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Standard XII

Chemistry

Introduction

When hydrogen...

Question

When hydrogen is passed over a black solid compound $A$ , the products are 'a colourless liquid' and 'a reddish brown metal $B$ '.
Substance $B$ is divided into two parts, each placed in separate test tubes.
Dilute $H C l$ is added to one part of substance $B$ and dilute $H N O_{3}$ to the other. Give two tests for the colourless liquid formed in the experiment.

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Solution

Compound A is black copper(II) oxide and B is copper, dark brown metal.
$C u O + H_{2} \to C u + H_{2} O$
Cu metal does not react with any acid as it is present below hydrogen in activity series so it is unreactive towards acid reaction. Positive hydrogen ions react with oxides and hydroxides to form water and with carbonates to form water and carbon dioxide.

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A

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Substance

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and dilute

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Substance B is divided into two parts, each placed in seperate test tubes.

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