1. Why is the calibration curve prepared using a higher concentration of Fe"?2. If not all of the SCN' reacts with Fe" when developing the calibration curve, how would the dataobtained in Part II of the experiment be affected?3. Using the mean value obtained for Keo, calculate the SCN equilibrium concentration in a solutionwith an initial Fe concentration of 5.5*102 M and the initial SCN concentration of 2.5*10 M.

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1. Why is the calibration curve prepared using a higher concentration of Fe"? - n hot all of the SCN' reacts with Fe" when developing the calibration curve, how would the data obtained in Part Il of the experiment be affected? 3. Using the mean value obtained for Keo, calculate the SCN equilibrium concentration in a solution with an initial Fe" concentration of 5.5*102 M and the initial SCN concentration of 2.5*10 M.

1. Why is the calibration curve prepared using a higher concentration of Fe"? - n hot all of the SCN' reacts with Fe" when developing the calibration curve, how would the data obtained in Part Il of the experiment be affected? 3. Using the mean value obtained for Keo, calculate the SCN equilibrium concentration in a solution with an initial Fe" concentration of 5.5102 M and the initial SCN concentration of 2.510 M.

Chemistry for Engineering Students

4th Edition

ISBN:9781337398909

Author:Lawrence S. Brown, Tom Holme

Publisher:Lawrence S. Brown, Tom Holme

Chapter12: Chemical Equilibrium

Section: Chapter Questions

Problem 12.41PAE: Because calcium carbonate is a sink for CO32- in a lake, the student in Exercise 12.39 decides to go...

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. Lead(II) chloride, PbCl2(s), dissolves in water to the extent of approximately 3.6102Mat 20 °C. Calculate Kspfor PbCl2(s), and calculate its solubility in grams per liter.
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Again the experiment in Exercise 12.33 was redesigned. This time, 0.15 mol each of N, and O2 was injected into a 5.0-L container at 2500 K, at which the equilibrium constant is 3.6 X 10-?. What was the composition of the reaction mixture at equilibrium? l'he following reaction establishes equilibrium at 2000 K: N2(g) + O2(g) *2 2 NO K = 4.1 X IO-4 If the reaction began with 0.100 mol L-1 of N2 and 0.100 mol L-’ ofO2, what were the equilibrium concentrations of all species?
The following question is taken from a Chemistry Advanced Placement Examination and is used with the permission of the Educational Testing Service. Solve the following problem: MgF2(s)Mg2+(aq)+2F(aq) In a saturated solution of MgF2 at 18 C, the concentration of Mg2+ is 1.21103M . The equilibrium is represented by the preceding equation. (a) Write the expression for the solubility-product constant, Ksp, and calculate its value at 18 C. (b) Calculate the equilibrium concentration of Mg2+ in 1.000 L of saturated MgF2 solution at 18 C to which 0.100 mol of solid KF has been added. The KF dissolves completely. Assume the volume change is negligible. (c) Predict whether a precipitate of MgF2 will form when 100.0 mL of a 3.00103 -M solution of Mg(NO3)2 is mixed with 200.0 mL of a .2.00103 -M solution of NaF at 18 C. Show the calculations to support your prediction.. (d) At 27 C the concentration of Mg2+ in a saturated solution of MgF2 is 1.17103M . Is the dissolving of MgF2 in water all endothermic or an exothermic process? Give an explanation to support your conclusion.
. The solubility product of iron(III) hydroxide is very small: Ksp=41038at 25 °C. A classical method of analysis for unknown samples containing iron is to add NaOH or NH3. This precipitates Fe(OH)3, which can then be filtered and weighed. To demonstrate that the concentration of iron remaining in solution in such a sample is very small, calculate the solubility of Fe(OH)3in moles per liter and in grams per liter.
Because calcium carbonate is a sink for CO32- in a lake, the student in Exercise 12.39 decides to go a step further and examine the equilibrium between carbonate ion and CaCOj. The reaction is Ca2+(aq) + COj2_(aq) ** CaCO,(s) The equilibrium constant for this reaction is 2.1 X 10*. If the initial calcium ion concentration is 0.02 AI and the carbonate concentration is 0.03 AI, what are the equilibrium concentrations of the ions? A student is simulating the carbonic acid—hydrogen carbonate equilibrium in a lake: H2COj(aq) H+(aq) + HCO}‘(aq) K = 4.4 X 10"7 She starts with 0.1000 AI carbonic acid. What are the concentrations of all species at equilibrium?
The experiment in Exercise 12.33 was redesigned so that the reaction started with 0.15 mol each of N2 and O2 being injected into a 1.0-L container at 2500 K. The equilibrium constant at 2500 K is 3.6 X 10“’. What was the composition of the reaction mixture after equilibrium was attained? The following reaction establishes equilibrium at 2000 K: N2(g) + O2(g) *2 2 NO K = 4.1 X IO-4 If the reaction began with 0.100 mol L-1 of N2 and 0.100 mol L-’ ofO2, what were the equilibrium concentrations of all species?
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. Calcium sulfate, CaSO4, is only soluble in water to the extent of approximately 2.05 g/L at 25 °C. Calculate Kspfor calcium sulfate at 25°C.
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What is the law of mass action? Is it true that the value of K depends on the amounts of reactants and products mixed together initially? Explain. Is it true that reactions with large equilibrium constant values are very fast? Explain. There is only one value of the equilibrium constant for a particular system at a particular temperature, but there is an infinite number of equilibrium positions. Explain.