Question

Calculate the pH corresponding to each of the pOH values listed, and indicate whether each solution is acidic, basic, or neutral. a. \(\mathrm{pOH}=4.32\) b. \(\mathrm{pOH}=8.90\) c. \(\mathrm{pOH}=1.81\) d. \(\mathrm{pOH}=13.1\)

Short answer

a. pH = 9.68 which corresponds to a basic solution. b. pH = 5.10 which corresponds to an acidic solution. c. pH = 12.19 which corresponds to a basic solution. d. pH = 0.9 which corresponds to an acidic solution.

Step-by-step solution

a. Calculate pH for pOH = 4.32

Using the relationship between pH and pOH, we can calculate the pH as follows: \(pH + pOH = 14\) \(pH = 14 - pOH\) \(pH = 14 - 4.32\) \(pH = 9.68\) The pH value is greater than 7, so the solution is basic.

b. Calculate pH for pOH = 8.90

Using the relationship between pH and pOH, we can calculate the pH as follows: \(pH + pOH = 14\) \(pH = 14 - pOH\) \(pH = 14 - 8.90\) \(pH = 5.10\) The pH value is less than 7, so the solution is acidic.

c. Calculate pH for pOH = 1.81

Using the relationship between pH and pOH, we can calculate the pH as follows: \(pH + pOH = 14\) \(pH = 14 - pOH\) \(pH = 14 - 1.81\) \(pH = 12.19\) The pH value is greater than 7, so the solution is basic.

d. Calculate pH for pOH = 13.1

Using the relationship between pH and pOH, we can calculate the pH as follows: \(pH + pOH = 14\) \(pH = 14 - pOH\) \(pH = 14 - 13.1\) \(pH = 0.9\) The pH value is less than 7, so the solution is acidic.

Key concepts

Understanding Acidic Solutions

An acidic solution is characterized by having a pH value of less than 7. When a solution is acidic, it means that it has a higher concentration of hydrogen ions (H⁺) compared to hydroxide ions (OH⁻). Acids can donate H⁺ ions to the solution, leading to the lower pH value. Common examples include lemon juice and vinegar.
An important thing to note is that the more acidic a solution is, the lower its pH value. For example, in the exercise given, when

• pOH = 8.90, the calculated pH is 5.10 making it acidic.
• pOH = 13.1, the calculated pH is 0.9 indicating a highly acidic solution.

Both examples have a pH less than 7, thereby categorizing them as acidic solutions.

Exploring Basic Solutions

Basic solutions, also known as alkaline solutions, have a pH value greater than 7. These solutions have a higher concentration of hydroxide ions (OH⁻) compared to hydrogen ions (H⁺). Bases can accept H⁺ ions or donate OH⁻ ions which increases the pH level. Examples of basic substances include baking soda and soapy water.
In the exercise provided, we can identify basic solutions by calculating their pH:

• pOH = 4.32 leads to a pH of 9.68, which is basic.
• pOH = 1.81 results in a pH of 12.19, also a basic solution.

Both pH values are greater than 7, which confirms their basic nature. Generally, the higher the pH, the more basic the solution.

Deciphering pOH Values

The pOH value is an important measure used to determine the alkalinity of a solution. pOH measures the concentration of hydroxide ions (OH⁻) in a solution and is used on the same scale as pH.
Here's the relationship:

• pH + pOH = 14
• This formula helps you convert between pOH and pH.

The lower the pOH, the more basic the solution. Conversely, a higher pOH indicates acidity, corelating inversely with the pH scale.
Understanding pOH is just as crucial as understanding pH, as it offers a complete picture of both acidity and alkalinity in a solution. For example, if the pOH is 1.81, the solution is basic as the pH turns out to be 12.19. Similarly, when pOH is 13.1, the pH is 0.9, indicating a highly acidic solution.