CHEM 1AA3 Lecture Notes - Equilibrium Constant, Potassium Thiocyanate, Thiocyanate

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blushfrog267

18 Apr 2014

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To find the equilibrium constant of the (kc) for the reaction: fe3+(aq) + scn-(aq) (aq) through several different concentrations of reactants, using spectrophotometric analysis. Please refer to the chem 1a03/1e03/1aa3 lab manual 2013, pages 43-47, for a detailed procedure. Table 1: values of absorbance and concentration for different volumes of potassium thiocyanate and 0. 200 mol/l ferric nitrate. Fescn2+(aq) and kscn (aq) were both clear, colourless liquids initially. Solution turned to an orange and brown colour when the ferric nitrate was added to the potassium thiocyanate. Fe3+(aq) + scn-(aq) n(scn-) = cv n(scn-) = (. 002 mol/l) (. 001(l)) n(scn-) = . 000002 mol. Due to 1:1 mol ratio, n(fescn2+) = . 000002mol. The above graph shows the proportional relationship between the concentration and the absrbance of fescn2+. Using a line of best fit, a proportional constant of 5223 is determined to be the slope. A = absorbance = 0. 243a y = proportionality constant = 5223 a/mol/l.

Related Questions

1) Consider the following equilibrium: Fe3+(aq) + SCN-(aq) â FeSCN2+(aq) Initial concentrations: [Fe3+] = 0.590; [SCN-] = 1.239; [FeSCN2+] = 0 The equilibrium concentration of [FeSCN2+]eq = 0.454 M. What is the numerical value of KC for this equilibrium? KC = __________________

2) Consider the following equilibrium: Fe3+(aq) + SCN-(aq) â FeSCN2+(aq) Initial concentrations: [Fe3+] = 0.370; [SCN-] = 0.777; [FeSCN2+] = 0 The equilibrium concentration of [FeSCN2+]eq = 0.285 M. What is the equilibrium concentration of Fe3+? [Fe3+]eq = _____________M

3) When the kinetic data is correctly plotted to determine the activation energy, Ea, for a chemical reaction, the slope for the straight line graph is found to be -4900. What is the activation energy, Ea, in kJ/mol? Enter your answer as a POSITIVE number. Ea = __________________kJ/mol

4) A standard reference FeSCN2+ solution (0.040 M) has an absorbance = 0.815. What is the concentration of an unkown FeSCN2+ solution that has an absorbance = 0.288. unknown [FeSCN2+] = _________ M

5) 4.00 mL of H2O and 4.00 mL of an aqueous 0.040 M SCN- solution were added to 13.50 mL of an aqueous 0.025 M Fe3+ solution. The total volume of the solution is 21.50 mL. What is the diluted Fe3+ concentration?

1) A solution is 1.00x10^-4 M in SCN^- an0.36 M in Fe³⁺ are mixed and react according to equationâ¨â¨

Fe³⁺_(aq)+SCN^-_(aq)<--> (Fe(SCN))²⁺_(aq)

Under these conditions, the equilibrium is driven all of the way tothe right. The absorbance of the solution at 447 nm is 0.500, andthe path length of the test tube is 1.00 cm. What is the value ofthe molar absorptivity, Îµ, for the complex FeSCN²⁺?

2) In a test tube, you combine the following:

2.00 mL of 0.00200 M Fe(NO₃)₃solution
2.00 mL of 0.00100 M KSCN solution
1.00 mL of 2.0 M HNO₃ solution
3.00 mL of distilled water

a) What are the initial concentration of the reactants (i.e.,assuming no reaction occurs)?
(Fe³⁺)_init = M
(SCN^-)_init= M

b) The absorbance of the resulting solution is 0.101 at 447 nm.What is the equilibrium concentration of the FeSCN²⁺product, based on the molar absorptivity determined above?

(FeSCN²⁺)_equil= M

c) Set up an ICE table for the reaction, and determine the value ofKc from the data

Kc=

blackminnow717

how do i find the linear regression equation and [FeSCN2+] at equilibrium? thank you in advance

CHEM 1AA3 Lecture Notes - Equilibrium Constant, Potassium Thiocyanate, Thiocyanate

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