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Important Questions Test: Acids Bases & Salts - Class 7 MCQ


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15 Questions MCQ Test - Important Questions Test: Acids Bases & Salts

Important Questions Test: Acids Bases & Salts for Class 7 2024 is part of Class 7 preparation. The Important Questions Test: Acids Bases & Salts questions and answers have been prepared according to the Class 7 exam syllabus.The Important Questions Test: Acids Bases & Salts MCQs are made for Class 7 2024 Exam. Find important definitions, questions, notes, meanings, examples, exercises, MCQs and online tests for Important Questions Test: Acids Bases & Salts below.
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Important Questions Test: Acids Bases & Salts - Question 1

State whether the following statement is True or False:

China rose indicator turns acidic solutions to dark pink (magenta) and basic solutions to green.

Detailed Solution for Important Questions Test: Acids Bases & Salts - Question 1
  • China rose indicator is like a magic potion that helps us know if a liquid is sour or sweet. When China rose meets something sour, like lemon juice, it turns the color to dark pink. But if it meets something sweet, like soda water, it changes to green.

  • So, when China rose indicator meets acidic solutions, it turns them dark pink (magenta). When it meets basic solutions, it changes them to green. That's why the statement is True!

Important Questions Test: Acids Bases & Salts - Question 2

What substance is commonly used to treat excessively acidic soil?

Detailed Solution for Important Questions Test: Acids Bases & Salts - Question 2
Excessively acidic soil is treated with bases like quick lime (calcium oxide) or slaked lime (calcium hydroxide). These substances neutralize the acidity of the soil, improving its suitability for plant growth.
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Important Questions Test: Acids Bases & Salts - Question 3

Why is it important to neutralize factory wastes before disposal into water bodies?

Detailed Solution for Important Questions Test: Acids Bases & Salts - Question 3
Factory wastes often contain acids, which can harm aquatic organisms by disrupting the water’s pH balance. Neutralizing these wastes before disposal helps protect the aquatic ecosystem by preventing the acid from causing harm.
Important Questions Test: Acids Bases & Salts - Question 4

On adding phenolphthalein indicator to a colourless solution, no change is observed. The nature of the solution may be

Detailed Solution for Important Questions Test: Acids Bases & Salts - Question 4

Since phenolphthalein turns pink in a basic solution and remains colourless in acidic and neutral solutions, if there's no change observed upon its addition, the solution must be either acidic or neutral.

Important Questions Test: Acids Bases & Salts - Question 5

Which of the following is not a base?

Detailed Solution for Important Questions Test: Acids Bases & Salts - Question 5

The correct answer is C: Hydrochloric acid.

Explanation:


  • Bases are substances that can accept hydrogen ions (protons) or more commonly produce hydroxide ions (OH⁻) in solution.

  • Magnesium hydroxide, calcium hydroxide, and sodium hydroxide are all bases because they produce hydroxide ions when dissolved in water.

  • Hydrochloric acid (HCl) is an acid, not a base. It donates hydrogen ions (H⁺) in solution, which is characteristic of acids.

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Important Questions Test: Acids Bases & Salts - Question 6
How can you identify a sugar solution, hydrochloric acid, and sodium hydroxide using turmeric indicator?
Detailed Solution for Important Questions Test: Acids Bases & Salts - Question 6
Using turmeric indicator, a sugar solution will not change color, hydrochloric acid will remain unchanged, and sodium hydroxide will turn the turmeric indicator red due to its basic nature.
Important Questions Test: Acids Bases & Salts - Question 7

Acid rain is formed when ______ dissolve in rain drops.

Detailed Solution for Important Questions Test: Acids Bases & Salts - Question 7

Acid rain is created when substances like carbon dioxide, sulphur dioxide, and nitrogen dioxide mix with raindrops in the air. These substances make the rain harmful and can damage buildings, plants, and animals.

Important Questions Test: Acids Bases & Salts - Question 8
What is the role of organic matter in treating basic soil?
Detailed Solution for Important Questions Test: Acids Bases & Salts - Question 8
Organic matter, such as compost, releases acids when decomposed. These acids help to neutralize the basic nature of the soil, making it more suitable for plant growth.
Important Questions Test: Acids Bases & Salts - Question 9
What is the role of an antacid such as milk of magnesia in treating indigestion?
Detailed Solution for Important Questions Test: Acids Bases & Salts - Question 9
Antacids like milk of magnesia contain basic substances that neutralize the excessive acid in the stomach, providing relief from the discomfort and pain associated with indigestion.
Important Questions Test: Acids Bases & Salts - Question 10

Complete the following analogy: Turmeric: Indicator:: Milk of magnesia:

Detailed Solution for Important Questions Test: Acids Bases & Salts - Question 10

Milk of magnesia is an antacid.
Antacids are medicines that counteract (neutralise) the acid in your stomach to relieve indigestion and heartburn

Important Questions Test: Acids Bases & Salts - Question 11

Which of the following is acidic in nature?

Detailed Solution for Important Questions Test: Acids Bases & Salts - Question 11

Apple juice is acidic in nature due to the presence of organic acids, such as malic acid, which lower its pH. Unlike soap solution, which is basic, and slaked lime, which is also basic, apple juice has a pH below 7, making it acidic. This acidity is what gives apple juice its characteristic tart taste.

Important Questions Test: Acids Bases & Salts - Question 12

What do we call substances that do not change the color of either red or blue litmus paper?

Detailed Solution for Important Questions Test: Acids Bases & Salts - Question 12

Neutral solutions are substances that do not change the color of either red or blue litmus paper. This means they are neither acidic nor basic.

Important Questions Test: Acids Bases & Salts - Question 13
How does an ant bite affect the skin, and what can neutralize this effect?
Detailed Solution for Important Questions Test: Acids Bases & Salts - Question 13
An ant bite injects formic acid, which is acidic. This effect can be neutralized by applying moist baking soda (sodium hydrogencarbonate) or calamine solution (zinc carbonate), both of which are basic and counteract the acidity.
Important Questions Test: Acids Bases & Salts - Question 14

Acid present in soured curd is __________ .

Detailed Solution for Important Questions Test: Acids Bases & Salts - Question 14
  • The curd is produced due to the presence of reaction between lactic acid bacteria and the milk protein casein.
  • When milk sugar or lactose undergoes fermentation, the product obtained is lactic acid.
Important Questions Test: Acids Bases & Salts - Question 15

What happens if you put a drop of soap solution on turmeric paper?

Detailed Solution for Important Questions Test: Acids Bases & Salts - Question 15
  • When you put a drop of soap solution on turmeric paper, the paper turns red.
  • This change in color happens because of a chemical reaction between the soap solution and the turmeric, showing that soap is a type of substance called a base.
  • So, when soap solution comes in contact with turmeric paper, it changes the color to red.
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