Question

________ reactions called the opposite of combination reactions.

Answer 1

Decomposition reactions are those in which a compound breaks down to form two or more substances. These reactions require a source of energy to proceed.

Thus, they are the exact opposite of combination reactions in which two or more substances combine to give a new substance with the release of energy.

Decomposition reaction : $AB+Energy\to A+B$

$2H_{2}O\left(l\right)\stackrel{Electrolysis}{\to }2H_2\left(g\right)+O_2\left(g\right)$

Combination Reaction : $A+B\to AB+Energy$.

$2H_2\left(g\right)+O_2\left(g\right)\to 2H_{2}O\left(l\right)+Energy$.

So, the correct answer is Decomposition.