Sheryl

Most popular questions and responses by Sheryl
  1. Same substances?

    Question: Two substances, A and B, have the same melting point. how can you determine if they are the same without using any form of spectroscopy? Explain in detail. My answer: Perform a mixture melting point. In this procedure, pulverize and mix A and B

    asked on October 1, 2006
  2. Phase diagram

    Question: A solid substance has a vapor pressure of 800 mm Hg at its melting point (80 degrees C). Describe how the solid behaves as temperature is raised from room temperature to 80 C while the atmospheric pressure is held constant at 760 mm Hg. I think

    asked on November 12, 2006
  3. Low recovery

    The question is: A student performs a crystallization on an impure sample of biphenyl. The sample weighs 0.5g and contains about 5% impurity. Using his knowledge of solubility, he decides to use benzene as a solvent. The final weight is only 0.02g. Why is

    asked on September 26, 2006
  4. Mobility and Rf

    We did a column chromatography then a TLC on extracted spinach pigments. Question: Why are the chlorophylls less mobile on column chromatography and why do they have lower Rf values than the carotenes? My answer: The chlorophylls are more polar than the

    asked on October 22, 2006
  5. TLC purity

    Question: A student spots an unknown sample on a TLC plate and develops it in dichloromethane solvent. Only one spot, for which the Rf value is 0.95, is observed. Does this indicate that the unknown material is a pure compound? What can be done to verify

    asked on October 13, 2006
  6. Concentration increase

    Question: What would happen to the Rf values of the pigments if you were to increase the relative concntration of acetone in the developing solvent? Note: The development solvent used was 70% hexane - 30% acetone. My answer: Acetone is more polar than

    asked on October 22, 2006
  7. Sample purity

    Question: A student spots an unknown sample on a TLC plate and develops it in pentane solvent. Only one spot, for which the Rf value is 0.05, is observed. Is the unknown a pure compound? What can be done to verify the purity of the sample using TLC? My

    asked on October 15, 2006
  8. Extraction equations

    We did an extraction. A solid including benzoid acid, p-nitroaniline, and napthalene was dissolved in dichloromethane. HCl was added to give the aqueous salt of p-nitroanaline. NaOH was added to give the aqueous salt of benzoic acid. Napthalene remained.

    asked on October 7, 2006
  9. Subliming a substance

    Question: A substance has a vapor pressure of 50 mmHg at the melting point (100C). Describe how you would experimentally sublime that substance. My answer: I would put the substance in a sidearm test tube apparatus, put ice in the smaller tube and apply

    asked on November 13, 2006
  10. Physics

    Five Boys are pushing a snowball, and each is pushing with a force of 10.0N. However, each boy is pushing in a different direction. They are pushing north, northeast, east, southeast, and south. (Each boy is pushing at an angle of 45.0 degrees relative to

    asked on January 14, 2014
  11. Mixed melting point

    Question: A compound melting at 134 degrees C was suspected to be either aspirin (mp 135C) or urea (mp 133C) Explain how you could determine whether one of these two suspected compounds was identical to the unknown compound without using any form of

    asked on October 1, 2006
  12. Physical Science

    Two tugboats are towing a ship. each exerts a horizontal force of 5 tons and the angle between their tow ropes is 90. what net force is exerted on the ship?

    asked on September 3, 2011
  13. Configuration

    What is the electronic configuration of carbide C-4? Thought it was 1s2 2s2 sp2. Thanks from Sheryl C is atomic number 6. Electronic configuration of the neutral atom is 1s2, 2s2, 2p2. The carbide ion, C^-4, has four more electrons. So the extra four

    asked on October 17, 2006
  14. Volatility

    Question: A mixture of p-nitrophenol and o-nitrophenol can be separated by steam distillation. The o-nitrophenol is steam volatile, and the para iosmer is not volatile. Explain. Base your answer on the ability of the isomers to form hydrogen bonds

    asked on November 22, 2006
  15. Rf values

    Question: Consider a sample that is a mixture composed of biphenyl, benzoic acid and benzyl alcohol. The sample is spotted on a TLC plate and developed in a dichloromethane-cyclobutane solvent mixture. Predict the relative Rf values for the three

    asked on October 14, 2006
  16. math

    Is there a common ratio for the geometric sequence and what are the missing terms? 16,40,100,?,? IS there a common ratio for the geometric sequence and what are the missing terms? 81,54,?,?,?

