A solution of the primary standard potassium hydrogen phthalate, KHC8H4O4, was prepared by dissolving 0.4877 g of potassium hydrogen phthalate in about 50 mL of water. Titration with a KOH solution required 17.65 mL to reach a phenolphthalein end point. What is the molarity of the KOH solution?
To find the molarity of the KOH solution, we can use the concept of stoichiometry and the formula of potassium hydrogen phthalate (KHC8H4O4).
First, let's calculate the number of moles of potassium hydrogen phthalate used in the solution. We can use the formula:
moles of solute = mass of solute / molar mass of solute
The molar mass of KHC8H4O4 can be calculated by summing the atomic masses of each element:
Molar mass of KHC8H4O4 = (1 x atomic mass of K) + (1 x atomic mass of H) + (8 x atomic mass of C) + (4 x atomic mass of H) + (4 x atomic mass of O)
Next, calculate the molarity of the KOH solution using the equation:
Molarity = moles of solute / volume of solution in liters
In this case, the volume of the KOH solution will be converted from milliliters to liters.
Now, let's plug in the values to find the molarity of the KOH solution.
1. Calculate the molar mass of potassium hydrogen phthalate (KHC8H4O4):
Molar mass of KHC8H4O4 = (1 x atomic mass of K) + (1 x atomic mass of H) + (8 x atomic mass of C) + (4 x atomic mass of H) + (4 x atomic mass of O)
2. Calculate the moles of potassium hydrogen phthalate used:
moles of KHC8H4O4 = mass of KHC8H4O4 / molar mass of KHC8H4O4
3. Convert the volume of KOH solution from milliliters to liters:
volume of KOH solution = 17.65 mL / 1000 mL/L
4. Calculate the molarity of the KOH solution:
Molarity of KOH = moles of KHC8H4O4 / volume of KOH solution
By following these steps, you can calculate the molarity of the KOH solution.