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For assistance with (but not answers to) homework problems.

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A simple reminder to all: this is the "Homework Help" forum, not the "Homework Answers" forum. We will not do your work for you, only point you in the right direction. Posts that do give the answers may be removed.

  1. i'm trying to work my way through this problem but i dont understand it. HCN is a weak acid and bromine is a good leaving group. so what i have here is a sn1 reaction. right? or is it an e1? the HCN is too weak to substitute the bromine so the bromine has to dissassociate in the first step before the CN- can attack. but what do i do then?

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  2. Started by Brazen,

    Chem: can someone tell what the structure is? I see from IR spectrum that I have OH, C-H sp2, C-H sp3, C=C aromatic, C-O groups. I see that I have 91, 134, and 149 fragments. I know that 91 is benzene-ch2+ fragment. I don't know what the 134 or 149 fragments are. I know that 149 is actually the whole structure. Looking at proton and C13 NMR i see that i have OH, benzene, CH3, CH2, CH groups, not sure if i got all of those groups right. I can't seem to get what the structure is. Here is spectra: http://i39.tinypic.com/zmjypd.png http://i44.tinypic.com/wkst91.jpg

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  3. .....CH3..............................................CH3 .....|....................................................| ..I-C-H................+ NaCN...->............CN-C-H.............+.......I- .....|....................................................| HO-C-H..........................................OH-C-H ......|...................................................| ....CH3................................................CH3 i have sneaky suspicion that after the CN takes the place of I it switches around to the back of the carbon chain, opposite the side of the OH, but thats as far as i can get.

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  4. Started by nitelyechos,

    i understand the halogen is substituted by the nucleophile (CH3O-) in most cases but how do i tell which is the exception? problem: R-X + CH3O- CH3OR + X- which haloalkane would not undergo the reaction above? CH2=CH-CH2-Br CH3Cl CH2=CH-I CH3CH2Br CH3CH2CH2Cl

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  5. Ok guys in my school we are on thesystem of IB curriculum, and over here we need to write this one 4000 wordessay on a particular area of knowledge (Mathematics in my case), its known asthe Extended Essay. Now i have a topic, i just dont know if its good enough,because no one in our school is that mathematically capable of overlooking atmy topic including the teachers, so i was thinking some more experienced peopleover here could help out. So here is my researchquestion: "Do all polygons with n number of sides associate with Φ ?, ifso, aspect the 3 dimensional polyhedron "dodecahedron" and"Hexahedron" in relation with the Golden ratio." How viable would this be to…

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  6. Started by angellee0113,

    Well, I'm using catechin for my polyphenol oxidase assay to determine the substrate specificity. But the problem is when I try to use 50mM above, the concentration seems to be very high which the spectrophotometer shows more than 4.500. What should I do?? I couldn find any info from the website or journals. Should I dilute it? And I should dilute the substrate only or together with the enzyme? The total volume is 2.9ml, so if i dilute it using 1:2 ratio, means 2ml of buffer and 1ml of substrate? The total volume of blank is 3.0ml of buffer + substrate. Please help me ! Thanks a lot !!

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  7. Hello everybody: Please, I need help interpreting what is being represented in an osmotic fragility curve of erythrocytes. I attached the pdf with the article. My questions are regarding the curve represented in Figure 1. I do not know what (C1-10, C1-50 ,C1-100 and C2-10, C2-50 and C2-100 represent). Also I don´t understand why (curcumin membrane-stabilized erythrocytes) need to be used as positive control. I would really appreciate your help. Looking forward to hear from you. 2886-22206-3-PB.pdf

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  8. Started by Neurokid,

    Hi there, I am currently doing an assignment for my undergrad degree and I am really struggling to figure out what the control conditions are in the following two studies: 1) http://www.hfac.gmu.edu/people/mpeters2/Courses/Psy768-s10/Readings/Blotvinick1999.pdf 2) http://scan.oxfordjournals.org/content/early/2012/01/20/scan.nss010.abstract I know it's a big ask, but if anybody is good at interpreting fMRI, then your help would be massively appreciated. Many thanks, John Just to clarify, I understand the methodology used and what they did. I'm just struggling to figure out if it is one of the conditions (i.e. compatible trial in the Botvinick pa…

