Achemical reaction in which two elements or radicals change places with two other elements or radicals is a reaction.
a. double replacement
b. combination
c. substitution
d. decomposition

Answer. Option A. double replacement. This means that a radical or element from one compound is exchanged by the radical or element from other compound. It is the typical case of the general equation salt + salt -> salt + salt. This is an example: NaCl + KBr -> NaBr + KCl. In this example Br from NaBr replaced Cl from NaCl and Cl from NaCl replaced Br from KBr, that is why it is called double replacement.

1. o2(g)as a product