Chapter 19, Problem 95A

Interpretation Introduction

Interpretation:

Chemical equations are to be written for the phenomena happening in given figure.

Concept introduction:

Reduced copper ions give a reddish brown tint while oxidized copper ions impart a greenish blue color.

Answer to Problem 95A

Equation for the reddish brown pottery:

$C{u}^{2+}+2e^{-}\to Cu(\text{reddish brown)}$

Equation for green blue pottery:

$Cu\to C{u}^{2+}(\text{greenish blue)}+2e^{-}$

Explanation of Solution

The greenish blue pottery has been glazed in oxidative conditions and the reddish brown pottery has been glazed in reductive conditions of sparse oxygen and more carbon dioxide. Due to these conditions, the oxidation and reduction of copper takes place as shown below:

$C{u}^{2+}+2e^{-}\to Cu(\text{reddish brown)}$

And,

$Cu\to C{u}^{2+}(\text{greenish blue)}+2e^{-}$