Synthesis reactions

Synthesis reactions are reactions in which 2 or more reactants join together in a single product.

Recognizing synthesis reactions

Synthesis reactions are easy to spot if you are given both sides of the reaction (reactants and products) – quite simply, there is only one product. That means, of course, one compound, not that the coefficient is one.So, both of these reactions are synthesis reactions:

Although there are many different synthesis reactions, you will only be able to predict the products (at least at this point in your chemistry career) if the reactants are elements. So, a reaction in which the only reactants are elements, must be a synthesis reaction.

Completing synthesis reactions

Simple synthesis reactions (the only ones you'll be completing at this point) combine two elements into a single ionic compound.

For example, the reaction between aluminum and chlorine makes aluminum chloride.

Of course, we need to make sure that the formulas are written correctly. So, since aluminum has a charge of +3 and chloride has a charge of -1, the product will be AlCl3.

Now, balancing will leave us with the finished reaction:

In those cases where the metal has more than one possible charge

the metal will end up with the most common charge (+2 for copper). Given the -3 charge for phosphide, the reaction will be written

and balanced