Posts by ~christina~

Total # Posts: 811

  1. chem

    If I understand your question, it would probably be how to calculate the mass of a molecule. ex. N2 mass N2 - 2(14.001) = 28.002 g/mol Thus 1 molecule of N2 = 28.002 g/mol
  2. Earth Science

    Low amounts of silica. Silica makes the magma more viscious and thus less likely to flow quickly. source: wikipedia (magma)
  3. chemistry

    That's what I was thinking I should do but wasn't sure. Thanks Dr.Bob p.s. I hope you've been doing well since the last time I was here. :)
  4. chemistry

    I have a question about m-Phenylenediamine. Is m-Phenylenediamine the same as m-Phenylenediamine hydrochloride? I apparently have to use the latter for a chemical test but we only have a bottle that is labeled as the former. Is it okay to use that and just dissolve it in water...
  5. Dr.Bob - Question

    I was just trying to figure out what I wanted to do. It's good to know that I don't have to choose right away though. I'll start getting things together and then apply. I appreciate your advice, Dr.Bob and GK. :-)
  6. Dr.Bob - Question

    I have just 1 year left before I graduate with another degree that is science related. It is not in chemistry but I have taken almost all of the chemistry classes that are usually taken by a chemistry major. (excluding inorganic and other more specific chemistry classes)There ...
  7. Dr.Bob - Question

    I would like to try the other chemistry classes and see how I like them. Thanks bobpursley.
  8. Dr.Bob - Question

    Thanks for your responses, Dr.Bob and bobpursley. I'm not too good in the area of biochemistry unfortunately. I was thinking about Analytical, Organic, Environmental, and Inorganic Chemistry. I haven't taken any inorganic classes in my school though, because they don&#...
  9. Dr.Bob - Question

    I'm know I'm interested in the chemistry field. The problem is that I have to further narrow down my field of interest. I was curious to know what type of chemistry did you specialize in in the past. -christina
  10. citation of UNEP PDF online assessment/report

    If it tells you in the document: Citation: AMAP/UNEP 2008 Technical Background Report to the............. Is that usable?
  11. citation of UNEP PDF online assessment/report

    How would I cite a document from the UNEP website? (PDF document) APA style? I've been looking but it looks like you have to cite it a special way? Is this true? I cannot personally find the, "session" or etc. It is a document evaluating the environment, not a ...
  12. science(chem)

    I dried a solution of solvent + unknown compound dissolved in it, and it would not fully evaporate off and leave a residue. What was left over no matter how much I heated the watchglass was stagnant droplets as if I was using dirty glass and I had poured a solution over it. (i...
  13. science(chem)

    I have a question about compounds that oil out of solvents after drying. How would I analyze this? Could I make a KBr pellet, or would I just be able to analyze it in UV spec? I assume that the solvents used to dissolve the compound, would be used as a blank, right? I tried to...
  14. english

    Thanks Ms Sue :)
  15. english

    I have a general problem with not being able to determine when it is appropriate to use semicolons. I usually use appostrophes and it is incorrect, of course. Is there a way to recognize the place where a semicolon should go? The examples I have seen are very obvious examples...
  16. science(chemistry)

    Thank you Dr.Russ.
  17. science(chemistry)

    I did try to use the GC to see what solvents I had (out of the above)but there was significant trailing in some of them so this complicated the situation. I initially thought that the trailing peak at about 4 min on polar, was the unknown compound but since octane and decane ...
  18. science(chemistry)

    I do have one last question. Is it possible to use the same solvent for dissolving the compound and for developing the plate as well? i.e. ethyl acetate for dissolving and running the plate. Thanks, Dr.Bob
  19. science(chemistry)

    Ah, alright. Actually thinking about it, it is not hard to spot the plate with the compound in the different solvents since I'm using the same developing solvent. Thanks, Dr.Bbo
  20. science(chemistry)

    I have a question about TLC plate solvents. What solvents will leave stains on a plate with a TLC plate out of the ones below and why?) (n-Octane, n-Hexane, Decane, Acetone, 1-Propanol, 2-Propanol, Ethanol, Toluene, Cyclohexane, Methanol, n-Heptane, n-Pentane, Butanol) I saw 2...
  21. science(chemistry) -Q for Dr.Bob

    Wait, the whole problem here is to determine whether there is or there is not water in the solvent layer. Utilizing the CaSO4 to dry the layer would not tell me if there was or was not water. basically, Is there any way to determine if there is water in solvent layer?
  22. science(chemistry) -Q for Dr.Bob

    Okay, I'll try that then. Thank you, Dr.Bob
  23. science(chemistry) -Q for Dr.Bob

