Definition of Acids and Bases
In chemistry, acids and bases are substances that react with each other to form a salt. Acids are defined as substances that donate hydrogen ions (H+) to other substances, while bases are defined as substances that accept hydrogen ions from other substances.
Theories of Acids and Bases
There are three main theories of acids and bases:
- Arrhenius theory
- Bronsted-Lowry theory
- Lewis theory
Arrhenius theory
The Arrhenius theory defines acids as substances that ionize (break apart) in an aqueous solution to produce hydrogen (H+) ions while bases produce hydroxide (OH-) ions in solution.
For example, hydrochloric acid (HCl) ionizes in water to produce hydrogen ions and chloride ions:
HCl + H2O → H+ + Cl-Sodium hydroxide (NaOH) ionizes in water to produce hydroxide ions and sodium ions:
NaOH + H2O → Na+ + OH-Bronsted-Lowry theory
The Bronsted-Lowry theory defines acids as substances that donate protons (H+) whereas bases are substances that accept protons.
A proton is a positively charged hydrogen ion.
For example, in the reaction between hydrochloric acid and sodium hydroxide, hydrochloric acid donates a proton to sodium hydroxide, forming water and sodium chloride:
HCl + NaOH → H2O + NaClLewis theory
The Lewis theory defines acids as electron pair acceptors while bases are electron pair donors.
An electron pair is a pair of electrons shared between two atoms.
For example, in the reaction between boron trifluoride and ammonia, boron trifluoride accepts an electron pair from ammonia, forming a complex ion:
BF3 + NH3 → [BF3NH3]Properties of Acids and Bases
Acids and bases have a number of properties in common, including:
- Sour taste
- Bitter taste
- Slippery texture
- Turn blue litmus red
- Turn red litmus blue
- React with metals to form salts
- React with bases to form salts
pH of Acids and Bases
The pH scale is a measure of how acidic or basic a substance is. The pH scale ranges from 0 to 14, with 7 being neutral. A pH below 7 indicates an acidic substance, while a pH above 7 indicates a basic substance.
For example, hydrochloric acid has a pH of 1, while sodium hydroxide has a pH of 14.
Uses of Acids and Bases
Acids and bases have a wide variety of uses, including:
- Food and beverage production
- Cleaning and disinfecting
- Metalworking
- Agriculture
- Medicine
- Research
Conclusion
Acids and bases are important substances with a wide variety of uses. They are defined by their ability to donate or accept hydrogen ions, and they have a number of properties in common, including a sour taste, a bitter taste, a slippery texture, and the ability to turn litmus paper red or blue. The pH scale is a measure of how acidic or basic a substance is.
