If you know the [OH^-], how can you determine the pH of a solution?

Verified step by step guidance

1. Step 1: Recall the relationship between pH, pOH, and the hydroxide ion concentration ([OH⁻]). The pOH is calculated using the formula: $\mathrm{pOH}=-log\left({\mathrm{[OH]}}_{-}\right)$.
2. Step 2: Use the value of [OH⁻] provided in the problem and substitute it into the formula for pOH. Take the negative logarithm (base 10) of the [OH⁻] concentration.
3. Step 3: Recall the relationship between pH and pOH, which is given by the equation: $\mathrm{pH}+\mathrm{pOH}=14$. This equation is valid for aqueous solutions at 25°C.
4. Step 4: Rearrange the equation to solve for pH: $\mathrm{pH}=14-\mathrm{pOH}$. Substitute the calculated pOH value from Step 2 into this equation.
5. Step 5: Perform the subtraction to determine the pH of the solution. Ensure that your final answer is reported with the correct number of significant figures based on the given [OH⁻] concentration.

Key Concepts

pH Scale

The pH scale measures the acidity or basicity of a solution, ranging from 0 to 14. A pH of 7 is considered neutral, values below 7 indicate acidity, and values above 7 indicate alkalinity. The scale is logarithmic, meaning each whole number change represents a tenfold change in hydrogen ion concentration.

Hydroxide Ion Concentration ([OH⁻])

The concentration of hydroxide ions, denoted as [OH⁻], is crucial in determining the pH of a solution. In basic solutions, higher [OH⁻] values correspond to lower hydrogen ion concentrations, which affects the pH. The relationship between [OH⁻] and pH is governed by the equation pOH = -log[OH⁻].

Relationship Between pH and pOH

pH and pOH are related through the equation pH + pOH = 14 at 25°C. This means that if you know the pOH, you can easily calculate the pH. Since pOH is derived from the hydroxide ion concentration, knowing [OH⁻] allows for the determination of both pOH and subsequently pH.