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A stirred tank with volume Vt(L) is charged with V](L) of

Elementary Principles of Chemical Processes | 3rd Edition | ISBN: 9780471687573 | Authors: Richard M Felder ISBN: 9780471687573 143

Solution for problem 8.94 Chapter 8

Elementary Principles of Chemical Processes | 3rd Edition

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Elementary Principles of Chemical Processes | 3rd Edition | ISBN: 9780471687573 | Authors: Richard M Felder

Elementary Principles of Chemical Processes | 3rd Edition

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Problem 8.94

A stirred tank with volume Vt(L) is charged with V](L) of a liquid, B. The space above the liquid (volume Vg = Vt - VI) is filled with a pure gas, A, at an initial pressure Po(atm). The initial system temperature is To(K). The stirrer in the tank is turned on, and A begins to dissolve in B. The dissolution continues until the liquid is saturated with A at the final system temperature (T) and pressure (P). The equilibrium solubility of A in B is governed by the following expression, which relates the molar A/B ratio in the liquid to the partial pressure of A in the gas phase (which in turn equals the pressure in the tank, since the gas is pure A): r(mol A/mol B) = ksPA(atm) where ks[mol A/(mol Batm)] = Co + c1T(K) *Computer problems. 437 When solving the problems to be given, use the following variable definitions: M A , MB = molecular weights of A and B CvA, CvB , Cvs[J/(g'K)] =constant-volume heat capacities of A(g), B(I), and solutions of A in B. respectively 5GB = specific gravity of B(l) 6.Us (llmol A dissolved) = internal energy ofsolution at 298 K (independent of composition over the range of concentrations to be considered) nAi), nso = g-moles of A(g) and B(l) initially charged into the tank nA(I), nA(v) = g-moles of A dissolved and remaining in the gas phase at equilibrium. respectively Make the following assumptions: A negligible amount of B evaporates. The tank is adiabatic and the work input to the tank from the stirrer is negligible. The gas phase behaves ideally. The volumes of the liquid and gas phases may be considered constant. The heat capacities CvA, Cvs, and Cvs are constant. independent of temperature and (in the case of C,JS ) solution composition. (a) Use material balances, the given equilibrium solubility relation. and the ideal gas equation of state to derive expressions for nAO, nso, nA(v), n-\(I). and P in terms of the final temperarure. T. and variables MA, MB, 5GB, Vt , VI, To. Po, Co, and Cl. Then use an energy balance to deri\'e the following equation: T = 298 + nAO)(-t:.Us) + (nAoMAC,'A + nBoMBC,s)(To - 298) nA(v)M.-\CvA + (nA(J)MA(l) + nSMB)C,-s (b) Write a spreadsheet to calculate T from specified values of MA ( = -+7)..HB( = 26). 5GB( = 1.-6). Vt ( = 20.0), VI( = 3.0), co( = 1.54 x 10-3 ), Cl (= -1.60 x 10-6 ). CrA( = 0.831). C B( = :.S51. Cvs( = 3.80), and t:.Us( = -1.74 x 105 ). and a number of different values of Tn and Pl. The spreadsheet should have the structure given below. (Calculated values are shown for one initial temperature and pressure.) i 8.94 I I I I i I i I I I i I I MB I ! 5GB I i Vt MA CvA CvB i cO cl Des CYS I I 20.0 26.0 I i 47.0 0.831 3.85 I 1.76 0.0015-+ -1.60E-06 -17-+000 .3.80 i i I I I I ! i I i I VI 3.0 3.0 TO 300 300 PO 1.0 5.0 Vg nBO nAO T nA(v) nA(I) P Tw.k i I 3.0 300 10.0 17.0 203.1 6.906 I 320.0 5.222 1.684 S.l 31-k2 I I i 3.0 300 I 20.0 ! 3.0 330 I l.0 I I I I I I I 3.0 330 5.0 I i 3.0 I 330 I 10.0 I ; I : I i 1 I 3.0 330 I 20.0 i The values of Vg, nso, and nAO should first be calculated from the given values of the other variables. Next, a value of T should be guessed (in the example in the table. the guessed \";llue 438 Chapter 8 Balances on Nonreactive Processes is 320 K), the values of nA(v), nA(l), and P should be calculated from the equations derived in part (a), and the temperature should be recalculated from the energy balance in the column labeled Teale (it equals 314.2 in the example). The value of T should then be varied until it equals the recalculated value of Teale. (Suggestion: Create a new cell as T - Teale and use goalseek to find the value of T that drives T - Tcalc to zero.) Enter the formulas in the cells for VI = 3.0 L, To = 300 K, and Po = 10.0 atm, and verify that your cell values match those shown above. Then find the correct value of Tusing the procedure just described, copy the formulas into the other rows of the table, and determine T fur each set of initial conditions. Summarize the effects of the initial temperature and pressure on the adiabatic temperature rise and briefly explain why your results make sense. (c) Write a computer program to perform the same calculations done with the spreadsheet in part (b). Define values of Vb MA , CvA , MB , CvB , SGB, Co, Cl, flOs, and Cvs ' Use the values shown in the fourth row of the spreadsheet. Read in a set of values of VB, To, and Po. Have the program terminate if VB :s 0.0. If a positive value is read in for VB, calculate Vo , nB, and nAO' Assume a value of T. (Try LITo as a first guess.) Calculate nAry), nA(l), and P from the equations derived in part (a), then recalculate T from the energy balance. Print out the values of T (assumed), P, nA(v), nAil), and T (recalculated). Ifthe assumed and recalculated values of T are within 0.01 K of each other, end the loop and go back to read the next set of input variables. Ifthey are not and more than 15 iterations have been performed, terminate with an error message. Otherwise, repeat the previous step, using the recalculated value of T as the assumed value for this iteration. Run the program for the eight sets of conditions shown in the spreadsheet table.

