CHEMISTRY (Part-IV) (Railway)

Those elements which have the same atomic number but a different mass number are called Isotopes. There are three isotopes of hydrogen namely, protium, ₁H¹, deuterium, ₁H² or D and lastly tritium, ₁H³ or T.

• Tritium comprises 2 neutrons and 1 proton in its nucleus.
• The atomic number of tritium is 1 and atomic mass of 3.

Cysteine is a sulfur-containing amino acid. It is a non-essential amino acid important for making protein and for other metabolic functions. It is found in beta-keratin.

Osmium is the densest naturally occurring element, with an experimentally measured (using x-ray crystallography) density of 22.65 g/cm³.

• The very small atomic radius of osmium results in a small metal-metal separation.
• This small atomic separation along with osmium's relatively high atomic number gives rise to osmium's high density.

Manmade fibers are made from various chemicals, or are regenerated from plant fibers.

• Rayon is a man-made fiber prepared from cellulose by chemical treatment.
• The cellulose required for making rayon is obtained from wood pulp. Rayon is obtained by the chemical treatment of wood pulp.

A paste of sodium hydrogen carbonate (sodium bicarbonate) is used to relieve the pain of an ant bite.

• Baking soda contains alkaline compounds that will help to neutralize skin's pH balance.
• This reduce inflammation round the affected area.
• This helps to alleviate soreness as well as itchiness.

The method of grouping the elements into different classes is known as the peri-odic classification of elements.

• Classification helps us to understand the properties of the elements and their compounds.
• Based on their position in the periodic table one can predict the properties of the elements and their compounds.
• It is easier to study, compare, and differentiate the properties of the elements and compounds from different groups.

When chlorine is passed over dry slaked lime, it results in the formation of bleaching powder or Calcium oxychloride.

• Chlorine gas is produced from the chlor-alkali process.
• Ca(OH)2 + Cl₂ → CaOCl₂ + H₂O

Raw potato contains approximately 17% starch.

• Iodine solution is used to test the presence of starch in food materials.
• When iodine solution is added to the raw potato sample, it turns blue-black. Iodine reacts with the starch present in the raw potato which results in the formation of a blue-black coloured complex.

S-8

P-4

Ne - 1

Ar - 1

Cyclohexane is a simple ring structure having 6 carbon atoms with the chemical formula of CH₁₂.

• It has six carbon-carbon single bonds and twelve carbon-hydrogen single bonds.
• Therefore, there are 18 covalent bonds in one molecule of cyclohexane.