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May 24, 2015

Homework Help: Chemistry

Posted by Leah on Thursday, February 14, 2013 at 12:14am.

Need help on a lab results write-up. The lab is the synthesis and analysis of a transition metal complex. General reaction was stated as:

Fe(III) + x(acac) -> Fe(acac)x - we were to determine x by completing experiment. x = 1, 2, 3, 4...

acac = 2, 4 pentanedione

Procedure of experiment: dissolve 2 g of sodium acetate trihydrate in 25mL of water and add it to a solution of 1 g iron (III) chloride hexahydrate in 25 ml of water. Add 2mL of 2,4-pentanedione with stirring and continue to stir for 10 minutes. Filter red solid product and wash with cold water. Let filter paper dry until next class period. Weigh the solid obtained and determine % yield.

HOW DO I DO THIS? I've done the experiment. .967 grams of product was obtained, but how do I determine theoretical and % yield?

Next, we were suppose to analyze by following this procedure:

The overall idea here is to destroy the complex and reduce the freed Fe (III) to Fe (II) with iodide ions. The iodide becomes iodine which is easily quantified by a titration using thiosulfate ions as the titrant. Fe+3 + 2I -> 3Fe+2 + I2 and I2 + 2[S2O3]-2 -> 2I + S4O6.

Gently heat two carefully weighed 0.17 grams each of your complex in a flask with 5mL HCL and 2.5 mL HNO3 for about 20 minutes. Cool and add 40mL of water, 10mL 3M HCL and 0.5 g urea. Heat this new solution for 5 minutes at 60degrees celcius. Cool again and add 2 gram KI and a little sodium bicarbonate. Keep the flask covered until you titrate it with 0.20 M thiosulfate to a starch endpoint. Find the % iron in your complex by working back through your balanced reactions and compare it with the % iron expected if x = 1, 2, 3, 4 in the general complex formula. Decide which formula is correct. Draw the structure.

PLEASE HELP. Two titrations were performed. The first one used 1.69mL, and the second one used 1.65mL

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