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 36.21 mL to reach a phenolphthalein end point. What is the molarity of the KOH solution?
0.0024 M KHC8H4O4 was calculated.
I keep getting the wrong answer
KHC8H4O4 + KOH ==>K2C8H4O4 + H2O
mols phthalate - grams/molar mass = ?
mols KOH = same (look at the coefficients in the balanced equation.)
M KOH = mols KOH/L KOH
I get about 0.066 M.
Post your work and I'll find the error.
Oh I was doing 1:2 ratio instead of 1:1... That is where I went wrong! When I recalculated it with 1:1 I got 0.066628 M
My answer is 0.06595. I used 204.22 for the molar mass of the phthalate. To get that value you had to use something like 198 for the molar mass of the phthalate. There is either a typo or you used the wrong molar mass.
To find the molarity of the KOH solution, we need to use the balanced chemical equation for the reaction between KHC8H4O4 and KOH.
The balanced equation is:
KHC8H4O4 + KOH -> K2C8H4O4 + H2O
The stoichiometry of the balanced equation shows that one mole of KHC8H4O4 reacts with one mole of KOH to produce one mole of K2C8H4O4 and one mole of water.
First, let's calculate the number of moles of KHC8H4O4 in the solution using its mass and molar mass. The molar mass of KHC8H4O4 is:
(1 * atomic mass of K) + (1 * atomic mass of H) + (4 * atomic mass of C) + (4 * atomic mass of H) + (4 * atomic mass of O)
Next, we need to determine the number of moles of KOH that reacted with KHC8H4O4. Since the balanced equation has a 1:1 mole ratio between KHC8H4O4 and KOH, the number of moles of KOH is also equal to the number of moles of KHC8H4O4.
Now, divide the number of moles of KOH by the volume in liters to find the molarity. The volume in liters can be determined by converting the volume in milliliters to liters (36.21 mL = 0.03621 L).
Finally, divide the number of moles of KOH by the volume (in liters) to find the molarity of the KOH solution.