Most popular questions and responses by GK
  1. 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?

    asked on September 20, 2013
  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?

    asked on September 20, 2013
  3. 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?

    asked on April 10, 2011
  4. 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

    asked on September 20, 2013
  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

    asked on June 18, 2013
  6. osmotic pressure chemistry.

    I thought I was answering: http://www.jiskha.com/display.cgi?id=1234647827

    asked on February 14, 2009
  7. osmotic pressure chemistry.

    For a given mass of solute per liter of solution, the larger to formula mass, the lower the osmotic pressure. Osmotic pressure depends on molar concentration. A large molar mass would tend to produce a lower concentration in terms of moles of particles per

    asked on February 14, 2009
  8. english

    un scramble the following words kerba ni that means enter illegally

    asked on February 2, 2009
  1. BEST

    thank you

    posted on June 19, 2013
  2. Physics :(( help please TT

    answer is 7

    posted on April 28, 2013
  3. Physics


    posted on April 13, 2013
  4. Physics

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

    posted on March 30, 2013
  5. Physics

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

    posted on March 27, 2013
  6. algebra!

    IT is Absolutely right . The answer is 8

    posted on March 11, 2013
  7. 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.

    posted on May 17, 2010
  8. 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

    posted on May 10, 2010
  9. 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

    posted on April 15, 2010
  10. 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

    posted on April 10, 2010
  11. 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

    posted on April 10, 2010
  12. 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.

    posted on March 29, 2010
  13. 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

    posted on March 29, 2010
  14. 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] =

    posted on March 28, 2010
  15. 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

    posted on March 25, 2010
  16. 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)

    posted on March 22, 2010
  17. 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

    posted on March 20, 2010
  18. Chemistry

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

    posted on March 20, 2010
  19. Organic chemistry

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

    posted on March 20, 2010
  20. 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

    posted on March 20, 2010
  21. 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

    posted on March 20, 2010
  22. Chemistry


    posted on February 15, 2010
  23. 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.

    posted on January 31, 2010
  24. 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.

    posted on January 17, 2010
  25. 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?

    posted on January 11, 2010
  26. 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

    posted on January 10, 2010
  27. 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

    posted on January 8, 2010
  28. 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.

    posted on January 4, 2010
  29. chemistry

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

    posted on January 3, 2010
  30. chemistry

    [Answered elsewhere]

    posted on January 1, 2010
  31. 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

    posted on January 1, 2010
  32. chemistry

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

    posted on January 1, 2010
  33. Chemistry

    Statements A, B, and C are correct.

    posted on January 1, 2010
  34. 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.

    posted on January 1, 2010
  35. 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

    posted on January 1, 2010
  36. 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.

    posted on January 1, 2010
  37. 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

    posted on January 1, 2010
  38. 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)

    posted on January 1, 2010
  39. 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:

    posted on December 27, 2009
  40. chemistry

    NaOH + HClO4 --> H2O + NaClO4

    posted on December 14, 2009
  41. 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

    posted on December 14, 2009
  42. 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

    posted on December 7, 2009
  43. 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)

    posted on December 7, 2009
  44. 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.

    posted on December 7, 2009
  45. Chemistry

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

    posted on December 7, 2009
  46. 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,

    posted on December 7, 2009
  47. 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.

    posted on December 6, 2009
  48. 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

    posted on December 6, 2009
  49. AP Chemistry (repost)

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

    posted on December 5, 2009
  50. 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

    posted on December 5, 2009
  51. 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]

    posted on December 4, 2009
  52. 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

    posted on December 4, 2009
  53. 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

    posted on December 4, 2009
  54. 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

    posted on December 4, 2009
  55. 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)

    posted on December 1, 2009
  56. 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

    posted on December 1, 2009
  57. 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

    posted on November 30, 2009
  58. 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.

    posted on November 26, 2009
  59. 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

    posted on November 8, 2009
  60. 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?

    posted on November 8, 2009
  61. 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.

    posted on November 8, 2009
  62. 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

    posted on November 8, 2009
  63. chemistry

    Yes, metals are deposited at the cathode.

    posted on November 8, 2009
  64. AP Chemistry

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

    posted on November 8, 2009
  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

    posted on November 8, 2009
  66. 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

    posted on November 2, 2009
  67. 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

    posted on November 2, 2009
  68. 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.

    posted on November 2, 2009
  69. 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.

    posted on November 2, 2009
  70. 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.

    posted on October 28, 2009
  71. 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

    posted on October 24, 2009
  72. 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.

    posted on October 24, 2009
  73. 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.

    posted on October 24, 2009
  74. 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

    posted on October 23, 2009
  75. 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.

    posted on October 23, 2009
  76. 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

    posted on October 23, 2009
  77. 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.

    posted on October 23, 2009
  78. 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

    posted on October 23, 2009
  79. 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

    posted on October 23, 2009
  80. chemistry

    Please post your questions only once.

    posted on October 22, 2009
  81. 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.

    posted on October 22, 2009
  82. 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

    posted on October 22, 2009
  83. 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

    posted on October 22, 2009
  84. 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.

    posted on October 20, 2009
  85. 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

    posted on October 20, 2009
  86. 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

    posted on October 20, 2009
  87. Chemistry

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

    posted on October 20, 2009
  88. 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

    posted on October 20, 2009
  89. 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

    posted on October 17, 2009
  90. 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.

    posted on October 14, 2009
  91. 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

    posted on October 11, 2009
  92. Chemistry

    Not arguing with DrBob. Just presenting another way of looking at it using change in oxidation numbers as the yardstick for electrons transfer. The balanced reaction is: 2C3H7OH + 9O2 --> 6CO2 + 8H2O Each of the 18 oxygen atoms in O2 changes from an

    posted on October 9, 2009