Question

Allen is carrying out reactions in a lab. One of the products in all reactions is found to be either a precipitate, a gas, or water. What is common between all these reactions?

Answer 1

All decomposition reactions.
Hope this helps!(:

Answer 2

Decomposition reaction.

Step-by-step explanation:

There is formation of a precipitate or evolution of gas or formation of water generally during decomposition reactions.

They involve breaking of a compound into two or more new compounds or one or more element.

Example:

Decomposition of calcium carbonate.

`CaCO_(3)--->CaO(s)+CO_(2)(g)`

`H_(2)SO_(3)--->H_(2)O+SO_(2)(g)`