Chemistry (Part-VII) (Railway)

Carbon compounds are covalent in nature.

• Covalent compounds do not dissociate into ions in aqueous solution and also it does not have free electrons.

• Since there is no flow of charge, they are bad conductors of electricity.

• It is a colorless, flammable liquid with a distinctive detergent-like odor, reminiscent of cleaning products (in which it is sometimes used).

• Cyclohexane is produced by hydrogenation of benzene (C₆H₆) in the presence of a nickel catalyst.

• H₂SO₄ + Zn → ZnSO₄ + H₂ is a double replacement reaction where Zn up replaces the H in the sulfuric acid

• The number of atoms of reactants and products remains the same.

• It failed for heavier elements.

• According to Octaves, when the elements were arranged in the order of increasing atomic weight, every first element had properties similar to that of the eighth element.

When aluminium is added to an aqueous solution of copper sulphate, Aluminium displaces the copper from its salt solution to form Aluminium Sulphate [Al₂(SO₄)₃].

• The colour of the solution changes from blue to transparent and copper is observed as a layer on the Aluminium piece. ​

If a substance gains oxygen during a reaction, it is being oxidized. If it loses oxygen, it is being reduced.

• Oxidation and Reduction always take place together, so that if one substance is oxidized, another is reduced.

• Example, in the reaction Mg + O₂ → 2MgO Mg gains oxygen, hence it is oxidized. ​

Unsaturated hydrocarbons are organic compounds that are entirely made up of carbon and hydrogen atoms and consist of a double or a triple bond between two adjacent carbon atoms. For example, CH₃CH₂CH = CH₂ (n-Butylene) & CH₃CH = CH₂ (Propylene).

• Unsaturated hydrocarbons, based on the types of bonds they contain, can be classified into alkenes, alkynes, and aromatic hydrocarbons.

• Some examples of natural indicators are red cabbage, Coloured petals of Hydrangea, turmeric, grape juice, coloured petals of Petunia, etc.

• For example, petals of Hydrangea become blue if the soil is acidic, purple if the soil is neutral, and pink if the soil is basic.

Chlorine (Cl) is a nonmetal in group 17 of the periodic table.

• It cannot conduct electricity, it is not flexible, and it is not hard.

• It belongs to the Halogen group and its properties are thus similar to fluorine, bromine, and iodine, and are largely intermediate between those of the first two.