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Practice Class 7 Science Chapter 5 Acids, Bases and Salts MCQ Questions with Answers based on the latest NCERT syllabus. Learn about formic acid, bases, neutralisation, litmus, and lactic acid with detailed explanations, exam tips, and original NCERT-based solutions for CBSE and State Board students.
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Chapter Information
Subject: Science
Class: 7
Chapter: Acids, Bases and Salts
Question Type: Multiple Choice Questions (MCQs)
Difficulty Level: Easy to Moderate
Based On: Latest NCERT Syllabus
Introduction
Acids, bases, and salts are common substances found in our daily life. They are present in foods, medicines, household products, and even in nature. This chapter helps students understand their properties, natural indicators, and the process of neutralisation. Learning these concepts develops scientific thinking and helps explain many everyday observations through simple chemical principles.
What You Will Learn
✔ Common acids found in daily life
✔ Properties of bases
✔ Neutralisation reaction
✔ Natural indicators such as litmus
✔ Acids present in food items
✔ Important NCERT concepts
Why This Topic Is Important?
The concepts of acids, bases, and salts are the foundation of chemistry. Questions from this chapter are frequently asked in school examinations, Olympiads, and scholarship tests. Understanding these topics also helps students relate chemistry to everyday life, such as ant bites, food substances, and household materials.
Exam Relevance
These questions are useful for:
✔ CBSE Exams
✔ State Board Exams
✔ School Tests
✔ Unit Tests
✔ Half-Yearly Exams
✔ Annual Exams
✔ Olympiad Preparation
✔ Scholarship Examinations
Q1. Which acid is released when an ant bites?
A) Hydrochloric acid
B) Formic acid
C) Sulphuric acid
D) Nitric acid
Answer: Formic acid
Concept Behind This Question
Some insects produce chemicals for protection and defence. Ants release formic acid when they bite or sting.
Step-by-Step Solution
The burning sensation caused by an ant bite is mainly due to formic acid. Applying a mild base, such as a baking soda solution (when appropriate), can help neutralise the acid.
Hydrochloric acid is present in the stomach, while sulphuric acid and nitric acid are strong mineral acids used mainly in industries.
Therefore, the correct answer is: Formic acid.
Exam Tip
Remember:
Ant Bite → Formic Acid
Q2. Bases are ______ in touch and ______ in taste.
A) Soapy, bitter
B) Bitter, sour
C) Salty, sweet
D) Sour, soapy
Answer: Soapy, bitter
Concept Behind This Question
Bases have characteristic physical properties that help identify them.
Step-by-Step Solution
Most bases:
- Feel soapy or slippery when touched.
- Have a bitter taste.
However, tasting chemicals is unsafe and should never be done in a laboratory.
Therefore, the correct answer is: Soapy, bitter.
Exam Tip
Remember:
Acids → Sour
Bases → Bitter and Soapy
Q3. The reaction between an acid and a base is called:
A) Photosynthesis
B) Neutralisation
C) Reduction
D) Oxidation
Answer: Neutralisation
Concept Behind This Question
When an acid reacts with a base, they neutralise each other’s properties.
Step-by-Step Solution
During a neutralisation reaction:
- An acid reacts with a base.
- Salt and water are formed.
- Heat is usually released.
This reaction reduces the acidic and basic properties of the reactants.
Therefore, the correct answer is: Neutralisation.
Useful Concept
Acid + Base → Salt + Water
Exam Tip
Neutralisation is commonly used in agriculture, medicine, and wastewater treatment.
Q4. Litmus, a natural dye, is extracted from:
A) Turmeric
B) Lichens
C) China rose
D) Beetroot
Answer: Lichens
Concept Behind This Question
Litmus is one of the most commonly used natural indicators.
Step-by-Step Solution
Litmus is obtained from lichens, which are organisms formed through a partnership between fungi and algae.
It is used to identify whether a substance is acidic or basic.
- Blue litmus turns red in acids.
- Red litmus turns blue in bases.
Therefore, the correct answer is: Lichens.
Exam Tip
Remember:
Litmus → Lichens
Q5. Which acid is present in curd?
