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Q67 (CDS-II/2026) Science & Technology › Basic Science (Physics, Chemistry, Biology)

Upon adding hydrochloric acid in copper oxide, it turns to blue-green color which is due to the formation of

Result
Your answer: —  ·  Correct: B

Explanation

When copper(II) oxide (CuO), which is a black basic oxide, reacts with dilute hydrochloric acid (HCl), a neutralization reaction takes place. The chemical equation for the reaction is:

CuO + 2HCl → CuCl2 + H2O

The blue-green color of the resulting solution is due to the formation of copper(II) chloride (CuCl2). In this reaction, the copper ions (Cu2+) in the aqueous solution impart the characteristic blue-green tint. Copper(I) chloride (CuCl) is a different compound where copper has a +1 oxidation state and is typically not formed in this direct reaction with CuO. "Copper hydrochloride" is an incorrect chemical name for the salt produced.

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