Railway Science (Chemistry-Carbon And its Compound)

Total Questions: 71

51. One reason for the formation of a strong bond by carbon is its _______ size. [RRB Group D 22/09/2018 (Afternoon)]

Correct Answer: (d) small
Solution:

Small size of the carbon atom allows its nucleus to strongly attract the shared electrons in a covalent bond. Carbon (C) - Atomic Number (6), atomic mass (12.011 u), group (14), period (2). Lavoisier proposed carbon in 1789. Radioactive isotope: carbon-14. Allotropes - Graphite, Diamond, Buckminsterfullerene, Graphene etc.

52. Unsaturated carbon compounds burn in oxygen giving ____________ flame with heavy black smoke. [RRB Group D 24/09/2018 (Evening)]

Correct Answer: (b) yellow
Solution:

It is due to the incomplete combustion of the hydrocarbon in the air. A large amount of carbon does not completely oxidize in the air and gives a sooty flame.

53. _______ is not an allotropic form of carbon. [RRB Group D 25/09/2018 (Afternoon)]

Correct Answer: (b) Coal
Solution:

Coal contains impurities like silica, sulfur, and other carbon compounds in addition to carbon. Allotropy: Property where some elements exist in multiple forms. Carbon exhibits allotropy with diamond, graphite, graphene, fullerene, etc.

54. The percentage of lead in lead pencil is _______. [RRB Group D 27/09/2018 (Evening)]

Correct Answer: (a) 0
Solution:

The “lead” in a pencil isn’t actually made from lead. It is made from an allotrope of carbon called graphite. The graphite is mixed with clay and formed into long thin pencil lead.

55. In a diamond, each carbon atom is bonded to: [RRB Group D 01/10/2018 (Evening)]

Correct Answer: (c) four other carbon atoms
Solution:

(tetrahedrally). Diamond: A crystalline allotrope of carbon and each carbon atom is tetrahedrally bonded to four other carbon atoms giving rise to a 3-D network. It is the hardest and has the highest thermal conductivity of any natural material.

56. One reason for carbon to form strong bonds is its _______. [RRB Group D 08/10/2018 (Morning)]

Correct Answer: (c) small size
Solution:

Carbon's small size allows its positively charged nucleus to have a strong hold on the shared electrons in its covalent bonds. This strong hold makes the bonds difficult to break, contributing to the stability of carbon-based molecules.

57. In__________ each carbon atom is bonded to three other carbon atoms in the same plane giving a hexagonal array. [RRB Group D 09/10/2018 (Morning)]

Correct Answer: (c) graphite
Solution:

Graphite (plumbago or black lead) is soft, greasy, dark greyish coloured crystalline solid and Good conductor of heat and electricity. It is chemically more reactive than diamond. Its layer structure is headed by weak van der Waals forces. Diamond is an allotrope of carbon where each carbon atom is bonded to four other carbon atoms in a three-dimensional tetrahedral arrangement. Benzene (C₆H₆) is a colorless and highly flammable liquid discovered by Michael Faraday. Propene (C₃H₆) a colorless, flammable, gaseous hydrocarbon.

58. Which of the below allotropes of carbon is in the form of geodesic globe? [RRB Group D 11/10/2018 (Morning)]

Correct Answer: (a) Fullerene
Solution:

Fullerene : C-60, atoms arranged in the shape of Football. Carbon nanotubes - Tubes made of carbon with diameters typically measured in nanometers.

59. Select the object that does not belong to this group. [RRB Group D 12/10/2018 (Morning)]

Correct Answer: (b) carbon
Solution:

It is non-metal. Graphite and diamond are the best forms of carbon. Gold, platinum, and copper are all metallic elements, known for their luster, malleability, and conductivity. They belong to the same category of metals.

60. In CO₂ , C and O₂ are present in the ratio __________ by mass. [RRB Group D 12/10/2018 (Evening)]

Correct Answer: (d) 3 : 8
Solution:

The total mass of carbon in one molecule of CO₂ is 12 u, and the total mass of oxygen is 32 u. So, the ratio of carbon to oxygen by mass is: Carbon : Oxygen = 12 u : 32 u. Simplifying the ratio, 12 : 32 = 3 : 8.