A) Oxalic acid
B) Citric acid
C) Acetic acid
D) Lactic acid
Answer: Lactic acid
Concept Behind This Question
Different food items naturally contain different organic acids.
Step-by-Step Solution
Curd is produced when bacteria convert milk sugar into lactic acid.
Lactic acid gives curd its characteristic sour taste.
Other common acids include:
- Citric acid → Lemon and orange
- Acetic acid → Vinegar
- Oxalic acid → Spinach
Therefore, the correct answer is: Lactic acid.
Exam Tip
Remember:
Curd → Lactic Acid
Vinegar → Acetic Acid
Lemon → Citric Acid
Important Formulas & Concepts
1. Properties of Acids
- Sour in taste
- Turn blue litmus red
- React with bases during neutralisation
2. Properties of Bases
- Bitter in taste
- Feel soapy or slippery
- Turn red litmus blue
3. Neutralisation Reaction
Acid + Base → Salt + Water
This reaction usually releases heat.
4. Natural Indicators
- Litmus → Obtained from lichens
- Turmeric → Natural indicator
- China rose extract → Natural indicator
5. Common Naturally Occurring Acids
| Acid | Common Source |
| Formic acid | Ant sting |
| Lactic acid | Curd |
| Citric acid | Citrus fruits |
| Acetic acid | Vinegar |
| Oxalic acid | Spinach |
6. Uses of Neutralisation
- Treating acidic soil
- Relief from indigestion (using suitable antacids)
- Neutralising insect stings in appropriate situations
- Industrial waste treatment
Related Practice Questions
- What colour change occurs when blue litmus is dipped in an acid?
- Name two natural indicators.
- Which acid is found in vinegar?
- What products are formed during neutralisation?
- Why is neutralisation useful in agriculture?
Mini Quiz Challenge
True or False
- Formic acid is present in an ant bite.
- Bases are generally bitter in taste.
- Litmus is obtained from lichens.
- Curd contains lactic acid.
- Neutralisation produces salt and water.
Exam Tips
✔ Learn common acids and their natural sources.
✔ Remember the colour changes of litmus paper.
✔ Revise the properties of acids and bases.
✔ Practice the neutralisation reaction.
✔ Memorize important examples from daily life.
Quick Revision Notes
✔ Ant bite contains formic acid.
✔ Bases are bitter and feel soapy.
✔ Acid + Base = Salt + Water.
✔ Litmus is obtained from lichens.
✔ Curd contains lactic acid.
✔ Blue litmus turns red in acids.
Common Mistakes Students Make
❌ Confusing citric acid with lactic acid.
❌ Thinking litmus is obtained from turmeric.
❌ Mixing up the properties of acids and bases.
❌ Forgetting that neutralisation forms both salt and water.
❌ Assuming all natural indicators work in the same way.
Key Takeaways
- Formic acid is responsible for the irritation caused by an ant bite.
- Bases generally have a bitter taste and a soapy feel.
- Neutralisation occurs when an acid reacts with a base.
- Litmus is a natural indicator obtained from lichens.
- Lactic acid gives curd its characteristic sour taste.
FAQs
1. Which acid is released during an ant bite?
Formic acid is released during an ant bite.
2. What are the common properties of bases?
Bases generally taste bitter and feel soapy or slippery.
3. What is a neutralisation reaction?
A neutralisation reaction is a chemical reaction in which an acid reacts with a base to form salt and water.
4. From where is litmus obtained?
Litmus is extracted from lichens.
5. Which acid is present in curd?
Curd contains lactic acid, which gives it a sour taste.
Conclusion
This Class 7 Science MCQ Practice Set helps students understand the essential concepts of Acids, Bases and Salts, including natural acids, properties of bases, indicators, and neutralisation. Practising these NCERT-based questions strengthens conceptual understanding, improves problem-solving skills, and prepares students for school examinations and competitive tests.
NCERT Reference
Book: NCERT Science Class 7
Chapter: Chapter 5 – Acids, Bases and Salts
Based On: Latest NCERT Curriculum (CBSE)
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