Acids, Bases and Salts - Characteristic Properties

Bases

Bases are chemical compounds that typically have a pH greater than 7. They are characterized by their ability to react with acids, neutralizing their acidity. A key property of bases is their formation from metals and oxides/hydroxides.

Bases can be classified into two main types:

• Metal Oxides: These are formed when a metal reacts with oxygen. For example, $Na_2O$ (sodium oxide) is a metal oxide.
• Metal Hydroxides: These are formed when a metal oxide reacts with water. For example, $NaOH$ (sodium hydroxide) is a metal hydroxide.

Alkalies are a specific type of base. They are soluble bases in water. Common examples include sodium hydroxide ($NaOH$), potassium hydroxide ($KOH$), and calcium hydroxide ($Ca(OH)_2$).

Table summarizing Bases

Type of Base	Chemical Formula (Examples)	Properties
Metal Oxide	$Na_2O$, $CaO$	React with water to form a base (though less strongly than hydroxides).
Metal Hydroxide (Alkali)	$NaOH$, $KOH$, $Ca(OH)_2$	Soluble in water. Strong bases. Feel slippery.

Key Characteristics of Bases

1. Feel Slippery: Bases, particularly alkalis, have a characteristic slippery feel due to the formation of soap (a salt of a fatty acid) when they react with fats.
2. Litmus Test: Bases turn red litmus paper blue.
3. pH: Bases have a pH greater than 7.
4. Neutralization: Bases neutralize acids.