    Drierite is CoCl2. The problem I have is that I'm not believing what I'm seeing. It did not turn from blue to pink like it would if it had water and the solvent just evaporated quickly after touching the drierite. BUT if there was water and there was just more organic ...
  24. science(chemistry) -Q for Dr.Bob

    I did see more than one solvent. That's what I was saying, but the last peak didn't look like a solvent peak. It just looked like a hill compared with the other peaks that were sharp. I have never used a drying agent in this particular lab before. I guess Drierite is a...
  25. science(chemistry) -Q for Dr.Bob

    hm...I was just reading that a flame ionization detector does not respond to water? now I'm confused.
  26. science(chemistry) -Q for Dr.Bob

    solvent layer: 1 solid precipitate: no I ran the solvent layer I got in my unknown in the GC and I had sharp peaks in the beginning but at about 4 min on the polar column, I got a broad peak that tailed off considerably. question is, Is it water? I'm not sure how water ...
  27. science(chemistry)

    Okay I guess the only solution is to find out what the solvent is and then make a mixture out of that. Thank you, GK
  28. science(chemistry)

    When performing vacuum filtration of a solid in an unknown solvent, is it necessary to go and find out the solvent composition, so that some fresh solvent can be used to wash the filtrate with?
  29. science(chemistry)

    Hm..very true. I now recall that different solvents will give you different results, based on their interactions with the compound in question. Just like a crime scene. My plan of attack is to evaporate and just try out different solvents. Thanks for all your help, Dr.Bob :D
  30. science(chemistry)

    I assume you mean to make a KBr pellet from the solid obtained from one of the layers. Most organic solvents will evaporate and I don't think there will be interference to worry about. Yes, I mean to add the dry solid to KBr to form a pellet. The chance of interference ...
  31. science(chemistry)

    I have a question about solvent evaporation. If I had an organic layer and an aqueous layer in an unknown mixture of liquids and wanted to obtain the solid of a compound(s) dissolved in the layers, is it reasonable to assume that I can run the compound in the IR spectrometer (...
  32. Chemistry

    Yes. It's chemical compound formula is SiO2.
  33. science(chemistry)

    Thank you GK
  34. science(chemistry)

    How would I compare using peak heights vs peak areas for GC quantitation? Thanks
  35. science

    It will be a curved exponentially increasingly sloped line.
  36. science

    a. Composition
  37. Dr.Bob, response to your reply to last answer

    Sorry, I didn't see this. Actually you have only one mixture; it happens to have two components. There is a more or less standard procedure for separating complete unknowns (that's where you know nothing about it) and if you know nothing about it that is where you ...
  38. Chemistry

    actual compound weight that should be produced/ theoretical weight of compound that should be produced x 100 thus, 1.34g MgO/ 1.44g MgO x 100= _____% yield of MgO
  39. science

    marine terraces are formed by the erosion of rock by wave action. (waves hitting the exposed rock) sand dunes aer formed by wind erosion. parallel hills, I'm not sure about but apparently they can be foremed by melting glacial ice (and thus they can have unsorted sediment...
  40. chemistry- Dr.Bob, can you help me out please?

    Now that you state it, I realise I have a problem with the separation part. I'm not sure how much sample I'm going to be given. I may come across as going backwards in a sense, but how would I separate two mixtures? Thanks, Dr.Bob
  41. chemistry- Dr.Bob, can you help me out please?

  42. chemistry- Dr.Bob, can you help me out please?

    If I had two unknown chemicals (in solid form) mixed together, how could I go about identifying the individual components of the mixture? Is it possible, by UV, IR, GC, or HPLC? The problem I have is that with: GC= sample is destroyed & if you don't know what compound you ...
  43. Chemistry

    The reason that your value is negative is that, it depends on which number you put first, when subtracting the accepted value from the experimental actual value, you have to put a | | (absolute sign) around the subtracted values. (that means that the value is accepted as being...
  44. Chemistry

    Answered below
  45. chemistry

    I think you need to convert the moles of sodium phosphate into grams of sodium phosphate. Then use that and divide by 300g of H20. Multiply the number that you get by 100, and it should give you the concentration in percentage mass of sodium phosphate in the ammount of water ...
  46. Chemistry

    Since KOH is a strong base, it totally dissociates, and thus the concentration of hydroxide ions in solution equals to the concentration of the KOH. 0.70M KOH note that: [H+][OH-]= 1.0 x 10^-14 so, [H+]= 1.0x10^-14 / [0.70M] = ______[H+] since pH = -log[H+] plug in the [H+] ...
  47. Physics

    The problem is that you divided the distance traveled by the raft by ..4.49s. I don't know where you got 4.49, but using the original time obtained by you with the time it takes for the rock to hit the water, would give you the answer in the book. (time it takes for stone ...
  48. Water Chemistry

