Synthesis Reaction: Definition, Formula & Examples

What is a Synthesis Reaction?

A cronut and crookie, two very hilarious food terms, they surely took the world by storm when making their grand debut. Did you know those are great examples of products made from a synthesis reaction? It may seem odd to mix a food term with a science term but it is definitely true. Before we discuss how this is so, let's go over what a synthesis reaction is.

A synthesis reaction is the joining together of two reactants, or compounds, to produce a complex product, also called a compound. Sometimes synthesis reactions can result in the formation of more than one product, as we'll see shortly with the process of photosynthesis.

Whether it is one complex product or multiple products, a great way to remember what a synthesis reaction is, is to think of the word 'combination.' Essentially, you are combining reactants to make a desired product. The formula for a synthesis reaction, involving the formation of a complex product, is shown here in Diagram 1. As you can see, substance D combines with substance R to produce a more complex compound, labeled DR.

Diagram 1: Formula for a synthesis reaction

As you can gather from the equation shown in Diagram 1, a synthesis reaction is not a multi-step process. That is, there is no need to be concerned with learning multiple steps for this reaction. In fact, a synthesis reaction is perhaps one of the most widely used reactions; not just in chemistry, but also in unconventional places, such as our kitchens.

Before we practice a few examples, there are two concepts to keep in mind regarding synthesis reactions. First, binary compounds can be produced from a synthesis reaction. A binary compound is a compound that contains only two different elements. For example, the combination of two reactants, iron and oxygen, will produce the binary compound iron oxide, commonly known as rust.

Second, always remember when working with synthesis reactions to balance your equation. As you will see shortly, coefficients, for example numbers, are sometimes required to ensure what is present on the left side of a reaction is equal in amount to what is present on the right side of a reaction. Now that we have addressed these two fundamental concepts, let's apply what we've learned to a few examples.

Examples

Example 1: You are working diligently in a scientific laboratory and decide to mix a solution containing lithium with another solution containing chlorine. What do you predict will be produced from the mixture of these solutions?

Elements under question: lithium (Li) and chlorine (Cl2)

Synthesis equation:

Balanced synthesis equation:

From this synthesis reaction, we can see that 2 molecules of lithium chloride (LiCl2) are produced. Because two molecules of chlorine (Cl2) are present as a reactant, this needs to be balanced for the product LiCl (where only one chlorine atom is present). The addition of a coefficient of 2 (in front of LiCl) will ensure all chlorine atoms, on both the reactant and product side, are balanced. However, we cannot stop right there with balancing. A coefficient of 2 must be added to the lithium atom on the reactant side, to ensure all lithium atoms (on both sides of the reaction) are balanced.

Example 2: The process of photosynthesis involves the use of a synthesis reaction. What is produced when carbon dioxide reacts with water during photosynthesis?

Elements under question: carbon dioxide (CO2) and water (H2O)

Synthesis equation (balanced):

This synthesis reaction resulted in the formation of glucose (C6H12O6) and oxygen (O2). Do you recognize the difference between the products formed from this example and the first example? Two products were formed from this synthesis reaction. Although it's fairly common to see a single complex compound formed, the ability to form more than one compound is certainly possible.

Cronuts And Crookies

We couldn't end this lesson without talking about the relationship between two foods and a chemical reaction. Now that we know what a synthesis reaction is, it makes sense why a cronut and a crookie are products of a synthesis reaction. But first, what is a cronut and crookie composed of? Great question! A cronut is produced from the combination of a croissant and a doughnut. A crookie is the result of the combination of a croissant with a cookie.

Do you see something similar between both definitions? The word 'combination' appears in both definitions. Recall that combination is a great way to define what synthesis reactions are. Thus, the makers of the cronut and crookie (although not possibly aware) used a synthesis reaction during the development phase of these treats.

Lesson Summary

Let's review. Synthesis reactions are very common in both everyday living and chemistry. A synthesis reaction is the process of joining two substances together to form one complex compound. This reaction is commonly referred to as a combination. The equations for synthesis reactions must always be checked for proper balancing. The number of molecules on both sides of the equation must be equal. Sometimes more than two products can be made from a synthesis reaction.

Binary compounds can also be produced from a synthesis reaction. These compounds are composed of exactly two different elements. Unconventional products made from synthesis reactions include cronuts and crookies.

Synthesis Reaction Key Terms & Examples

Natural synthesis reaction

• Synthesis Reaction: an action which takes place by the combining of two different reactants
• Binary Compounds: created by the combination of only two different elements
• Photosynthesis: reacts to the process of carbon dioxide combining with water
• Iron Oxide: the combination (synthesis reaction) of two elements (iron & oxygen) to create rust

Learning Outcomes

When you've watched and studied the lesson on synthesis reaction in its entirety, find out whether you can:

• Define synthesis reaction as the combination of two reactants
• Illustrate the way in which binary compounds combine only two elements
• Model the process of balancing the equation of a chemical synthesis reaction
• Understand the importance of combinations to synthesis reactions