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  1. H

    Gel filtration chromatography

    Hi, I am studying for my biochemistry lab exam. While going over one of the questions... I came across one that I can't answer...help will be appreciated. Question under analysis is related to a previous question. (Previous question) A gel filtration (size exlcusion) is set up and the...
  2. H

    Electron Configuration

    Yes, I found this guy's explanation very accurate. Check it out. 'At the beginning of the first transition series (scandium), the 4s orbital is lower in energy than the 3d orbitals. Thus Sc has the configuration [Ar] 4s2 3d1. This continues as far as V which has the configuration [Ar] 4s2 3d3...
  3. H

    Equilibrium problem

    how did you come to the conclusion that it is ammonium phosphate? Not challenging you, but your answer my help me understand your procedure better and potentially help you.
  4. H

    Electron Configuration

    Borek is correct, the d orbital is close in energy to the s orbital so when an electro jumps from s to d, the energy is much less than jumping from a p or f to a d. They are close enough to allow this.
  5. H

    Selectivity of free radicals in halogenation.

    thank you, but still dont understand about selectivity... :(
  6. H

    Selectivity of free radicals in halogenation.

    Hi, can anyone please explain what selectivity of free radicals is? For example, there is an MCAT question that I recently came across and that can't seem to make sense of the answer. Which of the following halogens will give the greatest percent yield of tertiary alkyl halide when reacted...
  7. H

    Question about spectrophotometry and resveratrol

    yes, I would definitely make a graph with different concentrations of resveratrol in ethanol, this will give you a good relantion between concentration and absorbance from there you can calculate the concentration of it. Also I would do 3 trials for each known concentration, just to make sure...
  8. H

    Chemistry: Mass to Mass Problem

    no problem bro, good luck
  9. H

    Chemistry: Mass to Mass Problem

    yeah that seems correct, i am getting the same thing (6.67 g of CH4)
  10. H

    Finding amount of iron from absorbance

    3.20 ppm of Fe3+ = 320mg/L Fe3+ = 0.320g/L Fe3+ (divide by molar mass) (0.320g/L)/(55.84g/mol) = 0.0057 mol/L -------> 5.7 * 10^-3 Molar Fe3+ ...(are you doing your math correctly?)
  11. H

    Chemistry: Mass to Mass Problem

    it seems correct to me (the procedure) i dont understand your numbers tho, but it seems that you are following what i said so that must be right..
  12. H

    Chemistry: Mass to Mass Problem

    ok first off, convert your grams of CHCl3 to moles of CHCl3... you should be able to do that. Then from your chemical formula, you are able to find the ratio needed to form a certain reactant. For example, 1 mole of CH4 will form 1 mole of CHCl3. The coefficient of each molecule will tell you...
  13. H

    Chemistry Finding the pressure required when given number of molecules.

    wait what? can you post the units for constant?
  14. H

    Chemistry Finding the pressure required when given number of molecules.

    You got it! :D your answer is in kPa( kilo pascal) 1 kPa = 10^3 Pa, so if you multiply your answer by 10^3 you get what you are supposed to... this comes from the fact that you chose R to be 8.314 and its units are L kPa K−1 mol−1 (note the kPa) ... good job! good luck
  15. H

    Chemistry Finding the pressure required when given number of molecules.

    you dont have to do it at STP because you are given a specific temperature, you only use STP when you are told to do so... in this case... T= 25 celsius (convert to Kelvin) and your pressure is what they are asking you... so P is your unknown.... your volume would be 0.001 L (1ml) ; read...
  16. H

    Chemistry Finding the pressure required when given number of molecules.

    I get a extremely small number when i divide 10^8 by 6.02 *10^23 .... are you doing this correctly? check your steps ..
  17. H

    Which of these is more polar?

    I agree, molecule 1, even though the caboxyl group is very polar (because of the high electron density) the molecule will no exhibit great polarity because R-group to the left is to big. Number 2, Br is not as electronegative as Oxygen (can you explain why? look at the electronegativity trend)...
  18. H

    Chemistry Finding the pressure required when given number of molecules.

    ok first you convert the number of molecules to moles using avogadros number. if you know that 1 mole = 6.02 * 10^23 molecules you need to find 'x' moles for 10^8 molecules Once you find the number of moles (which should be a tiny number) convert mL to L (have volume) You have Temperature...
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