Railway Science (Chemistry-Acid ,Bases and Salt) (Part-IV)

Total Questions: 23

21. Which of the following statements is wrong with regard to strong acids? [RRB ALP Tier - I (31/08/2018) Morning]

Correct Answer: (d) Acids are those chemical substances that have a salty taste.
Solution:

A chemical that gives off hydrogen ions in water and forms salts by combining with certain metals. Solutions having a value of pH ranging from 0 to 7 (Acidic), pH ranging from 7 to 14 (Basic) and pH equal to 7 (Neutral). pH value 0 denotes strong Acid and pH value 14 denotes strong Base. Acid turns blue litmus paper into Red.

22. Acids that contain Hydrogen and other non-metallic element (s), except Oxygen, are called: [RRB ALP Tier - I (31/08/2018) Morning]

Correct Answer: (b) Hydracids
Solution:

They are compounds formed by hydrogen and a nonmetal, a chalcogen (group 16) or halogen (group 17), in which the hydrogen has an oxidation number +1. In these compounds, hydrogen is written to the left of the nonmetal.
Example - HCl. Strong acid : an acid that is completely dissociated in an aqueous solution. Examples - HNO₃ , HCl, H₂SO₄ . Dilution : The process of lowering the concentration of a solute in a solution by simply adding more solvent to the solution, such as water.

23. Which of the following statements is INCORRECT? [RRB ALP Tier - I (31/08/2018) Afternoon]

I) Bleaching powder is a pale yellow powder
II) Dry NH₃ gas turns red litmus blue
III) The pH of rainwater is nearly 7
IV) The pH of acid rain is nearly 5.6

Correct Answer: (c) Only (II)
Solution:

Dry ammonia (NH₃) has no effect on the litmus paper but Ammonia solution turns red litmus paper into blue. pH paper is used to measure the acidity or alkalinity of a substance. Blue litmus paper turns red under acid conditions, and red litmus paper turns blue under alkaline (Basic) conditions.