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Things to Learn: Bielby – The Structure and Process of Sex Segregation  The general neoclassical economic way of explaining occupational segregation and wage inequality: There are 2 aspects to the neoclassical economic approach. Those 2 are Human Capital and Statistical Discrimination.  The various sociological approaches: o Social psychologists: They say gender inequality is due to gender roles and the ideas of gender roles within society, and this influences the wage/pay gap o Feminist scholars: They say that wage inequality is due to the patriarchy and the men who are for the patriarchy who are helping to perpetuate this system. o Marxists: They say that owners of the means of production make and produce conflicts so it is hard to fight the system (since there are conflicts between people to begin with, it will be harder to fight the owners of the means of production). o Organizational theorists: They say that (or otherwise are concerned) with organizations and their functions and structures and how these structures influence inequality.  From neoclassical economics: o What’s the “human capital” explanation: The human capital way of explaining things claims that women make or have less human capital, or more so put less time into acquiring human capital- they invest little into human capital due to focusing on childrearing, housework, and taking care of the family. Therefore, they have less actual reasons to invest in human capital, which would allow them to make more money and get into higher paying jobs.  What’s the “statistical discrimination” explanation: Statistical Discrimination analyzes how employers/business owners, particularly men, use trends and/or statistics (whether they are accurate or not!) for deciding who gets a position: man or woman. Example: An employer thinks “Well, Lisa is more likely to not work for me long- term because statistics show that she is likely to have children and quit the job sooner than Brian would.” Or “Trends show that less women work these types of jobs compared to men, so maybe I should just hire Brian instead.”  Trends in “effort” of women vs. men in the workplace: Women tend to work harder even if they are paid less than men who are working less hard but still making more money.  Trends in discriminatory policy, and the two main sources of these policies:  How is “statistical discrimination” a self-fulfilling prophecy: This has to do with feedback effects. An employer doesn’t want to (or is hesitant) to hire a woman because of supposed statistical trends… he or she then actually does not hire the woman due to these trends or statistics they are thinking about, so by not hiring the woman, the person is making these statistical trends come true or is affecting them- Feedback effects explain how gender differences in labor market outcomes “feedback” to the actual life of the woman: she is more likely to marry sooner and have children sooner and not work in these jobs if she can’t even get them in the first place.  Six kinds of approaches for explaining sex segregation and pay inequality: o Neoclassical o Social psychological o Institutional o Cultural o Political o Patriarchal  What do the Marxists, the radicals, and the Neoclassicals all ignore that creates the major flaw in their models They tend to ignore the gender and/or culture ideology…one cannot ignore this! Blau – The Sources of the Gender Pay Gap  The two broad causes of the gender pay gap: Gender differences in qualifications and Discrimination  Trends in gender differences in qualifications: A common claim for gender differences in qualifications says that women have or are at least perceived to have less human capital than men.  Trends in labor market discrimination: Discrimination is a stronger predictor of the pay gap and wage differences via empirical evidence. The glass ceiling problem is also prevalent, which demonstrates how women reach a plateau in the labor market- they get into decent positions and even positions that pay higher (higher positions overall), but they are not allowed in the extreme-upper positions.  Definition of “labor market discrimination”: Discriminating on the basis of gender in a job or position which cause wage or occupational differences in pay.  Economic explanations for wage inequality: Becker Model and Monopsony.  “monopsony” (this concept isn’t well-defined; look it up, and we’ll talk about it in class): It’s like a monopoly- a particular buyer or group(s) of buyers control a particular part of the system. They have power over female employees. Example: They control the flow of information, or in other words they control from the woman ever knowing that they make less than other women, so discrimination doesn’t seem as bad (to the women employed and making less) because not ALL women are making less wages than the men. Therefore, discrimination is less likely to be pointed out by people, particularly the women.  “Feedback effects”: Gender differences in labor market outcomes feedback to the actual life of the woman: She is more likely to marry sooner if she can’t get a job…then have kids. This makes it even more unlikely she will get a boost in any career field she is in or ever work full-time again (or at least in her near-future).  “Wage structure”: Looks at changes in wages over time.  What story does the empirical evidence support Discrimination  Why did gains in wage equality and desegregation slow down in the 1990s: The progress of women in the job market started to decrease in the 1990s after the “boom” in the 80s- partially due to the glass ceiling problem, which was mentioned earlier. This means that women have reached a plateau and are typically not allowed in extreme-upper level positions. Ridgeway – The Persistence of Gender Inequality  Central argument, about using gender as a framing device: Gender is an important and focused part of peoples’ every day lives, and they often use gender as a way to relate to others. Stereotypes are prevalent and often gender stereotypes influence negotiations between people. To add, gender relationships are changing and the inequalities that still exist are being questioned in many different aspects of society- work/institutions, home, etc. Ways in which we think about gender are carried into our every day lives.  “cultural lag”: This refers to the idea that culture (such as old ways about thinking of gender) influences current social problems as it takes time for culture to catch up with the “new” and technological innovations. Cultural lag causes people to confront new situations which may also be uncertain with traditional or culturally perceived gender beliefs. Therefore, individuals rely on these convenient ideas to create new ways of doing things.  The three primary categories of “person perception” in the US: Sex category, race category, and age category.  Institutional identities as foreground identities, and gender identities as background identities: Gender as a background identity means that although it is easy to see someone as a man or a woman, that isn’t the only way we can define these people. Sex categorization usually enables us to quickly make sense of the other- but it’s not enough to understand the person fully. Contrast to institutional identities, gender (background identities) are more implicit. Institutional identities as foreground identities refers to the idea that these identities are more distinct- they usually provide more contextual definitions of the person and their behavior. Gonzalez (on Hochschild) – The Second Shift and Workplace Policies  Definition of “gender roles”: These are roles which are assigned or socially ascribed to either male or female, and are known as a set of norms (social and behavioral) and duties.  Distinction between sex and gender: Sex is biological and gender is how you identify or what you consider yourself (either male or female).  How do workplace policies affect gender norms: People embody these gender norms and roles, and then frame policies based on them. In workplaces with more egalitarian policies, men and women tend to hold egalitarian views at home/outside of work. In workplaces where policies are more strict (only women get maternity leave, and even no pay for this leave as an example, and another example is more concrete work hours for both men and women) women and men tend to hold traditional gender roles. Johnson – Why American’s Women of Color Have Lost Ground Since The Great Recession  Impact of the 2008 recession on Black and Latina women, in terms of: o Employment rates: Lower employment rates o Net worth/wealth: Lower net worth and wealth- hit black and Latina women the hardest – “Nearly half of single women of color have zero or negative net worth, meaning their debts equal or exceed their total assets (Johnson).” o Access to health care: Returned to pre-recession levels with the help of the Affordable Care Act, although some states do not want to expand health coverage and this hurts many women because they are not necessarily at “poverty level” but a bit above- but they are still living in poverty!  Explanations for women of color suffering disproportionately from the effects of recession: There are not many that are in office (State or Government jobs), and the people who do hold office cannot connect or understand the circumstances women of color are in. Bedera – Is Barbie a Feminist Now  The “Imagine the Possibilities” ad campaign  How does the commercial present gendered opportunities Little girls playing with Barbie play sets that are occupational or male- dominated fields  How do the available products present gendered opportunities They influence little girls to seek different careers, including male- dominated careers

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Chapter 8, Problem 8.94 is Solved
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Textbook: Elementary Principles of Chemical Processes
Edition: 3
Author: Richard M Felder
ISBN: 9780471687573

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