Sodium hydroxide is a hygroscopic solid, meaning that it absorbs moisture from t
ID: 481759 • Letter: S
Question
Sodium hydroxide is a hygroscopic solid, meaning that it absorbs moisture from the atmosphere. Consequently, if the concentration of a NaOH solution must be known precisely, it must be standardized against an acid. Furthermore, the acid must be a primary standard, a substance that can be weighed precisely resulting in a well-known amount of acid. This process, called standardization, is a titration of the known quantity of acid with the NaOH solution. A commonly used primary standard weak, acid for standardizing NaOH solutions is potassium acid phthalate, often abbreviated "KHP". a. If 2.61 g NaOH was dissolved in 1 L of deionized water, estimate the resulting NaOH solution? Explain your rationale. c. Titrations of KHP with the NaOH solution were performed to determine the actual NaOH concentration. Data for titration of KHP with NaOH are provided below. Use the data to determine the actual concentration of the NaOH solution. Comment or the quality of the data provided. d. Given the concentrate determined by titration and the expected concentrate calculated comment on the purity of the weighed NaOH sample.Explanation / Answer
35. for the given reaction
a. concentration of NaOH solution = grams of NaOH/molar mass NaOH x volume of solution
= 2.61/40 x 1
= 0.06525 M
b. We would use, brosil glassware volumetric flask for the preparation of NaOH solution.
c. moles of KHP (first data) = 0.2432/204.22 = 0.0012 mols
moles of NaOH reacted = 0.0012 mols
molarity of NaOH solution = 0.0012 mols/0.01910 L
= 0.063 M
d. the concentration found by titration is lower than the one calculated irectly from the mass of NaOH taken to prepare the solution. This is because NaOH absorbs moisture and the solution gets diluted over time. Thus molarity found by titration is lower.
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