Explain on several examples the single and double displacements chemical reactions.

In the single displacement chemical reaction,  one element
is combining with a compound. This element switches it's place with an element from the
compound.

The general formula of this kind of chemical
reaction is:

x + yz --> xz +
y

As we can notice, the x element is replacing y element
from the original compound yz. The result is the new compound xz and the new element
y.

When magnesium is combined with water, the magnesium
element is replacing hydrogen from water. The result is magnesium hydroxide and H2
gas.

Mg + 2H2O --> Mg(OH)2 +
H2

The double displacement chemical reaction occurs when
anions and cations from different molecules are changing places, creating 2 new
compounds.

xy + zw --> xw +
yz

Conclusion: single displacement chemical
reaction: x + yz --> xz + y and double displacement chemical reaction: xy + zw
--> xw + yz.