Railway Science (Chemistry-Metals , Non-Metals and Alloys) (Part-II)

Total Questions: 50

41. To achieve higher temperatures, ____ is generally used in electric heating devices. [RRB Group D 12/10/2018 (Morning)]

Correct Answer: (b) alloy
Solution:

Alloys are used in electrical heating devices rather than pure metals because the resistivity of an alloy is more than the resistivity of a pure metal. Examples of commonly used alloys in electric heating devices include: Nichrome (nickel and chromium), Kanthal (iron, chromium, and aluminum).

42. What are the components of solder? [RRB Group D 12/10/2018 (Morning)]

Correct Answer: (a) Pb + Sn
Solution:

Solder has a low melting point and is used for welding electrical wires together. Other examples: Brass is an alloy of copper and zinc (Cu and Zn), and bronze, an alloy of copper and tin (Cu and Sn).

43. What are the constituents of bronze ? [RRB Group D 12/10/2018 (Evening)]

Correct Answer: (c) Cu+Sn
Solution:

An alloy is a homogenous mixture of two or more metals, or a metal and a nonmetal. The Cu + Zn alloy is called Brass. Pb + Sn alloy is called Solder. Al + Cu + Mn + Mg alloy is called Duralumin.

44. ________ are comparatively poor conductors of heat. [RRB Group D 12/10/2018 (Evening)]

Correct Answer: (d) Pb and Hg
Solution:

Metals are generally good conductors of heat due to the presence of free-moving electrons that can readily transfer thermal energy throughout the metal.

45. If you place _______ metal on your palm, that metal melts. [RRB Group D 15/10/2018 (Morning)]

Correct Answer: (b) Ga
Solution:

Gallium (Ga), atomic number 31, is a metal that has a melting point of approximately 29.76°C (85.57 F) which is just slightly above room temperature. Discovered year: 1875.

46. Nichrome is whose alloy? [RRB Group D 15/10/2018 (Morning)]

Correct Answer: (a) Ni, Cr, Mn and Fe
Solution:

Ni - Nickel, Cr - Chromium, Mn - Manganese, Fe - Iron. Other Commonly Used Alloys: Brass = Zinc + Copper; Bronze = Copper + Tin; Stainless steel = Iron + Chromium + Nickel; Magnalium = Aluminium + Magnesium.

47. Which of the following metals can form an amphoteric oxide ? [RRB Group D 15/10/2018 (Afternoon)]

Correct Answer: (a) Al
Solution:

Amphoteric oxides - The oxides that behave as both acidic and basic or that can react with acid as well as base. It dissolves in water to form alkaline solutions.
Examples - Aluminum oxide (Al₂O₃), Zinc oxide (ZnO). Physical Properties: Amphoteric oxides usually have extremely high melting and boiling points.
They have large covalent structures that take a lot of energy to dissolve. Chemical Properties: Reaction with an acid: Al₂O₃ + 6HCl → 2AlCl₃ + 3H₂O. Reaction with a base: Al₂O₃ + 2NaOH + 3H₂O → 2Na [Al(OH)₄ ].

48. ______has a very low melting point. [RRB Group D 15/10/2018 (Afternoon)]

Correct Answer: (c) Ga
Solution:

It belongs to the group 13 of the modern periodic table. It is found in trace amounts in zinc ores like sphalerite and bauxite. Melting point: 29.76 °C. It is a soft, silvery metal used primarily in electronic circuits, semiconductors and light-emitting diodes (LEDs). Metals and their melting point: Sodium (Na, 11) = 97.7 °C. Barium (Ba, 56) = 727 °C, Potassium (K,19) = 63.5 °C.

49. Which of the following alloys is made up of 4 components? [RRB Group D 15/10/2018 (Evening)]

Correct Answer: (b) nichrome
Solution:

It is an alloy of Ni, Cr, Mn, and Fe. Constantan: This alloy is typically composed of 55% copper and 45% nickel. Solder varies widely in composition, but commonly used solders are tin-lead alloys.

50. Compounds of which of the following metals are used in black and white photography ? [RRB Group D 16/10/2018 (Morning)]

Correct Answer: (a) Ag
Solution:

Its compounds, specifically silver bromide (AgBr) and silver chloride (AgCl), are photosensitive and react to light. This light sensitivity is essential for capturing the image on film.