CBSE Class 10 Science Notes - Carbon and Its Compounds PDF

Carbon and Its Compounds Soaps and Detergents:- Cleansing Action of Soap When soap is added to water, the soap molecules uniquely orient themselves to form spherical shape micelles. The non-polar hydrophobic part or tail of the soap molecules attracts the dirt or oil part of the fabric, while the...

Carbon and Its Compounds Soaps and Detergents:- Cleansing Action of Soap When soap is added to water, the soap molecules uniquely orient themselves to form spherical shape micelles. The non-polar hydrophobic part or tail of the soap molecules attracts the dirt or oil part of the fabric, while the polar hydrophilic part or head,(−COO N a , remains attracted to water − + molecules. The agitation or scrubbing of the fabric helps the micelles to carry the oil or dirt particles and detach them from the fibres of the fabric. Hard Water Hard water contains salts of calcium and magnesium, principally as bicarbonates, chlorides, and sulphates. When soap is added to hard water, calcium and magnesium ions of hard water react with soap forming insoluble curdy white precipitates of calcium and magnesium salts of fatty acids. 2C17 H35 COON a + M gCl2 → (C17 H35 COO)2 M g + 2N aCl 2C17 H35 COON a + CaCl2 → (C17 H35 COO)2 Ca + 2N aCl These precipitates stick to the fabric being washed and hence, interfere with the cleaning ability of the soap. Therefore, a lot of soap is wasted if water is hard. Covalent Bonds Difficulty of Carbon to Form a Stable Ion To achieve the electronic configuration of nearest noble gas, He, if the carbon atom loses four of its valence electrons, a huge amount of energy is involved. C ion hence formed will 4+ be highly unstable due to the presence of six protons and two electrons. If the carbon atom gains four electrons to achieve the nearest electronic configuration of the noble gas, Ne, C ion will be formed. But again, a huge amount of energy is required. 4− Moreover, in C ion it is difficult for 6 protons to hold 10 electrons. Hence, to satisfy its 4+ tetravalency, carbon shares all four of its valence electrons and forms covalent bonds. Ionic Bond Ionic bonding involves the transfer of valence electron/s, primarily between a metal and a nonmetal. The electrostatic attractions between the oppositely charged ions hold the compound together. Ionic compounds: 1. Are usually crystalline solids (made of ions) 2. Have high melting and boiling points 3. Conduct electricity when melted 4. Are mostly soluble in water and polar solvents Covalent Bond A covalent bond is formed when pairs of electrons are shared between two atoms. It is primarily formed between two same nonmetallic atoms or between nonmetallic atoms with similar electronegativity. Lewis Dot Structure Lewis structures are also known as Lewis dot structures or electron dot structures. These are basically diagrams with the element's symbol in the centre. The dots around it represent the valence electrons of the element. Lewis structures of elements with atomic number 5-8 Covalent Bonding in H2, N2 and O2 Formation of a single bond in a hydrogen molecule: Each hydrogen atom has a single electron in the valence shell. It requires one more to acquire nearest noble gas configuration (He). Therefore, both the atoms share one electron each and form a single bond. Formation of a double bond in an oxygen molecule: Each oxygen atom has six electrons in the valence shell (2, 6). It requires two electrons to acquire nearest noble gas configuration (Ne). Therefore, both the atoms share two electrons each and form a double bond. Formation of a triple bond in a nitrogen molecule: Each nitrogen atom has five electrons in the valence shell (2, 5). It requires three electrons to acquire nearest noble gas configuration (Ne). Therefore, both atoms share three electrons each and form a triple bond. Single, Double and Triple Bonds and Their Strengths A single bond is formed between two atoms when two electrons are shared between them, i.e., one electron from each participating atom. It is depicted by a single line between the two atoms. A double bond is formed between two atoms when four electrons are shared between them, i.e., one pair of electrons from each participating atom. It is depicted by double lines between the two atoms. A triple bond is formed between two atoms when six electrons are shared between them, i.e., two pairs of electrons from each participating atom. It is depicted by triple lines between the two atoms. Bond strength: - The bond strength of a bond is determined by the amount of energy required to break a bond. - The order of bond strengths when it comes to multiple bonds is: Triple bond>double bond>single bond - This is to signify that the energy required to break three bonds is higher than that for two bonds or a single bond. Bond length: - Bond length is determined by the distance between nuclei of the two atoms in a bond. - The order of bond length for multiple bonds is: Triple bond