CHEMISTRY (Part-V) (Railway)

Alkenes are defined as either branched or unbranched hydrocarbons that possess at least one carbon-carbon double bond (CC).

• They have a general formula of CH₂n.

• Because alkenes contain less than the maximum possible number of hydrogen atoms per carbon atom, they are said to be unsaturated.

NaCl (Sodium chloride) and AgNO₃ (silver nitrate) react to give AgCl (Silver chloride) and NaNO₃ (sodium nitrate).

• This is an example of a double displacement reaction.

• Here both silver nitrate and sodium chloride are colorless solutions, they form a white precipitate and a colorless solution.

• Here silver displaces sodium from the solution forming the white precipitate.

Chlor-alkali process is the one in which an electricity is passed through an aqueous solution of Sodium chloride or brine (NaCl) which decomposes to form hydroxide (NaOH), Sodium

• The products formed in this process are Hydrogen, chlorine (Cl₂) and Sodium hydroxide (NaOH).

• 2NaCl (aq) + 2H₂O(l) → 2NaOH (aq) + Cl₂(g) + H₂(g)

Washing soda (Na₂CO₃), also known as sodium carbonate, has detergent properties or cleansing properties because it can remove dirt and grease from dirty clothes, etc.

• It attacks dirt and grease to form water-soluble products, which are then washed away on rinsing with water.

• It is used in glass, soap, and paper industries.

Among chemical properties, Mendeleev concentrated on the compounds formed by the elements with Hydrogen and Oxygen.

• This was because these two elements are highly reactive and hence formed compounds with almost all the elements.

HNO₃ (aq) + KOH (aq) → KNO₃ (aq) + H₂O (l) is an example of double displacement reaction and neutralisation reaction.

• Neutralisation reactions occur between acids and bases forming salt and water.

• In the given reaction, Nitric acid (HNO₃) reacts with potassium hydroxide (KOH) to form Potassium nitrate (KNO₃) and Water (H₂O).

• Therefore, it is a neutralisation reaction.

In the periodic table there are 118 elements.

• Of these 118 elements, 94 occur naturally on Earth. Six of these occur in extreme trace quantities: technetium, promethium astatine, francium, neptunium, and plutonium.

A neutralisation reaction is a chemical reaction between an acid and a base to give salt and water.

• HCl is strong acid and Ca(OH)₂ is the strong base in this case.

• HCl and Ca(OH)₂ react to give CaCl₂ as salt and water as products.

Acids and bases react with each other to form salt and water. The salt formed is the derivative of the reacting acids and bases.

• So, potassium hydroxide (a base) reacts with nitric acid (an acid) to produce potassium nitrate (salt) and water.

• The balanced equation of this reaction is 2KOH (aq) + 2HNO (aq) → 2KNO (aq) + 2H₂O (1).

Both the statements are correct. Statement II is the correct explanation of statement I.

• Newlands' Law of Octaves stated that when elements are arranged according to their Increasing atomic weights then every eight elements have similar properties as the first element.

• It was applicable only upto calcium, as after calcium, every eighth element does not possess properties similar to that of the first.