What is the pH of an aqueous solution at 25°C in which [OH-] is 0.025 M?
pOH = -log(OH^-)
pH + pOH = pKw = 14
To determine the pH of the aqueous solution, you can use the formula: pH = 14 - pOH. Since the concentration of hydroxide ions ([OH-]) is given as 0.025 M, we can find the pOH first.
Step 1: Calculate pOH
pOH = - log [OH-]
pOH = - log (0.025)
pOH = - log (2.5 x 10^-2)
pOH = - (log 2.5 + log 10^-2)
pOH = - (0.39794 + (-2))
pOH = - (0.39794 - 2)
pOH = - (-1.60206)
pOH ≈ 1.602
Step 2: Determine pH
pH = 14 - pOH
pH = 14 - 1.602
pH ≈ 12.398
Therefore, the pH of the aqueous solution with [OH-] concentration of 0.025 M at 25°C is approximately 12.398.
To determine the pH of an aqueous solution, we need to know the concentration of hydrogen ions ([H+]). Given the concentration of hydroxide ions ([OH-]), we can use the relationship between [H+] and [OH-] to find the pH.
The relationship between [H+] and [OH-] is described by the equation for water dissociation:
[H+] × [OH-] = 1.0 × 10^(-14) M^2
Given that [OH-] is 0.025 M, we can rearrange the equation to solve for [H+]:
[H+] = (1.0 × 10^(-14) M^2) / [OH-]
Substituting the given value of [OH-]:
[H+] = (1.0 × 10^(-14) M^2) / 0.025 M
Simplifying the calculation:
[H+] = 4.0 × 10^(-13) M
Finally, we can use the definition of pH, which is the negative logarithm (base 10) of the hydrogen ion concentration:
pH = -log[H+]
Plugging in the calculated value of [H+]:
pH = -log(4.0 × 10^(-13) M)
Calculating the value using logarithm properties:
pH ≈ 12.4
Therefore, the pH of the aqueous solution with a [OH-] concentration of 0.025 M is approximately 12.4.