In this lab you will be performing a titration to determine the concentration of a base solution. This lab will be very similar to the last titration you performed, except that the amount of acid will be known and you will find the concentration of the base. Since you will be able to measure the amount of acid very accurately, you will end up knowing the concentration of base very accurately. Since this measured concentration of the base may not be exactly the same as the label on the bottle, this is known as "standardizing a base."
The acid to be used is called potassium acid phthalate (or potassium hydrogen phthalate). This is abbreviated "KHP." The "H" part is what makes it an acid. It has a formula mass of 204.23 g/mol. This acid is a solid, so you will be measuring it by it's mass.
You will use Phenolphthalein ("FEEN-ul-thay-leen") as your indicator again. Remember that this indicator is clear in acid solution and turns pink in base solution. An acid solution with phenolphthalein in it will be clear. If base is added a drop at a time, a pink tint will linger longer and longer after each drop, until it finally stays pink starting exactly when the acid is all neutralized.
Finally, the results section contains a category labeled “mmoles.” This is a millimole, or a thousandth of a mole. If a solution is 1.0 M, then it contains one mole in one liter, or one millimole in one mL. As far as units are concerned, [mol/L]x[mL] = mmol. Also, [mmole]x[g/mol] = mg.
Data & Results
|4.||Calculate the average concentration of the base. Part of your grade will be based on how accurate AND precise your results are. [Attach all sample calculations for Trial #1!]|
REMINDER - show ALL calculations for trial #1 on an attached sheet
[Standardization of a Base score sheet][MHS Chem page]