Acids, Bases, and Salts Questions and Answers Class 7 Science Part 1 Chapter 5 Assam State Education Board Syllabus 2025-2026 Covered
Acids, bases, and salts are essential chemical substances that play a significant role in daily life. This chapter explains their properties, reactions, and uses. Below are the important questions and answers from NCERT & SCERT Assam Class 7 Science Chapter 5 - Acids, Bases, and Salts, based on the Assam State Education Board syllabus for 2025-2026.
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Join Our WhatsAppIntroduction to Acids, Bases, and Salts
Acids and bases are two major categories of chemical compounds that react with each other to form salts and water. Acids are sour in taste, whereas bases are bitter and slippery.
Class 7 Science Question Answer – Part I All Chapters
Below are the chapters of Class 7 Science. Click on the chapter name to access the respective question-and-answer content:
- Nutrition in Plants
- Nutrition in Animals
- Heat
- Motion and Time
- Acids, Bases and Salts
- Physical and Chemical Changes
- Weather, Climate and Adaptations of Animals to Climate
- Winds, Storms and Cyclones
- Soil
1. State differences between acids and bases.
Ans:-
2. Ammonia is found in many household products, such as window cleaners. It turns red litmus blue. What is its nature?
Ans:- The answer is it is basic in nature.
3. Name the source from which litmus solution is obtained. What is the use of this solution?
Ans:- Litmus solution is extracted from lichens. Litmus solution is used as an indicator to find acidic and basic nature of a solution.
4. Is the distilled water acidic/basic/neutral? How would you verify it ?
Ans:- Distilled water is neutral in nature, and this can be tested by using red and blue litmus paper. In either of the cases, colour remains unchanged.
5. Describe the process of neutralisation with the help of an example.
Ans:- Neutralisation is a reaction between an acid and a base.
Here, both acids and bases get neutralised.
For example, when sodium hydroxide (NaOH) is added to hydrochloric acid (HCl), sodium chloride (NaCl) and water (H2O) are obtained.
NaOH + HCl → NaCl + H2O + Heat
6. Mark ‘T’ if the statement is true and ‘F’ if it is false.
(i) Nitric acid turns red litmus blue. (T/F)
(ii) Sodium hydroxide turns blue litmus red. (T/F)
(iii) Sodium hydroxide and hydrochloric acid neutralise each other and form salt and water. (T/F)
(iv) Indicator is a substance which shows different colours in acidic and basic solutions. (T/F)
(v) Tooth decay is caused by the presence of a base. (T/F)
Ans:-
i) False
ii) False
iii) True
iv) True
v) False
7. Dorji has a few bottles of soft drinks in his restaurant. But, unfortunately, these are not labelled. He has to serve the drinks on the demand of customers. One customer wants an acidic drink, another wants a basic drink, and the third one wants a neutral drink. How will Dorji decide which drink is to be served to whom?
Ans:- Dorji can taste a few drops out of soft drinks bottles; the acidic solution is sour in taste, the basic solution is bitter in taste, and the neutral solution has no taste. Along with tasting, Dorji can use litmus paper to test the nature of the soft drinks. He should use blue litmus paper to test the acidic solution. Dorji has to put a drop of solution on blue litmus. If it turns red, then the solution will be acidic in nature.
Similarly, he can use red litmus paper to test the basic solution. He has to put a drop of solution on red litmus. If it turns blue, then the solution will be basic in nature.
8. Explain why-
(a) An antacid tablet is taken when you suffer from acidity.
(b) Calamine solution is applied on the skin when an ant bites.
(c) Factory waste is neutralised before disposing it into the water bodies.
Ans:-
The antacid tablet contains base-like milk of magnesia, which neutralises the acid produced in the stomach. Hence, it is used while suffering from acidity.
When ant bites, it injects formic acid inside the skin. Calamine consists of Zinc carbonate which is basic in nature. Hence, calamine neutralises the effect of formic acid to bring relief for the affected person.
