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📘 Study MCQs
Q1. A student tests aerated water with litmus paper. What change will he observe on the blue litmus paper? SCIENCE
• Turns green
• Turns red
• No change
• Turns blue
Answer: Turns red
Aerated water contains carbon dioxide which forms carbonic acid, making it acidic. Acids turn blue litmus paper red.
Q2. Aerated water is tested with both red and blue litmus papers. What is the correct observation? SCIENCE
• Red litmus turns blue, blue litmus turns red
• Both litmus papers turn green
• Red litmus shows no change, blue litmus turns red
• Red litmus turns blue, blue litmus shows no change
Answer: Red litmus shows no change, blue litmus turns red
Aerated water is acidic. Acids do not change the color of red litmus but turn blue litmus red.
Q3. What can be inferred about the nature of aerated water based on its effect on litmus paper? SCIENCE
• It is basic
• It is acidic
• It is neutral
• It is salty
Answer: It is acidic
Since aerated water turns blue litmus red and does not affect red litmus, it is confirmed to be an acidic solution.
Q4. Common salt solution is tested with litmus paper. What will be the result on blue litmus paper? SCIENCE
• Turns red
• Turns blue
• Turns green
• No change
Answer: No change
Common salt solution is neutral. It does not change the color of either red or blue litmus paper.
Q5. A student dips both red and blue litmus papers in a beaker containing common salt solution. What will he observe? SCIENCE
• Red litmus turns blue, blue litmus turns red
• Both litmus papers turn green
• Both litmus papers show no change
• Red litmus turns blue, blue litmus shows no change
Answer: Both litmus papers show no change
Common salt (sodium chloride) dissolves in water to form a neutral solution. Neutral substances do not affect the color of either red or blue litmus paper.
Q6. What is the nature of common salt solution as indicated by the litmus test? SCIENCE
• Acidic
• Basic
• Neutral
• Slightly sour
Answer: Neutral
Since common salt solution does not change the color of either red or blue litmus paper, it is confirmed to be a neutral substance.
Q7. Shampoo solution is tested with red litmus paper. What change will be observed? SCIENCE
• No change
• Turns blue
• Turns red
• Turns green
Answer: Turns blue
Shampoo solution is generally basic in nature to effectively clean hair. Bases turn red litmus paper blue.
Q8. A student tests shampoo solution with both red and blue litmus papers. What will be his observation? SCIENCE
• Red litmus turns blue, blue litmus shows no change
• Red litmus shows no change, blue litmus turns red
• Both litmus papers turn green
• Both litmus papers show no change
Answer: Red litmus turns blue, blue litmus shows no change
Shampoo solution is basic. Bases turn red litmus blue but do not change the color of blue litmus.
Q9. Based on the litmus test, what can be inferred about the nature of shampoo solution? SCIENCE
• It is acidic
• It is neutral
• It is basic
• It is salty
Answer: It is basic
The observation that shampoo solution turns red litmus blue while leaving blue litmus unchanged confirms that it is a basic solution.
Q10. Baking soda solution is tested with blue litmus paper. What change will occur? SCIENCE
• Turns red
• Turns green
• No change
• Turns yellow
Answer: No change
Baking soda solution is basic. Bases do not change the color of blue litmus paper. They only affect red litmus paper.
Q11. A student places a drop of baking soda solution on red litmus paper. What will he observe? SCIENCE
• The red litmus paper turns blue
• The red litmus paper turns green
• The red litmus paper shows no change
• The red litmus paper turns yellow
Answer: The red litmus paper turns blue
Baking soda (sodium hydrogen carbonate) dissolves in water to form a basic solution. A basic solution will turn red litmus paper blue.
Q12. What is the nature of baking soda solution as shown by the litmus test? SCIENCE
• Acidic
• Neutral
• Basic
• Sour
Answer: Basic
Since baking soda solution turns red litmus blue and does not affect blue litmus, it is confirmed to be a basic substance.
Q13. Lemon juice is tested with red litmus paper. What will be the result? SCIENCE
• Turns blue
• Turns green
• No change
• Turns black
Answer: No change
Lemon juice is acidic. Acids do not change the color of red litmus paper. They only affect blue litmus paper.
Q14. A student tests lemon juice with blue litmus paper. What change will he observe? SCIENCE
• No change
• Turns blue
• Turns red
• Turns green
Answer: Turns red
Lemon juice contains citric acid, making it an acidic solution. Acids turn blue litmus paper red.
