Posts by GK

Total # Posts: 639

  1. physics

    Cheerleaders at sporting events will often use a bullhorn to make themselves louder. A bullhorn is simply a hollowed out cone - you speak into the narrow end and your voice comes out the wide end, channeled by the cone so it is louder than it would be otherwise. At a sporting ...
  2. physics

    From the surface of a cylindrical wire of radius R=1 cm carrying a current I=1 mA an electron escapes with velocity v0=30 m/s perpendicular to the surface of the wire. What will be the electron's maximum distance in meters from the axis of the wire? Details and assumptions...
  3. physics

    From the surface of a cylindrical wire of radius R=1 cm carrying a current I=1 mA an electron escapes with velocity v0=30 m/s perpendicular to the surface of the wire. What will be the electron's maximum distance in meters from the axis of the wire? Details and assumptions...
  4. BEST

    thank you
  5. BEST

    how do i calculate the point on the curve when the ordinate changes 8 times faster than abscissa in the equation 6y=x^3+2
  6. Physics

    answer is 7
  7. Physics

    .84
  8. Physics

    precisely 299.99999999 by the formula I=P/r(pi)r^2 .
  9. Physics

    absolutely the answer is zero. note the question it says net force .
  10. algebra!

    IT is Absolutely right . The answer is 8
  11. Chemistry

    15 ml of 0.5 M of HCl is added to a 100 ml sample of 0.2 M HNO2 (Ka for HNO2= 4.0 x 10^(-4)). What is the equilibrium concentration of NO2- ions?
  12. chemistry

    The answer is "yes" but I am not sure what formula you are referring to. Are you expected to use the absorbance v. time graph to get the half-life? If so, •Select a point on the graph with a high value for absorbance, A. Read the time in minutes, T1. •On ...
  13. Chemistry

    [H+] = 10^-2 = 0.01M 10 ml = 0.010L (0.01mol/L)(0.010L) = 0.0001 mole of H+ or HCl moles of Zn = (0.0001 mol HCl)(1mol Zn/2mol.HCl)= 0.00005 moles Zn Convert moles of Zn to grams
  14. chemistry

    3.15 mol / 0.250 kg = 12.6 mol/kg or 12.6 molal The boiling point of a solution is Tb = Tb(H2O) + deltaT = 100º + deltaT deltaT = Kb*m = (0.512deg.kg/mol)(12.6mol/kg) NOTE: C2H6O2 is not ethylene. It may be CH3-O-O-CH3 whose solubility could not be 12.6molal. It is a bad ...
  15. Chemistry

    Chemical means of fighting oil spills are generally detergents which break up big blobs of oil into small liquid drops that are dispersed and eventually broken down by bacteria. This involves a whole sequence of physical and chemical changes. You can't write a simple ...
  16. Chemistry 2 Questions

    1. sodium metal reacts (burns) in chlorine gas forming sodium chloride, NaCl. 2. The ability of water to dissolve ionic solids (most salts) and polar molecular compounds (sugars, alcohols, ammonia, etc) is because of its polarity and its ability to form "hydrogen bonds&...
  17. college chemistry

    KClO3 decomposes to KCl and O2 which it escapes. A sample of KClO3 that has had some decomposition will contain some KCl. A sample of this mixture could be dissolved in water and tested with AgNO3. Pure KClO3 would not produce a precipitate since AgClO3 is soluble in water. ...
  18. chemistry

    If anyone can prepare a 1 M solution of Mg(OH)2, I would like to see it. The solubility of of magnesium hydroxide in water is 12 mg/L. The Ksp is 4.5x10^-11.
  19. chemistry

    I assume the desired pH is 8.65 although you did not label it, as DrBob pointed out. Ka = [H+][NO2-] / [HNO2] [H+] = antilog(-8.65)=2.24x10^-9 (a basic solution) [OH-] = Kw / [H+] [OH-] = (1x10^-14)/(2.24x10^-9) = 4.47x10^(-6) Ka = [H+][NO2-] / [HNO2] = 4.5x10^-4 (looked up) ...
  20. Chemistry

