On Campus Experiment 26

STANDARDIZATION AND TITRATION OF SOLUTIONS

The following discussion and videos can be used to complete this On Campus Experiment 26 laboratory assignments

The assignments that must be completed are:

Complete the pre laboratory writing assignment before the lab session begins.
Complete the Buret Tutorial and Buret Quiz in Canvas
Complete the pre laboratory problems before coming to the class meeting.
Using the class data of collected data in the experiment to complete ALL trials of Part I and both bleach samples in Part II
Complete the laboratory report, show calculations of each result determined for the thiosulfate solution and the bleach solutions.
Complete the conclusion paragraph for this experiment.

O-Experiment 26

Experiment 26

This is the presentation I use in class for the pre laboratory lecture.

Pre laboratory assignments

Complete the pre laboratory writing assignment in your laboratory notebook. The prewriting must be completed before the laboratory session begins. The writing should include a purpose/hypothesis of the experiment, a discussion or theory, a detailed step by step summary of the procedure explaining what data will be collected and how you will collect it. Data Tables or space to collect the data should be included within the procedure discussion. Look up any SDS on chemicals that you are not familiar.

Complete the pre laboratory problems before coming to the class meeting.

Experiment 26 Pre Laboratory Problems

Procedure

Part I. Standardization of a Thiosulfate solution.

We will use a reaction in which the primary standard potassium ferricyanide is used to titrate a solution of sodium thiosulfate using potassium iodide and a starch indicator. The reactions needed for this experiment are the reduction of ferricyanide, Fe(CN)₆^3-, to ferrocyanide, Fe(CN)₆^4- with the oxidation of iodide, I^- to iodine, I₂ forming the triiodide ion which reacts with thiosulfate, S₂O₃^2- to tetrathionate ion, S₄O₆^2- while triiodide ion is reduced to iodide ion completes the overall reaction

2 Fe(CN)₆^3- + 2 S₂O₃^2- ⇋ S₄O₆^2- + 2 Fe(CN)₆^4-

From the mass, the moles of K₃Fe(CN)₆ can be used to determine the moles of Na₂S₂O₃ and the molarity of the solution.

Use the class data provided to determine the molarity of the sodium thiosulfate solution for all trials.

O-Exp 26 Class Data

https://youtu.be/RKR0XFFcbnk

Iodimetric titration: standardization of thiosulfate

Jeffrey Mills

Part II. Analysis of Commercial Bleach

We will use the solution of sodium thiosulfate that was standardized to a known concentration in part I to titrate a commercial solution of bleach containing the active ingredient, sodium hypochlorite. The reactions needed for this experiment are the reduction of hypochlorite ion ClO^1-, to chloride ion, Cl^1- with the oxidation of iodide, I^- to iodine, I₂in a basic solution and the oxidation of thiosulfate, S₂O₃^2- to tetrathionate ion, S₄O₆^2- while triiodide ion is reduced to iodide ion. The overall reaction is

H₂O + ClO^1- + 2 S₂O₃^2- ⇋ S₄O₆^2- + Cl^1-+ 2 OH^1-,

Use the class data provided to determine the molarity and mass percent of the bleach solution for all trials of both bleach samples.

https://youtu.be/u_N_u2BqmFs

Percentage of Hypochlorite in Bleach

Pdst Chemistry

Report and Conclusion Paragraph

Complete the data and result tables, graphs, calculations and answer all required questions.

Complete a conclusion paragraph using the RERUNS method. A discussion of how to write a conclusion paragraph is given in Appendix D: How to Write a Formal Laboratory Report

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