Nota Terkini

Saturday, March 13, 2010

[Chemistry Form 4] Ions In Solution

Swedish chemist Arrhenius defined acids as substances that, when dissolved in water, produce hydrogen ions (H+). Eg: When gaseous hydrogen chloride reacts with water, the amount of hydrogen ions in the water increases and hydrochloric acid is thus produced.

HCl (g) ---> H+ (aq) + Cl- (aq)
Acid
(H+ producer)

Some of the food and medicines that we take contain acids. Ethanoic (acetic) acid in vinegar and acetylsalicyclic acid in aspirin, for instance.

Contrary to acids, bases are defined as substances that, when dissolved in water, yield hydroxide ions (OH-). Eg: When sodium hydroxide dissolves in water, the amount of hydroxide ions in the water increases and the alkaline solution is thus produced.

NaOH (s) ---> Na+ (aq) + OH- (aq)
Base
(OH- producer)

Did You Know?
The compounds responsible for colours in plants are often sensitive to acids and alkalis. For example, blue hydrangeas grow only in acidic soils; in neutral or alkaline soils, they turn to pink.

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