    That's correct.
  49. chem lab

    I suspect that the absorbance would increase. The fingerprint would cause the light going through the cuvette to be distorted somewhat. This would lead to less light hitting the detector and thus, a higher absorbance.
  50. math need help please

    -9^2-(-6)^2= -81-36= ____
  51. science(chem)

    If I have a graph of concentration in Absorbance at 400nm vs [micromolar]of para-nitrophenol The slope would be the extinction coefficient. (y=mx) if forced through 0 The problem is what is y? I know y is the absorbance but it's given on a paper i have as, y= Absorbance at...
  52. Graphing interpretation

    What would it mean if the line of a linear regression graph went through the origin? If it doesn't go through the origin and I make it go through the origin, what am I doing? I was looking for the answer to this and all I came up with was that if the line goes through the ...
  53. science(chem) Dr.Bob Question from before

    Okay, I get it. No it wasn't to 5 decimal places. I'm not looking at my notebook but it was 1.0---. Thanks for your help
  54. science(chem) Dr.Bob Question from before

    The only reason I asked about the balance is that most analytical balances in use in schools weigh to the nearest 0.1 mg although that may have changed since I retired. There are semi-micro balances that weigh to 5 places and micro-balances that weigh to 6 places but those ...
  55. science(chem)

    I weighed the K2Cr2O7 on an analytical balance. (solid) correction: needed 0.85015g actually weighed out: 0.8508g I actually used 0.8508g but I needed 0.85015g, I just hope it doesn't make the results funny...but I hear that it does not need to be accurate.(how it is..I ...
  56. science(chem)

    O.O I don't remember...It might have been a more general question on solutions though. Ah, I was going to ask about the density but I forgot. I had to prepare 10% H2SO4 solution using stock and I was wondering about if I had to convert the grams to ml using density and I ...
  57. science(chem)

    I'm making different concentrations of ethanol and I just wanted to check my calculations and method. Making ethanol concentrations of: 0.40% 0.30% 0.20% 0.10% 0.05% To make the 0.40% ethanol from stock solution using 100ml volumetric flask: (xg ethanol)/(100ml) x 100= 0....
  58. Chemistry

    solve for ml (it's a dilution equation) You have the initial concentration and final concentration with volume of it that you want. All you need is the initial volume of concentrated nitric acid you want to remove from the concentrated stock volume, to use to dilute to the...
  59. science(chem)

    I'll see how I do with that site, first. Thanks Dr.Bob
  60. science(chem)

    The pKa of HEPES is 7.55 at 20C and it's MW is 238.31. Calculate the amounts of HEPES in grams and of 1.0M NaOH in ml that would be needed to make 300ml of 0.2M HEPES buffer at 7.2. I'm not sure how to go about doing this problem. Help please.
  61. science(chem) Dr.Bob Question from before

    Okay, thanks Dr.Bob.
  62. science(chem) Dr.Bob Question from before

    I'm doing an experiment and I'm supposed to have neutral basic and acid samples of solution. I just wanted to make sure that I knew which was which. (If I'm incorrect, please correct me) Acid: 0.7ml 10% H2SO4 + 0.7ml 10% Na2WO4(sodium tungstate) Basic: 0.7ml NaOH...
  63. science(chem)

    I'm doing an experiment and I'm supposed to have neutral basic and acid samples of solution. I just wanted to make sure that I knew which was which. (If I'm incorrect, please correct me) Acid: 0.7ml 10% H2SO4 + 0.7ml 10% Na2WO4(sodium tungstate) Basic: 0.7ml NaOH...
  64. science(chem)

    It was not stated, so I assume that I will be making them at std room temp. Thanks for the help, bobpursley.
  65. science(chem)

    I was wondering how does one make a saturated chemical solution? I'm supposed to make one, is there a way I can determine the ammount solute needed for a certain amount of solvent? If not, how do I make a saturated solution? Thank you
  66. science(chem)

    I need help finding information on how the conway microdiffusion is done/how it works. And why the sample is titrated. Thank you
  67. science(chem)

    Thank you SraJMcGin, I'll check those out. If they don't turn out to be what I need, I'll ask and hopefully Dr.Bob will be here, and able to help.
  68. science(chem)

    I need help finding information on how the conway microdiffusion is done/how it works. And why the sample is titrated. Thank you
  69. science(chem)

    Yes I saw that. I thoroughly looked this up before I came here... That doesn't tell me what will I see. What does "Agregate," mean? I found out what I needed, I think. Thank you for looking, Dr.Bob.
  70. science(chem)

    UV I was just wondering how a solvent would affect the spectra of a compound. Like a polar or nonpolar solvent for example: polar: Methylene chloride Nonpolar: cyclohexane, hexane, or ethanol Thanks
  71. Sci

