What mass of KOH is necessary to prepare 799.9 mL of a solution having a pH = 11.53?
KOH is a strong base in aqueous solution; therefore, the (KOH) = (OH%-).
For pH = 11.53, use pH + pOH = pKw = 14 to solve for pOH, then from
pOH = -log (OH^-), solve for OH^-. That will give you the molarity of the KOH you want for that pH.
Then M = moles/L. Substitute L and solve for moles.
Then moles = grams/molar mass, solve for grams.
112. 57
105. 84
4. 5×10^-13
To determine the mass of KOH necessary to prepare the solution, we need to follow a series of steps:
Step 1: Calculate the concentration of hydroxide ions ([OH-])
The pH value is a measure of the concentration of hydrogen ions ([H+]) in a solution. To find the concentration of hydroxide ions ([OH-]) from the pH, we can use the equation:
pH + pOH = 14
Since we know the pH value is 11.53, we can find the pOH value:
pOH = 14 - 11.53 = 2.47
Now, convert the pOH value to the concentration of hydroxide ions using the equation:
pOH = -log[OH-]
2.47 = -log[OH-]
Now, solve for [OH-]:
[OH-] = 10^(-2.47)
Step 2: Calculate the concentration of KOH
Since KOH dissociates completely in water, the concentration of KOH will be equal to the concentration of hydroxide ions ([OH-]). Therefore:
[OH-] = concentration of KOH
Step 3: Determine the number of moles of KOH
To find the number of moles of KOH, we need to use the equation:
moles = concentration × volume
Volume = 799.9 mL = 0.7999 L (since 1 L = 1000 mL)
Now, substitute the values into the equation:
moles = [OH-] × volume
moles = concentration of KOH × volume
Step 4: Convert moles of KOH to grams
To convert moles of KOH to grams, we need to use the molar mass of KOH, which is the sum of the atomic masses of potassium (K), oxygen (O), and hydrogen (H).
The molar mass of KOH = 39.10 g/mol (K) + 16.00 g/mol (O) + 1.01 g/mol (H)
Finally, calculate the mass of KOH by multiplying the number of moles by the molar mass:
mass of KOH = moles × molar mass
Following these steps will give you the mass of KOH necessary to prepare the solution.