Ch.4 - Reactions in Aqueous Solution

McMurry8th EditionChemistryISBN: 9781292336145당신이 사용하는 게 아니라요?교과서 변경

McMurry 8th Edition

Ch.4 - Reactions in Aqueous Solution

문제 42

4장, 문제 42

The concentration of an aqueous solution of NaOCl (sodium hypochlorite; the active ingredient in household bleach) can be determined by a redox titration with iodide ion in acidic solution:
Assume that the blue spheres in the buret represent I-ions, the red spheres in the flask represent OCl-ions, the con-centration of the I-ions in the buret is 0.120 M, and the volumes in the buret and the flask are identical. What is the concentration of NaOCl in the flask? What percentage of the I-solution in the buret must be added to the flask to react with all the OCl-ions?

검증된 단계별 안내

Write the balanced redox reaction between NaOCl and I- in acidic solution: OCl^- + 2 I^- + 2 H^+ -> I2 + Cl^- + H2O.

Determine the number of moles of I- in the buret using the concentration (0.120 M) and the volume (assume V).

Count the number of OCl- ions in the flask from the image (10 red spheres) to determine the moles of OCl-.

Use the stoichiometry of the balanced equation to find the moles of I- needed to react with the moles of OCl-.

Calculate the percentage of the I- solution in the buret that must be added to the flask by comparing the moles of I- needed to the total moles of I- available.

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주요 개념

질문에 올바르게 답하기 위해 반드시 이해해야 하는 핵심 개념들은 다음과 같습니다.

Redox Reactions

Redox reactions involve the transfer of electrons between two species, resulting in oxidation and reduction processes. In this titration, iodide ions (I-) are oxidized to iodine (I2), while hypochlorite ions (OCl-) are reduced. Understanding the electron transfer is crucial for determining the stoichiometry of the reaction and calculating concentrations.

Titration

Titration is a quantitative analytical technique used to determine the concentration of a solute in a solution. In this case, the volume of iodide ions added from the buret to the flask containing sodium hypochlorite is measured to find the endpoint of the reaction. The relationship between the volumes and concentrations of the reactants allows for the calculation of the unknown concentration of NaOCl.

Stoichiometry

Stoichiometry is the calculation of reactants and products in chemical reactions based on balanced equations. It allows for the determination of the amount of I- needed to completely react with the OCl- in the flask. By using the molarity and volume of the solutions, one can derive the concentration of NaOCl and the percentage of I- solution required for the reaction.

관련 실천

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Assume that an aqueous solution of a cation, represented as a blue sphere, is allowed to mix with a solution of an anion, repre-sented as a red sphere, and that the following result is obtained: Which combinations of cation and anion, chosen from the fol-lowing lists, are compatible with the observed results? Explain Cations: Na+, Ca2+, Ag+, Ni2+ Anions: Cl-, CO3 2-, CrO4 2-, NO3

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The following pictures represent aqueous solutions of three acids HA (A = X, Y, or Z), with surrounding water mol-ecules omitted for clarity. Which of the three is the strongest acid, and which is the weakest?

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교과서 질문

Assume that the electrical conductivity of a solution depends on the total concentration of dissolved ions and that you measure the conductivity of three different solutions while carrying out titration procedures: (a) Begin with 1.00 L of 0.100 M KCl, and titrate by adding 0.100 M AgNO₃. (b) Begin with 1.00 L of 0.100 M HF, and titrate by adding 0.100 M KOH. (c) Begin with 1.00 L of 0.100 M BaCl₂, and titrate by adding 0.100 M Na₂SO₄. Which of the following graphs corresponds to which titration?

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