Which of the following combinations of reactants will result in a synthesis reaction?

Cl2 + BaF2

Mg + HClO3

Li + H2O

SO2 + H2O

Correct Answer: Option D i. e. SO2 + H2O

Reason:

A synthesis reaction occurs when two or more reactants combine to form a single product. This reaction can be represented as A + B → AB.

In the present case, SO2 + H2O → H2SO3

Hence, it is an example of synthesis reaction.

The first reaction from the scale Cl2 + BaF2 is decomposition, remember! that H20 should be broken down.

The third one is metal ion substitution

The last one is decomposition again.

The second one is H2 + Cl2 has been combined in order to synthesize 2HCl, so that's the answer.