    asked on March 31, 2011
  17. Purity

    The question asked is: Using yur results as a guide, comment on the purity of the material in the green and yellow bands. (from a TLC of spinach extraction pigments.) I'm not quite sure what they want here and my plate is in the lab, not here. There were

    asked on October 22, 2006
  18. Buchner funnel

    Question: What would happen if a hot saturated solution were filtered by vacuum filtration using a Buchner funnel? Hint: Cooling will occur. My answer: A Buchner funnel is primarily used to collect a solid from a liquid. When the hot solution cools when

    asked on September 26, 2006
  19. More spots

    Question: A colorless unknown substance is spotted on a TLC plate and developed in the correct solvent. The spots do not appear when visualization with a UV lamp or iodine vapors is attempted. What could you do to visualize the spots if the compound is the

    asked on October 15, 2006
  20. Eugenol

    I isolated eugenol from cloves in the lab using extraction and steam distillation but we did not do infrared. The lab report question is: Description of Method. I'm not sure what to put. We prepared the spice, did steam distillation, extracted the

    asked on November 21, 2006
  21. Compound recovery

    The problem: Write an equation to show how you could recover the parent compounds from their respective salts shown in Figure 12.10. Figure 12.10 is a type of flow chart but I will put it down as best I can. This is an extraction. R-Phenol + RCOOH + RNH2 +

    asked on October 2, 2006
  22. Science

    Lithium atoms, like hydrogen atoms, have only a single electron in their outer shells, yet lithium atoms do not join together to form Li2 molecules the way hydrogen atoms form H2 molecules. Instead, lithium is a metal with each atom part of a crystal

    asked on October 22, 2011
  23. Polarity

    Benzyl alcohol is not a good sovent with which to crystallize fluorenol. The melting point looks okay so I'm assuming that polarity is the problem. Benzyl alcohol looks polar to me because it has an OH but it is only partly soluble in water. Couldn't find

    asked on September 26, 2006
  24. Visualizing spots

    Question: A colorless unknown substance is spotted on a TLC plate and developed in the correct solvent. The spots do not appear when visualization with a UV lamp or iodine vapors is attempted. What could you do to visualize the spots if the compound is the

    asked on October 15, 2006
  25. Filtration

    Problem: In each of the following situations, what type of filtration device would you use? A. Remove powdered decolorizing charcoal from 20mL of solution? My answer: Filter Aid or Celite (diatomaceous earth) B. Collect crystals obtained from crystallizing

    asked on September 30, 2006
  26. Naphthalene

    Question: You are about to purify an impure sample of naphthalene by column chromatography. What solvent should you use to elute the sample? My answer: Naphthalene is very nonpolar so a very nonpolar solvent like hexane should be used.

    asked on October 22, 2006
  27. Difference?

    What is the difference between these two questions? They look the same to me, like they're asking the same thing. Not likely. Question: A student spots an unknown sample on a TLC plate and develops it in dichloromethane solvent. Only one spot, for which

    asked on October 14, 2006
  28. science

    Why do you think the wave aspect of light was discovered earlier than its particle aspect?

    asked on October 9, 2011
  29. Chemistry

    Which has a larger radius, the oxygen atom (O) or oxygen ion (O-2) ? Explain. Isn't the ion bigger because negative ions are bigger than atom's radius. im not sure though.

    asked on October 23, 2010
  30. Solvent

    Question: A student dissolved 0.30 g of a crude product in 10.5mL (the minimum amount required) of ethanol at 25 degrees C. He cooled the solution in an ice-water bath for 15 minutes and obtained beautiful crystals. he filtered the crystals on a Hirsch

    asked on September 27, 2006
  31. science

    Which of the following substances are homogeneous and which are heterogeneous? Blood, carbon dioxide gas, solid carbon dioxide, rock, steak, iron, rust, concrete, air, oxygen, salt, milk.

