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Science (086) — CBSE Class 10 board question

Q1. [1] § 1.2.4 Double Displacement Reaction
In the following equation x KI + H₂O₂ ⎯→ I₂ + y KOH x and y respectively are :
  1. (A) 2, 2
  2. (B) 1, 2
  3. (C) 2, 1
  4. (D) 1, 1
Previously asked in CBSE board exam
2026 31/3/1 Q19
Generated by claude-sonnet-4-6 · 2026-06-14 10:31 · grounding rag
Model Answer

Balancing the equation: 2KI + H₂O₂ → I₂ + 2KOH

LHS: 2K, 2I, 2H, 2O — RHS: 2K, 2I, 2H, 2O ✓

So x = 2 and y = 2. Answer: (A) 2, 2

Explanation

Balance by inspection: 2 KI provides 2 I atoms (needed for I₂) and 2 K atoms, which combine with the 2 OH from H₂O₂ to give 2 KOH. Both x and y are 2. Always verify atom count on both sides for balancing MCQs.

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