Q15. What inference can be drawn from the litmus test on lemon juice? SCIENCE
• It is basic
• It is neutral
• It is acidic
• It is soapy
Answer: It is acidic
The observation that lemon juice turns blue litmus red while leaving red litmus unchanged confirms that it is an acidic solution.
Q16. Hydrochloric acid solution is a strong mineral acid. What will be its effect on blue litmus paper? SCIENCE
• No change
• Turns blue
• Turns green
• Turns red
Answer: Turns red
Hydrochloric acid (HCl) is a strong acid. All acids, whether strong or weak, turn blue litmus paper red.
Q17. A student tests hydrochloric acid with both red and blue litmus papers. What will he observe? SCIENCE
• Red litmus turns blue, blue litmus shows no change
• Both litmus papers turn green
• Red litmus shows no change, blue litmus turns red
• Both litmus papers show no change
Answer: Red litmus shows no change, blue litmus turns red
Hydrochloric acid is an acidic solution. Acids do not affect red litmus but will turn blue litmus paper red.
Q18. Based on the litmus test, what is the nature of hydrochloric acid solution? SCIENCE
• Basic
• Neutral
• Acidic
• Salty
Answer: Acidic
Since hydrochloric acid turns blue litmus red and has no effect on red litmus, it is confirmed to be an acidic solution.
Q19. Nitric acid is another strong mineral acid. What will be its effect on red litmus paper? SCIENCE
• Turns blue
• Turns green
• No change
• Turns black
Answer: No change
Nitric acid (HNO₃) is an acid. Acids do not change the color of red litmus paper. They only change the color of blue litmus paper.
Q20. A student performs a litmus test on nitric acid solution. What will he observe on the blue litmus paper? SCIENCE
• It turns red
• It turns blue
• It turns green
• No change
Answer: It turns red
Nitric acid is an acidic solution. The defining property of an acid in the litmus test is that it turns blue litmus paper red.
Q21. What inference can be made about nitric acid from the litmus paper test? SCIENCE
• It is basic
• It is neutral
• It is acidic
• It is soapy
Answer: It is acidic
The observation that nitric acid turns blue litmus red, but does not change the color of red litmus, confirms that it is an acid.
Q22. Washing soda solution is commonly used as a cleaning agent. What will be its effect on red litmus paper? SCIENCE
• No change
• Turns blue
• Turns red
• Turns green
Answer: Turns blue
Washing soda (sodium carbonate) dissolves in water to form a basic solution. Bases turn red litmus paper blue.
Q23. A student tests washing soda solution with both red and blue litmus papers. What will he observe? SCIENCE
• Red litmus turns blue, blue litmus shows no change
• Red litmus shows no change, blue litmus turns red
• Both litmus papers turn green
• Both litmus papers show no change
Answer: Red litmus turns blue, blue litmus shows no change
Washing soda solution is basic. Bases turn red litmus blue but do not change the color of blue litmus paper.
Q24. Based on the litmus test, what is the nature of washing soda solution? SCIENCE
• Acidic
• Neutral
• Basic
• Sour
Answer: Basic
Since washing soda solution turns red litmus blue and has no effect on blue litmus, it is confirmed to be a basic solution.
Q25. Limewater is used to test for carbon dioxide gas. What will be its effect on blue litmus paper? SCIENCE
• Turns red
• No change
• Turns blue
• Turns green
Answer: No change
Limewater is a solution of calcium hydroxide, which is a base. Bases do not change the color of blue litmus paper.
Q26. A student dips red litmus paper into a beaker of limewater. What will he observe? SCIENCE
• The red litmus paper turns blue
• The red litmus paper turns green
• The red litmus paper shows no change
• The red litmus paper turns yellow
Answer: The red litmus paper turns blue
Limewater (calcium hydroxide solution) is basic in nature. A characteristic property of bases is that they turn red litmus paper blue.
Q27. What can be inferred about the nature of limewater from its effect on litmus paper? SCIENCE
• It is acidic
• It is neutral
• It is basic
• It is sour
Answer: It is basic
Q28. Which of the following solutions will turn blue litmus paper red? SCIENCE
• Soap solution
• Limewater
• Lemon juice
• Baking soda solution
Answer: Lemon juice
Only acidic solutions turn blue litmus red. Among the options, lemon juice (containing citric acid) is acidic, while soap, limewater, and baking soda are all basic.
Q29. Which of the following solutions will turn red litmus paper blue? SCIENCE
• Vinegar
• Lemon juice
• Aerated water
• Shampoo solution
Answer: Shampoo solution
Only basic solutions turn red litmus blue. Among the options, shampoo is basic, while vinegar, lemon juice, and aerated water are all acidic.
