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

Total Questions: 50

11. When the litmus solution is neither acidic nor basic, its colour is: [RRB Group D 05/10/2018 (Evening)]

Correct Answer: (c) Purple
Solution:

Litmus solution is a type of dye which acts as an indicator for acidic and basic solutions. It is commonly available in two forms: blue litmus paper and red litmus paper. Blue litmus paper turns red in acidic solutions and Red litmus paper turns blue in basic or alkaline solutions.

12. ________ flower leaves do not indicate the presence of acid or base in a solution. [RRB Group D 08/10/2018 (Morning)]

Correct Answer: (d) Jasmine
Solution:

Petunia, Geranium, and Hydrangea: These flowers contain pigments that change color depending on the pH of a solution. In acidic solutions, they show pink or red hues, while in basic solutions, they turn blue or purple.

13. Which of the following statements is not correct regarding alkali? [RRB Group D 09/10/2018 (Afternoon)]

Correct Answer: (a) sour in taste
Solution:

Chemical properties of alkalis: Alkali is bitter in taste and feels soapy. It turns red litmus paper blue. The alkali has a pH value of more than 7. Alkali reacts with an acid to produce salt and water. When alkali is heated with ammonia salt, it produces ammonia gas.

14. ______ is most commonly formed by reaction of an acid and an alcohol . [RRB Group D 09/10/2018 (Evening)]

Correct Answer: (b) Ester
Solution:

Alcohols and phenols react with carboxylic acids, acid chlorides and acid anhydrides to form esters and this process is known as Esterification. In this process, the hydrogen atom (H) in the -COOH group of the acid is replaced by the alkyl group (-OR) from the alcohol. As a result, an ester and water are formed. Chemical equation: Acid + Alcohol → Ester + Water.

15. If the pH of a salt is 7, then this salt is _________ . [RRB Group D 11/10/2018 (Afternoon)]

Correct Answer: (b) Strong acid and strong base
Solution:

16. pH value of a highly acidic mixture is ________. [RRB Group D 11/10/2018 (Evening)]

Correct Answer: (d) 0
Solution:

The pH scale measures the acidity or basicity of a solution. It ranges from 0 to 14, where: pH values less than 7 indicate acidity, pH values equal to 7 indicate neutrality, and pH values greater than 7 indicate alkalinity. A highly acidic mixture would have a pH value close to 0, indicating a high concentration of hydrogen ions (H⁺) in the solution.

17. If the pH value of a salt is 12 then it is the salt of ________. [RRB Group D 11/10/2018 (Evening)]

Correct Answer: (c) weak acid and strong base
Solution:

A pH value of 12 indicates a basic solution. If pH is high (basic), it suggests that the salt is formed from a strong base and a weak acid. When a strong base reacts with a weak acid, the resulting salt solution tends to be basic.

18. If the pH value of a salt is zero then it is a salt of ________. [RRB Group D 12/10/2018 (Morning)]

Correct Answer: (a) Strong Acid and Weak Base
Solution:

A highly alkaline solution has a pH of 14.
A weak acid has a pH of not less than 7.
A neutral solution has a pH of 7.

19. If the pH value of a salt is 14, then it is a salt of _________ . [RRB Group D 12/10/2018 (Evening)]

Correct Answer: (c) weak acid and strong base
Solution:

The pH value of a solution indicates its acidity or alkalinity. A pH of 7 is neutral, below 7 is acidic and above 7 is alkaline. Examples - Sodium carbonate (Na₂CO₃), formed from the weak acid, {carbonic acid (H₂CO₃)} and the strong base, {sodium hydroxide (NaOH)} has a pH of around 11.

20. ____ reacts with acids and bases. [RRB Group D 15/10/2018 (Morning)]

Correct Answer: (b) AI₂O₃
Solution:

Aluminium oxide is an amphoteric oxide that reacts with both acid and base to form salts and water. It behaves as an acidic oxide because it reacts with a base to form salts and water. Example: AI₂O₃ + 2NaOH → 2NaAlO₂ + H₂O. It also behaves as a basic oxide because it reacts with an acid to form salts and Water. Example: Al₂O₃ +6HCl→ 2AlCl₃ + 3H₂O.