    asked on October 17, 2011
  32. science

    Why can neutrinos travel immense distances through matter whereas other elementary particles cannot?

    asked on October 2, 2011
  33. accounting

    a partial balance sheet and income statement for King Corproation follow: KING CORPORATION Partial Balance Sheet December 31,2009 Assets Current assets: Cash $33,493 Marketable securities $215,147 Trade receivables, less allowance of $6,000 $255,000

    asked on November 18, 2010
  34. Decolorizing

    Question: A compound you have prepared is reported in the literature to have a pale yellow color. When the substance is dissolved in hot solvent to purify it by crystallization, the resulting solution is yellow. Should you use decolorizing charcoal before

    asked on September 27, 2006
  35. Solvents

    Question: Each of the solvents given should effectively separate one of following mixtures by TLC. Match the appropriate solvent with the mixture that you would expect to separate well with that solvent. Select your solvent from the following: hexane,

    asked on October 14, 2006
  36. Best solvent?

    What is the best solvent for impure fluorene? The possibilities are methyl alcohol, water, and toluene. I'm betting toluene but I don't know its boiling point. Thanks from Sheryl My Merck Index lists 9H-Fluorene as freely soluble in glacial acetic acid and

    asked on September 25, 2006
  37. Analgesics

    We're doing a TLC analysis of analgesic drugs. One of my prelab questions is: Name some advantages of using acetaminphen (Tylenol) instead of aspirin as an analgesic. They were probably dissolved in methylene chloride amd ethanol and I'm assuming that's

    asked on October 12, 2006
  38. Solvent

    Question: A sample was placed on a chromatography column. Methylene chloride was used as the eluting solvent. All of the components eluted off the column but no separation was observed. What must have been happening during this experiment:? How would you

    asked on October 23, 2006
  39. TLC error correction

    Question: Consider the following errors that could be made when running TLC. Indicate what should be done to correct the error. A. A two-component mixture containing 1-octene and 1,4-dimethylbenzene gave only one spot with an Rf value of 0.95. The solvent

    asked on October 14, 2006
  40. Sublimes?

    Question: An unknown compound gave a melting point of 230C. When the molten liquid solidified, the melting point was redetermined and found to be 131C. Give a possible explanation for this discrepancy. My answer: The compound sublimed. How would

    asked on October 1, 2006
  41. Filtration?

    Question: While performing a crystallization, you obtain a light tan solution after dissolving your crude product in hot solvent. A decolorizing step is determined to be unnecessary, and there are no solid impurities present. Should you perform a

    asked on September 27, 2006
  42. math

    Gary has 10 coins in his pocket. 2 quarters 5 dimes 3 nickels without looking, Gary pulls 1 coin from his pocket and puts it on a table. Then, he pulls one more coin from his pocket. What is the probability that the first coin is a dime and the second coin

    asked on March 31, 2013
  43. Crystallization experiment

    We will be conducting a crystallization experiment this week. I was wondering what the most common materials used for this experiment are and what are their best solvents. Thanks from Sheryl alum in water is really good, however, it takes some time for the

    asked on September 24, 2006
  44. Chemistry

    i have to round each to 3 significant figures, then to one significant figure, in standard form, how? a) 87.073 m b) 4.3621 x 10^8 m c) 0.01552 m d) 9009 m e) 1.7777 x 10^-3 m f)629.55 m

    asked on September 18, 2015
  45. science

    The reaction 2SO + O2 ¨ 2SO3 is exothermic. (a) How will a rise in temperature affect the yield of SO3 in an equilibrium mixture of the three gases? (b) Will an increase in pressure raise or lower the yield? (c) In what possible way can the speed of the

    asked on October 26, 2011
  46. science

    If you were an astronaut making a space walk outside your space station when your jet pack runs out of fuel. How can you use your empty jet pack to get back to the station?

    asked on July 22, 2008
  47. Identical compounds?