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  9. Started by ryguynumba5,

    I'm sorry for this noob topic but I really need help. I'm not asking anyone to do the program for me but I need some guidance and my professor did not help me at all when I went to visit him. Assignment: This assignment is designed to help you get more familiar with basic assembly language instructions, the IO macros, and the bsvc system. For this assignment, you will write a program in Motorola M68000 assembler that takes as input a four digit year, and prints the day of the week for Christmas of that year. Here is the formula to solve the problem: Input: Month Hardcoded, month = 12 Day Hardcoded, day = 25 …

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  10. Hi I was wondering if someone could provide a link or post/attach the full reaction mechanism (including all steps) of the dehydration of a secondary alcohol, say 2-butanol including all the end products (is there a hydrogen ion left at the end?) My instructior showed the reaction with H2PO as the catalyst but I think I copied it wrong and I haven't been able to find it online. Thanks.

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  11. In the following problems, Θ = 20 + units digit of your day of birth. For example, if you were born on April 1st, then Θ = 20 + 1 = 21. If you were born on March 30th, then Θ = 20 + 0 = 20. 1. Alok and Bhanu play the following game on arithmetic expressions. Given the expression N = (Θ + A)/B + (Θ + C + D)/E where A, B, C, D and E are variables representing digits (0 to 9), Alok would like to maximize N while Bhanu would like to minimize it. Towards this end, they take turns in instantiating the variables. Alok starts and, at each move, proposes a value (digit 0-9) and Bhanu substitutes the value for a variable of her choice. Assuming both play to their opti…

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  12. We did an experiment to find out how much sulphate was in a sample of homemade fertiliser. This is the method: Å Finely grind a small quantity of fertiliser using a mortar and pestle. Weigh out accurately about 1.0 g of fertiliser into a 100 mL beaker. Record the mass of fertiliser to three decimal places. Ç Add about 50 mL of deionised water and stir to dissolve as much of the fertiliser as possible. Filter the mixture into an approx. 500 mL beaker, washing the residue (the solid trapped in the filter paper) several times with a small amount of deionised water. É Add about 3 mL of 2 M hydrochloric acid to the filtrate (the solution passes throug…

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  13. Started by 3dDesign,

    hello i am making a research and i need you to take this survey plz 2012 Survey i need it so much thank u any way

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  14. Started by tomyoung,

    Hi, I'm having some problems with home work and i stuck. 1. How you would prepare 5 mL of a 75 ppm Cu solution from a 0.015 mol/L solution of copper (II) nitrate. Show full details of your working I know that 75 ppm Cu is equal to 75 mg of CU per litre of solution, so in 5ml we have: 0.075 g L(-1) x 5 x 10(-3) = 0.375 x 10(-3)g mollar mass of Cu(NO3)2 = 187,55 g/mol, it's really confused me the information of 0.015 mol/L solution. 2. A 400 µL sample of a water sample from a polluted river was added to a 25 mL volumetric flask and tested for phosphate using a colourimetric method by adding the required reagents and making to the mark with …

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  15. Started by modou,

    Given the network address as : 193.12.111.0 and subnet mask as: 255.255.255.224 . <br style="font-family: verdana, geneva, lucida, 'lucida grande', arial, helvetica, sans-serif; font-size: 14px; "><br style="font-family: verdana, geneva, lucida, 'lucida grande', arial, helvetica, sans-serif; font-size: 14px; "># how to calculate the Total Subnet ?<br style="font-family: verdana, geneva, lucida, 'lucida grande', arial, helvetica, sans-serif; font-size: 14px; ">#How many unusable host/Subnet?<br style="font-family: verdana, geneva, lucida, 'lucida grande', arial, helvetica, sans-serif; font-size: 14px; ">#What is the IP address of : 193.12.111.109 -u…

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  16. I have to write the background/introduction (part of my report) on this: How does salt effect the boiling point of water? Basically, my teacher only wants me to do the physics side of this experiment, not the chemical side. She also wants the background to be about 1+ page/s (purely on the background). Could anyone just give me some pointers on what to write in the paragraphs and what issues/topics I should address within the background...(also because if you wrote it for me it would be breaking the rules, and also copyright) Thanks in advance oh, and by the way, I'm new to SFN (as in today new) so please don't be hard on me and it's grade 11 work, but it…

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  17. Started by dr. undefined,

    Can anyone help me by a generalized equation for the time period of all types of pendulums?

