Determination of Acetic Acid in Vinegar Data Sheet Standardization Volume NaOH M

Question

Determination of Acetic Acid in Vinegar Data Sheet Standardization Volume NaOH MNaOH Moles KHP Final Initial (moles) burette burette Trial Mass KHP (g) reading readingdelivered (mL) (mL) (mL) Trial #1 1192 Trial #2 1054a Trial #3 Trial #4 (if | necessary) Trial #5 (in necessary) Average Molarity Standard Deviation: 1. Show your work for the calculation of the molarity of NaOH from one of the trials above. 2. How many significant figures should your answers for molarity have? Explain. -107- Determination of Acetic Acid in Vinegar

Explanation / Answer

To titrate 1 mole of KHP you need 1 mole of NaOH

Molar mass of KHP 204.22 g/gmol

you need to calculate the number of moles of KHP with the formula:

moles = mass / molar mass, mass must be in grams

trial 1, moles of KHP.

moles = 0.5343 / 204.22 = 0.002616 moles of KHP, to titrate this you need to add the same number of moles of NaOH so it is right to say that you have 0.002616 moles of NaOH in 27.98 ml (the volume you used that is reported in the statement), divide this by 1000 to get 0.02798 Lites

Molarity NaOH = moles / volume

Molarity = 0.002616 / 0.02798 = 0.0935 M

For Trial 2

moles of KHP = mass / molar mass

moles of KHP = 0.5389 / 204.22 = 0.002638 moles

Molarity of NaOH = 0.002638 / 0.02832 = 0.0932 M

For Trial 3

moles of KHP = mass / molar mass

moles of KHP = 0.5478 / 204.22 = 0.00268

Molarity of NaOH = 0.00268 / 0.02887 = 0.0928 M

Average molarity is 0.0936 M, add the molarities and divide them by 3

Standard deviation is 0.000331, I calculated this value using a spreadsheet

Your molarity should have 4 significant digits, this is because you have provided 4 digits for mass of KHP and 4 digits of volume.

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