The pH scale & indicators topic is a frequent scorer in APECET/TSECET Chemistry. Whether in general science or applied chemistry, these questions often test your ability to interpret pH values and identify the correct indicators for acids, bases, and neutral substances. This is a short, high-return topic—ideal for securing easy marks in ECET 2026.
📘 Concept Notes – pH Scale & Indicators
📏 pH Scale Basics:
- pH = Potential of Hydrogen.
- Measures hydrogen ion concentration in a solution.
- Scale: 0 to 14
- pH < 7 → Acidic
- pH = 7 → Neutral
- pH > 7 → Basic (Alkaline)
🎨 Indicators:
Indicators are chemical substances that change color based on the pH of the solution.
🔹 Common Indicators:
- Litmus:
- Acid: Blue → Red
- Base: Red → Blue
- Phenolphthalein:
- Acid: Colorless
- Base: Pink
- Methyl Orange:
- Acid: Red
- Base: Yellow
- Universal Indicator:
- Shows different colors for each pH value on the scale.
🧪 Applications in ECET:
- Predicting pH from solution type.
- Matching indicator with reaction.
- Understanding neutralization changes in pH.
🔟 10 Most Expected MCQs – ECET 2026 [pH Scale & Indicators]
Q1. A solution with pH = 2 is:
A) Weak acid
B) Strong acid
C) Weak base
D) Neutral
Q2. A solution with pH = 7 is:
A) Acidic
B) Basic
C) Neutral
D) Alkaline
Q3. Which indicator turns pink in a basic solution?
A) Litmus
B) Phenolphthalein
C) Methyl orange
D) Universal indicator
Q4. pH > 7 indicates:
A) Neutral solution
B) Acidic solution
C) Basic solution
D) Strong acid
Q5. Methyl orange in acid solution shows:
A) Yellow
B) Pink
C) Red
D) Colorless
Q6. Which indicator shows different colors for each pH value?
A) Litmus
B) Phenolphthalein
C) Universal Indicator
D) Methyl orange
Q7. Which of the following turns red litmus blue?
A) HCl
B) NaOH
C) H₂SO₄
D) CH₃COOH
Q8. Phenolphthalein in acid solution is:
A) Pink
B) Red
C) Colorless
D) Yellow
Q9. pH value of a strong base is:
A) Less than 7
B) Equal to 7
C) Greater than 7
D) Zero
Q10. Universal indicator shows green color at:
A) Acidic pH
B) Neutral pH
C) Basic pH
D) Strong acidic pH
✅ Answer Key Table
| Q.No | Answer |
|---|---|
| Q1 | B |
| Q2 | C |
| Q3 | B |
| Q4 | C |
| Q5 | C |
| Q6 | C |
| Q7 | B |
| Q8 | C |
| Q9 | C |
| Q10 | B |
🧠 Explanations of All Answers
- Q1 → B: pH 2 means high H⁺ concentration = strong acid.
- Q2 → C: pH 7 indicates a neutral solution (pure water).
- Q3 → B: Phenolphthalein turns pink in basic mediums.
- Q4 → C: pH above 7 = basic or alkaline solution.
- Q5 → C: Methyl orange is red in acidic medium.
- Q6 → C: Universal indicator gives a full pH color range.
- Q7 → B: Bases like NaOH turn red litmus to blue.
- Q8 → C: In acidic medium, phenolphthalein is colorless.
- Q9 → C: Strong bases have pH much greater than 7.
- Q10 → B: Green in universal indicator means pH = 7 (neutral).
🎯 Why This Practice Matters for ECET 2026
The pH scale & indicators topic is direct and factual, making it one of the quickest to revise and attempt in the exam. ECET papers often include 1–2 questions from this concept, so being familiar with indicator behavior and pH values ensures you can answer confidently and save time for harder sections.
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