Q30. A solution has no effect on either red or blue litmus paper. Which of the following could it be? SCIENCE
• Lemon juice
• Common salt solution
• Washing soda solution
• Vinegar
Answer: Common salt solution
A solution that does not change the color of any litmus paper is neutral. Common salt solution is neutral, while lemon juice and vinegar are acidic, and washing soda is basic.
Q31. Four solutions are tested with litmus paper. Which one is most likely to be aerated water? SCIENCE
• Turns red litmus blue, no change on blue litmus
• Turns blue litmus red, no change on red litmus
• No change on either litmus
• Turns both litmus papers green
Answer: Turns blue litmus red, no change on red litmus
Aerated water is acidic. The pattern for an acid is: no change on red litmus, and blue litmus turns red.
Q32. Four solutions are tested with litmus paper. Which one is most likely to be shampoo solution? SCIENCE
• Turns blue litmus red, no change on red litmus
• Turns red litmus blue, no change on blue litmus
• No change on either litmus
• Turns both litmus papers red
Answer: Turns red litmus blue, no change on blue litmus
Shampoo is basic. The pattern for a base is: red litmus turns blue, and no change on blue litmus.
Q33. A liquid ‘X’ is tested with litmus paper. Red litmus turns blue, but blue litmus shows no change. What is the nature of liquid ‘X’? SCIENCE
• Acidic
• Basic
• Neutral
• Sour
Answer: Basic
This is the classic test for a base. Bases are the only substances that turn red litmus paper blue without affecting blue litmus.
Q34. A liquid ‘Y’ is tested with litmus paper. Blue litmus turns red, but red litmus shows no change. What is the nature of liquid ‘Y’? SCIENCE
• Basic
• Neutral
• Acidic
• Soapy
Answer: Acidic
This is the classic test for an acid. Acids are the only substances that turn blue litmus paper red without affecting red litmus.
Q35. A liquid ‘Z’ is tested with litmus paper and shows no change on either red or blue litmus. What is the nature of liquid ‘Z’? SCIENCE
• Acidic
• Basic
• Neutral
• Can be acidic or basic
Answer: Neutral
If a substance does not change the color of either type of litmus paper, it is neither acidic nor basic. It is a neutral substance.
Q36. Which of the following is a pair of acidic solutions based on their effect on litmus? SCIENCE
• Limewater and soap solution
• Aerated water and lemon juice
• Baking soda and washing soda
• Shampoo and common salt
Answer: Aerated water and lemon juice
Both aerated water (contains carbonic acid) and lemon juice (contains citric acid) are acidic. The others are either basic or neutral.
Q37. Which of the following is a pair of basic solutions based on their effect on litmus? SCIENCE
• Vinegar and lemon juice
• Aerated water and hydrochloric acid
• Shampoo and limewater
• Common salt and sugar solution
Answer: Shampoo and limewater
Shampoo and limewater (calcium hydroxide) are both basic solutions. Vinegar, lemon juice, aerated water, and HCl are acidic, while common salt is neutral.
Q38. A student has four unlabeled beakers containing aerated water, common salt solution, shampoo, and lemon juice. How can he identify the beaker with common salt solution using only litmus paper? SCIENCE
• It will turn red litmus blue
• It will turn blue litmus red
• It will turn both litmus papers green
• It will not change the color of either litmus paper
Answer: It will not change the color of either litmus paper
Common salt solution is the only neutral solution among them. Acids (aerated water, lemon juice) affect blue litmus, and bases (shampoo) affect red litmus. The neutral salt solution will not affect either.
Q39. A student finds that a solution turns blue litmus red. Which of the following could the solution NOT be? SCIENCE
• Lemon juice
• Vinegar
• Limewater
• Hydrochloric acid
Answer: Limewater
A solution that turns blue litmus red is an acid. Limewater is a base, so it would turn red litmus blue, not the other way around. The other three are all acids.
Q40. A student finds that a solution turns red litmus blue. Which of the following could the solution NOT be? SCIENCE
• Soap solution
• Washing soda solution
• Baking soda solution
• Aerated water
Answer: Aerated water
A solution that turns red litmus blue is a base. Aerated water is acidic, so it would turn blue litmus red. The other three are all basic solutions.
Q41. You are given three solutions: P, Q, and R. P turns blue litmus red. Q turns red litmus blue. R shows no change on either litmus. Which option correctly identifies P, Q, and R? SCIENCE
• P-Base, Q-Acid, R-Neutral
• P-Acid, Q-Base, R-Neutral
• P-Neutral, Q-Acid, R-Base
• P-Acid, Q-Neutral, R-Base
Answer: P-Acid, Q-Base, R-Neutral
Turning blue litmus red is the property of an acid (P). Turning red litmus blue is the property of a base (Q). No change on either litmus is the property of a neutral substance (R).
