Problem 55 - Chemistry Matter and Change

Question

In terms of ion concentrations, distinguish between acidic, neutral, and basic solutions.

Step-by-Step Solution

Answer

Acidic solutions have more 14{H^+}15 ions, neutral solutions have equal 14{H^+}15 and 14{OH^-}15 ions, and basic solutions have more 14{OH^-}15 ions.

Step 1: Understanding Acids

Acids are substances that increase the concentration of hydrogen ions (14{H^+}15) when dissolved in water. This means that an acidic solution will have a higher concentration of 14{H^+}15 ions than hydroxide ions (14{OH^-}15). The pH of an acidic solution is less than 7.

Step 2: Understanding Neutral Solutions

In a neutral solution, the concentration of hydrogen ions (14{H^+}15) equals the concentration of hydroxide ions (14{OH^-}15). This results in a pH of exactly 7, which is the case in pure water where neither 14{H^+}15 nor 14{OH^-}15 ions predominate.

Step 3: Understanding Bases

Bases are substances that decrease the concentration of hydrogen ions (14{H^+}15) by increasing the concentration of hydroxide ions (14{OH^-}15) in a solution. Thus, in a basic solution, 14{OH^-}15 ion concentration is higher than 14{H^+}15 ion concentration, resulting in a pH greater than 7.

Key Concepts

pH scale

In the realm of acid-base chemistry, the pH scale is an essential tool used to measure the acidity or basicity of a solution. The pH scale ranges from 0 to 14 and is a logarithmic scale, which means each whole number pH change represents a tenfold change in hydrogen ion concentration.

• A pH less than 7 indicates that the solution is acidic.
• A pH of exactly 7 describes a neutral solution.
• A pH greater than 7 shows that the solution is basic (or alkaline).

For instance, pH 6 is ten times more acidic than pH 7, while pH 8 is ten times more alkaline than pH 7. Understanding the role of the pH scale helps in identifying how much H+ or OH- ions prevail within a given solution, thereby indicating whether it is acidic, neutral, or basic.

hydrogen ions (H+)

Hydrogen ions, abbreviated as H+, play a crucial role in determining the acidity of a solution. These ions form when an acid dissolves in water, releasing H+ ions into the solution. The more hydrogen ions present, the more acidic the solution becomes.
Moreover, the concentration of H+ ions is inversely related to the pH value. As the concentration of hydrogen ions increases, the pH decreases, indicating increasing acidity.
To put it simply:

• A high concentration of H+ ions usually means an acidic solution with a low pH (below 7).
• Conversely, a lower concentration of H+ ions leads to a higher pH, identifying either a neutral or basic solution.

Understanding the concentration of hydrogen ions in a solution is key to determining its acidic nature.

hydroxide ions (OH-)

Hydroxide ions, denoted as OH-, are fundamental to the basicity of a solution. When a base dissolves in water, it either releases hydroxide ions directly or increases their concentration.
The presence of a large number of OH- ions signifies a solution's basic nature. The concentration of OH- ions directly corresponds to the pH level, with higher concentrations leading to higher pH values.
Key points include:

• An abundance of OH- ions results in a basic (or alkaline) solution, which has a pH greater than 7.
• Fewer OH- ions imply a less basic and perhaps even acidic solution entirely based on H+ concentration.

Understanding hydroxide ions' role helps in identifying the basicity of a solution and thus its place on the pH scale.

neutral solutions

Neutral solutions are perfectly balanced in terms of ion concentration. This means that in a neutral solution, the concentration of hydrogen ions (H+) is equal to the concentration of hydroxide ions (OH-).
For a solution to maintain neutrality, it must have a pH of 7, like pure water. In such solutions, neither H+ nor OH- ions predominate enough to alter the equilibrium visibly.
Key aspects of neutral solutions include:

• The state of equilibrium in neutral solutions is where there is no net charge due to ion concentrations.
• A neutral pH of 7 is crucial for many natural and biological processes where balanced condition is necessary.

By understanding neutral solutions, you can grasp how equilibrium state is crucial for various chemical reactions and processes in nature.