Posts by DrBob222

Total # Posts: 56,441

  1. Chemistry

    q= mass x specific heat x delta T. I don't know what units you want sp.h. in but I would convert kJ to J and kg to g. That way sp.h. comes out in J/g*C and you can convert to whatever you want.
  2. Chemistry

    B, Al, Ga. See this.
  3. Chemistry

    What do you not understand about how to do this? Here are the rules.
  4. Chemistry

    First, that C line is -x.........x.......x and not -2x ane the E line is 0.123-x.......x.......x Then you have Kp = 0.0121 = (x)(x)/(0.123-x) and solve that quadratic. I get 0.032996 which rounds to 0.0330
  5. Chemistry question!

    Follow the instructions for part a which I worked for another student. oops. here is the link.
  6. Science HELP!!!!!
  7. Chemistry

    Ksp = (Ag^+)(OH^-) You know Ks and OH^-, substitute and solve for (Ag^+) (in mols/L). b. So you know (Ag^+) in mols/L. In 2.0L you will have twice as many mols. Then grams = mols x molar mass = ?
  8. Chemistry

    Use the Henderson-Hasselbalch equation. Post your work if you run into trouble.
  9. Solubility

    See your other problem below that is the same type.
  10. Solubility

    .....................CaF2 ==> Ca^2+ + 2F^- Write the Ksp expression for CaF2, the problem gives you the value for Ca^2+ and for F^-, cubstitute those values and solve for Kp. NOTE: The problem tells you that the (F^-) is 0.02M. Do NOT mutiply that by 2.
  11. Solubility

    .........Ag2SO4 ==> 2Ag^+ + [SO4]^2- I..........solid..............0.............0 C,,,,,,,,solid.............2x.............x E........solid.............2x.............x Write the Ksp expression for Ag2SO4, plug in the E line and solve for x = (Ag2SO4)
  12. Chemistry: Equilbrium

    Le Chatelier's Principle says in very unsophisticated terms that if we do something to a system at equilibrium that the equilibrium will shift so as to undo what we did to it. So if you increase NH3 the reaction will shift so as to reduce the NH3 concn which means it will ...
  13. Chemistry: Equilibrium

    So Kp = p(H2O)^2/p(H2)^2*p(O2) A large Kp means high p for H2O and low p for H2 and O2. If you have low p for H2 there isn't much there.
  14. Chemistry

    2HNO3 + Ba(OH)2 ==> 2H2O + Ba(NO3)2 mols Ba(OH)2 = M x L = ? From the equation, you know mols HNO3 = twice moles Ba(OH)2 Then M HNO3 = mols HNO3/L HNo3
  15. Physical Sci

    Is this an exam? Where are your thoughts? Numbers 2 and 3 have more than one answer.
  16. Chemistry

    Yes, you have it. Good work.
  17. Chemistry

    1. Go through and assign oxidation numbers to each element. 2. Mark those that have changed. 3. Determine the ones that lost/gained electrons. 4. The oxidizing agent gains electrons; the reducing agent loses electrons. Post your work or explain in detail what you don't ...
  18. Chemistry

    I'm confused. 1. Apparently you want the cell construction so as to generate a voltage. 2. However, you don't say what you want. 3. I assume you want to know the voltage generated. M ==> M^3+ + 3e........Eo = -0.29 v N^2+ + 2e ==> N.......Eo = 0.61 v...
  19. Chemistry lab

    That's what I gave you but I made a typo. That .2 cm^3 should have been 0.2 dm^3. 2.65 g x (1 dm^3/0.2 cm^3) = ? In any event, the answer is the same.
  20. Chemistry lab

    I think you must have meant to calculate the molarity; however, you said g/dm^3 so 2.65 g x (1 dm^3/0.2 cm^3) = ?
  21. Chemistry lab

    If you've done anything in the lab you can do this without our help.
  22. organic chemistry

    oops. No, what you have proposed with the CH3 below is 2-methylbutane EXCEPT that you have a 5-valent C on C2. If you want 2-ethylbutane you want a CH3CH2 (or C2H5) below the second CH2. But when you attach the C2H5 group you must remove one of the H atoms. You can write it ...
  23. Chemistry Post a specific question if you run into trouble.
  24. chemistry