Q42. Which of the following statements about nitric acid is correct based on its litmus test? SCIENCE
• It turns red litmus blue
• It has no effect on blue litmus
• It turns blue litmus red
• It turns both litmus papers red
Answer: It turns blue litmus red
Nitric acid is an acid. The correct observation for any acid is that it turns blue litmus red and has no effect on red litmus.
Q43. Which of the following statements about washing soda solution is correct based on its litmus test? SCIENCE
• It is acidic and turns blue litmus red
• It is basic and turns red litmus blue
• It is neutral and has no effect on litmus
• It turns both litmus papers blue
Answer: It is basic and turns red litmus blue
Washing soda solution is basic. The defining characteristic of a base in the litmus test is that it turns red litmus paper blue.
Q44. If you accidentally mix an acid and a base, the resulting solution might show what litmus test result? SCIENCE
• It will definitely turn blue litmus red
• It will definitely turn red litmus blue
• It might show no change on either litmus if they exactly neutralize each other
• It will turn both litmus papers green
Answer: It might show no change on either litmus if they exactly neutralize each other
When an acid and a base react, they neutralize each other to form salt and water. If the quantities are exactly equal, the resulting solution will be neutral and show no change on litmus paper.
Q45. Hydrochloric acid and nitric acid are both strong acids. How will their effect on litmus paper compare? SCIENCE
• HCl will turn blue litmus red, but HNO₃ will turn it blue
• HCl will turn red litmus blue, but HNO₃ will turn it red
• Both will have the same effect: turn blue litmus red
• Both will have no effect on litmus paper
Answer: Both will have the same effect: turn blue litmus red
All acids, regardless of their strength or source, share common properties. One of these properties is turning blue litmus paper red. Therefore, both HCl and HNO₃ will show the same result.
Q46. Baking soda solution and washing soda solution are both basic. How will their effect on red litmus paper compare? SCIENCE
• Baking soda will turn it blue, but washing soda will turn it red
• Both will turn red litmus paper blue
• Baking soda will have no effect, but washing soda will turn it blue
• Both will have no effect on red litmus
Answer: Both will turn red litmus paper blue
All bases share common properties. A key property of any base is its ability to turn red litmus paper blue. Therefore, both basic solutions will show the same result.
Q47. A solution is known to be either limewater or lemon juice. A single drop on red litmus paper will help identify it. How? SCIENCE
• If it turns red litmus blue, it is lemon juice
• If it turns red litmus blue, it is limewater
• If it turns red litmus green, it is limewater
• If it has no effect, it is limewater
Answer: If it turns red litmus blue, it is limewater
Limewater is a base and will turn red litmus blue. Lemon juice is an acid and will not change the color of red litmus. So, a change on red litmus identifies limewater.
Q48. A solution is known to be either aerated water or common salt solution. Testing it with blue litmus paper will reveal its identity. How? SCIENCE
• If it turns blue litmus red, it is common salt solution
• If it turns blue litmus red, it is aerated water
• If it turns blue litmus blue, it is aerated water
• If it has no effect, it is aerated water
Answer: If it turns blue litmus red, it is aerated water
Aerated water is acidic and will turn blue litmus red. Common salt solution is neutral and will not change the color of blue litmus. So, a color change identifies aerated water.
Q49. A teacher showed that shampoos are generally basic. If a particular brand of shampoo were acidic, how would its litmus test result differ? SCIENCE
• It would turn red litmus blue instead of having no effect
• It would turn blue litmus red instead of having no effect
• It would have no effect on red litmus, which it should
• It would turn both litmus papers red
Answer: It would turn blue litmus red instead of having no effect
A basic shampoo shows: red litmus turns blue, blue litmus no change. If it were acidic, the pattern would change to: red litmus no change, blue litmus turns red. The main difference would be its effect on blue litmus.
Q50. Based on the provided data, which of the following conclusions is correct? SCIENCE
• Only mineral acids turn blue litmus red
• Substances that turn red litmus blue are all soaps
• A substance that does not change red litmus could be acidic or neutral
• Baking soda and washing soda have different effects on red litmus
Answer: A substance that does not change red litmus could be acidic or neutral
Acids (like lemon juice, HCl) have no effect on red litmus. Neutral substances (like common salt) also have no effect on red litmus. Therefore, if a substance does not change red litmus, it could be either acidic or neutral. Further testing with blue litmus is needed to confirm.