A student analyzed a 0.6124 g sample containing aspirin using a 0.2300 M NaOH so

Question

A student analyzed a 0.6124 g sample containing aspirin using a 0.2300 M NaOH solution and the indicator phenolphthalein. The student determined that the % purity of the sample was 82.94%. The molar mass of aspirin is 180.16 g/mol. a. Calculate the actual moles of aspirin in the sample based on the titration analysis. b. Determine the volume (in mL) of NaOH that was required to reach the equivalence point. c. Phenolphthalein changes color at the equivalence point for the titration. If a student decides to use the indicator methyl orange for this titration instead, would the volume of base added to get to the endpoint be less than, equal to, or greater than the equivalence point volume you determined in part (b)? Briefly explain your answer. The indicator methyl orange is red below pH 3.2 and yellow above pH 4.4.

Explanation / Answer

mass of Aspirin in the sample = 0.6124 * 82.94 % = 0.508 gm

Molar mass of aspirin = 180.16 gm/mol

Moles of aspirin present in the sample = 0.508 gm/180.16g/mol = 2.82*10^-3 moles

--------------------------------------------------------------------

at equivalence point ,moles of aspirin = moles of NaOH

or, 2.82*10^-3 moles = 0.23 M * V L

or, V = 0.0123 L = 12.3 mL

--------------------------------------------------

methyl organge shows color change in the acidic range while phenolphthalein shown color change in pH = 8-10 . If methyl orange is used, it will show color change before all the aspirin in neutralize. Thus if methyl orange is used, less volume of NaOH will be required.

Related Questions

Navigate

• Browse (All)
• Browse A
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.