium hypochlorite               : bleach

Properties of Acids and Bases



A table of these properties is shown here which distinguishes  acids and bases apart from one another by some of their easily observed chemical and physical properties.

	Acid	Base
Definition Arrhenius Definition:	An acid is any chemical compound which when dissolved in water gives a solution with a hydrogen ion activity greater than in pure water.	A base is an aqueous substance that can accept hydrogen ions.
Bronstead Lowry Definition:	An acid is an substance which donates a proton.	A base is any substance which accepts a proton.
Physical characteristics	Depending on the temperature, acids can occur in solid, liquid or gaseous form. Taste sour.	Bases feel slippery because of the reaction of the base with the oils of your hand. Frequently solids except ammonia which is a gas. Taste bitter.
Phenolphthalein	colorless	pink
Strength	depends on concentration of the hydronium ions	depends on concentration of the hydroxide ions
Dissociation	Acids free hydrogen ions (H+) when mixed with water.	Bases free hydroxide ions (OH-) when mixed with water.
Chemical Formula	An acid has a chemical formula with H at the beginning of it. There is one exception to his rule, CH3COOH = Acetic Acid (vinegar)	A base has a chemical formula with OH at the end of it
Litmus test	Acids change litmus paper red.	Bases change litmus paper blue.
Examples	Acetic acid i.e.CH3COOH and Sulfuric acid	Sodium Hydroxide (NAOH) and Ammonia (NH3)

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