    We need the chemical equation for the reaction between CH4 and O2. I assume it was: 2CH4 + 3O2 -->2CO + 4H2O To answer your question, 1. Divide 45.6g by the molar mass of CH4 to get the number of moles of CH4. 2. Divide 73.2g O2 by the molar mass of O2 to get the moles of ...
  21. chemistry

    The mass of 1 liter of water is very close to 1 kg q = (specific heat)*(mass)*deltaT specific heat of water = 4.18kJ/kg.C q = (4.18kJ/kg.C)(1.00kg)(85ºC-18ºC)
  22. Chemistry

    Salicylic acid which was probably used to make aspirin is a phenol. The negative phenol test indicates that all of the salicylic acid reacted. However, the aspirin produced was not pure. Impurities lower the melting point and make the melting point range wider. It would be ...
  23. College Chemistry

    The deltaH for the decomposition of 1 mole of Al2O3 is half of 351.4 kJ since the chemical equation shows 2 moles of Al2O3. Convert 12.50g Al2O3 to moles by dividing it by the molar mass of Al2O3. Multiply your answer by 351.4kJ to get the enthalpy of decomposition of 12.50g ...
  24. Organic chemistry

    CH3CH2CH2CH2OH + NaBr --> CH3CH2CH2CH2Br + NaOH. NaOH would react with H2SO4 to form Na2SO4 which may precipitate in a mixture of organic solvents.
  25. Chemistry

    Para (p-), meta (m-), and ortho (o-) are only used for derivatives of benzene. Your acid was probably 4-methylcyclohexanoic acid.
  26. Chemistry

    Start with: CH3CH2CH2-C-OCH(CH3)2 To the middle -C-, attach an -OH (up) and an -H (down). See also: http://en.wikipedia.org/wiki/Hemiacetal
  27. Chemistry

    2-methyl-2-pentanol
  28. chemistry

    1. Errors related to the measurement of volume of acetic acid (what volumetric glassware was used and how it was used). 2. Errors related to using and reading the buret with the NaOH solution. 3. Errors related to reaching the endpoint. Color, etc. 4. Possible error in the ...
  29. chemistry

    The unpaired electron in the ethyl radical can be more easily delocalized by two carbon atoms, and through the increase in the number of resonance forms in a two-carbon chain.
  30. chemistry

    nf would be the square root of some positive value, but your (A) and (B) look the same. Did you copy these alternate answers correctly?
  31. chemistry

    1/lambda = R/ni^2–R/nf^2 y = mx + b (standard form) of a linear equation) x = (y-b)/m Let, y = 1/lambda m = -R x = 1/nf^2 b = R/ni^2 1/nf^2 = [(1/lamda)-(R/ni^2)]/(-R) Solve for nf
  32. Chemistry

    Surface tension is the result of intermolecular forces. Viscosity is also the result of intermolecular forces plus additional factors such as entanglement of long molecules. What intermolecular forces are involved from C6H14 to C9H20? How would the increasing length plus ...
  33. Chemistry

    •Find the difference in electronegativity between H and F. •Find the difference in elctronegativity between H and I. •Compare the two differerences. The larger difference indicates the larger polarity.
  34. chemistry

    The equilibrium constant expression is: K(eq)=[N2][O2] / [NO]^2 = 8.36*10^3 Substitute the concentrations given and solve for [NO]
  35. chemistry

    The oxidizing agent, Ag+, gained an electron and is reduced to Ag(s). The reducing agent loses an electron and is oxidized from Fe^2+ to Fe^3+: Ag^+(aq) + Fe^2+(aq) --> Ag(s) + Fe^3+(aq)
  36. Chemistry

    Convert degrees C to degrees K. K = C + 273 Convert torrs to atm. atm = torrs / 760 Substitute in PV = nRT and solve for V
  37. Chemistry

    Convert deg. C to deg. K, then substitute into the Combined Gas Law: P1V1/T1 = P2V2/T2 Solve for V2. Your answer is not correct.
  38. chemistry