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  18. Started by nelson1990911,

    could anyone tell me functions and mechanisms of P2Yreceptors in detail?

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  19. Started by Chocotaco,

    I have a small case study, nothing special but it kinda got me a bit. The main topic is pretty much on the Central Nervous System, Action Potentials, and so on. It asks what would happen if the extracellular potassium is ten times higher than normal in the brain tissue. I know it would cause some sort of seizure, the extra potassium would make it depolarize to make an action potential. But I don't know how it would cause a seizure effect. Would that skip the refractory period forcing it to depolarize at a faster rate giving you seizures?

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  20. Started by casa,

    what would be the most suitable antibody to detect a tumor antigen (a murine monoclonal antibody, chimeric or humanized. knowing that the three antibodies are specific for the same tumor antigen and that it s for a screening test, I think the three can be used but the most suitable would be the one that is least costly to produce, so the murine antibody. any idea ?

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  21. Started by hdr,

    A coal-fired steam power plant operates on the ideal Rankine cycle. Feedwater from the condenser at P1 = 10 kPa is pumped to the boiler at P2 = P3 = 20 MPa, where it is superheated and exits the boiler at T3 = 550 °C. The moisture content in the turbine is not to exceed 12% (i.e. steam quality is to be maintained above x = 0.88 throughout the turbine). Up to two reheat stages can be added to the steam cycle to satisfy this requirement. If needed, one stage can be added to reheat the steam to T5 = 525 °C at P4 = P5 = 10 MPa. If more reheating is required, a second stage can be added to reheat the steam to T7 = 500 °C at P6 = P7 = 2.5 MPa. A …

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  22. Started by hdr,

    A gas turbine power plant operates on the regenerative Brayton cycle as shown in the figure. Compression occurs in two stages, with interstage cooling, and expansion in the turbine likewise occurs in two stages, with interstage reheating. The cycle operates between the pressure limits of P1 = P9 = P10 = 100 kPa and P4 = P5 = P6 = 1200 kPa. Interstage cooling/heating occur at the thermodynamic optimum P2 = P3 = P7 = P8 = 346.4 kPa (i.e. the geometric mean of the intake air and combustor pressures). Air enters each compression stage at T1 = T3 = 300 K. Combustion gases enter the first and second stages of the turbine at T6 = 1400 K and T8 = 1300 …

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  23. Started by Born Science,

    I need help for my huge homework in projectiles before my exam starts on 13/12/2012 and I am waiting for the first reply who can do this for me... There are 4 exercises, each exercise has a related questions between (14 and 20) the answers are short but hard to find out if my homework is right or wrong. Special thanks. Edit: I don't really need the answers... I just need to figure out how to really solve each problem-solving in each exercises. Thank you

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  24. Started by Vastor,

    hey guys, from the (math)textbook, The distance between the points [math]P(x_1, y_1)[/math] and point [math]Q(x_2, y_2)[/math] is [math] \sqrt{(x_2 - x_1)^2 + (y_2- y_1)^2}[/math] what does the intuition behind the statement? it look like much Phytaghoras theorem, does anything related here? another thing is the intercept form [math] \frac{x}{a} + \frac{y}{b} = 1 [/math], where a = x-intercept, and b = y-intercept. anyone can give how does this formula formed from? or atleast any intuitive behind this equation? hope anyonce can help, btw, if anyone got good website/tutorial about coordinate geometry, please send me links.. thnx

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  25. Started by Z(o3o),

    Hello, my teacher gave us an assignment to ask someone with a science degree questions to put in a portfolio project that we are doing. I would greatly appreciate it if one..or a few...of you could answer the questions below. thanks in advance. 1. What motivated you to pursue a career in thefield of science? 2. What advice do you have for people planning topursue a career in the field of science? 3. Your favorite science related experience? 4. Your favorite element? 5. What do you think will be the next greatadvancement in science? 6. Anything else you would like to add?

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