Redox Titration Calculations

Redox Titration Calculations - REDOX TITRATION ­often,...

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Unformatted text preview: REDOX TITRATION ­often, solutions need to be analyzed by "titration". Usually this is done to determine the concentration of the solution being studied. Example... A potassium permanganate solution is made by adding water to 12.0g of KMnO4(s) until there is 500 mL of solution. What is the concentration of the KMnO 4(aq) solution? Title: Mar 20­2:02 PM (1 of 12) Examining a potassium permanganate solution using REDOX theory we see that the solution will react spontaneously after it is made... What effect will this have on the concentration of the K + and MnO4 ­ ions in the solution? Title: Mar 20­2:06 PM (2 of 12) If the permanganate solution is prepared on Monday, but it is not used until Friday, its concentration will change! Before we use the solution in any experiment we must determine its exact concentration. Once we determine the exact concentration of the potassium permanganate solution, we say it has been standardized We determine its concentration by titrating the permanganate solution with a "primary standard" (a solution whose exact concentration is already known) * a good choice of a primary standard to use for standardizing potassium permanganate is a 0.0500 mol/L acidified tin(II) chloride solution Title: Mar 20­2:10 PM (3 of 12) Title: Mar 20­2:17 PM (4 of 12) Predict the REDOX reaction between a potassium permanganate solution and an acidic tin(II) chloride solution. Title: Mar 20­2:20 PM (5 of 12) Determine the concentration of a 10.0 mL sample of the potassium permanganate solution if 8.20 mL of acidified tin(II) chloride are needed to reach the endpoint. (permangante ions are purple; when completely reacted to produce colourless Mn 2+ ions, the solution will turn clear and colourless). Title: Mar 20­2:22 PM (6 of 12) Title: Mar 20­2:51 PM (7 of 12) Example Question: Problem: What is the concentration of chromium(III) ions in a solution obtained from a stainless steel alloy? Experimental Design: A standardized potassium dichromate solution is used to oxidize chromium(II) ions (blue) to chromium(III) ions (green) in an acidic solution Evidence: TITRATION OF CHROMIUM(II) SOLUTION (Volume of 0.125 mol/L K 2Cr2O7(aq) required to react with 10.00 mL of chromium(II) solution) Trial 1 2 3 4 Final buret reading (mL) 17.5 34.9 18.9 36.5 Initial buret reading (mL) 0.1 17.5 1.5 18.9 Volume of K2Cr2O7(aq) (mL) Title: Mar 20­2:29 PM (8 of 12) Title: Mar 20­2:51 PM (9 of 12) Example Question: Problem: What is the concentration of a tin(II) chloride solution prepared from a sample of tin ore? Experimental Design: Potassium dichromate solution is first standardized by titration with 10.0 mL of an acidified 0.0500 mol/L solution of the primary standard, iron(II) ammonium sulfate­6­water. Then a 10.0 mL sample of the acidified tin(II) chloride solution is titrated with the standardized dichromate solution. Evidence: TITRATION OF IRON(II) SOLUTION (Volume of K 2Cr2O7(aq) required to react with 10.00 mL of 0.0500 mol/L Fe 2+ ) (aq) Trial 1 2 3 4 Final buret reading (mL) Initial buret reading (mL) 13.8 2.3 24.4 13.8 35.2 24.4 45.9 35.2 TITRATION OF TIN(II) SOLUTION (Volume of K 2Cr2O7(aq) required to react with 10.00 mL of Sn 2+ ) (aq) Trial 1 2 3 4 Final buret reading (mL) Initial buret reading (mL) 45.0 33.9 Title: Mar 20­2:41 PM (10 of 12) 11.8 0.3 22.9 11.8 33.9 22.9 Title: Mar 20­2:51 PM (11 of 12) Assignment... complete the worksheet "REDOX TITRATION" you may use extra paper, but make sure it is attached to the worksheet when you submit it next class this will be marked as a written response question on the standard 5­point scale so show all work and communicate clearly and concisely in your response... ORGANIZED CALCULATIONS!! Title: Mar 20­2:51 PM (12 of 12) ...
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This note was uploaded on 11/12/2011 for the course CHEM chem 2a taught by Professor Cabrera during the Spring '09 term at San Jose City College.

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