# Chapter 21 - Chemistry of the Main-Group Elements I: Groups 1, 2, 13, and 14 - 21-12 Concept Assessment - Page 968: 21-12

Metallic tin reduces $\mathrm{Sn}^{4+}$ to $\mathrm{Sn}^{2+}$as shown in the following spontaneous reaction: $$\mathrm{Sn}^{4+}(\mathrm{aq})+\mathrm{Sn}(\mathrm{s}) \longrightarrow 2 \mathrm{Sn}^{2+}(\mathrm{aq})$$ $E_{\text {cell }}^{\circ}=0.154 \mathrm{V}-(-0.137 \mathrm{V})=0.017 \mathrm{V} .$ So, the presence of $\mathrm{Sn}(\mathrm{s})$ decreases the oxidation of $\mathrm{Sn}^{2+}(\mathrm{aq})$ to $\mathrm{Sn}^{4+}(\mathrm{aq})$.