    Question: You and another student were each given an unknown compound. Both samples contained colorless material. You each used the same brand of commercially prepared TLC plate and developed the plates using the same solvent. Each of you obtained a single

    asked on October 13, 2006
  48. Computers

    In Python - A state creates license plates, each containing two letters followed by three digits. The first letter must be a vowel (A,E,I,O,U), and duplicate letters and digits are allowed. The second letter can be any letter of the alphabet. The state

    asked on April 22, 2013
  49. Science

    The binding energy of 20 10 Ne is 161 MeV. Find its atomic mass.

    asked on October 2, 2011
  50. Rate determining step

    I don't understand how to get a rate determining step. I have an energy diagram for a two-step conversion where the first step Ea is about 18 units. The energy then goes down about 4 units and rises again about 10 units to the peak of the second step. Why

    asked on December 5, 2006
  51. Solvent temp

    Question: A student dissolved 0.30 g of a crude product in 10.5mL (the minimum amount required) ethanol at 25 degrees C. He cooled the solution in an ice-water bath for 15 minutes and obtained beautiful crystals. He filtered the crystals on a Hirsch funnel

    asked on September 30, 2006
  52. Honors Trig

    a plane is flying in the direction of 190 degrees with an air speed of 400 mph. Its course and ground speed are 200 degrees and 350 mph respectively. What is the speed and direction of the wind?

    asked on May 8, 2013
  53. Resonance structures

    I won't try to draw one here but take for example, CH3CH2COO-. This has two resonance structures but they look the same to me. The CH2-C single bond can rotate and it looks like you can just flip the COO- section and it looks like the same structure. Maybe

    asked on September 30, 2006
  54. Global Politics

    Describe the difference between intergovernmentalism and supranationalism. Provide useful examples from the European Union, NATO, and the United Nations.

    asked on November 13, 2011
  55. accounting

    The following financial data were taken from the annual financial statements of Smith corporation: 2007 2008 2009 Current assets $450,000 $400,000 $500,000 Current liabilities $390,000 $300,000 $340,000 Sales $1,450,000 $1,500,000 $1,400,000 Cost of goods

    asked on November 18, 2010
  56. science

    Why is the Bohr Theory incompatible with the uncertainty principle?

    asked on October 9, 2011
  57. Spinach

    I did a column chromatography on spinach and then a TLC. On the TLC I got five visible bands of colors. On the extracted yellow substance I got one yellow band (carotene) and on the green I also got only one green band. I thought there would be more bands

    asked on October 23, 2006
  58. Thin layer chromatography

    I've done some TLC plates using ethyl acetate with 0.5% glacial acetic acid as a solvent. The structure of these substances looks polar to me. I"m assuming that ethyl acetate is not very polar. Is this correct? Acetaminophen barely travelled any distance

    asked on October 18, 2006
  59. physical science

    The ionization energies of Li, Na, K, Rb, and Cs are respectively 5.4, 5.1, 4.3, 4.2, and 3.9 eV. All are in Group 1 of the periodic table. Explain the decrease in ionization energy with increasing atomic number in this group.

    asked on October 17, 2011
  60. Math 209-College Mathematics II

    How do you factor this completely: x^3 + ax + 3a + 3x^2

    asked on May 29, 2010
  61. algebra

    you rollerblade at an average speed of 8 miles per hour. the number of miles m you rollerblade during h hours is modeled by m=8h. do these two quantities have direct variation?

    asked on October 3, 2009
  62. Principle of operation

    Regarding extraction, the heading is: Descripton of method. Principle of operation. My description is: Extraction is based on the principle that a certain solute will dissolve in two immiscible phases, one of which is usually liquid. For example, where one

    asked on October 7, 2006
  63. math

    Melissa earned a score of 75% on her first test. She wants to earn an 85% on her second test. What is the percent increase, rounded to the nearest whole number, from 75% to 85%?

