Question

Using squares to represent atoms of one element (or cations) and circles to represent the atoms of the other element (or anions), represent the principal species in the following pictorially. (You may represent the hydroxide anion as a single circle.) (a) a solution of \(\mathrm{HCl}\) (b) a solution of HF (c) a solution of \(\mathrm{KOH}\) (d) a solution of \(\mathrm{HNO}_{2}\)

Short answer

Question: Represent the principal species in each of the following solutions using squares for one element or cation and circles for the other element or anion: a) HCl, b) HF, c) KOH, d) HNO₂. Answer: a) HCl solution: (□)(∘), b) HF solution: (□F)(∘), c) KOH solution: (□)(∘), d) HNO₂ solution: (□NO₂)(∘)

Step-by-step solution

Identify the principal species in HCl solution

In a solution of HCl, it dissociates into H⁺ (cation) and Cl⁻ (anion). So, the principal species are H⁺ and Cl⁻.

Represent the principal species using symbols

We will use squares to represent H⁺ (cation), and circles to represent Cl⁻ (anion). HCl solution: (□)(∘) #b) Representing a solution of HF#

Identify the principal species in HF solution

In a solution of HF, it weakly dissociates into H⁺ (cation) and F⁻ (anion). The principal species are HF, H⁺, and F⁻.

Represent the principal species using symbols

We will use squares to represent H⁺ (cation), and circles to represent F⁻ (anion). HF solution: (□F)(∘) #c) Representing a solution of KOH#

Identify the principal species in KOH solution

In a solution of KOH, it dissociates into K⁺(cation) and OH⁻ (anion). The principal species are K⁺ and OH⁻.

Represent the principal species using symbols

We will use squares to represent K⁺(cation), and circles to represent OH⁻ (anion). KOH solution: (□)(∘) #d) Representing a solution of HNO₂#

Identify the principal species in HNO₂ solution

In a solution of HNO₂, it weakly dissociates into H⁺ (cation) and NO₂⁻ (anion). The principal species are HNO₂, H⁺, and NO₂⁻.

Represent the principal species using symbols

We will use squares to represent H⁺ (cation), and circles to represent NO₂⁻ (anion). HNO₂ solution: (□NO₂)(∘)

Key concepts

Cations and Anions

Understanding cations and anions is key to grasping chemical solutions. Cations are positively charged ions. They form when an atom or molecule loses electrons. Common examples include hydrogen ion (H⁺) and potassium ion (K⁺). Both have lost electrons, making them positive.
Anions, on the other hand, gain electrons, creating negative charges. Chloride (Cl⁻), fluoride (F⁻), and hydroxide (OH⁻) are examples. In solutions, these ions attract each other because positive and negative charges attract.
Representing cations and anions pictorially helps in visualizing chemical interactions. For instance, squares might represent cations and circles for anions in diagrams. This visualization makes it easier to understand chemical reactions and interactions in solutions.

Dissociation in Solution

Dissociation in solution is a crucial concept for understanding how substances interact in water. When an ionic compound dissolves in water, it splits into its constituent ions. This process is known as dissociation.
For example, hydrochloric acid ( HCl) dissociates completely in water, producing H⁺ and Cl⁻ ions. This strong dissociation makes HCl a strong acid. Similarly, potassium hydroxide (KOH) dissociates into K⁺ and OH⁻ ions, classifying it as a strong base.
Some compounds, like hydrofluoric acid (HF) and nitrous acid (HNO₂), dissociate weakly. This means not all the molecules break apart into ions. HF and HNO₂ solutions contain a significant amount of undissociated molecules along with some ions. This weak dissociation is important for understanding their behavior as weak electrolytes.

Representation of Chemical Species

Representing chemical species makes it easier to understand chemical solutions. Using symbols like squares and circles can simplify complex interactions. A typical representation uses squares for cations and circles for anions.
In a solution of HCl, it fully dissociates to form H⁺ (represented as a square) and Cl⁻ (a circle). This shows how HCl acts as a strong acid. In HF, the weak dissociation is illustrated by showing both HF molecules and its ions (H⁺ and F⁻) through a combination of square and circle symbols.
Representation is not only useful for visual learning but also helps in predicting the outcomes of reactions. By visualizing the species present in a solution, we gain a deeper understanding of chemical behavior. Accurate representation guides chemists in experimentation and application in various chemical processes.