Factory wastes are acidic in nature which may cause harm to aquatic life. Hence, they are neutralised by using a base before disposing it into the water bodies.
9. Three liquids are given to you. One is hydrochloric acid, another is sodium hydroxide, and the third is a sugar solution. How will you identify them? You have only turmeric indicator.
Ans:-
The following steps are taken to test the given liquids:-
Put a drop of provided liquid on the turmeric indicator. The solution that changes the colour of the indicator to red is sodium hydroxide, which is basic in nature.
Now, to make two mixtures, add a drop of sodium hydroxide on the other two liquids individually.
The drop of each combination added to the turmeric indicator one after another.
The mixture that changes the indicator to red colour includes a neutral solution of sugar.
While the mixture contains hydrochloric acid that has been neutralised by the addition of sodium hydroxide, which does not show any colour change in the indicator.
10. Blue litmus paper is dipped in a solution. It remains blue. What is the nature of the solution? Explain.
Ans:- The above solution may be neutral or basic in nature as both will not change the colour of the blue litmus paper.
11. Consider the following statements:
(a) Both acids and bases change colour of all indicators.
(b) If an indicator gives a colour change with an acid, it does not give a change with a base.
(c) If an indicator changes colour with a base, it does not change colour with an acid.
(d) Change of colour in an acid and a base depends on the type of the indicator.
Which of these statements are correct ?
(i) All four
(ii) a and d
(iii) b, c and d
(iv) only d
Ans:-
(iv) Only d is correct
Class 7 Science Chapter 5 - Important Questions & Answers
Q1: What are acids? Give examples.
Answer: Acids are substances that have a sour taste and turn blue litmus paper red. They release hydrogen ions (H⁺) in aqueous solutions. Examples:
Sulfuric Acid (H₂SO₄)
Citric Acid (found in lemons)
Q2: What are bases? Give examples.
Answer: Bases are substances that have a bitter taste and turn red litmus paper blue. They release hydroxide ions (OH⁻) in aqueous solutions. Examples:
Calcium Hydroxide (Ca(OH)₂)
Ammonium Hydroxide (NH₄OH)
Q3: What are salts? How are they formed?
Answer: Salts are compounds formed when acids react with bases in a neutralization reaction. They consist of a metal ion and a non-metal ion. Example: (Sodium Chloride is formed when Hydrochloric Acid reacts with Sodium Hydroxide.)
Q4: What is neutralization? Give an example.
Answer: Neutralization is a chemical reaction where an acid reacts with a base to form salt and water. Example: (Sulfuric Acid reacts with Calcium Hydroxide to form Calcium Sulfate and Water.)
Q5: What are indicators? Name different types of indicators.
Answer: Indicators are substances that change color in the presence of an acid or a base. Types of indicators:
Synthetic Indicators: Phenolphthalein, Methyl Orange
Q6: Why do acids and bases conduct electricity?
Answer: Acids and bases conduct electricity because they release ions in solution, which help in carrying electric current.
Q7: What is the pH scale?
Answer: The pH scale measures the strength of acids and bases, ranging from 0 to 14.
pH = 7: Neutral solution
pH > 7: Basic solution
FAQs on Acids, Bases, and Salts
Q1: Why should we avoid tasting acids and bases?
Answer: Many acids and bases are corrosive and can cause harm if ingested.
Q2: What happens when an acid reacts with a metal?
Answer: Acids react with metals to produce salt and hydrogen gas.
Q3: What are strong and weak acids?
Answer:
Weak Acids: Partially ionize in water (e.g., Acetic Acid, Citric Acid).
Q4: How does baking soda help relieve acidity in the stomach?
Answer: Baking soda (NaHCO₃) neutralizes excess stomach acid, providing relief from acidity.
Q5: What are the uses of salts in daily life?
Answer:
Calcium Carbonate (CaCO₃): Used in cement
Sodium Bicarbonate (NaHCO₃): Used in baking powder
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