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Science — AI-generated practice question

AI-generated practice question — model-generated for extra practice, not a previous-year CBSE board question.

Q1. [1] straightforward exam-ready
The chemical formula of washing soda is: (a) Na₂CO₃ (b) Na₂CO₃.10H₂O (c) NaHCO₃ (d) NaOH
  1. a Na₂CO₃
  2. b Na₂CO₃.10H₂O
  3. c NaHCO₃
  4. d NaOH
Generated by claude-sonnet-4-6 · 2026-06-17 12:36 · grounding rag
Model Answer

(b) Na₂CO₃.10H₂O

Washing soda is sodium carbonate decahydrate, with the chemical formula Na₂CO₃.10H₂O.

Source: Chapter 2, Section 2.4.3

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Explanation

The key distinction here is between Na₂CO₃ (anhydrous sodium carbonate) and Na₂CO₃.10H₂O (washing soda). Washing soda is the hydrated form — it contains 10 water molecules of crystallisation. The textbook explicitly states: "Na₂CO₃ + 10H₂O → Na₂CO₃.10H₂O (washing soda)." Options (c) NaHCO₃ is baking soda, and (d) NaOH is caustic soda — common distractors in this type of MCQ.

Previous-year CBSE Grade 10 board exam questions, organised by subject and chapter, each with a model answer — free to read and print.