The pOH of a solution is 6.0. Which statement is correct? Use [tex]$pOH =-\log \left[ OH ^{-}\right]$[/tex] and [tex]$pH + pOH =14$[/tex].
A. The pH of the solution is 20.0.
B. The concentration of [tex]$OH ^{-}$[/tex] ions is [tex]$1.0 \times 10^{-8} M$[/tex].
C. The concentration of [tex]$OH ^{-}$[/tex] ions is [tex]$1.0 \times 10^6 M$[/tex].
D. The pH of the solution is 8.0.
Answer (1)
Calculate the pH using the formula p H + pO H = 14 , which gives p H = 14 − 6.0 = 8.0 .
Calculate the hydroxide ion concentration using the formula [ O H − ] = 1 0 − pO H , which gives [ O H − ] = 1 0 − 6 M .
Compare the calculated values with the given statements.
The correct statement is that the pH of the solution is 8.0 .
Explanation
Problem Analysis We are given that the pOH of a solution is 6.0. We need to determine which of the given statements is correct using the formulas pO H = − lo g [ O H − ] and p H + pO H = 14 .
Calculating pH First, let's calculate the pH of the solution using the formula p H + pO H = 14 . Substituting the given pOH value, we get: p H + 6.0 = 14
pH Value Solving for pH, we have: p H = 14 − 6.0 = 8.0
Calculating Hydroxide Ion Concentration Now, let's calculate the concentration of O H − ions using the formula pO H = − lo g [ O H − ] . We can rewrite this as: [ O H − ] = 1 0 − pO H
Hydroxide Ion Concentration Value Substituting the given pOH value, we get: [ O H − ] = 1 0 − 6.0 = 1.0 × 1 0 − 6 M
Comparison with Given Statements Now, let's compare our calculated values with the given statements:
The pH of the solution is 20.0. (Incorrect, we found pH = 8.0)
The concentration of O H − ions is 1.0 × 1 0 − 8 M . (Incorrect, we found [ O H − ] = 1.0 × 1 0 − 6 M )
The concentration of O H − ions is 1.0 × 1 0 6 M . (Incorrect, we found [ O H − ] = 1.0 × 1 0 − 6 M )
The pH of the solution is 8.0. (Correct, we found pH = 8.0)
Final Answer Therefore, the correct statement is: The pH of the solution is 8.0.
Examples
Understanding pH and pOH is crucial in many real-world applications, such as monitoring water quality in aquariums or controlling the acidity of soil for optimal plant growth. For example, if you're maintaining an aquarium and the pOH is 6.0, you know the pH is 8.0, indicating a slightly alkaline environment. Adjusting the pH to the optimal range ensures the health and survival of the aquatic life. Similarly, in agriculture, knowing the pH and pOH helps farmers select the right fertilizers and soil treatments to create the ideal conditions for their crops.