    Use mass = volume x density
  25. Chemistry

    a. dH is -. By definition that is exothermic. b. You get 821.8 kJ for 2*23 or 46 g Na. So 5.6 g Na will give you 821..8 kJ x 5.6/46 = ? kJ. c. Rearrange part b. You have 821.8 kJ when 2*58.5 g NaCl are formed. So 2*58.5 g NaCl x 16.5 kJ/821.8 kJ = ? d. See b and c parts. Post ...
  26. Chemistry

    dGo rxn = (n*dGo products) - (n*dGo reactants) Then dGo = -RTlnK
  27. Chemistry

    1. Go through and assign oxidation numbers to EACH element/ion/etc. Do you know how to do that? I can give you links if you don't. On the left, H is +1, Cl is -1, Zn is 0. On the right, Zn is +2, Cl is -1 (each) and H2 is 0. 2. Look to see which elements/ions/etc have ...
  28. Chemistry

    The tendency for students is to say that the (OH^-) is 1E-6M but this is only 10 times more than is in H2O when it ionizes; therefore, we must add that in to the mixture. Here is how you do it. NaOH is a strong electrolyte; therefore it will ionize 100% as follows...
  29. chemistry

    Do an ebuilloscopic ( boiling point elevation) or cryoscopic (freezaing point depression) experiment.
  30. Chemistry

    C2H4O2 = A with molar mass approx 60. C2H3OCl = B with molar mass approx 78, Note that all of these numbers are estimates so you should recalculate throughout for more accurate values. A + PCl3 = B Since the yield is 78.2% and not 100%, you will need to prepare 75.0/0.782= ...
  31. Chemistry

    You are absolutely right. BaSO4 is barium sulfate. BaS is barium sulfide and I misread the question.BaS is soluble and a reaction will take place. Cu(NO3)2 + BaS ==> Ba(NO3)2 + CuS You can turn that into an ionic equation. The net equation is Cu^2+(aq) + S^2-(aq) ==> CuS...
  32. Chemistry

    If you're reacting Cu(NO3)2 and BaSO4, they don't react. BaSO4 is insoluble
  33. Chemistry

    Ba(NO3)2(aq) + Na2SO4(aq) ? BaSO4(s) + 2NaNO3(aq) mols Ba(NO3)2 = grams/molar mass = ? How much BaSO4 will be produced? Since 1 mol Ba(NO3)2 will produce 1 mol BaSO4, you will produce mols BaSO4 = mols Ba(NO3)2. Convert mols Ba(NO3)2 to grams. grams = mols x molar mass = ? ...
  34. Chemistry

    No. What in the world is H3NO3.? H2O + 3NO2 ==> 2HNO3 + NO
  35. chemistry

    mols HCl you have = M x L = ? mols Mg needed = 1/2 mols HCl because you know 1 mol Mg reacts with 2 mols HCl. grams Mg = mols Mg x atomic mass Mg.
  36. Chemistry

    q = mass Au x specific heat Au x delta T. Substitute and turn the crank.
  37. AP Chemistry

    Coulombs = amperes x seconds = ? You gave amperes; you need seconds. You know 63.5/2 grams Cu (approx 32 g) will be deposited with 96,485 coulombs so 96,485 coulombs x (10.5/32) = approx 30000, Note that my numbers are approx so you need to go through and refine ALL of them ...
  38. Chemistry

    dH rxn = (n*dHo formation products) - (n*dHo reactants) Post your work if you get stuck.
  39. Chemistry

    1 mol Ca = 40 grams. Atom in 1 mol Ca = 40 g Ca = 6.02E23 So atoms in 4 g Ca = 6.02E23 x 4/40 = 6.02E22 Now we have 6.02E22 atoms Na. How many mols is that? 6.02E22 atoms Na x (1 mol/6.02E23) = 0.1 mol Na 1 mol = 23 g Na. So 0.1 mol = ? grams.
  40. Chem 2

    Thank you for letting me know.
  41. Chem 2

    2Al(s) ==> 2Al^3+ + 3e Eo ox = +1.66 v 3Cd^2+ + 2e ==> 3Cd(s) Eo red = -0.40 -------------------------------------------------------- 2Al(s) + 3Cd^2+ ==> 2Al^3+ + 3Cd(s) So Eo cell = Eo ox + Eo red = +1.66-0.40 = ? You know Ecell from the problem of 1.299. Plug those ...
  42. Chemistry

    3Ni^2+ + 2e ==> 3Ni(s) Eo red = - -0.26 2Cr(s) ==> 2Cr^3+ + 3e Eo ox = +0.74 .................Eocell = Eo red + Eo ox = -0.26+ 0.74 = ?
  43. Chemistry

    ...................HA ==> H^+ + A^- I..................3.0.........0.........0 C................-x............x.........x E................3.0-x.......x.........x Write the K expression, plug in the numbers and solve for x. Use the value of x to determine the values of HA, ...
  44. Chemistry

    Keq = (concn of right side)^coefficients/(concn left side)^coeff or Keq = (C)(D)/(A)^2(B)
  45. Chemistry

