Question

Explain the difference between a synthesis reaction and a decomposition reaction. (p. 27)

Short answer

Short Answer Question: Define synthesis and decomposition reactions and provide one example of each type of reaction. Short Answer: Synthesis reactions, also known as combination reactions, involve the combination of two or more simple substances to form a single, more complex product, typically requiring energy in the form of heat or light. An example of a synthesis reaction is 2H₂(g) + O₂(g) → 2H₂O(l), where hydrogen and oxygen combine to form water. Decomposition reactions, also known as analysis reactions, involve the breakdown of a single compound into simpler substances, usually under the influence of heat, light, or other external factors. An example of a decomposition reaction is CaCO₃(s) → CaO(s) + CO₂(g), where calcium carbonate decomposes into calcium oxide and carbon dioxide when heated.

Step-by-step solution

Define a Synthesis Reaction

A synthesis reaction, also known as a combination reaction, is a type of chemical reaction in which two or more simple substances (elements or compounds) combine to form a single, more complex product. In a synthesis reaction, energy in the form of heat or light is usually needed to facilitate the combination of the reactants.

Provide an example of a Synthesis Reaction

An example of a synthesis reaction is the formation of water from hydrogen and oxygen: 2H_2(g) + O_2(g) → 2H_2O(l) In this reaction, two molecules of hydrogen gas (H_2) react with one molecule of oxygen gas (O_2) to produce two molecules of water (H_2O).

Define a Decomposition Reaction

A decomposition reaction, also known as an analysis reaction, is a type of chemical reaction in which a single compound breaks down into simpler substances (elements or other compounds) under the influence of heat, light or other external factors. This is essentially the opposite process of a synthesis reaction.

Provide an example of a Decomposition Reaction

An example of a decomposition reaction is the breakdown of calcium carbonate to calcium oxide and carbon dioxide: CaCO_3(s) → CaO(s) + CO_2(g) In this reaction, calcium carbonate (CaCO_3), upon heating, decomposes into calcium oxide (CaO) and carbon dioxide gas (CO_2).

Key concepts

Synthesis Reaction

Imagine building blocks coming together to create a complex structure. That's what a synthesis reaction in chemistry is like. It's where multiple reactants, which can be elements or compounds, combine to form a single product. This process often requires an input of energy, such as heat or light, to get going.

For instance, the simple gases hydrogen (H_2) and oxygen (O_2) can engage in a synthesis reaction to create water (H_2O), a compound essential to life. Here's a quick breakdown:

• Reactants: 2H_2(g) + O_2(g)
• Product: 2H_2O(l)

This change from simpler substances to a more complicated one demonstrates the principle of a synthesis reaction.

Decomposition Reaction

Where a synthesis reaction builds up, a decomposition reaction breaks down. It's similar to demolishing a wall into individual bricks. In this reaction, a single compound decomposes into two or more simpler substances. These reactions can be initiated by various factors such as heat, light, or an electrical current.

For example, calcium carbonate (CaCO_3), when heated, undergoes a decomposition reaction to form calcium oxide (CaO) and carbon dioxide (CO_2), as follows:

• Reactant: CaCO_3(s)
• Products: CaO(s) + CO_2(g)

The breakdown showcases how a decomposition reaction simplifies compounds into their constituent parts.

Chemical Reaction Examples

Chemical reactions are all around us, from the baking of bread to the rusting of iron. To better understand the variety of chemical reactions, let's look at a few more examples:

• Combustion: C_3H_8(g) + 5O_2(g) → 3CO_2(g) + 4H_2O(g) - Propane burns in oxygen to form carbon dioxide and water vapor.
• Acid-Base Neutralization: HCl(aq) + NaOH(aq) → NaCl(aq) + H_2O(l) - Hydrochloric acid reacts with sodium hydroxide to produce saltwater.

Each example shows a different type of chemical change, illustrating the diverse reactions substances can undergo.

Reactants and Products

In the world of chemistry, every reaction involves a transformation. The substances that start the reaction are known as reactants, and what they make are called products. You can think of reactants as the ingredients of a recipe, while the finished dish is the product.

During a reaction, the reactants undergo a chemical change to form the products. This change is typically shown in a chemical equation, which balances the amount of each substance to obey the Law of Conservation of Mass. Here's a general representation:

• Reactants → Products

Remember, although the form and arrangement of atoms change, no atoms are lost or gained in a chemical reaction. They're simply rearranged to form new substances.