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
- 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
- React with basic or metallic oxides to form salt:
- ext{Acidic oxide} + ext{Basic oxide} o ext{Salt}
- 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
- Dissolve in water, forming alkaline solutions:
- ext{Basic oxide} + ext{Water} o ext{Base (Alkali)}
- React with acidic oxides to form salts.
- 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
- Powerful oxidizing agents that react by losing oxygen.
- 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.