    (A) = 1 mol/2L = 0.500M (B) = 0.800/2 = 0.400 M ,,,,,,,,,,,,,,,,,,,,,,2A (aq) + B (aq) <-> C (g) + D (g) I.....................0.5.........0.4...............0.........0 C,,,,,,,,,,,,,,,,,,,,-2x.........-x...............+x........+x E.................0.5-2x......0.4-x...
  46. Chemistry

    You can't solve this without knowing the equation. A + 2B => D or 2A + B = 2D or etc.
  47. Chemistry

    Convert pH to pOH. Convert pOH to OH Then since there are two mols OH ions in 1 mol Ca(OH)2, convert mols OH to mols Ca(OH)2.
  48. Chemistry (pressure)

    Use PV = nRT
  49. Chemistry

    Make the superscripts and the subscripts add to the same number on both sides of the equation. For example, the top numbers would look like this. ?? ==> 15/7 N + 0/-1 e 15X ==> 15/7 N + 0/-1 e and you know that number is 15 because on the right you hve 15 + 0 = 15. Now ...
  50. Chemistry (specific heat)

    This is exactly the same kind of problem I did for you yesterday. Work this one the same way.
  51. Chemistry

    Write the expression for Keq, plug in the numbers and calculate K.
  52. Chemistry

  53. Chemistry

    M X = mols X/L. You know M and L, solve for mols X Then mols X = grams/molar mass. You know grams and mols, solve for molar mass X.
  54. Chemistry

    0.0026 is the correct answer. Check the problem to make sure you typed it in correctly. If the problem is typed in correctly then the prof didn't give the correct answer as one of the choices.
  55. Chemistry

    I don't think 0.130 x 0.02 = 0.026 either.
  56. Chemistry

    I think you punched in the wrong numbers; i.e., hit a wrong key. mols LiOH = mols HCl = M HCl x L HCl = ?
  57. Chemistry (concentration)

  58. Chemistry (concentration)

    Then 3.2 mols LiOH will form 3.2/2 = 1.6 mols Li2SO4 grams Li2SO4 = mols x molar mass = ? (Li2SO4) in g/L = grams Li2SO4/L solution.
  59. Chemistry

    I believe that will be 4th order which is highly unlikely to happen in real life. 1X comes together SIMULTANEOUSLY with 3 z to form 2 L and 4T/ It is unlikely because it is essentially impossible for 1 x and 3z to come together in the exact same second (nanosecond?) to bond.
  60. Chemistry

    C=C-C=C-C-C-C 2 H on C1 1 H on C2 1 H on C3 1 H on C4 2 H on C5 2 H on C6 3H on C7 So that straight chain diene is C7H12, Take one of the H atoms off any C and replace with a Br to make C7H11Br. OR this way. Draw the straight chain C with C-C-C etc. Put two double bonds in. ...
  61. Chemistry

    I don't see how it can be C7H13Br, I think you put in your drawing only one double bond.
  62. Chemistry

  63. Chemistry (electron transfer)

  64. Chemistry

    You are right. That is the only one listed that is NOT redox and that's what the problem wanted: i.e., the equation that was not redox.
  65. Chemistry

    C'mon. The only way to do this problem is not to guess. You go through and assign oxidation states to each element and the ones that don't change are not redox; those that do change are redox. For your second guess here are the numbers. On the left C is -4, H is +1, O ...
  66. Chemistry

    absolutely not correct because:. KClO3 ==> KCl + 3/2 O2 Cl on the left is +5 oxidation state and on the right it is -1 while O on the leftr is -2 and on the right is zero. Loss and gains of electrons certainly is redox.
  67. Chemistry

    For first order, ln(No/N) = kt No = given N = given t = given Plug and chug.
  68. Chemistry

    M H2O - (27.0/18/5) = ? M H2 = (0.25/2/5) = ? M O2 = (16.0/32/5) = ? But note that I don't think those gases will dissolve in that little water. ....................2H2O(g) ? 2H2(g) + O2(g) E........................?..............?..............? from above. Write the Kc ...