    Is the question about the mole ratio in the product or the mixture?? If the product is CuS, the mole ratio in the product is 1molCu/1molS=1 molCu/molS The mole ratio of the masses of the elements in any compound is definite, not dependent on the reactants ratio in making it.
  39. Chemistry

    A gas mixture in a container may start heterogeneous but the constant, random motion of the molecules in it will make it homogeneous in a very short time.
  40. Chemistry

    Statements A, B, and C are correct.
  41. chemistry

    K(eq) = [CH3OH] / [CO][H2]^2 let [CH3OH] = [x] Substituting, 10.2 = [x] / [0.02][0.02]^2 Solve for [x]
  42. chemistry

    In a Bronsted-Lowry acid-base reaction with a high Keq value, Acid + Base = Weaker acid + Weaker Base Acid1 + Base1 = Base2 + Acisd2 Acid1 is stronger than Acid2, and, Base1 is stronger than Base2 In your question, the equilibrium constant is small. The forward (left to right...
  43. chemistry

    [Answered elsewhere]
  44. Chemistry

    Cm has 96 electrons. The previous noble gas is radon, Rn, with 86 electrons. It is a 7th row element and a member of the actinide series which starts with Ac, 3rd element on the 7th row and 7th element on the actinium series. The electron configuration is: [Rn] 7s^2, 6d^1, 5f^...
  45. chemistry

    Valence electrons are easier to remove (ionize) than electrons in the shell under the valence shell. A complete shell, closer to the nucleus is more difficult to disturb. After the valence electrons are removed, removal of an electron from the shell below requires much more ...
  46. chemistry

    NaOH + HClO4 --> H2O + NaClO4
  47. Chemistry

    The reaction is: Al2S3 + 6AgNO3(aq) --> 3Ag2S(s) + 2Al(NO3)3(aq) Find the formula mass (molar mass) of Al2S3. Divide 300.23 g by the formula mass to get moles of Al2S3. Moles of Ag2S = (__moles Al2S3)(3) Moles of Al(NO3)3 = (__moles Al2S3)(2)
  48. Chemistry

    The reaction written correctly is: 2NiO (s)--> 2Ni(s) + O2 (g) 1. Divide 25.67g NiO by the formula its mass to get the number of moles of NiO. 2. Since 2 moles NiO produce 1 mole O2, moles of O2 = ( ___mol NiO)(1/2) 3. Look up the vapor pressure of water, P(vapor), at 40.0 ...
  49. Chemistry

    Yes, since we have only two groups of valence electrons around the central atom, C: H : C : : : N :
  50. chemistry

    Most fuels are molecular (covalent) compounds as bobpursley pointed out. Ionic compounds do not burn. Note: Some ionic materials may decompose violently or support combustion (NaNO3, KClO4, etc.) Cesium sulfide is a stable compound that does not burn. Other flammable materials...
  51. chemistry

    The unbalanced chemical equation is: H2SO4 + Pb(OH)4 --> Pb(SO4)2 + H2O Balancing the SO4 groups (2 of them): 2H2SO4 + Pb(OH)4 --> Pb(SO4)2 + H2O Balancing the H's (8 of them): 2H2SO4 + Pb(OH)4 --> Pb(SO4)2 + 4H2O
  52. chemistry

    The phosphate formula depends on the oxidation state of the vanadium ion. For example, vanadium(III) phosphate would be VPO4 and vanadium(II) phosphate V3(PO4)2.
  53. AP Chemistry (repost)

    Check the previous post at: http://www.jiskha.com/display.cgi?id=1260062043
  54. Chemistry

    Every chemical reaction involves definite mole ratios. That is the meaning of stoichiometry. A baking cake involves several complex chemical changes with precise mole ratios of reactants and products to each other. That is difficult to show and has little to do with the ...
  55. ap chemistry

    (a) A high activation energy may slow down a spontaneous reaction to the point that it does not occur at a visible rate. (b) A reaction is spontaneous because it leads to lower potential energy (deltaH is negative) and/or it increases entropy (deltaS is positive). DeltaH and ...
  56. Organic Chemistry

