Problem 117 - Introductory Chemistry Atoms First

Question

Is the reaction \(\mathrm{LiOH}+\mathrm{HCN} \rightarrow \mathrm{H}_{2} \mathrm{O}+\mathrm{LiCN}\) a combination, decomposition, single-replacement, or double-replacement?

Step-by-Step Solution

Answer

The given reaction \(\mathrm{LiOH}+\mathrm{HCN} \rightarrow \mathrm{H}_{2}\mathrm{O}+\mathrm{LiCN}\) is a double-replacement reaction, as the cations and anions in the reactants exchange places to form H2O and LiCN.

Step 1: Identify the reactants and products

In the given chemical equation, the reactants are Lithium hydroxide (LiOH) and Hydrogen cyanide (HCN), and the products are Water (H2O) and Lithium cyanide (LiCN).

Step 2: Definitions of reaction types

Let's recall the definitions of the four possible reaction types: 1. Combination reaction: Two or more substances combine to form a single product. 2. Decomposition reaction: A single substance breaks down into two or more simpler substances. 3. Single-replacement reaction: One element in a compound is replaced by another element. 4. Double-replacement reaction: The cations and/or anions in two compounds are exchanged.

Step 3: Compare the given reaction with reaction types

Now, we can compare the reactants and products in the given reaction with these definitions: - It's not a combination reaction because there are two products instead of one. - It's not a decomposition reaction because there are two reactants instead of one. - It doesn't fit the single-replacement reaction because both elements in the reactants are replaced by each other. The given reaction fits the definition of a double-replacement reaction because the cations and anions in the reactants exchange places: Li from LiOH replaces H in HCN, and H from HCN replaces Li in LiOH. This results in the formation of H2O and LiCN.

Step 4: Conclusion

Therefore, the given reaction $$\mathrm{LiOH}+\mathrm{HCN} \rightarrow \mathrm{H}_{2}\mathrm{O}+\mathrm{LiCN}$$ is a double-replacement reaction.

Key Concepts

Chemical Reactions

Chemical reactions are processes where substances, known as reactants, are transformed into different substances called products. This transformation involves breaking and forming chemical bonds, which alters the arrangement of atoms.
In a chemical reaction, it's crucial to understand:

• The identity of the reactants and products
• The rearrangement of atoms and molecules
• Any energy changes that accompany the reaction

Identifying these elements helps define the type of reaction occurring. For instance, in the reaction \(\mathrm{LiOH} + \mathrm{HCN} \rightarrow \mathrm{H}_{2}\mathrm{O} + \mathrm{LiCN}\), we transform lithium hydroxide and hydrogen cyanide into water and lithium cyanide. A chemical reaction reorganizes these components, maintaining the conservation of mass and atoms.

Reaction Types

In chemistry, understanding different reaction types helps predict the outcomes of reactions and manage chemical processes effectively. The primary reaction types include:

• **Combination reactions:** Two or more substances unite to form a single product.
• **Decomposition reactions:** A single compound breaks down into two or more simpler products.
• **Single-replacement reactions:** An element in a compound is replaced by another element.
• **Double-replacement reactions:** The anions and cations of two different compounds exchange places, forming two new compounds.

In the double-replacement reaction, \(\mathrm{LiOH} + \mathrm{HCN} \rightarrow \mathrm{H}_{2}\mathrm{O} + \mathrm{LiCN}\), the lithium (Li) ions swap places with the hydrogen ions (H) from hydrogen cyanide. This results in new products—water and lithium cyanide—showing clear characteristics of a double-replacement reaction.
Analyzing reaction types allows chemists to forecast what new substances will form and understand the reactions' outcomes.

Reactants and Products

In any chemical equation, reactants and products are the two main components. Reactants are the starting substances that undergo change, while products are the result of this chemical transformation. Understanding these components is fundamental to analyzing any chemical equation.
For the reaction \(\mathrm{LiOH} + \mathrm{HCN} \rightarrow \mathrm{H}_{2}\mathrm{O} + \mathrm{LiCN}\), the reactants involved are lithium hydroxide (LiOH) and hydrogen cyanide (HCN). The products formed from this reaction are water (H₂O) and lithium cyanide (LiCN).

• Reactants: Initial substances in a reaction
• Products: New substances formed in the reaction

During the reaction, chemical bonds in the reactants are broken, and new bonds form to create the products, showcasing the dynamic nature of chemical changes. The transformation is often represented as a balanced equation, ensuring the number of atoms for each element is conserved from reactants to products.