Search results

  1. F

    Polar aprotic solvent sn2 rate

    In a Finkelstein rxn, if more acetone is added so that the total volume of the solution is doubled, would the reaction be faster or slower and by how much? Polar aprotic solvents (like acetone) increase the rate of SN2 reactions by dissolving the ionic nucleophile and yet not solvating the...
  2. F

    Redox with 3 half reactions

    KBrO2 + KI + HBr ---> KBr + I2 + H2O eq1 KBrO2 ---> KBr 4e- + 4H+ +KBrO2 ---> KBr + 2H2O eq2 2KI ---> I2 + 2K+ + 2e- 4KI ---> 2I2 + 4K+ + 4e- eq3 HBr ---> KBr K+ + HBr ---> KBr + H+ since the charges in eq3 are +1=+1 you don't have to multiply this equation by 4 do you...
  3. F

    [OH-] or [H+] ?

    __________HA <------> H+ + A- initial (mol) .1 ________ 0 ___ 0 change __ -x _______ +x ___ +x final _____.1-x _______ x ___ x Ka = 10^-8 find pH of .1 mol acid since ka X 100 = 10^-6 < .1 can use initial concentration: .1-x = .1 Ka = [H+][A-]/[HA]...
  4. F

    Molar conc.

    If 25 mL of 12 M HCl are added to 475 mL of distilled water, what is the molar concentration of the diluted hydrochloric acid? c1v1=c2v2 25*12=475c c=.63 M HCL book has the answer as .60 M HCL Isn't the answer .63?
  5. F

    Paternity test identical twins

    Identical twins both mate with a female and produce a child. How could you determine who the father is? Identical twins result from when the zygote splits, so both twins will have the exact same DNA unless there was a mutation to the germ cells?
  6. F

    Algal bloom oxygen level?

    photosynthetic algae - photosynthesis takes place during daylight, CO2 is used and O2 is released. At night, aerobic respiration occurs, O2 is used and CO2 is given off. If these two processes are in balance with each other (or are they?), how would an algal bloom decrease the O2 level in...
  7. F

    Gram negative bacteria and antibiotics?

    A high level of peptidoglycan (polysaccharide) in the cell wall of bacteria will be stain gram positive (purple). Cells with a lower concentration of peptidoglycan in the cell walls are gram negative (pink). Gram negative cells have an outer membrane that is toxic to mammalian physiology and...
  8. F

    Molarity of solution

    Is this how you work this problem: A sulfuric acid solution has a density of 1.49 g/mL and contains 59 percent H2SO4 by mass. what is the molarity of this solution? .59x98g = 57.82g H2SO4 1mL/1.49g x 57.82g H2SO4 = .0388L 57.82g H2SO4/ 98g H2SO4 = .59 mol .59 mol/.0388L = 15.206 M...
  9. F

    Regenerative chemical turns muscle cells into stem cells

    found an interesting article on new stem cell research: "La Jolla, CA. December 22, 2003—A group of researchers from The Scripps Research Institute has identified a small synthetic molecule that can induce a cell to undergo dedifferentiation—to move backwards developmentally from its current...
  10. F

    Lactose intolerance

    I was trying get more info about what causes lactose intolerance (caused by mutation or by inherited mutations?) and came across this link: which is part of what Dr. Peltonen was discussing in the 30 min. lecture link. (UCLA and...
  11. F

    Dangerous lab experiment?

    Last semester we did a lab separating the components of a mixture. Part of the experiment involved subliming NH4CL (ammonium chloride) in an evaporating dish but instead of placing the dish in the hood (as outlined in the lab procedure), our class had to use open air bunsen burners. There were...
  12. F

    Power dissipated in RLC circuit

    An RLC series circuit constists of a resistor of 100 ohm, a capacitor of 10.0uF, and an inductor of 0.250 H. The circuit is connected to a power supply of 120 V and 60 Hz. What is the power dissipated in the circuit? I got 37 W (rounding 2 S.F's) the solutions manual has the answer as 73 W...
  13. F

    Current through resistor

    what is the current through the 2 ohm resistor? what is the current through the 8 ohm resistor? 8 V ......! |............ . empty space . . empty space . I . empty space . ...2 ohm Res.... . empty space . . empty space 8 ohm Res . empty space . I_2 . empty space ...
  14. F

    Check physics answers

    problem #1 Two point charges of +3.0uC and -7.0uC are placed at x=0 and x=.20m, respectively. What is the magnitude of the electric field at the point midway between them (x=.10m)? E3 = (kq)/r^2 = [(9x10^9 )(3x10^-6 C)]/.10m^2 = 2.7x10^6 N/C E7 = (kq)/r^2 = [(9x10^9 )(7x10^-6 C)]/.10m^2 =...
  15. F

    Atoms in a gas

    Gas is N2O4. fill in the chart. I've got all but atoms. how do I get the # of atoms? why wouldn't it be the same as molecules: 1 mol/22.4L * 6.02x10^23 molecules/1 mol * 5.02L = 1.35x10^23 molecules molecules of are: 1.35x10^23 why couldn't I just replace the word 'molecules' with atoms...
  16. F

    Thermal efficiency

    A heat engine has an efficiency of 25.0% and its heat input is 600J per cycle from the high-temperature reservoir. What is the rate of heat output to the low-temperature reservoir per cycle? E=(Qh-Qc)/Qh .25=(600J-Qc)/600J Qc=450J book has the answer as 800J. How are they getting 800J...
  17. F

    Volume expansion and pressure change

    A brass cube, 10 cm on a side, is heated with a temperature change of 200 deg. C. By what percentage does its volume change? Vo = 10cm = 1000cm^3 = .001m^3 T = 200 C brass = 19x10^-6 coefficient of linear expansion V=Vo(1+3 x brass x T) or change in V = Vo(3 x brass x T) =...
  18. F

    Inclined plane and a box

    a box on a smooth inclined plane with an angle of 20 degrees to the horrizontal. If the inclined plane is 5 m long, how long does it take for the mass to reach the bottom of the inclined plane after the mass is released? I did sin 20 degrees x 5.0 m = 1.71 m how do i get the mass from this...