Tuesday
October 21, 2014

Posts by ~christina~


Total # Posts: 812

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
June 10, 2010

Earth Science
Low amounts of silica. Silica makes the magma more viscious and thus less likely to flow quickly. source: wikipedia (magma)
September 20, 2009

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. :)
September 20, 2009

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...
September 20, 2009

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. :-)
June 27, 2009

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 ...
June 27, 2009

Dr.Bob - Question
I would like to try the other chemistry classes and see how I like them. Thanks bobpursley.
June 27, 2009

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&#...
June 27, 2009

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
June 27, 2009

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?
June 23, 2009

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 ...
June 23, 2009

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...
May 5, 2009

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...
May 5, 2009

english
Thanks Ms Sue :)
April 26, 2009

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...
April 26, 2009

science(chemistry)
Thank you Dr.Russ.
April 24, 2009

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 ...
April 24, 2009

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
April 24, 2009

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
April 24, 2009

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...
April 24, 2009

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?
April 20, 2009

science(chemistry) -Q for Dr.Bob
Okay, I'll try that then. Thank you, Dr.Bob
April 20, 2009

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 ...
April 20, 2009

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...
April 20, 2009

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.
April 20, 2009

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 ...
April 20, 2009

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
April 17, 2009

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?
April 17, 2009

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
April 17, 2009

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 ...
April 17, 2009

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 (...
April 17, 2009

Chemistry
Yes. It's chemical compound formula is SiO2.
March 20, 2009

science(chemistry)
Thank you GK
March 20, 2009

science(chemistry)
How would I compare using peak heights vs peak areas for GC quantitation? Thanks
March 20, 2009

science
It will be a curved exponentially increasingly sloped line.
March 4, 2009

science
a. Composition
March 4, 2009

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 ...
February 19, 2009

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
February 16, 2009

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...
February 16, 2009

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
February 16, 2009

chemistry- Dr.Bob, can you help me out please?
no?
February 16, 2009

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 ...
February 16, 2009

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...
February 16, 2009

Chemistry
Answered below
February 10, 2009

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 ...
February 10, 2009

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+] ...
February 10, 2009

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 ...
December 28, 2008

Water Chemistry
That's correct.
December 27, 2008

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.
November 13, 2008

math need help please
-9^2-(-6)^2= -81-36= ____
November 5, 2008

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...
October 10, 2008

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 ...
October 6, 2008

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
October 4, 2008

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 ...
October 4, 2008

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 ...
October 1, 2008

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 ...
October 1, 2008

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....
October 1, 2008

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...
October 1, 2008

science(chem)
I'll see how I do with that site, first. Thanks Dr.Bob
September 21, 2008

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.
September 21, 2008

science(chem) Dr.Bob Question from before
Okay, thanks Dr.Bob.
September 20, 2008

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...
September 20, 2008

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...
September 20, 2008

science(chem)
It was not stated, so I assume that I will be making them at std room temp. Thanks for the help, bobpursley.
September 20, 2008

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
September 20, 2008

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
September 13, 2008

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.
September 12, 2008

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
September 12, 2008

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.
September 7, 2008

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
September 7, 2008

Sci
Energy could be in the form of a) heat b) light
September 3, 2008

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 ...
September 3, 2008

Sci
Then the blood would become basic.
September 2, 2008

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...
September 1, 2008

chemistry
Post your question above, not below another question.
September 1, 2008

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 ...
August 30, 2008

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 ...
August 30, 2008

MAth
incorrect 3.75gal (8.34 lb/1gal)= ______
July 28, 2008

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?
July 27, 2008

chemistry
What are these questions refering to? It is complete to just ask these questions without knowing, for what experiment they are for.
July 27, 2008

science(chem)
I never knew that you could have a, "between areas," Ph.D Thanks for all the advice, Dr.Bob
July 26, 2008

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 ...
July 26, 2008

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 ...
July 26, 2008

Chemistry problem
This is Actually chemistry related problem above. I don't understand the mEq so I cannot be of assistance.
July 21, 2008

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
July 21, 2008

alg 2
what are you trying to "do" exactly?
June 16, 2008

Chemistry
balance then. =) (that did seem wrong when I typed it but...)lol. very funny
June 16, 2008

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.
June 16, 2008

Chemistry
Under the middle of the beaker.
June 16, 2008

Chemistry
middle of the beaker I assume.
June 16, 2008

Law
Thank you drwls =)
June 7, 2008

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 ...
June 7, 2008

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
June 7, 2008

Chemistry
Melting ice: physical change
June 5, 2008

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 confused..it took me awhile to figure ...
June 5, 2008

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....
June 5, 2008

stoichiometry--big fix.
This is what happens when one multitasks, unfortunately. =|
June 5, 2008

stoichiometry--big fix.
Um..just listen to Dr.Bob (I've confused myself very much now) I'm sorry.
June 5, 2008

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 ...
June 5, 2008

stoichiometry
edit. ___mol BaCrO4(_________g BaCrO4 /1molBaCrO4)= __________g BaCrO4
June 5, 2008

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