Chemistry

what is the purpose of changing the eluting solvent from pentane to ether between the two fractions? please explain your answer, being sure to mention important intermolecular forces and how they relate to the compounds being eluted
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!!(100 points)!! What is a valence electron? Which elements on the periodic table have the most valence electrons?
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Determine whether the following formulas representan atom, molecule or formula unit.a) NaOb) PO5c) Cld) Aue) (NH4)2SO4
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Which emission spectrum represents the copper? A.) Spectrum A B.) Spectrum B C.) Spectrum C
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How many moles of MgS are in 100.g MgS?
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draw the structure of ammonium acetate. why do you think that you need to use this compound in the solvent mixture for your tlc analysis in week 2?
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What is the mass of9.03 x 1023 atoms S? The molar mass of S is 32.07 g/mol.A. 1.5gSC. 0.047 g SB. 48.1 g SD. 2.82 x 10 g S
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particulate matter can increase global warming by reacting with chlorofluorocarbons. reducing surface absorption of ultraviolet radiation. producing additional nitrous oxides. reflecting radiation. lowering surface albedo.
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a piece of metal block is 12.3 in by 4.5 in. the mass of the block is 1.23 lb. if the density is 2.3 g /ml what is the tickness of the block in mm? multistep show work problem. no work no credit
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a compound containing only carbon and hydrogen has a carbon to hydrogen ratio of 11.89 . which carbon to hydrogen mass ratio is possible for another compound composed only of carbon and hydrogen?
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gaas is a common semiconductor used to make solid state lasers used in cd and dvd players. how covalent are the bonds in gaas?
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which will form hydrogen bonds between its molecules? a) ch3ch2ch2f b) ch3ch2ch2ch3 c) (ch3)3n d) ch3ch2och3 e) ch3nhch2ch
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what would the ph of a buffer solution containing 0.350 moles acetic acid and 0.225 moles sodium acetate be when enough water is added to make 0.6 l of solution?
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The mass of a hydrate is 12.75g. The hydrate is heated and the resulting mass of theanhydrate is 9.87g. Calculate the experimental percentage of water by mass.
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With 14 liters of loratadine we can fill 135 bottles. How many milliliters of loratadine are needed to fill 106 bottles
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what is the ph after 0.150 mol of hcl is added to the buffer from part a? assume no volume change on the addition of the acid.
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A calorimeter contains 21.0 mL of water at 13.5 C. When 1.70g of X (a substance with a molar mass of 77.0 g/mol) is added, it dissolves via the reaction X(s)+H2O(l)X(aq) and the temperature of the solution increases to 25.0 C.Calculate the enthalpy change, H , for this reaction per mole of X.Assume that the specific heat of the resulting solution is equal to that of water [4.18 J/(gC)], that density of water is 1.00 g/mL, and that no heat is lost to the calorimeter itself, nor to the surroundings.Express the change in enthalpy in kilojoules per mole to three significant figures.
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which isotope, when bombarded with nitrogen-15, yields four neutrons and the artificial isotope dubnium-260?
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what percentage of air is oxygen?
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why is it less likely that water is contaminating the product (based on what you did and the appearance of the product that you submit)
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explain exactly why a stoichiometric balance of a combustion reaction must demonstrate conservation of mass, but not conservation of moles.
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What mass (g) of NaN3 is required to provide 40.0 L of N2 at 25.0C and 763 torr?
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what is the ph of 0.352 m ethylammonium chloride, c2h5nh3cl. the kb of ethylamine, c2h5nh2, is 4.3 x 10-4.
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How would you interpret that all four C-H bonds of methane are identical?
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