Railway Science (Chemistry-Organic Chemistry) (Part-II)

Total Questions: 50

41. Which of the following represents the correct decreasing order of hydrogen atoms? [RRB Group D 05/10/2018 (Morning)]

Correct Answer: (c) alkanes, alkenes, alkynes
Solution:

Alkanes (CₙH₂ₙ₊₂) - Saturated hydrocarbons, which means that they have all of their carbon atoms bonded to as many hydrogen atoms as possible. Examples- Ethane (C₂H₆).
Alkenes (CₙH₂ₙ) - Unsaturated hydrocarbons, which means that they have one or more double bonds between carbon atoms.
Examples - Ethene(C₂H₄). Alkynes (CₙH₂ₙ₋₂) - Also unsaturated hydrocarbons, but they have one or more triple bonds between carbon atoms. Examples - Ethyne (C₂H₂).

42. In which of the following functional groups is COOH present? [RRB Group D 05/10/2018 (Morning)]

Correct Answer: (b) carboxylic acid
Solution:

Functional groups in organic chemistry - Alcohols (R-OH), Aldehydes (R-CHO), Ketones (R-CO-R), Amines (R-NH₂), Ethers (R-O-R), Halides (R-X).

43. _____ is the simplest alcohol. [RRB Group D 09/10/2018 (Afternoon)]

Correct Answer: (d) Methanol
Solution:

Methanol: (CH₃OH), also known as wood alcohol. Butanol: This is a four-carbon alcohol with the formula C₄H₁₀O. Ethanol: This is a two-carbon alcohol with the formula C₂H₅OH.

44. Which of the following is an odd compound? [RRB Group D 09/10/2018 (Afternoon)]

Correct Answer: (b) Ethene
Solution:

Methane (CH₄) is the first compound in the homologous series of alkanes followed by Ethane (C₂H₆), Propane (C₃H₈), Butane (C₄H₁₀) etc. All the compounds in this homologous series can be represented by the same general formula CₙH₂ₙ₊₂.

45. ______ reacts in the presence of an acid or base to give back alcohol and carboxylic acid. [RRB Group D 10/10/2018 (Morning)]

Correct Answer: (c) Ester
Solution:

Esters are organic compounds that are formed from the reaction between an alcohol and a carboxylic acid. Esterification: Carboxylic acids are esterified with alcohols or phenols in the presence of a mineral acid such as concentrated Sulfuric Acid (H₂SO₄) or Hydrogen chloride (HCl) gas as a catalyst.

46. In which of the following there is a triple bond ? [RRB Group D 11/10/2018 (Afternoon)]

Correct Answer: (d) Propyne
Solution:

This molecule has a triple bond between two carbon atoms. Triple bond - It is made of two pi bonds (π-bonds) and one sigma bond (σ bonds). Other Examples - Nitrogen gas, Cyanide ion, Acetylene, and Carbon monoxide.

47. Which of the following compounds has a double bond ? [RRB Group D 11/10/2018 (Evening)]

Correct Answer: (c) Propene
Solution:

Propene (also known as propylene) is an alkene with the chemical formula C₃H₆ . It is an alkene that is propane with a double bond at position 1. It has a role as a refrigerant and a xenobiotic.
Propane is a simple hydrocarbon with the chemical formula C₃H₈ . Propanol is an alcohol with the chemical formula C₃H₇OH. Propyne (C₃H₄) - It appears as a colorless liquefied gas with a sweet odor.

48. How many Isomers does C₆H₁₄ have ? [RRB Group D 22/10/2018 (Afternoon)]

Correct Answer: (d) 5
Solution:

Isomerism is a phenomenon where two or more compounds have the same chemical formula but possess different structural formulas and different properties. Hexane ( C₆H₁₄) is an unbranched hydrocarbon.

49. To prevent misuse of ethanol produced for industrial use, it is declared unfit for drinking by adulteration with toxic substances such as _________. [RRB Group D 30/10/2018 (Morning)]

Correct Answer: (a) methanol
Solution:

methanol (CH₃OH). Ethyl alcohol (C₂H₅OH) is a useful solvent in industries for making things like paints, dyes, and cosmetics. It's also found in drinks like beer and whiskey. To prevent people from drinking industrial alcohol, a little bit of copper sulfate, methanol, and pyridine are added to make it unsafe to drink. This process is called denaturation, and the alcohol produced is called denatured alcohol.

50. The boiling point of ethanol is: [RRB Group D 31/10/2018 (Afternoon)]

Correct Answer: (a) 78° C
Solution:

Ethanol (C₂H₆O) is commonly called alcohol and is the active ingredient of all alcoholic drinks. Uses of Ethanol: Manufacture of paints, varnishes, lacquers, medicines, perfumes, dyes, soaps and synthetic rubber. Methanol (CH₃OH) - Boiling point (65°C). Uses: Fuel, solvents, and antifreeze.