📘 Chapter 2 – Exploring Substances: Acidic, Basic, Neutral

🔹 Part 1: Acids and Bases (Q1–Q25)

Q1. Which of the following is a natural source of acid?

A) Soap
B) Lemon juice
C) Baking soda
D) Toothpaste

✅ Answer: B) Lemon juice

Explanation:

• Soap → Basic in nature.
• Lemon juice → Contains citric acid, hence acidic (Correct).
• Baking soda → Mild base.
• Toothpaste → Slightly basic.

Q2. Bases generally taste:

A) Sweet
B) Sour
C) Bitter
D) Salty

✅ Answer: C) Bitter

Explanation:

• Sweet → Sugary substances, not bases.
• Sour → Acids.
• Bitter → Characteristic taste of bases like baking soda and soap (Correct).
• Salty → Salts.

Q3. Which gas is released when an acid reacts with a metal?

A) Oxygen
B) Nitrogen
C) Hydrogen
D) Carbon dioxide

✅ Answer: C) Hydrogen

Explanation:

• Oxygen → Not released in this reaction.
• Nitrogen → No role.
• Hydrogen → Characteristic gas released (Correct).
• Carbon dioxide → Released only when acids react with carbonates.

Q4. Which of the following is a weak acid?

A) Sulphuric acid
B) Citric acid
C) Nitric acid
D) Hydrochloric acid

✅ Answer: B) Citric acid

Explanation:

• Sulphuric acid → Strong acid.
• Citric acid → Naturally weak acid (Correct).
• Nitric acid → Strong acid.
• Hydrochloric acid → Strong acid.

Q5. Which of these is a strong base?

A) Soap solution
B) Ammonia solution
C) Sodium hydroxide
D) Baking soda

✅ Answer: C) Sodium hydroxide

Explanation:

• Soap → Weak base.
• Ammonia → Weak base.
• Sodium hydroxide → Strong base (Correct).
• Baking soda → Mild base.

Q6. Which of the following is used in antacids?

A) Hydrochloric acid
B) Sodium hydroxide
C) Magnesium hydroxide
D) Nitric acid

✅ Answer: C) Magnesium hydroxide

Explanation:

• Hydrochloric acid → Stomach acid, causes acidity.
• Sodium hydroxide → Too strong, dangerous.
• Magnesium hydroxide → Mild base that neutralises stomach acid (Correct).
• Nitric acid → Strong acid.

Q7. Acids turn blue litmus:

A) Red
B) Green
C) Yellow
D) No change

✅ Answer: A) Red

Q8. Which of these is a mineral acid?

A) Citric acid
B) Acetic acid
C) Sulphuric acid
D) Lactic acid

✅ Answer: C) Sulphuric acid

Q9. Which of the following substances is basic in nature?

A) Vinegar
B) Curd
C) Baking soda
D) Lemon

✅ Answer: C) Baking soda

Q10. Which acid is present in our stomach?

A) Citric acid
B) Hydrochloric acid
C) Sulphuric acid
D) Acetic acid

✅ Answer: B) Hydrochloric acid

Q11. Bases turn red litmus:

A) Blue
B) Yellow
C) Green
D) No change

✅ Answer: A) Blue

Q12. Which of the following is not a property of acids?

A) Sour taste
B) Turns blue litmus red
C) Releases hydrogen gas with metals
D) Feels soapy

✅ Answer: D) Feels soapy

Q13. Which acid is found in vinegar?

A) Acetic acid
B) Citric acid
C) Lactic acid
D) Formic acid

✅ Answer: A) Acetic acid

Q14. The substance used to make soaps is:

A) Strong acid
B) Weak acid
C) Strong base
D) Weak base

✅ Answer: C) Strong base

Q15. Which acid is found in ant sting?

A) Formic acid
B) Acetic acid
C) Lactic acid
D) Citric acid

✅ Answer: A) Formic acid

Q16. Which of these is an alkali?

A) NaOH
B) Ca(OH)₂
C) KOH
D) All of these

✅ Answer: D) All of these

Explanation:
All are soluble bases, hence alkalis.

Q17. Which base is used in window cleaners?

A) NaOH
B) KOH
C) Ammonium hydroxide
D) Ca(OH)₂

✅ Answer: C) Ammonium hydroxide

Q18. Which of these is NOT an organic acid?

A) Citric acid
B) Hydrochloric acid
C) Acetic acid
D) Lactic acid

✅ Answer: B) Hydrochloric acid

Q19. Which acid is present in curd?

A) Citric acid
B) Lactic acid
C) Acetic acid
D) Tartaric acid

✅ Answer: B) Lactic acid

Q20. Which of the following acids is used in car batteries?

A) Nitric acid
B) Hydrochloric acid
C) Sulphuric acid
D) Acetic acid

✅ Answer: C) Sulphuric acid

Q21. Which of these is a base found in lime water?

A) Sodium hydroxide
B) Calcium hydroxide
C) Magnesium hydroxide
D) Potassium hydroxide

✅ Answer: B) Calcium hydroxide

Q22. Which acid is present in tomato?

A) Oxalic acid
B) Acetic acid
C) Formic acid
D) Citric acid

✅ Answer: A) Oxalic acid

Q23. Which base is used in manufacture of paper?

A) NaOH
B) Ca(OH)₂
C) KOH
D) Mg(OH)₂

✅ Answer: A) NaOH

Q24. Which of these is NOT a base?

A) Soap
B) Baking soda
C) Vinegar
D) Lime water

✅ Answer: C) Vinegar

Q25. Which property is true for both acids and bases?

A) Both turn blue litmus red
B) Both taste sour
C) Both are electrolytes in solution
D) Both are soapy

✅ Answer: C) Both are electrolytes in solution

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