The pOH of a solution is 10.75. What is the concentration of OH– ions in the solution?
Use [OH
−
]=10
−pOH
. A. 3.162×10−11M
B. 1.778×10−11M
C. 1.075×102M
D. 5.623×10
10
M
The Correct Answer and Explanation is :
The correct answer is : B. (1.778 \times 10^{-11} \, \text{M})
To find the concentration of hydroxide ions ([OH^-]) in a solution given a pOH of 10.75, we can use the formula:
[
[OH^-] = 10^{-pOH}
]
Substituting the given pOH value into the formula:
[
[OH^-] = 10^{-10.75}
]
Calculating (10^{-10.75}):
[
[OH^-] \approx 1.778 \times 10^{-11} \, \text{M}
]
Thus, the concentration of hydroxide ions ([OH^-]) is approximately (1.778 \times 10^{-11} \, \text{M}).
Explanation
pOH is a measure of the hydroxide ion concentration in a solution and is defined as the negative logarithm (base 10) of the hydroxide ion concentration. The relationship between pOH and hydroxide ion concentration is logarithmic, meaning that small changes in pOH correspond to significant changes in ([OH^-]).
The formula ( [OH^-] = 10^{-pOH} ) derives from the definition of pOH:
[
pOH = -\log[OH^-]
]
When we take the inverse logarithm (base 10) of the pOH, we find the hydroxide ion concentration.
In practical applications, understanding ([OH^-]) is essential for assessing the acidity or basicity of a solution. The pH scale, which measures the concentration of hydrogen ions ([H^+]), is directly related to pOH. The relationship is expressed by the equation:
[
pH + pOH = 14
]
In this case, with a pOH of 10.75, we can determine the corresponding pH:
[
pH = 14 – pOH = 14 – 10.75 = 3.25
]
This indicates that the solution is acidic since the pH is below 7. Understanding these relationships is crucial in fields such as chemistry, biology, and environmental science, where the behavior of acids and bases affects various processes.
Final Answer
The correct answer is B. (1.778 \times 10^{-11} \, \text{M}).