Synthesis Reactions

In a synthesis reaction, two elements form one compound.

Chemists should always use an ion chart when predicting products of reactions because the compound formed must always be neutral.  Always "criss-cross" the charges of the ions when you write the chemical formula of the product.

Examples:  

1.  K_(s) +  Cl_2(g)  ---> 

• First, identify the reaction as "synthesis."   Element + Element --->  Compound

• Write the reactants and products in words.

                       Potassium + Chlorine ---> Potassium Chloride

• Write the correct formula of the product by checking the ion chart:

                        Potassium Chloride = KCl

• Write the equation fully using chemical symbols.

K + Cl₂  -->  KCl

• Balance the equation by adding coefficients.

2K  +  Cl₂  ---> 2KCl

2.  Al_(s) + O_2(g) ---> 

• First, identify the reaction as "synthesis."   Element + Element --->  Compound

• Write the reactants and products in words.

                       Aluminum + Oxygen ---> Aluminum Oxide

• Write the correct formula of the product by checking the ion chart.  Remember to criss-cross the ion charges so that the compound formula is correct!

                        Aluminum Oxide=  Al₂O₃

• Write the equation fully using chemical symbols.

                       Al + O₂  --->  Al₂O₃

• Balance the equation by adding coefficients.

                        4Al + 3O₂  ---> 2Al₂O₃