The document describes 4 chemical reactions. The first reaction involves carbon dioxide and calcium oxide to form calcium carbonate. The second reaction involves copper oxide reacting with water to form copper hydroxide. The third reaction involves hydrochloric acid reacting with zinc to form zinc chloride and hydrogen gas. The fourth reaction involves sodium chloride reacting with copper to form copper chloride and sodium hydroxide.

1. O
O
O
C
O
Ca
O
O
CaO C
O
C
1

2. H
HO
O
Cu
H
HOHO
HHOO
Cu
2

3. HCl
HCl HCl
HCl
Zn
H
H
Cl
Cl
Zn
3

4. Na HO
Na HO
Cl
Cl
Cu
Cl
Cl
Cu
ClNa
ClNa
HONa
Cu
HONa
H O Na
H O Na
4