Railway Science (Chemistry-Chemical Properties)

Total Questions: 52

41. Which of the following statements is/are true? [RRB Group D 22/10/2018 (Evening)]

A.  A balanced chemical equation contains equal numbers of atoms of different elements in the reactants and products.
B.  If the surface of a reactive metal is damaged by contact with air, water or other substances in its surroundings, it is called corrosion and this effect is called rancid.

Correct Answer: (a) Only A is true
Solution:

Corrosion - The surface of iron metal is corroded when they are exposed to moist air for a long period of time. It can be prevented by Painting, Oiling, Greasing, Galvanising, and Chrome plating.
Rancidity refers to the spoilage of fats, oils, or other organic compounds due to oxidation, hydrolysis, or other chemical reactions that result in unpleasant odors.

42. Which of the following has the maximum force of attraction between its molecules ? [RRB Group D 23/10/2018 (Afternoon)]

Correct Answer: (d) solid
Solution:

Solid has the highest force of attraction followed by liquid and then the gas has the least attractive forces. Therefore the particles of solid are closely packed and the particles of gas are free to move.

43. Relative density is equals to: [RRB Group D 22/10/2018 (Afternoon)]

Correct Answer: (b) density of a substance / density of water.
Solution:

Relative density: This unitless quantity compares the density of a substance to a reference material, typically water. Water has a density of 1 gram per cubic centimeter (g/cm³) at 4°C, making it a convenient and consistent reference point.

44. The element with atomic number _______ will form basic oxide. [RRB Group D 22/10/2018 (Evening)]

Correct Answer: (c) 11
Solution:

Basic oxides are oxides of metals that react with water to form basic solutions (alkaline solutions). The element with atomic number 11 is sodium (Na), which belongs to Group 1 of the periodic table. Sodium (Na) forms basic oxide such as sodium oxide (Na₂O) when it reacts with oxygen.

45. Elements in the same group are similar____. [RRB Group D 24/10/2018 (Morning)]

Correct Answer: (a) chemical properties
Solution:

Elements in the same group show similar chemical properties because they have the same number of electrons in the outermost shell. The elements in a row show a gradual change in chemical properties because their valence shell electron configuration changes gradually along the row.

46. Colors are added to alcohol to make it blue so that it can be easily recognized. This alcohol is called ______ alcohol. [RRB Group D 24/10/2018 (Afternoon)]

Correct Answer: (c) Poisonous (deformed)
Solution:

Denatured alcohol is ethanol which is made unfit for drinking by adding poisonous substances like methanol or any other substance that will impart bad taste, foul smell, or color.
A blue dye is also added to it so that it is easily recognized. The 4 types of alcohol are - Isopropyl alcohol, Ethyl, Methyl, and Distilled ethanol.

47. Which of the following sodium compounds is used to normalize hard water ? [RRB Group D 17/12/2018 (Afternoon)]

Correct Answer: (d) Sodium carbonate
Solution:

sodium carbonate (Na₂CO₃), also known as washing soda, can remove both temporary and permanent hardness of water by precipitating calcium and magnesium ions as insoluble carbonates. Water containing more than 50-60 mg/L of calcium/Magnesium carbonate is termed as hard water.

48. Which of the following are not the properties of an ionic compound? [RRB ALP Tier - I (10/08/2018) Evening]

Correct Answer: (a) Low melting and boiling points
Solution:

Ionic compounds are pure substances consisting of chemically bonded ions. Properties - Solid Structure and hard surface, High Melting and boiling points (due to the strong forces of attraction), Solubility in water. Examples - Sodium bromide (NaBr), Potassium bromide (KBr) and Sodium chloride (NaCl).

49. A/an ______ flame is produced when the oxygen supply is sufficient. [RRB ALP Tier - I (14/08/2018) Afternoon]

Correct Answer: (d) blue
Solution:

A blue gas flame indicates complete combustion. Red, orange and green gas flames could be the sign of incomplete combustion. With hydrocarbon flames, the amount of oxygen supplied with the gas determines the rate of combustion. The primary components of liquefied petroleum gas (LPG) - Propane (C₃H₈), butane (C₄H₁₀), propylene (C₃H₆), butylene (C₄H₈), and isobutane (C₄H₁₀).

50. Which of the following glows with special colour depending on the nature of gas in the fluorescent tube? [RRB ALP Tier - I (17/08/2018) Morning]

Correct Answer: (d) Plasma
Solution:

Plasma (4th state of matter): identified by - Sir William Crookes (1879); first described by - Irving Langmuir (1928); It has no fixed shape or volume, and is less dense than solids or liquids. Bose-Einstein condensates (BEC) are super cold atoms. It was first predicted by Satyendra Nath Bose and Albert Einstein in 1924.