Home / Topic / Acid-base indicators
Topic Acid-base indicators
Asked 2 times across 2 UPSC exams over 5 years (2020–2025), peaking in 2020.
Key insights
- Most tested in NDA — 1 of 2 PYQs
- Most asked in 2020
- Recurs across 2 years (2020–2025)
How it travelled across exams
First appearance in each exam — the same idea, reframed.
NDA 2020 → GEO 2025
How the concept evolved
Rising — more than half its appearances (2 of 2) are since 2016.
Sample questions
You've seen the pattern — here are a few of the actual PYQs.
GEO2025
Which one among the following is an example of olfactory indicator?
- A Litmus
- B Methyl orange
- C Phenolphthalein
- D Onion ✓
✓ Correct answer: (D)
Science & Technology › Physics & Chemistry
NDA2020
Which one of the following is the correct sequence of change in colours when a turmeric stain on white clothes is scrubbed by soap and then washed with water ?
- A Yellow – pink – blue
- B Yellow – reddish brown – yellow ✓
- C Yellow – reddish brown – blue
- D Yellow – blue – pink
✓ Correct answer: (B)
Science & Technology › Physics & Chemistry
Study how UPSC repeats — not just the papers
₹199 / 1 year · Founding Member
Full access unlocks the three things no PYQ PDF gives you:
① Cross-exam learning — see the same idea recur across CSE, CAPF, CDS and NDA.
② Topic evolution — how each idea is framed, year by year.
③ Question intelligence — every PYQ + answer, linked to related concepts and similar questions.
e.g. Round Table Conference: CDS 2017 → CSE 2017 → … → CAPF 2024
15 days free, no card required — then ₹199 for 1 year.
Start your 15-day free trial →