Chapter 5, Problem 70RQ

When chromium metal is dipped into a solution of nickel(II) chloride, some Cr dissolves and Ni metal deposits on the surface of the chromium. When chromium metal is dipped into a solution of ytterium(III) chloride, no reaction occurs. Referring to Problem 5.68 which of these reactions will occur spontaneously? Explain the reason for your choice.

$\begin{array}{l}\left(\text{a}\right){\text{2Mo}}^{\text{3+}}\text{+ 3Cr}\stackrel{}{\to }{\text{3Cr}}^{\text{2+}}\text{+ 2Mo}\hfill \\ \left(\text{b}\right){\text{2Mo + 3Cr}}^{\text{2+}}\stackrel{}{\to }{\text{ 2Mo}}^{\text{3+}}\text{+ 3Cr}\hfill \end{array}$

The following reactions occur spontaneously.

$\begin{array}{l}{\text{2Y + 3Ni}}^{\text{2+}}\underset{}{\to }{\text{2Y}}^{\text{3+}}\text{+ 3Ni}\hfill \\ {\text{2Mo + 3Ni}}^{\text{2+}}\underset{}{\to }{\text{ 2Mo}}^{\text{3+}}\text{+ 3Ni}\hfill \\ {\text{Y}}^{\text{3+}}\text{+ Mo }\stackrel{}{\to }{\text{Y + Mo}}^{\text{3+}}\hfill \end{array}$

List the metals Y, Ni, and Mo in order of increasing ease of oxidation.