Chemistry Notes PDF

# Chemistry Notes ## 0.4) Describe Covalent bond in detail: - A Coordinate bond, also known as dative covalent bond, is a type of covalent bond where one atom donates both electrons to the bond. - Here are some details about coordinate bonds: ### Formations: - A Coordinate bond forms when one at...

# Chemistry Notes ## 0.4) Describe Covalent bond in detail: - A Coordinate bond, also known as dative covalent bond, is a type of covalent bond where one atom donates both electrons to the bond. - Here are some details about coordinate bonds: ### Formations: - A Coordinate bond forms when one atom donates a lone pair of electrons to another atom that lacks electrons. For example, in an ammonia molecule, the nitrogen atom donates a lone pair of electrons to another atom. ### Properties: - Coordinate bonds are often found in coordination compounds, which are molecules that have a metal ion surrounded by ligands and having a greater bond length than standard covalent bonds. - They are also known for being highly polar. - Lewis acid-base theory: Coordinate bonds are often considered to be formed through Lewis acid-base chemistry. A Lewis base is an electron donor and a Lewis acid is an electron acceptor. - Ex: The compounds O3, SO3, and H2SO4 all contain Coordinate bonds. ## 22) What is ionic bond? Explain it formally with two examples: - Ionic bond is a type of chemical bonding where one or more electrons are transferred between atoms, resulting in the formation of ions with opposite charges. ### Formation of ionic bond: - Metal atom loses electrons to become a positively charged ion (cation). - Non-metal atom gains electrons to become a negatively charged ion (anion). - Oppositely charged ions attract each other forming an ionic bond. ### Example 1: Sodium Chloride (NaCl) - Table Salt. - Sodium (Na) atom loses 1 electron to become Na+ cation - Chlorine (Cl) atom gains 1 electron to become Cl- anion - Na+ and Cl- ions attract each other forming an ionic bond. - Na → Na+ (sodium loses electron) - Cl → Cl- (chlorine gains electron) - Na+ Cl- → NaCl (ionic bond forms) ### Example 2: Calcium oxide (CaO) - Calcium (Ca) atom loses two electrons to become Ca2+ cation ## Assignment - 1 ## 21) Describe postulates of electronic theory of valency: - Electronic theory of valence was proposed by Kossel and Lewis in 1916. They gave a logical explanation of valence which was based on the inertness of noble gases (that is, octet rule developed by Lewis). - According to Lewis, the atom can be pictured in terms of a positively charged "kernel" (the nucleus plus inner electrons) and outer shell that can accommodate a maximum of eight electrons. This octet of electrons represents a stable electronic arrangement. - Thus, according to this theory, during the formation of a chemical bond, each atom loses, gains, or shares outer electrons so that it achieves a stable octet. - The formation of NaCl involves transfer of one electron from sodium (Na) to chlorine (Cl). Na+ and Cl- ions are formed, which are held together by chemical bond. The formation of H2, F2, Cl2, HCl, etc. involves sharing of a pair of electrons between the atoms. In both the cases, each atom attains a stable outer octet of electrons. ## 1) Occurrence of Metal: - Metal can be found in nature in both free and combined states depending on their reactivity. ### 1) Free State: - Metals that are less reactive or noble can exist in their elemental or native (free) state in nature - Ex: The metals that occur in a free state include Gold, Silver, Platinum, and Mercury. ### 2) Combined State: - Most metals are active and combine with other elements to form compounds such as oxides, carbonates, sulfites. These metals are found in nature in a combined state. - Metals that occur in both free and combined states include Copper and Silver. - Ex: Silver Chloride (AgCl), Silver Oxide, (Ag2O), Silver Nitrate, (AgNO3), Copper Sulphide (CuS) and Copper Oxide (CuO) ## 2) Metallurgy: - Metallurgy is defined as "A process that is used for the extraction of metals in their pure form. ### Basic Concepts: - **Minerals:** A naturally occurring inorganic compound is known as minerals. - **Ore:** Minerals from which a metal can be extracted. - **Gangue:** Impurities present in the ore. - **Flux:** A substance used to remove impurities from an ore. - **Slag:** A waste material formed during metal extraction. - **Alloy:** A mixture of two or more elements of which at least one metal. - During smelting, volatile impurities like Sulphur, arsenic, antimony are removed in the form of their oxide. - Ex: Sulphide ore: Galena(PbS), Zinc Blende, (ZnS), and Copper Pyrites (CuFeS2) - 2ZnS + 3O2 → 2ZnO + 2SO2 - CuS + 2O2 → CuO + SO2 ### **Reduction:** - There is the important part of metallurgy which the concentrated ore is reduced to a metal by the following reductions: - Smelting - Alumino-thermic process - Electrolysis - Reduction is carried out in the blast furnace. - Another type of furnace is used for heating, named as a muffle furnace. ### **Smelting:** - The oxide of metal is heated in the presence of air, it is known as roasting. ### **Chemical Process:** - **Calcination:** It is the process of heating the ore in the absence of air or limited supply of air. Calcination consists of thermal decomposition of calcium ore; carbon dioxide is given out as a byproduct. - During calcination, moisture is removed from the ore. - The process is carried out in a reverberatory furnace. - CaCO3 → CaO +CO2 - Calcium carbonate (CaCO3) and hydroxide (Fe2O3.3H2O) types of ore. ### Types of Ore: - **Roasting:** The process of heating the ore in the presence of air is known as roasting. - The process is used for sulphide ore. - The purpose of roasting is to make the ore into a suitable form which can be reduced to metal, also to remove moisture. ## 3) Electro-magnetic Separation: - It is the process of removing magnetic materials from relatively non-magnetic materials using electromagnets which travel along a conveyor belt. - Ex: In tin stone (core of tin) impurities of iron (Fe) and magnesium (Mn) are non-magnetic while the ore is magnetic in nature. - **Process:** In this method, powdered ore is melted to fall through the hopper on a leather rubber belt moving over magnetic rollers. The magnetic particles fall below the magnetic roller in a heap while non-magnetic particles fall away from the roller in a separate heap. ### Chemical Process: ## 2) Steps Involved in Gravity Separation method: - **Crushing:** The feed (mixture is crushed into smaller pieces to increase surface area. - **Pulverizing:** The crushed material is classified or pulverized into a fine powder to increase surface area. - **Classification:** The pulverized material is classified based on the size of the particles. - **Gravity separation:** Classified material is fed into a gravity separator, where the denser particles settle at the bottom and the lighter particles rise to the top. - **Concentration:** The denser particles (concentrate) are collected from the bottom of the separator. - **Tailings:** The lighter particles (tailings) are collected from the top of the separator. ## Flux: - Fe2O3 Flux → Fe + O3 - Gangue - Cu2O Flux → Cu + O - Gangue - Cu2S → Cu +S ## Some Important Ores of Metals: ### Oxides: - **Bauxite:** Al2O3 - **Haematite:** Fe2O3.2H2O - **Cuprite:** Cu2O - **Pinstone:** SnO2 - **Ansite:** ZnO - **Magnetite:** Fe3O4 - **Pyrolusite:** MnO2 ### Sulphides: - **Zinc blende:** ZnS - **Cinnabar:** HgS - **Galena:** PbS - **Copper pyrite:** CuFeS2 - **Copper glance:** Cu2S ### Carbonates: - **Dolomite:** CaCO3.MgCO3 - **Malachite:** CuCO3