Ch.17 - Additional Aspects of Aqueous Equilibria

Brown - Chemistry: The Central Science 14th Edition

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Brown 14th Edition

Ch.17 - Additional Aspects of Aqueous Equilibria

Problem 104

Chapter 17, Problem 104

A solid sample of Fe1OH23 is added to 0.500 L of 0.250 Maqueous H2SO4. The solution that remains is still acidic. Itis then titrated with 0.500 M NaOH solution, and it takes12.5 mL of the NaOH solution to reach the equivalencepoint. What mass of Fe1OH23 was added to the H2SO4solution?

Verified step by step guidance

Step 1: Identify the balanced chemical equations for the reactions. The Fe(OH)2 reacts with H2SO4 to form FeSO4 and water. The remaining H2SO4 is then neutralized by NaOH to form Na2SO4 and water.

Step 2: Calculate the moles of NaOH used in the titration. This can be done by multiplying the volume (in liters) by the molarity of the NaOH solution.

Step 3: Use stoichiometry to determine the moles of H2SO4 that were neutralized by the NaOH. Since the reaction between H2SO4 and NaOH is a 1:2 ratio, the moles of H2SO4 will be half the moles of NaOH.

Step 4: Subtract the moles of H2SO4 that reacted with NaOH from the initial moles of H2SO4 (which can be calculated from the initial volume and molarity) to find the moles of H2SO4 that reacted with Fe(OH)2.

Step 5: Use stoichiometry to calculate the moles of Fe(OH)2 that reacted with H2SO4. Since the reaction between Fe(OH)2 and H2SO4 is a 1:1 ratio, the moles of Fe(OH)2 will be the same as the moles of H2SO4 that reacted with it. Then, convert the moles of Fe(OH)2 to grams using its molar mass to find the mass of Fe(OH)2 that was added to the H2SO4 solution.

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Key Concepts

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

Stoichiometry

Stoichiometry is the calculation of reactants and products in chemical reactions. It involves using balanced chemical equations to determine the relationships between the amounts of substances consumed and produced. In this question, stoichiometry is essential for relating the moles of H2SO4 and NaOH to the moles of Fe(OH)2 involved in the reaction.

Titration

Titration is a laboratory technique used to determine the concentration of a solution by reacting it with a solution of known concentration. In this scenario, the titration of the acidic solution with NaOH allows for the determination of the amount of acid present, which can then be used to find the mass of Fe(OH)2. The equivalence point indicates that the acid and base have reacted completely.

Molar Mass

Molar mass is the mass of one mole of a substance, typically expressed in grams per mole (g/mol). It is crucial for converting between moles and grams in stoichiometric calculations. To find the mass of Fe(OH)2 added to the H2SO4 solution, one must first calculate the moles of Fe(OH)2 based on the titration results and then use its molar mass to convert moles to grams.

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