Inorganic Chemistry: p-Block Elements - SS3 Chemistry Past Questions and Answers - page 4

H2O (water) is not a hydride of a p-block element. Hydrides are compounds formed by p-block elements with hydrogen.

SO2 (sulphur dioxide) is responsible for acid rain when it reacts with atmospheric water to form sulfuric acid.

F2 (fluorine gas) is a halide and is a gas at room temperature.

SiH4 (silane) is used in the semiconductor industry for the deposition of silicon in the fabrication of microelectronic devices.

P4O10 (phosphorus pentoxide) is used as a drying agent and a dehydrating agent due to its strong affinity for water.

Cl2 (chlorine gas) is used as a disinfectant and water purifier due to its ability to kill bacteria and other harmful microorganisms.

H2S (hydrogen sulphide) is a toxic gas with a characteristic rotten egg or garlic-like odour.

CO2 (carbon dioxide) is used as a fire extinguishing agent because it displaces oxygen, smothering the fire.

Properties of Oxides of p-block Elements:

Oxides of p-block elements are compounds composed of oxygen and p-block elements. They exhibit a wide range of properties depending on the specific element and oxidation state involved:

1.    Acid-Base Character: Oxides of metals (e.g., sodium oxide, Na2O) are generally basic, reacting with water to form metal hydroxides. Nonmetals' oxides (e.g., carbon dioxide, CO2) are typically acidic and react with water to form acidic solutions.

2.    Reactivity with Acids: Basic oxides react with acids to form salts and water. For example, magnesium oxide (MgO) reacts with hydrochloric acid (HCl) to form magnesium chloride (MgCl2) and water.

3.    Reactivity with Bases: Acidic oxides react with bases to form salts and water. For instance, sulphur dioxide (SO2) reacts with sodium hydroxide (NaOH) to form sodium sulfite (Na2SO3) and water.

Preparation Methods:

1.    Combustion: Some p-block elements, like carbon and sulphur, readily react with oxygen in the air during combustion, producing carbon dioxide (CO2) and sulphur dioxide (SO2), respectively.

2.    Direct Combination: Some metals directly react with oxygen to form metal oxides. For example, sodium (Na) reacts with oxygen (O2) to form sodium oxide (Na2O).

3.    Decomposition: Certain metal oxides can be obtained by decomposing their corresponding salts. For example, heating copper(II) nitrate (Cu(NO3)2) decomposes it into copper(II) oxide (CuO) and nitrogen dioxide (NO2).

Significance:

1.    Industrial Applications: Metal oxides find numerous industrial applications, such as in the manufacturing of cement, glass, and ceramics.

2.    Environmental Impact: Oxides play a significant role in environmental processes. For example, carbon dioxide is a greenhouse gas contributing to global warming.

3.    Biological Relevance: Some metal oxides are crucial in biological systems, like the role of calcium oxide (CaO) in bone formation.

Characteristics of Halides of p-block Elements:

Halides of p-block elements are compounds formed between halogens (Group 17 elements) and other elements. These compounds exhibit various characteristics:

1.    Ionic Nature: Halides typically form ionic compounds with metals, such as sodium chloride (NaCl) or potassium bromide (KBr), where halogens gain an electron to form halide ions (X-) with a -1 charge.

2.    Solubility: The solubility of halides varies with different halogens and cations. For example, sodium chloride (NaCl) is highly soluble in water, while silver chloride (AgCl) is sparingly soluble.

3.    Reactivity: Halides can participate in various chemical reactions, including precipitation reactions and redox reactions.

Preparation Methods:

1.    Direct Combination: Halogens react directly with metals to form metal halides. For instance, chlorine gas (Cl2) reacts with sodium metal (Na) to form sodium chloride (NaCl).

2.    Replacement Reactions: Halogens can displace each other from their salts through replacement reactions. For example, chlorine gas (Cl2) reacts with potassium bromide (KBr) to form potassium chloride (KCl) and bromine gas (Br2).

Uses of Halides:

1.    Sodium Chloride (NaCl): Common table salt used for seasoning food and as a preservative.

2.    Potassium Iodide (KI): Used in iodized salt and as a supplement for iodine deficiency.

3.    Silver Halides (AgX): Used in photography, where they react to light exposure to produce images.

4.    Aluminium Fluoride (AlF3): Used as a flux in aluminium smelting and the production of ceramics.

5.    Hydrogen Halides (HX): Used in the preparation of various industrial chemicals.

Halides of p-block elements have diverse applications in various industries, from food preservation to photography, and are essential compounds in everyday life.