CHEMISTRY (Part-VI) (Railway)

• The reaction is expressed as 2Cl₂ + 2Ca(OH)₂ → Ca(OCI)₂ + CaCl₂ + 2H₂O

• Each carbon atom shares its four electrons with the hydrogen atoms and with the other carbon atoms to complete the octet configuration.

• There are 8 carbon-hydrogen covalent bonds and 2 carbon-carbon covalent bonds present in the propane molecule.

• It is composed primarily of impure aluminum hydroxides along with a lot of silica, iron and other impurities.

• It is usually formed as a weathering product of rocks rich in aluminium silicates.

● For example, in NaOH(aq) + HCl(aq) → NaCl(aq) + H₂O(l),
the reaction between hydrochloric acid with sodium hydroxide is a neutralisation reaction since it gives sodium chloride and water as products.

● The same type of reaction is seen in HNO₃(aq) + KOH (aq) → KNO₃ (aq) + H₂O(l) and in HCl (aq) + NaOH (aq) → NaCl (aq) + H₂O (l)

The structure of hydrogen is similar to that of alkali metals (ns¹), which contains one electron in their outermost shell. It also exists as a diatomic molecule similar to that of halogens.

● Magnesium (Mg) is one of the alkaline metals of Group 2 (IIa) of the periodic table.

● Both Sodium and Magnesium have third electron shell 3s as their outermost valence electrons, therefore they are in the same period.

Mendeleev concentrated on the compounds formed by the elements with Hydrogen and Oxygen as they are highly reactive and hence formed compounds with almost all the elements.

● Mendeleev concentrated on the oxides and hydrides of various elements to study their chemical properties.

The reaction of calcium with copper sulfate produces calcium sulfate and copper.
CuSO₄ + Ca → CaSO₄ + Cu

● This reaction is an example of single displacement reaction in which one element takes the position of the other.

Fuels burn when they react with oxygen in the air. If there is plenty of air, complete combustion happens.

● Both coal and petroleum consist of carbon. During complete combustion, carbon is oxidised to carbon dioxide.

● If there is insufficient air for complete combustion, incomplete happens. Carbon monoxide (CO) is formed instead of carbon dioxide.

When magnesium reacts with aluminium sulphate solution, there is a formation of magnesium sulphate and solid aluminium metal occurs.

● 3Mg + Al₂(SO₄)₃ → 3MgSO₄ + 2Al

● Magnesium displaces aluminium from aluminium sulphate as magnesium is more reactive than aluminium.