Baking soda solution is added to beetroot extract used as an acid-base indicator. What colour change would you observe, and what does it indicate about the nature of baking soda solution?
Generated by claude-sonnet-4-6 · 2026-06-26 01:03 · grounding rag
Model Answer
When baking soda solution is added to beetroot extract, the colour of the extract changes from red/pink to yellow (or greenish-yellow).
This colour change indicates that baking soda (NaHCO₃) solution is basic (alkaline) in nature, as beetroot extract shows a different colour in basic solutions compared to acidic ones.
Source: Chapter 2, Group Activity — Prepare your own indicator
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Explanation
- Beetroot extract acts as a natural acid-base indicator — it gives one colour in acid and a different colour in base.
- Baking soda = sodium hydrogencarbonate (NaHCO₃), which is a base.
- Examiners expect two points: (1) the colour change observed, and (2) what it tells us about the nature of baking soda solution (i.e., it is basic/alkaline). Each point carries 1 mark.
- Avoid writing that it is a strong base — NaHCO₃ is a mild/weak base.