To identify which equation is an example of a synthesis reaction, let's first define what a synthesis reaction is. In a synthesis reaction, two or more simple substances combine to form a more complex product. The general form is A + B → AB.
Now, let's analyze each of the given options:
A. [tex]\(CH_4 + 2 O_2 \rightarrow 2 H_2O + CO_2\)[/tex]
This equation represents the combustion of methane where methane and oxygen react to produce water and carbon dioxide. This is a combustion reaction, not a synthesis reaction.
B. [tex]\(HNO_3 + KOH \rightarrow KCl + H_2O\)[/tex]
This equation is a neutralization reaction where an acid (HNO_3) reacts with a base (KOH) to produce a salt (KCl) and water (H_2O). This is not a synthesis reaction.
C. [tex]\(2 Li + CaCl_2 \rightarrow 2 LiCl + Ca\)[/tex]
Here, lithium reacts with calcium chloride to produce lithium chloride and calcium. This is a single replacement (or displacement) reaction, not a synthesis reaction.
D. [tex]\(S + O_2 \rightarrow SO_2\)[/tex]
In this equation, sulfur (S) combines with oxygen (O_2) to form sulfur dioxide (SO_2), which is a single compound. This fits the criteria for a synthesis reaction, as two simple substances are combining to form a more complex product.
Therefore, the correct answer is:
D. [tex]\(S + O_2 \rightarrow SO_2\)[/tex]