    Energy could be in the form of a) heat b) light
  72. Sci

    I wrote: - theres a smell of ordur odor - change in color - fizzing or bubbling - percipitate forms precipitate - difficult to reverse I think the last one doesn't fit. Temperature change is another way to tell a chemical rxn has took place. I also corrected some spelling ...
  73. Sci

    Then the blood would become basic.
  74. chemistry

    Density of water: 1.0 g/mL Principle: If an objects density is greater than water density, it will sink in water. If an object's density is lower than water density, it will float in water. Now, what will the liquid do? (I think you can figure it out from what I said above...
  75. chemistry

    Post your question above, not below another question.
  76. science

    Again, you need to be more specific. Do you want to know what it does or etc? If you want to know what it does, I'll post that below. From wikipedia: In animals, the brain is the control center of the central nervous system, responsible for behavior. In mammals, the brain ...
  77. science

    The reason plants bear fruit is because it's a adaptation that allows them to spread their seeds in different locations. Animals, such as birds eat them and then disperse them in their droppings. You have to be more specific as to your second question of, "what are ...
  78. MAth

    incorrect 3.75gal (8.34 lb/1gal)= ______
  79. chem

    My question below was asking about the experiment that you are doing. The handout is obviously about this experiment. If we do not know the experiment, how are we going to answer these questions?
  80. chemistry

    What are these questions refering to? It is complete to just ask these questions without knowing, for what experiment they are for.
  81. science(chem)

    I never knew that you could have a, "between areas," Ph.D Thanks for all the advice, Dr.Bob
  82. science(chem)

    (proceeds to slam head on desk) I have all my books but if I'm not incorrect, this isn't going to help in the, "real world." =/ I knew I was supposed to actually remember everything. The thing is that you remember it during the sememster and then it starts ...
  83. science(chem)

    I was just wondering if it was necessary to remember each branch of chemistry learned. I can't really remember general chemistry and I'm sort of loosing the organinc. I mostly remember the calculations and the starting part of each course, but other than that it's ...
  84. Chemistry problem

    This is Actually chemistry related problem above. I don't understand the mEq so I cannot be of assistance.
  85. math

    Not sure if this is correct, but this is how I'd do this problem. 20kg x (1 lb)/(2.20kg )= 9.09 lbs 9.09 lbs x (50mg) / (1 lb)= 454.5 mg 454.5 mg x(1ml)/(100mg)= 4.545ml
  86. alg 2

    what are you trying to "do" exactly?
  87. Chemistry

    balance then. =) (that did seem wrong when I typed it but...)lol. very funny
  88. Chemistry

    Using weighing paper increases the risk of dropping your sample when transfering it to your container after weighing it on the scale. If you tarry a beaker and then add the sample to the beaker then that risk is mostly eliminated.
  89. Chemistry

    Under the middle of the beaker.
  90. Chemistry

    middle of the beaker I assume.
  91. Law

    Thank you drwls =)
  92. Law

    can someone give me a site that tells me the order of the courts in a state? I don't want to say the state but if needed I will (not sure if each state is different) My teacher isn't clear and thinks that the whole class took law.. divisions civil apella division high ...
  93. Algebra 1

    well it is simple as stated. for the second one it is: [-3+sqrt 29]/2 so 1. sqrt 29 2. -3 + (sqrt 29) 3. (divide the number found in 2. by the number 2 which would be=> [-3+sqrt 29]/2
  94. Chemistry

    Melting ice: physical change
  95. stoichiometry

    Yes, maybe I'm slow then. I see that the leftover unreacted Ba(NO3)2 is 0.00085 mols but I had gotten confused with the KNO3 being another product of the reaction. And since you did not include K2CrO4 in the calculations above I was took me awhile to figure ...
  96. stoichiometry

    Actually I think that my method was correct.(Just makeing sure though, I am posting how I did it) So actually focusing on the problem and solving this on paper.. 1 Ba(NO3)2 + 1 K2CrO4 => 1 BaCrO4+ 2 KNO3 3.50x10^-3mol Ba(NO3)2 265ml = 0.265L 0.265L (0.0100mol/L K2CrO4)= 0....
  97. stoichiometry--big fix.

    This is what happens when one multitasks, unfortunately. =|
  98. stoichiometry--big fix.

    Um..just listen to Dr.Bob (I've confused myself very much now) I'm sorry.
  99. stoichiometry--big fix.

    Well another correction...stupid mistake of mine (slap forehead) Just use this not the above...(just removed something balance the equation (they give you reactants and product(s)) 3.50x10^-3 mol Ba(NO3)2(__mol BaCrO4/__mol Ba(NO3)2)= ___mol BaCrO4 formed from Ba(NO3)2 ...
  100. stoichiometry

    edit. ___mol BaCrO4(_________g BaCrO4 /1molBaCrO4)= __________g BaCrO4
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