Hard

Exploring Substances: Acidic, Basic, and Neutral — Hard

15 questions 18 min PYQ-grade reasoning

Q1. A solution turns red litmus paper to blue. Excess addition of which of the following solutions would reverse this change?
- A. Lime water
- B. Baking soda
- C. Vinegar
- D. Common salt solution
Q2. Three unknown solutions A, B and C are tested. A few drops of red litmus turn solution A blue. A few drops of turmeric solution turn solution B red. A few drops of red rose extract turn solution C green. The natures of A, B and C respectively are
- A. Acidic, acidic and acidic
- B. Neutral, basic and basic
- C. Basic, basic and acidic
- D. Basic, basic and basic
Q3. A liquid is tested with three indicators. Red litmus: no change. Blue litmus: turned red. Turmeric: no change in colour. The liquid is
- A. Acidic in nature
- B. Basic in nature
- C. Neutral in nature
- D. Cannot be decided from the data
Q4. Three liquids are given — vinegar, baking soda solution and sugar solution. Sangita uses only turmeric paper to identify them. Which of these can she identify with certainty?
- A. All three liquids
- B. Only baking soda solution
- C. Only vinegar
- D. Only sugar solution
Q5. Red rose extract turns liquid X green. When excess amla juice is added to liquid X, what is most likely to happen?
- A. The mixture stays green because the colour is permanent
- B. The mixture turns yellow because amla bleaches it
- C. The mixture turns red because amla is acidic and neutralises the basic liquid X, eventually making it acidic
- D. The mixture turns blue because amla is basic
Q6. Activity 2.7 places one drop of lemon juice in a test tube. A drop of blue litmus solution turns the contents red. Lime water is added drop by drop. Eventually the colour changes from red to blue. The best interpretation is
- A. Lime water has bleached the litmus dye
- B. Lime water has neutralised the lemon juice and has made the solution basic
- C. Lemon juice has evaporated, so the litmus returned to blue
- D. The lime water is acidic and reacts with litmus dye
Q7. Consider the following statements about Activity 2.2 (relating taste to nature). I. The activity uses taste of edible substances to introduce 'sour means acidic'. II. The chapter cautions students not to taste any unknown substance. III. The chapter says students may taste any laboratory chemical to identify its nature. Which statements are correct?
- A. I and II only
- B. II and III only
- C. I and III only
- D. All three
Q8. Statements about Activity 2.4 (red rose extract testing): I. In test tube A, on adding lemon juice, the extract becomes red. II. In test tube B, on adding soap solution, the extract becomes green. III. In a tube with sugar solution, the extract turns blue. Which statements are correct?
- A. I and II only
- B. II and III only
- C. I and III only
- D. All three
Q9. Ashwin's friend Gurbir lives near an industrial area where the fish population in a lake is declining because acidic factory waste is being released. According to the chapter, the best remedy before releasing the waste into the lake is
- A. Dilute it with more acidic chemicals
- B. Heat it strongly to evaporate the acid
- C. Add basic substances to neutralise it
- D. Add sugar solution to mask the acid
Q10. If the soil in a field is found to be basic, the chapter suggests treating it by adding
- A. Lime (chuna)
- B. Common salt
- C. Vinegar in large quantity
- D. Organic matter like manure and composted leaves
Q11. A farmer's plants are not growing well, yet the soil tests neutral with an indicator. The chapter's most likely explanation is
- A. The soil is actually acidic and the indicator is faulty
- B. Neutral soil cannot support any plant growth
- C. Even when soil is neutral, plants may show poor health due to deficiency of nutrients in the soil
- D. The plants need to be moved to acidic soil immediately
Q12. Aman spilt vinegar on pieces of eggshell or marble and noticed bubbles. On another piece of eggshell or marble he poured soap solution, but no bubbles appeared. Why did bubbles occur with vinegar but not with soap solution?
- A. Vinegar is basic and reacts with eggshell to give bubbles
- B. Vinegar is acidic and reacts with the basic content of eggshell or marble (calcium carbonate) to release gas; soap solution is itself basic and does not react
- C. Soap solution evaporates faster, so bubbles cannot form
- D. Marble does not react with any liquid
Q13. The chapter's Fascinating Facts box on hydrangea states that the flower colour depends on the nature of soil. Which of these matches the chapter?
- A. Acidic soil → pink/red flowers; basic soil → blue flowers
- B. Acidic soil → blue flowers; basic soil → pink or red flowers
- C. Acidic soil → yellow flowers; neutral soil → white flowers
- D. Soil nature does not affect hydrangea colour
Q14. Grape juice is mixed with red rose extract and the mixture acquires a light red tint. If baking soda is now added to this mixture, what will happen?
- A. The mixture remains light red
- B. The mixture turns yellow
- C. The mixture turns green because baking soda is basic and red rose extract is green in a basic solution
- D. The mixture turns black
Q15. Keerthi writes a secret message to her grandmother using orange juice on white paper. Which of these indicators is best suited to make the message visible?
- A. Tap water
- B. Sugar solution
- C. Common salt solution
- D. Blue litmus solution

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