    No such thing as cis/trans cyclohexane. However, there is such a thing as cis- or trans- 1,2-dimethylcyclohexane. There must be two non hydrogen atoms or functional groups attached to two different carbon atoms on the cyclohexane ring to get this type of isomerism. cis/trans ...
  57. chemistry

    Cu^+2 ions in an electrochemical cell would tend to be reduced to Cu. The half cell potential is +0.159 volts. MnO4^-, MnO2, and Mn^+2 (in MnCl2) are all oxidizing agents and tend to take electrons from a reducing agent. They could not provide electrons for the reduction of Cu...
  58. chemistry.

    Do you mean: What mass of ethanoic acid would you use and how would you prepare 0,500 dm3 of a 0,500 mol/ dm3 ethanoic acid solution? (molecular mass of ethanoic acid=60,0 g/mole)? ---------- (0,500 dm3)(0,500 mol/ dm3) = 0,250 mol ethanoic acid. (0,250 mol)(60,0g/mol) = 15,0 ...
  59. chemistry

    (a) 3NiCl2(aq) + 2Na3PO4(aq) ---> Ni3(PO4)2(s) + 6NaCl (b) 3Ni^+2(aq) + 6Cl^-(aq) + 6Na^+(aq) + 2PO4^-3(aq) ---> Ni3(PO4)2(s) + 6Cl^-(aq) + 6Na^+(aq) (c) [Cancel out the ions that have not changed to get the net ionic equation]
  60. chemistry

    Do you mean in determining the volume of that solid? If so, we can find the volume from the measured dimensions only for geometrical solids (cube, rectangle, cylinder, cone, sphere, etc.). For irregular solids, measurement of dimensions can't be done very precisely.
  61. Chemistry

    The 2nd reaction is 2FeCl3(aq) + 3Zn(s)--> 3ZnCl2(aq) + 2Fe(s) The excess zinc removal reaction is Zn(s) + H2SO4(aq) --> ZnSO4(aq) + H2(g)
  62. chemistry

    In the original question, C6H12 is the formula of cyclohexane, not hexane. DrBob interpreted it appropriately as cyclohexane. The "chair" and "boat" forms of cyclohexane are conformational isomers that exist in any sample of cyclohexane, They are not ...
  63. chemistry

    There is no "correct" value of a probability but some estimates are better than others. The "standard deviation" is probably better than the average deviation as a measure of uncertainty.
  64. 9th Chemistry

    I think you mean big spaces IN the 2nd and 3rd periods. There are no elements in columns #3 to #12 because there is no "2d" subshell of electrons. Also because the energy of the 3d subshsell is higher than that of the "4s" subshell. The first row of ...
  65. AP Chemistry

    The Chemical reaction is: Mg + 2HCl --> MgCl2 + H2 1) Divide the grams of Mg by the atomic mass of Mg to get moles of Mg. 2) Moles of HCl = (2)(moles of Mg) 3) Moles of HCl = (V)(5.0 mol/L) or Volume of HCl = (mol. HCl) / (5.0 mol/L) --------- NOTE: The volume of HCl will ...
  66. AP Chemistry

    Complete and balance the reactions below: a) HClO4 + KOH --> b) CsOH + HNO3 --> c) Ca(OH)2 + HI -->
  67. chemistry

    Yes, metals are deposited at the cathode.
  68. chemistry

    In #2, the two F- ions are "donating" electron pairs to the Be atom in forming covalent bonds with Be. That makes F- a Lewis base and the Be atom a Lewis acid. In #1 there is a transfer of electrons from Ca to S in forming two ions. No covalent bonds are formed. Is ...
  69. Chemistry

    CH3 is not a molecule. It is a functional group in a molecule. It could also be an unstable anion or cation. The Lewis structure depends on what that CH3 represents.
  70. Organic Chemistry