    asked on March 31, 2013
  64. math

    how dO find the missing terms for the geometric sequence o,?, ?, ?...... 16, 40, 100......

    asked on March 31, 2011
  65. MATH

    IF the first term in a geometric sequence is 0 and no other terms are given what is pattern?

    asked on March 31, 2011
  66. basic critical thinking

    select a topic of interest to you and explain how you would come up with a reliable sample for obtaining peoples' opinions.

    asked on November 18, 2010
  67. Solvents

    Question: When a TLC plate ws developed, the solvent front ran off the top of the plate. What should be done to correct the error. Me: The only reason I'm giving you this question to check is that it seems too simple. My answer would be to stop development

    asked on October 15, 2006
  68. Extraction equations

    Extraction procedure and equations: Thought I'd better post this on the current page. I need the reaction equations checked. I tried to put them in bold but can't. They should all be after Reaction: Solid benzoic acid, p-nitroaniline and napthalene ->

    asked on October 8, 2006
  69. Grams

    How many grams are there in an ounce? Thanks from Sheryl There are 453.592 grams in a pound so divide that by 16 to get 1 oz = 28.3495231 grams How can I teach someone else to read? That's a good question and I'll let the experts give you a complete

    asked on October 7, 2006
  70. HIrsch funnel

    From part of an earlier question: My question: D. What filtration device would you use to isolate 2.0 g of crystals from about 50 mL of solution after performing a crystallization? My answer was a Buchner funnel Your answer: It would need to be a SMALL

    asked on October 1, 2006
  71. math

    Cece scored a 78 on her first math test. She scored an 84 on her second test. What is the percent increase, rounded to the nearest tenth, from Cece's first score to her second score?

    asked on March 31, 2013
  72. science

    When carbon in the form of diamond is burned to produce CO2, more heat is given off than when carbon in the form of graphite is burned. What form of carbon is more stable under ordinary conditions? What bearing does this conclusion have on the origin of

    asked on October 25, 2011
  73. science

    Under what circumstances would you expect the shared electron pair to be equal distances on the average from each of the atoms participating in a covalent bond?

    asked on October 15, 2011
  74. science

    Find the Kinetic energy (in keV) of 12 6 C atom of mass 12.0 u whose speed is 2 x 10^6 m/s.

    asked on October 1, 2011
  75. Algebra 2

    1. A rectangle has an area of x3 + x2 – 7x + 2 square meters and a width of x – 2 meters. Find its length.

    asked on May 30, 2011
  76. algebra 116

    I am supposed to graph it and tell what the slope is and what the y-intercept is. I am totally confused.

    asked on December 5, 2009
  77. Chemistry

    I did a lab where I had to decompose the compund patassium cholorate (KClO3)by heating,I had to weight the test tube then the test tube with the potassium chlorate to get the weight. I then had to heat it for several minutes and letting it cool down before

    asked on March 23, 2009
  78. Chemistry

    I'm going to buy a Bunsen burner to be used with a propane tank. Is it very important to get a propane burner or does the natural gas one do the same thing? Any advice on what type of burner to get? I'll be working on distilling alcohol and steam

    asked on August 28, 2008
  79. Azeotrope

    I'm having trouble understanding what an azeotrope is. Any clarification is appreciated. Sheryl Two liquids with different boiling points normally can be separated by fractional distillation; i.e., the lower boiling point material boils first and when all

    asked on November 5, 2006
  80. Methylene chloride

    Question: A sample was placed on a chromatography column. Methylene chloride was used as the eluting solvent. All of the components eluted off the column, but no separation was observed. What must have been happening during this experiment? How would you

    asked on October 22, 2006
  81. Chem teacherf

    My teacher last year in General Chemistry was really great. She was highly organized, always prepared for class, approachable and fair. Chemistry is such a hard class that she really helped me get through it. My Organic teacher is another story. She is a

    asked on October 7, 2006
  82. math

    It the track is 1/4 mile around and you do 3 laps in 4 and 1/2 min, how many mile per hour do you run?