    I found this site.
  70. Chemistry

    [mass metal x specific heat metal x (Tfinal-Tinitial)] + [mass H2O x specific heat H2O x (Tfinal-Tinitial) = 0 Plug in all the numbers and solve for specific heat metal. Post your work if you run into trouble.
  71. Chemistry

    1. 5.0 M x [215/750] = ? 2. NaOH + HCl ==> NaCl + H2O mols NaOH = M x L = ? The equation is 1 mol HCl to 1 mol NaOH; therefore, mols HCl = mols NaOH Then M HCl = mols HCl/L HCl = ?
  72. Chemistry

    3H2O + 4e + 2NO2^- ==> N2O + 6OH^- 4OH^- + H2 ==> 2OH^- + 2e + 2H2O which becomes 2OH^- +H2 ==> 2e + 2H2O For balanced equation multiply the 1st one by 1 and the last one by 2 and add the two. Check my work.
  73. Chemistry

    Please don't change screen names. Refer to your post above under anonymous. For help on balancing redox equation see this link.
  74. Chemistry

    Do you know the erquation. 15 M HNO2 is strong, look on Google to find the reaction with concentrated HNO3.
  75. Chemistry

    I agree. Do you have a reason for your answer? It's important to know why.
  76. Chem

    I agree
  77. Chemistry

    Start counting at either methyl group with 1, the next carbon will be 2, next will be 3 and the other methyl group will be 4 so it would be 1,4-dimethyl benzene; otherwise known as p-methyl benzene.
  78. Chemistry (bonds)

    I agree
  79. Chemistry

    I assume you mean to say nitric acid. Trioxonitrate V acid for HNO3 is rubbish. The reason HNO3 is not used is because HNO3 is such a strong oxidizing agent that you don't get H2 gas but rather either NO2 gas or NO gas depending upon how strong the HNO3 is.
  80. Chemistry

    Note: Kevin, you should tell us what you don't understand and what you understand about a problem like this and don't leave us up in the air. You don't show any work at all so I'm giving you a heads up that you can't gret another freebie like this again. ...
  81. Chemistry

    In the future please show how you cam up with this answer. Yes, -286 is correct but I spent considerable time putting all of this together to work the problem and to check your answer. I could hve checked your equatiions much faster and helped others.
  82. Chemistry

    Your equations are OK. If you plugged in correctly and did the math right you're OK.
  83. Chemistry

    (Mg^2+) = 0.01 x (400/700) = ? pH of NaOH = 9 so pOH is 14-9 = 5 and (OH^-) = 1E-5M initially. After dilution it is 1E-5 x (300/700) = ? Qsp = (Mg^2+)(OH^-)^2. Plug in the numbers to calculate Qsp then compare with Ksp for Mg(OH)2. If Qsp > Ksp a ppt will form. Post your ...
  84. chemistry

    You must be kidding? Goggle it.
  85. Chemistry

    That looks ok to me.
  86. Chemistry

    I don't get that. If you will post your work I will check it. Did you remember that dG and dH are in kJ/mol and S is in J/mol?
  87. Chemistry

    To extend the answer from Damon, you probably meant CH3Cl + HCl. This is not a double replacement reaction. It is a redox reaction. In some organic circles this is called a substitution reaction; i.e., you're substituting a Cl atom for a H atom.
  88. Chem - Redox rxn

    I don't know what your definition is of oxidation/reduction. Your answeres ae not right. My definition is that oxidation is the loss of electrons and reductin is the gain of electrons. You have the oxidation states marked correctly. So Cl goes from 0 on the left to -1 on ...
  89. Chemistry

    9.8 grams of WHAT? mols = 9.8g/molar mass of whatever = ? Then M = mols/0.500 L = ?
  90. chem

    ??? This is a question only you can answer. It is based on an experiment you have done and you didn't furnish any of the data from the experiments/
  91. Chemistry

    2.0 WHAT long tube. feet, inches, cm, miles? I will assume 2 meters. Let distance NH3 travels = x Then HCl travels 2.0-x rate NH3 = x/time rate HCl = 2-x/time time NH3 = time HCl so (x/t)/(2-x/t) = sqrt(36.5/17) Solve for x and 2-x
  92. Chemistry

    I don't know what n_hi means.
  93. Chemistry

    See your post below. Both of those sites give you the value and you can calculate them from the formula.
  94. Chemistry

    Here it is calculated for you.
  95. Chemistry

    This site gives you the formula for the Balmer series lines and shows the wavelengths for the first few lines. Note that the lines are decreasing in wavelength as the n2 level is increasing so if you plug 0 in for 1n22 you can calculate the shortest wavelength in the series.. ...
  96. Chemistry

    4p5, 5p5, 3p5 should tell you that all want to gain one electron to fill the outside shell. So all have an oxidation state of -1. If you will go to Google and type in chlorine, bromine, iodine,(individually) and scroll down on each to chemical properties, you will be able to ...
  97. Chemistry

  98. Chemistry

    Apply the same reasoning to the Co question that we now know is the correct way to look at the problem.
  99. Chemistry

    I don't think the answer is Ba. I agree it is a 4d electron for l = 2
  100. Chemistry

    Thank you for letting me know. You can apply that same reasoning then to your Ba? problem.
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