    The sand bath is not a primary source of heat. It must be heated by a flame or a hot plate. Does that give you any ideas on how to adjust its temperature and the reaction rate?
  71. chemistry, science

    Calcium Carbonate, CaCO3, which can form from Ca^+2 and CO3^-2 ions. Bicarbonate ions, HCO3^-, change to CO3^-2 ions in sea-water since sea-water is basic.
  72. Chemistry

    The chemical equation is: 2Na(s) + 2H2O --> 2NaOH + H2 Divide the grams of Na by the atomic mass of Na to get the moles of Na. The number of moles of NaOH are equal to the number of moles of Na.
  73. Chemistry

    The formula equation is: Ca(OH)2 + 2HC2H3O2 --> Ca(HC2H3O2)2 + 2H2O HC2H3O2 and H2O are molecular substances and you do not break them up into ions. The ionic reaction is: Ca^+2(aq) + 2OH^-(aq) + 2HC2H3O2 --> Ca^+2(aq) + 2C2H3O2^-(aq) + 2 H2O Cancelling out the "...
  74. chemistry

    4. Graphite is a good electrical conductor and does not react chemically with most electrolytes. 5. (a) Ionic solids have high melting points and many of them have high solubility in water. (b) Molecular solids have low melting points and many of them do not dissolve in water.
  75. chemistry

    1 mole of K3PO4 contains 4 moles of ions: 3 moles K+ ions and 1 mole of PO4^-3 ions. Multiply the number of moles of the compound by 4 ions/mole.
  76. Chemistry

    A metal that reacts vigorously with water must belong to Groups I-A (alkalis) or II-A (alkaline earths). Not reacting with K+ and Ca^+2 is no help at all. Not many other species do, either. Besides, Ca+2(s) is pure nonsense. Reacting with Na+ is unlikely. Reaction with Co+2(aq...
  77. Chemistry

    From DrBob's and my answer, I hope you can see that a metal surface can be protected in two ways: 1. Coat the active metal with the less active metal. This works well if coating stays in place and does not allow oxidizing agents through it. Cu and Sn on iron fit that ...
  78. Chemistry

    Zinc is higher on the Metal Activity Series than iron. That means zinc metal oxidizes more easily than iron. The metal that oxidizes more easily can protect another metal that oxidizes less easily but not the other way around.
  79. chemistry

    The reaction is: 3Ca(NO3)2 + 2Na3PO4 --> Ca3(PO4)2 + 6NaNO3 moles of Ca(NO3)2 = (0.025L)(1.0mol/L) = 0.0250 mol moles of Na3PO4 = (0.0150L)(1.5 mol/L) = 0.0225 mol The mole ratio of Na3PO4/Ca(NO3)2 is 2/3 BUT we are mixing the two reagents at the ratio of 0.0225 / 0.0250 = ...
  80. chemistry

    1. Divide 50.0g of Si by the atomic mass of Si. That will give you the moles of silicon. 2. Equal moles of any two elements contain equal numbers of atoms. Based on that, multiply the previous answer by the atomic mass of copper to get the number of grams of copper with the ...
  81. general chemistry

    Let the initial and final concentrations be Co and Ct. To find k: ln(Ct/Co)=-kt ln(0.5) = -k(410s) k = ____? To find the concentration at (4)(410s), use the same equation: ln(Ct/Co)=-kt Use the value of k from the first part, and t = 4x410=1640s, then solve for for Ct.
  82. chemistry

    5% means 5.00g acetic acid in 100 mls of solution. That is equivalent to 50.0 g acid/L. The molar mass of acetic acid is about 60.05g/mole (50.0 g acid/L.)(1 mol / 60.05g) = 0.8326 mol/L The reaction is: HC2H3O2 + NaOH --> NaC2H3O2 + H2O based on the reaction, moles of ...
  83. chemistry

    These two solutions do not react but you can write a chemical equation anyway: 2KCl+ CuSO4 --> K2SO4 + CuCl2 If you include complex ion formation, what happens depends on the concentrations of the ions formed in solution.
  84. chemistry

