Which of the following combinations of reactants will result in a synthesis reaction? A. Li + HCl B. Al + O2 C. Ca + H2O D. F2 + HCl

The answer is B. Al + O2.

In a synthetic reaction, two (or more) compounds combine and form one complex product. It can be expressed as:

A + B → AB

So, let's go through all of the reactions:

A. 2Li + 2HCl → 2LiCl + H₂

B. 4Al + 3O₂ → 2Al₂O₃

C. Ca + 2H₂O → Ca (OH) ₂ + H₂

D. F₂ + 2HCl → 2HF + Cl₂

So, in all of these reactions, there are two products except in the choice B, where only one product. So, the example of synthesis reaction is: 4Al + 3O₂ → 2Al₂O₃.