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Ch.4 - Reactions in Aqueous Solution
McMurry - Chemistry 8th Edition
McMurry8th EditionChemistryISBN: 9781292336145Not the one you use?Change textbook
All textbooksMcMurry 8th EditionCh.4 - Reactions in Aqueous SolutionProblem 145
Chapter 4, Problem 145

A mixture of acetic acid (CH3CO2H; monoprotic) and oxalic acid (H2C2O4; diprotic) requires 27.15 mL of 0.100 M NaOH to neutralize it. When an identical amount of the mixture is titrated, 15.05 mL of 0.0247 M KMnO4 is needed for complete reaction. What is the mass percent of each acid in the mixture? (Acetic acid does not react with MnO4 equation for the reaction of oxalic acid with MnO4 given in Problem 4.133.)

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Identify the reactions involved: Acetic acid (CH3CO2H) reacts with NaOH, and oxalic acid (H2C2O4) reacts with both NaOH and KMnO4.
Write the balanced chemical equations: CH3CO2H + NaOH -> CH3CO2Na + H2O and H2C2O4 + 2NaOH -> Na2C2O4 + 2H2O for the neutralization reactions. For the redox reaction, 5H2C2O4 + 2KMnO4 + 6H+ -> 10CO2 + 2Mn2+ + 8H2O + 2K+.
Calculate the moles of NaOH used: Use the volume and molarity of NaOH to find the total moles of NaOH used in the neutralization reaction.
Calculate the moles of KMnO4 used: Use the volume and molarity of KMnO4 to find the moles of KMnO4 used in the redox reaction with oxalic acid.
Set up equations based on stoichiometry: Use the stoichiometry of the reactions to set up equations relating the moles of acetic acid and oxalic acid to the moles of NaOH and KMnO4 used, then solve for the mass percent of each acid in the mixture.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Acid-Base Neutralization

Acid-base neutralization is a chemical reaction where an acid reacts with a base to produce water and a salt. In this context, acetic acid (a monoprotic acid) and oxalic acid (a diprotic acid) react with sodium hydroxide (NaOH) to form their respective salts and water. The volume and molarity of NaOH used in the titration provide information about the total moles of acid present in the mixture, which is essential for calculating the mass percent of each acid.
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Titration and Stoichiometry

Titration is a quantitative analytical method used to determine the concentration of a solute in a solution. In this case, the titration of the acid mixture with potassium permanganate (KMnO4) allows for the determination of the amount of oxalic acid present, as it reacts with KMnO4 in a known stoichiometric ratio. Understanding stoichiometry is crucial for converting the volume and molarity of KMnO4 used into moles of oxalic acid, which can then be related back to the mass percent of each acid in the mixture.
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Mass Percent Calculation

Mass percent is a way of expressing the concentration of a component in a mixture as a percentage of the total mass of the mixture. To calculate the mass percent of acetic acid and oxalic acid in the mixture, one must first determine the moles of each acid from the titration data, convert these moles to grams using their molar masses, and then use the total mass of the mixture to find the percentage of each acid. This concept is fundamental for expressing the composition of the acid mixture in a meaningful way.
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Related Practice
Textbook Question
A 100.0 mL solution containing aqueous HCl and HBr was titrated with 0.1235 M NaOH. The volume of base required to neutralize the acid was 47.14 mL. Aqueous AgNO3 was then added to precipitate the Cl-and Br-ions as AgCl and AgBr. The mass of the silver halides obtained was 0.9974 g. What are the molarities of the HCl and HBr in the original solution?
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Textbook Question
A sample of metal (M) reacted with both steam and aqueous HCl to release H2 but did not react with water at room tem-perature. When 1.000 g of the metal was burned in oxygen, it formed 1.890 g of a metal oxide, M2O3. What is the iden-tity of the metal?
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Textbook Question
An unknown metal (M) was found not to react with either water or steam, but its reactivity with aqueous acid was not investigated. When a 1.000 g sample of the metal was burned in oxygen and the resulting metal oxide converted to a metal sulfide, 1.504 g of sulfide was obtained. What is the identity of the metal?
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Textbook Question
Iron content in ores can be determined by a redox procedure in which the sample is first reduced with Sn2+, as in Problem 4.130, and then titrated with KMnO4 to oxidize the Fe2+ to Fe3+. The balanced equation is What is the mass percent Fe in a 2.368 g sample if 48.39 mL of a 0.1116 M KMnO4 solution is needed to titrate the Fe3 + ?
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Textbook Question
A mixture of FeCl2 and NaCl is dissolved in water, and addi-tion of aqueous silver nitrate then yields 7.0149 g of a pre-cipitate. When an identical amount of the mixture is titrated with MnO4 -, 14.28 mL of 0.198 M KMnO4 is needed for complete reaction. What are the mass percents of the two compounds in the mixture? (Na+ and Cl-do not react with MnO4 -. The equation for the reaction of Fe2+ with MnO4 was given in Problem 4.146.)
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Textbook Question
Salicylic acid, used in the manufacture of aspirin, contains only the elements C, H, and O and has only one acidic hydrogen that reacts with NaOH. When 1.00 g of salicylic acid undergoes complete combustion, 2.23 g CO2 and 0.39 g H2O are obtained. When 1.00 g of salicylic acid is titrated with 0.100 M NaOH, 72.4 mL of base is needed for complete reaction. What are the empirical and molecular formulas of salicylic acid?
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