Question

There is much overlapping of the classification schemes for reactions discussed in this chapter. Give an example of a reaction that is, at the same time,an oxidation-reduction reaction, a combustion reaction, and a synthesis reaction.

Short answer

The combustion of hydrogen gas (H₂) in the presence of oxygen (O₂) to form water (H₂O) is an example of a reaction that is simultaneously an oxidation-reduction, combustion, and synthesis reaction. The chemical equation for the reaction is: \[2H_{2} + O_{2} \rightarrow 2H_{2}O\]. In this reaction, electrons are transferred between reactants, heat and light energy are released, and two simple molecules combine to form a more complex compound.

Step-by-step solution

Understanding oxidation-reduction reactions

Oxidation-reduction reactions, also known as redox reactions, occur when electrons are transferred between reactants. They involve a change in oxidation states for at least two elements.

Understanding combustion reactions

Combustion reactions involve the reaction of a substance with oxygen, typically producing heat and light energy. These reactions often produce water and carbon dioxide as products, particularly when the reactant is a hydrocarbon.

Understanding synthesis reactions

Synthesis reactions occur when two or more reactants combine to form a single product. In other words, elements or simple compounds come together to form a more complex compound.

Finding a reaction that is oxidation-reduction, combustion, and synthesis

Now, let's find a suitable reaction that fits all three criteria. One example is the combustion of hydrogen gas (H₂) in the presence of oxygen (O₂) to form water (H₂O). Chemical equation: \[2H_{2} + O_{2} \rightarrow 2H_{2}O\] This is an example of: 1. Oxidation-reduction: Hydrogen's oxidation state increases from 0 to +1, and oxygen's oxidation state decreases from 0 to -2. Electrons are transferred between reactants, making it a redox reaction. 2. Combustion: Hydrogen gas reacts with oxygen to produce water with the release of heat and light energy, which is a typical characteristic of combustion reactions. 3. Synthesis: Two simple molecules, hydrogen (H₂) and oxygen (O₂), combine to form a more complex compound, water (H₂O). So, the reaction of hydrogen gas with oxygen to form water is an example of a reaction that is simultaneously an oxidation-reduction reaction, a combustion reaction, and a synthesis reaction.

Key concepts

Combustion Reactions

Combustion reactions are fascinating to study because they are both highly visible and impactful in our daily lives. Picture a campfire or the burning of gasoline in your car's engine; these are instances of combustion reactions where substances combine with oxygen, often exuding heat and light. If you witness a substance burning in air, often producing a flame, you are observing a combustion reaction.

For a reaction to be classified as combustion, it must involve oxygen as a reactant and typically generate water (H₂O) and carbon dioxide (CO₂) as products when organic compounds are ignited. However, combustion reactions are not limited to hydrocarbons; other types of reactants can also undergo combustion. For instance, the reaction between hydrogen gas (H₂) and oxygen (O₂), results in water, showcasing a clean combustion without carbon dioxide. It is vital to remember that combustion reactions are exothermic, releasing energy, which is why they are widely employed in energy generation systems.

Synthesis Reactions

Synthesis reactions differ from other chemical processes as they essentially stand for the building blocks of more complex substances. Imagine playing with building blocks where you start with individual pieces and assemble them to create an intricate structure. Similarly, in a synthesis reaction, two or more reactants bind together to form a single, more complicated product. This type of reaction is fundamental in the formation of many compounds we use in our everyday life, for example, the manufacturing of ammonia for fertilizers or the synthesis of water from hydrogen and oxygen.

One of the simplest illustrations of a synthesis reaction is when elemental hydrogen and oxygen gases combine under the right conditions to create water, expressed as \(2H_{2} + O_{2} \rightarrow 2H_{2}O\). This synthesis reaction is not only a great example of how complex molecules are formed from simpler ones but also doubles as a combustion and an oxidation-reduction reaction, thus demonstrating the cross-cutting nature of many chemical processes.

Chemical Equations

Understanding chemical equations is crucial for anyone who delves into the world of chemistry. Chemical equations are not just lines of symbols and numbers; they tell a story of how substances react and transform. They reflect reactants, products, and their proportions during chemical changes, working like a recipe explaining the ingredients and the outcome of a reaction.

Let's break down a simple yet comprehensive chemical equation – the formation of water from hydrogen and oxygen:\(2H_{2} + O_{2} \rightarrow 2H_{2}O\). This equation informs us that two molecules of hydrogen gas react with one molecule of oxygen gas to yield two molecules of water. The numbers before the chemical formulas are the coefficients; they convey the relative amounts of each reactant and product needed to balance the equation, abiding by the law of conservation of mass. Learning to read and write chemical equations empowers students to understand and predict the results of chemical reactions, a skill indispensable for further exploration in chemistry.