    Do you mean higher ionization energy? Phosphorus has a higher first ionization energy. Its 2p subshell is half-filled with one eletron in each orbital. The three electrons have identical (parallel) spins. A sulfur atom has one more electron than phosphorus in the 2p subshell. ...
  85. chemistry

    The molar mass of KHC8H4O4 is 204.22g Use the above value to convert 0.3589g of "KHP" to moles. The mole ratio of NaOH to KHP is 1/1 (same number of moles). Molarity = moles / 0.01496 L = __________M
  86. Chemistry

    CuSO4.5H2O ---> CuSO4+5H2O is correct if the heating is somewhat gentle. The solid product, anhydrous CuSO4 is white. If you heat the hydrate too strongly, you will end up with black CuO.
  87. chemistry

    The DeBroglie wavelength of a moving body is given by: wavelength = h / mv h = 6.63x10^-34 Js m = 0.0459 kg v = 80.0 m/s Substitute the above values into the formula to find the wavelength.
  88. chemistry

    Please post your questions only once.
  89. Chemistry

    Freq. = 2.40 GHz = 2.40x10^9 waves/second velocity of light = (wavelength)(frequency) Wavelength = (velocity of light) / (frequency) Wavelength = (3.00x10^8 m/s) / (2.40x10^9waves/sec) = ______________ m/wave ---------------- NOTE: "Light" is used in the sense of ...
  90. Chemistry

    Convert frequency from MHz to Hz. wavelength = (3.00x10^8m/s) / (frequency in Hz)
  91. Chemistry

    Intermolecular forces in a solid (lard) are stronger than intermolecular forces in a liquid (oil). The intermolecular forces in saturated fatty acids which are the main components of solid fats are stronger than those in unsaturated fatty acids which are more common in oils. ...
  92. Chemistry

    Esterification = Reaction of an organic acid with an alcohol to form an ester and water. Saponification = Reaction of a basic (NaOH) solution with an ester to form a salt of the organic acid and the alcohol in the ester. The acid in the ester is pulled out as a salt (soap) ...
  93. chemistry

    Yes, if the the molecule is symmetrical enough for the bond dipoles to cancel out. Example: O=C=O has polar bonds but their dipoles cancel out because of molecular symmetry.
  94. organic chemistry

    The ideal solvent for recrystallization is one in which the solute has high solubility at high temperature and low solubility at low temperature. You could try to look up solubilities in chemistry handbooks or experiment with different solvents. If you have to do that you ...
  95. Chemistry 130

    pH = -log[H+] The above relationship can also be expressed as: [H+] = 10^(-pH) or [H+] = 1 / 10^(pH) That shows the hydrogen ion concentration is inversely proportional to the pH.
  96. Chemistry

    The correct answer is (a) based on the first chemical equation below. The mole ratio of NaOH to H3PO4 determines which salt is produced. Only the first one produces Na3PO4: H3PO4 + 3NaOH ---> Na3PO4 + 3H2O H3PO4 + 2NaOH ---> Na2HPO4 + 2H2O H3PO4 + NaOH ---> NaH2PO4 + ...
  97. CHEMISTRY

    It could be an alkene as DrBob indicated or an ether depending on experimental conditions such as temperature.
  98. Chemistry

    ΔE = q - w ΔE is the change in internal energy of a system q is the heat flowing into the system w is the work being done by the system The 2424 J is released to the surroundings. It should be assigned a negative sign. The 6 KJ is work done against the surroundings. ...
  99. Chemistry

    According to the Work-Energy Theorem, Work = Ek(final) - Ek(initilal) Ek(initilal) = (1/2)mv^2 = (1/2)(0.17kg)(4.5 m/s)^2 Ek(final) = (1/2)mv^2 = (1/2)(0.17kg)(4.0 m/s)^2 Work = ?__________ NOTE: This looks like a Physics question.
  100. Chemistry

    This looks like diatomic species (molecules or ions) of third row elements with 14 electrons. It may be Cl2, SCl-, etc. You should be able to come up with a couple more.
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