Inorganic Compounds and Their Properties

3.1 Introduction

• Inorganic compounds are all compounds that do not contain carbon (except simpler carbon compounds like oxides, carbonates, and carbides).
• They consist of minerals from the earth and are found in nonliving things.
• Compounds in living organisms are organic in nature.
• Most metal compounds are inorganic.
• Common inorganic compounds in nature include silicates, oxides, carbonates, sulphides, sulphates, chlorides, nitrates, etc.

3.2 Oxides

• Formation: Oxides are formed by the reaction between metals, non-metals, or metalloids and oxygen.
• Chemical Reaction:
  • ext{Metal/Non-metal/Metalloid} + O_2 o ext{Oxides}

A. Acidic Oxides

• Formed by oxygen with nonmetals from Groups 14-17 (non-metal oxides).
• Examples:
  • ext{CO}2 , ext{NO}2 , ext{SO}_2
• Some acidic oxides (e.g., ext{SiO}_2 ) do not react directly with water but can form acids by other methods.

Chemical Properties

1. Dissolve in water, forming acidic solutions:
   • ext{Acid anhydride} + ext{Water} o ext{Acid}
     • ext{CO}2 + ext{H}2O o ext{H}2 ext{CO}3
2. React with basic or metallic oxides to form salt:
   • ext{Acidic oxide} + ext{Basic oxide} o ext{Salt}
3. React with bases to form salt and water (neutralization):
   • ext{Acidic oxide} + ext{Base} o ext{Salt} + ext{Water}

Basic Oxides

• Composed of metals and oxygen.
• Examples: ext{Li}2 ext{O} , ext{Na}2 ext{O} , ext{K}_2 ext{O} , ext{MgO} , ext{CaO} , ext{BaO} , ext{CuO} .

Chemical Properties

1. Dissolve in water, forming alkaline solutions:
   • ext{Basic oxide} + ext{Water} o ext{Base (Alkali)}
2. React with acidic oxides to form salts.
3. React with acids to form salt and water (neutralization).

C. Amphoteric Oxides

• Characterized by showing both acidic and basic behavior.
• Examples: ext{Al}2 ext{O}3 , ext{ZnO} , ext{PbO} , ext{SnO}_2 .

D. Neutral Oxides

• Do not react with acids or bases.
• Examples: Water ( ext{H}2 ext{O}), carbon monoxide ( ext{CO}), dinitrogen monoxide ( ext{N}2O).

E. Peroxides

• Contain ext{O}_2^{2-} : Oxidation number of oxygen is -1.
• Examples: ext{H}2 ext{O}2 , ext{Na}2 ext{O}2 .

Chemical Properties

1. Powerful oxidizing agents that react by losing oxygen.
2. React with acids to form hydrogen peroxide.

F. Superoxides

• Oxidation number of oxygen is -0.5 (containing ext{O}_2^{-} ).
• Examples: ext{KO}2 and ext{RbO}2 .

3.3 Acids

General Properties

• Taste: Sour, e.g., vinegar contains acetic acid.
• Indicators: Change litmus from blue to red.
• React with metals to produce hydrogen gas. e.g., 2 ext{HCl}(aq) + ext{Mg} o ext{MgCl}2(aq) + ext{H}2(g) .

Classification of Acids

A. Based on Ionizable Hydrogen Ions

• Monoprotic: One ionizable H (e.g., ext{HCl} ).
• Diprotic: Two ionizable H (e.g., ext{H}2 ext{SO}4 ).
• Triprotic: Three ionizable H (e.g., ext{H}3 ext{PO}4 ).

B. Based on Elements

• Binary acids: Two elements (e.g., ext{HCl} ).
• Ternary acids: Three elements, usually including oxygen (e.g., ext{H}2 ext{SO}4 ).

C. Based on Strength

• Strong acids: Completely dissociate (e.g., ext{HCl}, ext{HNO}_3 ).
• Weak acids: Partially dissociate (e.g., ext{CH}_3 ext{COOH} ).

3.5 Salts

• Formed from the neutralization of an acid and base.
• Names derived from metals and acids, following specific naming conventions:
  • Oxygen-free acids: Hydro- prefix dropped, ending -ic changes to -ide (e.g., ext{NaCl} ).
  • Oxyacids: Ending -ic changes to -ate, -ous to -ite (e.g., ext{KNO}_3 to potassium nitrate).

Precautions in Handling Acids and Bases

• For Acids: Wear goggles, gloves, wash spills, dilute acid in water, seek medical help for spills.
• For Bases: Use protective gear, rinse spills, wash affected areas immediately.

pH Measurement

• pH is the measure of acidity in a solution, scale 0-14.
• Neutral water has a pH of 7.
• pH can be calculated using:
  • ext{pH} = - ext{log}[ ext{H}^+]
  • ext{pH} + ext{pOH} = 14 .

Examples of Reactions Leading to Preparation of Acids

• Reaction of oxides with water, direct combination of nonmetals, heating salts with non-volatile acid.