Question

What is the pOH range for a basic solution?

Short answer

The pOH range for a basic solution is less than 7.

Step-by-step solution

Understanding the pOH Scale

The pOH scale measures the hydroxide ion concentration in a solution, similar to how the pH scale measures the hydrogen ion concentration. The pOH scale ranges from 0 to 14, where lower values indicate higher hydroxide ion concentration (more basic) and higher values indicate lower hydroxide ion concentration (less basic or more acidic).

Defining a Basic Solution

A basic solution is any solution with a pH greater than 7. In terms of the pOH scale, this corresponds to a pOH less than 7 because pH and pOH are related by the equation: \[ \text{pH} + \text{pOH} = 14 \] This means as pH increases above 7, pOH must decrease below 7.

Determining the Basic Range for pOH

Since basic solutions have a pH greater than 7, their corresponding pOH values will be less than 7 due to the relation \[ \text{pH} + \text{pOH} = 14 \] . Hence, the pOH range for a basic solution is any value less than 7.

Key concepts

pH Scale

The pH scale is a measurement used to determine the acidity or basicity of a solution. Ranging from 0 to 14, it indicates the concentration of hydrogen ions (\[ [H^+] \]) in the solution. A pH value of 7 is considered neutral, meaning the solution has an equal concentration of hydrogen and hydroxide ions.

• Values lower than 7 indicate acidic solutions, with higher hydrogen ion concentrations.
• Values higher than 7 indicate basic solutions, where hydroxide ions are more concentrated.

The formula used to calculate pH is:\[ \text{pH} = -\log_{10} [H^+] \]This logarithmic scale means that each unit change represents a tenfold change in hydrogen ion concentration.

pOH Scale

Much like the pH scale, the pOH scale is used to measure the concentration of hydroxide ions (\[ [OH^-] \]) in a solution. It also ranges from 0 to 14, but operates opposite to the pH scale.

• Lower pOH values (below 7) indicate basic solutions with higher hydroxide ion concentrations.
• Higher pOH values (above 7) indicate acidic solutions with lower hydroxide ion concentrations.

The relationship between pH and pOH is crucial and is given by the equation:\[ \text{pH} + \text{pOH} = 14 \]This equation helps to find the pOH when the pH of a solution is known and vice versa.

Hydroxide Ion Concentration

The concentration of hydroxide ions in a solution plays a crucial role in determining whether a solution is acidic or basic. It is closely linked to the pOH scale:

• High hydroxide ion concentration corresponds to low pOH values, indicating a basic solution.
• Low hydroxide ion concentration corresponds to high pOH values, indicating an acidic solution.

The concentration of hydroxide ions can be calculated from pOH using the formula:\[ [OH^-] = 10^{-\text{pOH}} \]This equation provides a direct way to determine hydroxide ion concentration from the pOH value of the solution.

Acidic vs. Basic Solutions

Understanding the difference between acidic and basic solutions is fundamental in chemistry:

• Acidic solutions have a pH less than 7, high hydrogen ion concentration, and are characterized by a pOH greater than 7.
• Basic solutions have a pH greater than 7, high hydroxide ion concentration, and are characterized by a pOH less than 7.

These properties are essential in various chemical processes and reactions. Acidity and basicity affect the behavior of substances in a solution, influencing reactions they undergo and their applications. The interplay between \( ext{pH} \) and \( ext{pOH} \) guides the preparation and use of numerous chemical solutions in everyday life. It highlights why solutions that are more basic have lower pOH values.