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Q45 (NDA-I/2016) Science & Technology › Basic Science (Physics, Chemistry, Biology) › Basic chemical principles Answer Verified

Which one of the following oxides dissolves in water ?

Result
Your answer: —  Â·  Correct: D
Explanation

Most metal oxides are insoluble in water; however, certain alkali metal oxides dissolve to form strong alkalis [1]. Sodium oxide (Na2O) is a highly reactive basic oxide that dissolves in water to produce sodium hydroxide (NaOH), a process that releases hydroxide ions into the solution [1]. The chemical reaction is represented as Na2O + H2O → 2NaOH. In contrast, Copper(II) oxide (CuO) and Iron(III) oxide (Fe2O3) are insoluble in water. Aluminium oxide (Al2O3) is amphoteric and does not react with or dissolve in water in a simple way because its oxide ions are held too strongly in the solid lattice. Therefore, among the given options, only sodium oxide (Na2O) is soluble in water, forming a basic solution with a high pH.

Sources

  1. [1] Science , class X (NCERT 2025 ed.) > Chapter 3: Metals and Non-metals > Activity 3.9 > p. 41
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