Chapter 5.3, Problem 5.12P

Classify each reaction as a combination, decomposition, single replacement, or doublereplacement reaction.

1. $\text{2 HgO}\to {\text{2 Hg+O}}_{\text{2}}$
2. ${\text{Mg + ZnCl}}_{\text{2}}\to {\text{MgCl}}_{\text{2}}\text{ + Zn}$
3. ${\text{H}}_{\text{2}}{\text{C}}^{\text{=}}{\text{CH}}_{\text{2}}\text{+ HBr}\to {\text{CH}}_{\text{3}}{\text{CH}}_{\text{2}}\text{Br}$
4. ${\text{KNO}}_{\text{3}}\text{+ HBr}\to {\text{KBr+ HNO}}_{\text{3}}$