Railway Science (Chemistry-Acid ,Bases and Salt)

Total Questions: 50

11. Consider the below statements and identify the correct answer. [RRC Group D 26/08/2022 (Morning)]

Statement-1: An Olfactory indicator is a material whose smell varies depending on whether it is mixed with an acidic or basic solution.
Statement-II: Onion, clove oil and vanilla extract are examples of some olfactory indicators

Correct Answer: (b) Both the statements are true.
Solution:

A substance whose smell varies when it is mixed with an acidic or basic solution. Such substances can be used in the laboratory to test whether a solution is a base or an acid, and this process is called olfactory titration. Examples - Vanilla extract, All onion, and clove oil.

12. Which of the following is not an acid - base indicator? [RRC Group D 26/08/2022 (Afternoon)]

Correct Answer: (b) starch paper
Solution:

Acid-Base Indicators - Substances whose solutions change color due to changes in pH. They are usually weak acids or bases, but their conjugate base or acid forms have different colors due to differences in their absorption spectra. Examples - Methyl violet (Yellow on acid, Blue on base), Thymol blue - (Red on acid, Yellow on base), Methyl orange - (Red on acid, Yellow on base), Bromocresol green - (Yellow on acid, Blue on base).

13. Consider the statements given below, and choose the correct answer. [RRC Group D 26/08/2022 (Evening)]

Statement-I: Salts of strong acid and strong base are neutral, and their pH value is 7.
Statement-II : Salts of strong acid and weak base are acidic, and have pH value less than 7.

Correct Answer: (d) Both the statements are true.
Solution:

Example of strong Base and strong Acid reaction - NaOH (Sodium Hydroxide) + HCl (Hydrochloric Acid) → NaCl (Sodium Chloride) + H₂O (water) . Example of weak Base and strong Acid reaction - NH₄OH (Ammonium Hydroxide) + HCl (Hydrochloric Acid) → NH₄Cl (Ammonium Chloride) + H₂O . Example of strong Base and weak Acid - NaOH + CH₃COOH (Acetic Acid) → CH₃COONa (Sodium Acetate) + H₂O . Example of weak Base and weak Acid - NH₄OH + CH₃COOH → CH₃COONH₄ (Ammonium ethanoate) + H₂O.

14. A litmus paper was used to check the pH of a solution. The solution turns blue litmus red, its pH is likely to be: [RRC Group D 30/08/2022 (Morning)]

Correct Answer: (c) 5
Solution:

Litmus is mainly used to assess whether a solution is acidic or basic. Litmus paper is a type of pH paper made by treating the paper with natural dyes from lichens. Red paper turns blue when the pH is alkaline, while blue paper turns red when the pH is acidic. So the given solution is acidic. And the acidic solution has a pH value less than 7. So, the pH is likely to be 5.

15. Conversion of ethanol to ethanoic acid is catalyzed by: [RRC Group D 30/08/2022 (Afternoon)]

Correct Answer: (b) Alkaline KMnO₄ and Acidified K₂Cr₂O₇
Solution:

Conversion of ethanol to ethanoic acid is an oxidation reaction. The addition of an oxygen atom to ethanol produces ethanoic acid. The oxidizing agent used can be alkaline solution of potassium permanganate (KMnO₄) and heat, acidified potassium dichromate(K₂Cr₂O₇), Jones reagent (CrO₃/H₂SO₄ ), etc., adding any one of them can oxidize ethanol to ethanoic acid.

16. Washing soda is ______ in nature. [RRC Group D 30/08/2022 (Afternoon)]

Correct Answer: (c) basic
Solution:

(Sodium carbonate decahydrate - Na₂CO₃.10H₂O) is an alkaline compound with a pH value of 11. The preparation of washing soda involves Solvay process. Some other Compounds - Baking Soda ( Sodium bicarbonate - NaHCO₃ ), Caustic Soda (Sodium hydroxide - NaOH), Salt (Sodium Chloride - NaCl).

17. When an acid is allowed to react with a base to form salt and water, this chemical reaction is named as: [RRC Group D 30/08/2022 (Afternoon)]

Correct Answer: (d) neutralization reaction
Solution:

A chemical reaction in which an acid and base quantitatively react together to form a salt and water as products. The products of this reaction are salt and water. In this reaction, there is a combination of H⁺  ions and OH⁻ ions which form water. It can be represented as acid + base (alkali) → salt + water. Example - Formation of Sodium Chloride (Common Salt) - HCl + NaOH → NaCl + H₂O.

18. Consider the below statements and identify the correct answer. [RRC Group D 30/08/2022 (Evening)]

Statement-I: The p in pH stands for 'potenz' in German, meaning power. Statement-II: On the pH scale we can measure pH generally from 0 to 16.

Correct Answer: (a) Statement-I is true, and Statement-II is false.
Solution:

pH stands for 'potential of Hydrogen' which measures the acidity or alkalinity of aqueous solution developed in 1909 by Sorenson. The pH of a solution varies from 0 to 14. Solutions having a value of pH ranging from 0 to 7 are termed as acidic and the value of pH ranging from 7 to 14 are known as basic solutions. pH equal to 7 are known as neutral solutions. pH of some solutions Conic HCl (0), Saliva before meal (7.4), Toothpaste (8.0), Gastric Juice (1.4), Blood (7.4), Lemon Juice (2.5), Vinegar (4.0) , Apples (3), Bananas (4), Butter (6), Water (7), Borax - (9), Lime water (12).

19. Consider the below statements and identify the correct answer. [RRC Group D 30/08/2022 (Morning)]

Statement-I: Sodium hydroxide is prepared by chlor-alkali process. Statement-II: Three products chlorine gas, hydrogen gas and sodium hydroxide are produced in this process.

Correct Answer: (b) Both the statements are true.
Solution:

Electricity is passed through the aqueous solution of Sodium Chloride which decomposes to form Sodium hydroxide. When the concentrated Sodium chloride undergoes electrolysis, then three products are formed - chlorine gas, hydrogen gas and sodium hydroxide. Sodium hydroxide (lye or caustic soda) is an inorganic compound with the formula NaOH. It is a strong base.

20. Consider the statements given below, and choose the correct answer. [RRC Group D 01/09/2022 (Afternoon)]

Statement-1 : Litmus solution is a purple dye, which is extracted from lichen, a plant belonging to the class Thallophyta.
Statement-II : There are many natural materials like red cabbage leaves, turmeric, colored petals of some flowers, which indicate the presence of an acid or a base in a solution.

Correct Answer: (d) Both the statements are true.
Solution:

Litmus is a natural dye (purple colour), extracted from lichen (a plant belonging to the class Thallophyta). When added to an acidic solution, it turns red and when added to a basic solution, it turns blue. There are many other natural materials like red cabbage leaves, turmeric, coloured petals of some flowers such as Hydrangea, Petunia and Geranium, which indicate the presence of acid or base in a solution. These are called Natural acid-base indicators.