lecture 17 - Turn on Camptasia Recording Office Hours this...

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Unformatted text preview: Turn on Camptasia Recording! Office Hours this week 1-2:30 Friday in the CRC. Positions f student peers to assist with summer orientation in P iti for t d t t i t ith i t ti i 2008. Students from the College of Natural Science and Mathematics are wanted. The application deadline is March 28th at 5 p.m. Applications can be found at: <http://www.umass.edu/advising>www.umass.edu/advising under "Wh t' New." Pl d "What's N " Please f l f feel free t contact : to t t Tonya Blundon Academic Advisor Undergraduate Advising 615 Goodell (413)545-2191 ... 1 BioSci Presentation Working in the Pharmaceutical Industry. Industry Monday March 10th 5:30 pm ... 2 Why does the CoCl2 change color at different temperatures? Pink to blue Co(H2O)6Cl2 ---> Co(H2O)4Cl2 + 2 H2O Blue to pink Co(H2O)4Cl2 + 2 H2O ---> Co(H2O)6Cl2 A. Cobalt is insoluble in the cold B. The equilibrium reaction is different at different temperatures C. The equilibrium constant is temperature dependent. D. The equilibrium constant is temperature independent. ... 3 2 NH3(g) N2(g) + 3 H2(g) If 8.39e-4 moles of NH3(g), 0.469 moles of N2, and 0.283 moles of H2 are at equilibrium in a 13.6 L container at 858 K, the value of the equilibrium constant is: A. 18.71 B. 8 x 10-3 C. 81.7 D. 118.7 E. 8.7 x 102 ... 4 Nitrogen Dioxide Equilibrium N2O4(g) 2 NO2(g) ... 5 Nitrogen Dioxide Equilibrium N2O4(g) 2 NO2(g) If initial concentration of N2O4 is 0.50 M, what are the equilibrium concentrations? ... 6 Nitrogen Dioxide Equilibrium N2O4(g) 2 NO2(g) ... 7 This is a QUADRATIC EQUATION ax2 + bx + c = 0 ... 8 Nitrogen Dioxide Equilibrium N2O4(g) 2 NO2(g) ... 9 If the initial concentration of PCL5 is 1.60 M, what will be the concentrations of PCl3 when the sample reaches equilibrium? K = 1.20 ... 10 Do you always have to use the quadradic formula? We can use an approximation: Approximation can not be used when K is 1 or greater. ... 11 ... 12 ... 13 What answer do we get if we solve the full quadradic equation? ... 14 PRS If initial concentration of N2O4 is 0.50 M, what is the equilibrium concentration of NO2? Kc( 273 K)=0.00077 N2O4(g) 2 NO2(g) ... 15 ... 16 Writing and Manipulating K Expressions Changing coefficients S(s) + 3/2 O2(g) 2 S(s) + 3 O2(g) SO3(g) 2 SO3(g) ... 17 ... UMass Amherst Biochemistry Teaching Initiative Writing and Manipulating K Expressions Changing direction S(s) + O2(g) ( ) SO2(g) SO2(g) S(s) + O2(g) ... 19 Writing and Manipulating K Expressions Adding equations for reactions S(s) + O2(g) SO2(g) SO3(g) SO2(g) + 1/2 O2(g) Net equation S(s) + 3/2 O2(g) SO3(g) Knet = K1 K 2 ... 20 ... UMass Amherst Biochemistry Teaching Initiative Writing and Manipulating K Expressions Concentration Units g We have been writing K in terms of mol/L. These are designated by Kc But with gases, P = (n/V)RT = conc RT P is proportional to concentration, so we can write K in terms of P. These are designated by Kp. Kc and Kp may or may not be the same. ... 22 Writing and Manipulating K Expressions K using concentration and pressure units Kp = Kc (RT)n ( ) For S(s) + O2(g) SO2(g) n = 0 and Kp = Kc For SO2(g) + 1/2 O2(g) SO3(g) n = 1/2 and Kp = Kc(RT)1/2 ... 23 ...
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