Question

There are four basic types of chemical reactions, as shown in the table below. $$ \begin{array}{|c|c|} \hline \text { Reaction Type } & \text { General Example } \\ \hline \text { Combination } & \mathrm{A}+\mathrm{B} \rightarrow \mathrm{C} \\\ \hline \text { Decomposition } & \mathrm{C} \rightarrow \mathrm{A}+\mathrm{B} \\\ \hline \text { Single displacement } & \mathrm{A}+\mathrm{BC} \rightarrow \mathrm{B}+\mathrm{AC} \\ \hline \text { Double displacement } & \mathrm{AB}+\mathrm{CD} \rightarrow \mathrm{AC}+\mathrm{BD} \end{array} $$ The balanced chemical equation describing the reaction between hydrogen and fluorine is shown below. $$ \mathrm{H}_2+\mathrm{F}_2 \rightarrow 2 \mathrm{HF} $$ Which of the four basic types of chemical reactions is this? A. combination B. decomposition C. single displacement D. double displacement

Short answer

A. combination

Step-by-step solution

Identify the reactants and products

First, we need to identify the reactants and products in the given reaction. In this case, our reactants are hydrogen gas (\(\mathrm{H}_{2}\)) and fluorine gas (\(\mathrm{F}_{2}\)), and the product is hydrogen fluoride (\(2 \mathrm{HF}\)).

Compare the given reaction to the general examples

Now, we will compare the given reaction to the general examples of the four basic types of chemical reactions to determine which one it best fits. - Combination: A + B → C - Decomposition: C → A + B - Single displacement: A + BC → B + AC - Double displacement: AB + CD → AC + BD

Determine the reaction type

Comparing the given reaction (\(\mathrm{H}_{2}+\mathrm{F}_{2} \rightarrow 2 \mathrm{HF}\)) to the general examples, we can see that it matches the combination reaction type. In a combination reaction, two reactants come together to form a single product. In this case, hydrogen gas (\(\mathrm{H}_{2}\)) and fluorine gas (\(\mathrm{F}_{2}\)) combine to produce hydrogen fluoride (\(2 \mathrm{HF}\)), making this a combination reaction. The correct answer is A. combination.

Key concepts

Combination Reaction

A combination reaction is a type of chemical process where two or more reactants unite to form a single new product. Imagine combining different ingredients to bake a cake; once they mix, you can no longer see the individual components, just like in a combination reaction.
For example, when hydrogen gas \(\mathrm{H}_2\) reacts with fluorine gas \(\mathrm{F}_2\), they combine to form hydrogen fluoride \(2\mathrm{HF}\). Here, both reactants are gases that produce a singular compound, hydrogen fluoride, demonstrating how two elements or compounds produce one distinct product.
Combination reactions are also known as synthesis reactions. These reactions are fundamental in chemistry because they often correspond to the formation of complex compounds from simpler substances.

• Simple example: Combining element A with element B to get compound C (\(\mathrm{A} + \mathrm{B} \rightarrow \mathrm{C}\)).
• Significance: These reactions are crucial in chemical manufacturing processes, like creating fertilizers, plastics, and medicines.

Decomposition Reaction

In decomposition reactions, a complex compound breaks down into two or more simpler substances. It’s quite the opposite of combination reactions. Think of it as breaking a Lego house back into individual blocks.
Using a simple analogy, if you start with a whole compound (like a big Lego structure), a decomposition reaction takes it apart, returning to its original components. For chemical reactions, this means breaking down one large molecule into smaller, more basic units.
For example, when you heat calcium carbonate \(\mathrm{CaCO}_3\), it breaks down into calcium oxide \(\mathrm{CaO}\) and carbon dioxide \(\mathrm{CO}_2\). This reaction highlights how one compound can split into simpler materials:

• Essential Example: \(\mathrm{C} \rightarrow \mathrm{A} + \mathrm{B}\).
• Real-life application: Commonly found in processes like electrolysis or the breakdown of organic matter.

Displacement Reactions

Displacement reactions are a fascinating category where one element displaces another in a compound, essentially taking its place. There are two types to consider: single displacement and double displacement reactions. Each changes the partners in a chemical dance, much like switching partners during a dance session.
In a single displacement reaction, one element takes the place of another in a compound, such as when metal A displaces metal B from a compound BC: \(\mathrm{A} + \mathrm{BC} \rightarrow \mathrm{AC} + \mathrm{B}\).
Double displacement reactions involve an exchange of partners between two reacting compounds. For example, in the reaction of silver nitrate \(\mathrm{AgNO}_3\) with hydrochloric acid \(\mathrm{HCl}\), silver chloride \(\mathrm{AgCl}\) and nitric acid \(\mathrm{HNO}_3\) form, reflecting two elements switching places: \(\mathrm{AB} + \mathrm{CD} \rightarrow \mathrm{AC} + \mathrm{BD}\).

• Single Displacement: More active metals displace less active metals from their compounds.
• Double Displacement: Ions in two compounds exchange places to form two new compounds.

Identifying Reaction Types

Identifying the type of chemical reaction is essential in understanding how substances interact at the molecular level. It’s like solving a puzzle where each clue fits into distinct categories. When analyzing a reaction, compare it against four main types: combination, decomposition, single displacement, and double displacement.
Here’s a simple approach:

• Combination: Look for the merger of two or more reactants forming a single product.
• Decomposition: Spot a singular compound breaking down into simpler elements or compounds.
• Single Displacement: Observe one element replacing another in a compound.
• Double Displacement: Notice the exchange of components between two compounds leading to two new combinations.

Each reaction type tells a different story of elemental interactions, reflecting different scientific principles. By identifying the reaction type, you gain deeper insight into the processes occurring, which can be crucial for lab work, chemical industry applications, and academic studies.