Railway Science (Chemistry-Chemical Properties)

Silver reacts with sulfur compounds such as Hydrogen Sulphide (H2S) present in the air. It darkens the silver because Silver Sulphide (Ag₂S) is black. The chemical change is called "Corrosion" and is also known as "Tarnishing of Silver". Reaction: 2Ag(s) + H₂S(g) → Ag₂S(s) + H₂(g).

NH₃ (Ammonia) is a nutritious, inorganic nitrogen compound that is found naturally in the air, soil, water and living tissues. Acid rain, also called acid precipitation or acid deposition, precipitation possessing a pH of about 5.2 or below primarily produced from the emission of sulfur dioxide (SO₂) and nitrogen oxides (Combination of NO and NO₂) from human activities, mostly the combustion of fossil fuels.

Some metallic oxides exhibit a dual behaviour. They show characteristics of both acidic as well as basic oxides. Such oxides are known as amphoteric oxides. They react with acids as well as alkalies. Example - Aluminiuim Oxide (Al₂O₃).

Barium (Ba) :- Atomic number -56. Metal salts commonly used in firework displays include Calcium chloride, Sodium nitrate, Barium chloride, copper chloride. Blue flame (Copper, Cu), Orange flame (Calcium, Ca), Yellow flame (Sodium, Na), Red flame (Lithium, Li). Gold (Au) - Atomic number - 79, Golden sparks are produced by iron filings (magnetite, hematite) and small pieces of charcoal.

Acid Rain - It is defined as the precipitation of acid in the form of rain. When atmospheric pollutants like oxides of nitrogen (N) and sulfur (S) react with rainwater.
Causes -Sulphur and nitrogen particles which get mixed with the wet components of rain. These two gases react with water in the atmosphere and oxygen (O₂) in the air to form sulphuric acid (H₂SO₄) and nitric acid (HNO₃).

Calcium Hypochlorite} is made by the action of chlorine gas on Calcium hydroxide. Uses - As disinfectant in water purification, in textile, pulp and paper industries.
In a chemical reaction the substance to which oxygen is added or hydrogen is removed is said to be oxidized and the substance oxidized is the reducing agent and the substance which gets reduced is the oxidizing agent.
A blister agent (vesicant), is a chemical compound that causes severe skin, eye and mucosal pain and irritation. Examples - Lewisite, nitrogen mustard, and sulfur mustard. Sulfonating agents are sulfur trioxide (SO3), oleum, sulfuric acid and chlorosulfuric acid.

Sodium (Na, Atomic number - 11) reacts vigorously with oxygen and moisture due to its high reactivity so keeping it in kerosene. It catches fire and starts burning when kept open in the air.
Kerosene (paraffin or paraffin oil) is a flammable hydrocarbon liquid commonly used as a fuel. It is typically colorless and has a not-unpleasant characteristic odor.
It is obtained from the fractional distillation of petroleum and is used as fuel component for jet engines, and as a solvent for greases and insecticides.

The halogens are the elements in group 17 of the periodic table. The halogen elements and their atomic number - fluorine (F-9), chlorine (Cl-17), bromine (Br-35), iodine (I-53), astatine (At-85) , and tennessine (Ts-117).
Properties of Halogens - The valency of halogens is 1, Reactivity of halogens decreases on moving down the Group, Melting and Boiling Points (increases down the group), Atomic Radius (increases down the group), Electronegativity (decreases down the group).

Bee sting contains formic acid (HCOOH) which can be neutralized by a base such as Baking soda (NaHCO₃). Baking Soda is industrially produced by Solvary process. It is non-flammable, odorless and basic in nature. Uses - To Reduce the acidity in the stomach, fire extinguishers, pesticide, ear drops, cosmetics and personal care products.

Examples - Isotope of carbon : Carbon-12, Carbon-13, and Carbon-14; Isotope of Hydrogen: Hydrogen - 1, Deuterium - 2, and Tritium -3; Isotope of Uranium : Uranium - 235, Uranium - 238.
Isomers : Chemical compounds that have identical chemical formulas but differ in properties and structure. Example - Ethyl alcohol and dimethyl ether with same formula (C₂H₆O) ; Pentane, iso-pentane and Neopentane.
Isobars : Elements having the same mass number but the different atomic number. Example - ₁₉K⁴⁰, ₁₈Ar⁴⁰ , ₂₀Ca⁴⁰ and ₁₁Na²⁴ , ₁₂Mg²⁴ .