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Science — CBSE Class 10 board question

Q1. [1]
Solid Calcium oxide reacts vigorously with water to form Calcium hydroxide accompanied by the liberation of heat. From the information given above it may be concluded that this reaction
  1. (A) is endothermic and pH of the solution formed is more than 7.
  2. (B) is exothermic and pH of the solution formed is 7.
  3. (C) is endothermic and pH of the solution formed is 7.
  4. (D) is exothermic and pH of the solution formed is more than 7.
Previously asked in CBSE board exam
2024 31/2/1 Q1
Generated by claude-sonnet-4-6 · 2026-06-14 10:28 · grounding rag
Model Answer

(D) is exothermic and pH of the solution formed is more than 7.

Heat is liberated → exothermic. Ca(OH)₂ is a base → its solution is alkaline → pH > 7.

Explanation

Two facts decide the answer: (1) heat is released = exothermic (not endothermic), eliminating A and C; (2) Ca(OH)₂ is a base, so its aqueous solution is alkaline with pH > 7 (not = 7), eliminating B. Both conditions together point to option D.

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