    asked on May 1, 2016
  83. Chemistry

    a diver swimming at a depth of 10m under the water observes that the size of his air bubbles increase in volume as they rise to the waters surface. which gas law does this relate to?

    asked on November 6, 2015
  84. health

    All of the following should be considered competitors, with the exception of which one? Existing competitors, Indirect competitors, Potential competitors, Direct competitors

    asked on November 10, 2013
  85. Criminal Justice

    Create an analysis chart in Word to compare and contrast the various theories on Domestic Violence. The theories suggested are: biological, psychological, sociological, feminist, and patriarchal. I am not sure how to set this up. Thanks

    asked on January 15, 2012
  86. science

    Find the frequency and wavelength of a 50-MeV gamma-ray photon.

    asked on October 9, 2011
  87. science

    Why can neutrinos travel immense distances through matter whereas other elementary particles cannot?

    asked on October 1, 2011
  88. Physical Science

    The brakes of a care are applied to give it an acceleration of -3m/s^2. The car comes to a stop in 5 s. What was its speed when the brakes were applied?

    asked on September 3, 2011
  89. Dividing Polynomials

    I do NOT get this, please help: (11x^2+2x^3+14+17x)/(2x+5)

    asked on May 30, 2011
  90. Chem tutorial

    Is there a good tutorial on how to read phase diagrams? Thanks from Sheryl I don't know how good this site is but it has a discussion as well as some questions (with hints) at the end. http://www.science.uwaterloo.ca/~cchieh/cact/c123/phasesdgm.html

    asked on November 12, 2006
  91. Resonance structures

    I'm trying to figure out some incorrect answers on my last test. I'll try to explain what the original structure looks like and hope you can decipher it. It is a cyclohexane with two double bonds. Carbon # 1 has a double bond to its left and none to its

    asked on October 24, 2006
  92. Coordination

    Is coordination the same as ionic bonding? Sheryl As I understand coordination, as in coordination number, no. It is more covalent or more precisely called coordinate covalent if we are talking abouat the same thing. Then I guess 'salt formation' would be

    asked on October 21, 2006
  93. Soxhlet extractor

    Does anyone know what kindo of chemistry lab course(Organic, Physical, etc.) might use a soxhlet extractor in the experiments? Sheryl http://en.wikipedia.org/wiki/Soxhlet_extractor Certainly Organic It is used in organic chemistry. The URL provided by

    asked on October 9, 2006
  94. Reverse Equations

    a four-component mixture was extracted. In the mixture was R-phenol, RCOOH, RNH2 and R-(C=O)-R in solution with ether and aqueous NaHCO3. RCOO-NA+ was separated out on the water layer. Aq. NaOH was added to the ether layer and R-benzene-O-Na+ was separated

    asked on October 7, 2006
  95. Melting point

    Do you have any idea what the melting points and range might be for a 50/50 mixture of: 1. Benzoin (M.P.: 135-136) and succinimide M.P.: 121-123 and 2. Benzoic acid M.P.: 121-122 and succinimide M.P.: 122-124 I'm doing a lab with really laughable melting

    asked on October 1, 2006
  96. Acids

    A strong acid readily donates a proton. Inductive effects and other factors can stabilize the negative charge of the conjugate base. The more stable the conjugate base, the more acidic the acid. What I don't understand is that it seems to me that a more

    asked on September 29, 2006
  97. Math

    Mr. Lin baked banana bread for a bake sale to raise money for the math team. He said that he added a spoonful of walnuts for each of the students in his three classes, and that he added more than 250 walnuts. He used the inequality 16w + 24w + 10w > 250 to

    asked on March 9, 2018
  98. science

    Find the mass of 1.6 mol of magnesium, Mg. How many atoms are present in such a sample?

    asked on October 25, 2011
  99. science

    Why do you think the wave aspect of light was discovered earlier than its particle aspect?

    asked on October 9, 2011
  100. Science

    What kind of experiment might you use to distinguish between a gamma ray of wavelength 10^-11m and an electron whose de Broglie wavelength is also 10^-11m?

    asked on October 9, 2011

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