Final answer:
To find the pH of a potassium hydroxide solution, convert the given mass of KOH to moles, calculate molarity, use this to find [OH-], and calculate pOH. Then subtract pOH from 14 to find the pH.
Step-by-step explanation:
The question involves calculating the pH of a solution when a known amount of potassium hydroxide (KOH) is dissolved in a certain volume of water. The mass of KOH is given as 885 mg, which needs to be dissolved in 190 mL of water to make the solution. Potassium hydroxide is a strong base, so it will dissociate completely in water to yield hydroxide ions (OH-).
To calculate the molarity of the KOH solution, we first convert the mass of KOH to moles:
Number of moles = Mass of KOH (g) / Molar mass of KOH (g/mol)
Molarity (M) = Number of moles / Volume of solution (L)
After computing the molarity, we use the following relationship to determine the concentration of hydroxide ions [OH-]:
[OH-] = Molarity of KOH
Since KOH is a strong base, the relationship is direct and 1 mole of KOH yields 1 mole of OH-.
To find the pH, we first calculate the pOH of the solution by taking the negative logarithm of the hydroxide ion concentration:
pOH = -log[OH-]
Finally, since pH + pOH = 14 (at 25°C), the pH of the solution can be found by:
pH = 14 - pOH
Performing these calculations will provide us with the pH of the solution.