# Which of the following reactions are redox reactions? A. Ba+Mg^(2+)rarrBa^(2+) + Mg. B. H^+ +HO^(-)rarrH_2O C. CO_2(g) +H_2O(l)rarrHCO_3^(-) + HO^(-) D. Cr(s) + 3H^(+)rarrCr^(3+) + 3/2H_2

Oct 12, 2016

The redox reactions are: $\left(a\right)$; $\left(c\right)$; and $\left(d\right)$.

#### Explanation:

$\left(a\right)$: barium is oxidized; magnesium is reduced.

$\left(c\right)$: calcium is oxidized; silicon is reduced.

$\left(d\right)$: chromium is oxidized; hydrogen is reduced.

In general, metals are electron rich species. Given that oxidation is loss of electrons, metals tend to be oxidized. On the other hand, over on the other side of the Periodic Table, non-metals tend to have greater nuclear charges, and tend to gain electrons; they are thus oxidizing, and tend to be reduced, cf combustion.

You probably should learn about oxidation numbers.