Posts by DrBob222

Total # Posts: 56,180

  1. Chemistry - acid base

    Thanks for showing your work. At the end of part A, you're correct that you have 0.1333 mols TrisH+ and 0.0666 mols Tris. So when you remove half of it (500 mL of the 1L) you have 0.1333/2 mols TrisH+ and 0.0666/2 mols Tris. Those are the numbers you're starting with ...
  2. Chemistry - equm acid base

    A mixture of a weak acide (HNO2) and its salt (NaNO2) is a buffer solution and you should be using the Henderson-Hasselbalch equation. pH = pKa + log (base)/(acid). NaNO2 is the base and HNO2 is the acid. Find pH and convert to H3O^+.
  3. chemistry

    (V1/T1) = (V2/T2) Remember T must be in kelvin. kelvin = 2734.15 + degreed C Post your work if you get stuck.
  4. chem

    I don't see a formula but it is this. Ptotal = pbutane + pH2O Look in your text for a table of vapor pressures for water or look on google to that and record that as pH2O. The total pressure will be the atmospheric pressure at the time you did the experiment. Substitute ...
  5. Science Chemical Reactions

    no way.
  6. chem

    Calculate mols gas A from PV = nRT. You know its partial pressure, volume, R, T (remember T must be in kelvin). Calculate mols gas B from PV = nRT in a similar manner. Add mols gas A, mols gas B + 0.210 from the third gas. Use PV = nRT using total mols and solve for P which ...
  7. chem

    The problem doesn't say the conditions you want for the density; i.e., is that density at 53 C and 1.10 atm or density at STP. I will assume you want it at STP. Therefore, we must correct the volume from 1.85 L to the volume at STP. So T goes from 326 K (273 + 53) to 273 K...
  8. Chem

    You can look at this in a slightly different fashion. You know 1 mol gas occupies 22.4 L at STP so 1.99 L/22.4 L = number mols. Then mols x 6.022E23 = number of molecules.
  9. Science

    Air rises, water vapor condenses.
  10. Chemistry

    Draw the Lewis structures. The one with the uneven number of electrons will be the one.
  11. Chem

    See your other post below.
  12. chem

    No, What do you not understand? T must be in kelvin P is pressure in atmospheres. V = volume in L n = mols R = ideal gas constant T = temperture in kelvin (273.15 +|C = K)
  13. chem

    Use PV = nRT
  14. chemistry

    There is no reaction. There is only a mixing of the ions after the two salts have dissolved..
  15. chemistry

    Use PV = nRT.
  16. chemistry

    mols TiCl4 = grams/molar mass = ? mols Cl = 4 x mols TiCl4. g Cl = mols Cl x atomic mass Cl = ?
  17. Chemistry

    2C6H14 + 19O2 ==> 12CO2 + 14H2O mols hexane = grams/molar mass = ? Using the coefficients in the balanced equation, convert mols Hexane to mols CO2. You can see that 2 mols hexne will produce 12 molsl CO2. Convert mols CO2 to grams. grams = mols x molar mass
  18. Chemistry stoichionetry

    C6H12O6 + 6O2 => 6CO2 + 6H2O mols C6H12O6 = grams/molar mass = ? Using the coefficients in the balanced equation, convert mols glucose to mols CO2. That is done this way. ?mols CO2 = mols glucose from above x (6 mols CO2/1 mol glucose) = ? Then convert mols CO2 to grams. ...
  19. Chemistry

    C(graphite) + 2H2(g) + 1/2 O2(g) ==> CH3OH(l) dH = -283.6 kJ CH3OH(g) ==> CH3OH(l) dH = -35.2 kJ. Add equation 1 to the reverse of equation 2 to obtain elements to CH3OH(g), then add the dH for each reaction to obtain total rxn. Post your work if you get stuck.
  20. Chemistry

    dHo rxn = (n*dHo products) - (n*dHo reactants)
  21. chem

    Here is how you do these. Use this as an example to work yours. /display.cgi?id=1520308699#1520308699.1520310308
  22. Chemistry

    Tell me your problem in solving this.
  23. science
  24. Science Chemistry
  25. chemistry

    This would make more sense if we could draw structures that isn't possible on this forum. C6H5(OH)COOH + HOCH3 ==> C6H5(OH)COOCH3 + H2O salicylic acid + methyl alcohol ==> methyl ester of salicylic acid
  26. Chemistry

    I'll do one and the others are yours. There are several steps to this. 1. Write and balance the molecular equation. 2AgNO3(aq) + MnCl2(aq) ==> 2AgCl(s) + Mn(NO3)2(aq) 2. Convert the molecular equation into a total ionic equation. The following rules apply. a. Salts ...
  27. Chemistry

    q = mass x specific heat x ((Tfinal-Tinitial0 You know mass is 200 g Specific heat is given in J You have Tfinal and Tinitial. Substitute and solve for q. Remember this is an exothermic reaction (it gives off heat), so place a negative sign for the number is J. Convert to kJ. ...
  28. Chemistry

    A couple of points here. First, mol = grams/molar mass and not what you have. Then mols/L/s will give you about 0.0344 M/s and not mols/s.
  29. P.S.--ap chemistry

    Check your post and the problem you copied. I don't believe the correct answer is listed. Perhaps you made a typo.
  30. ap chemistry

    Here is one of the best sites I've found that explains how to write the rate law. Be sure and read the first part in order to get the essentials but the second part is the one you want. It explains how to do problems in which the first step is fast and the second step is ...
  31. AP Chem

    k = 0.693/t1/2 Solve for k and substitute into the below equation. Then ln(No/N) = kt No = 0.14 N = 0.07 although you should be able to do this in your head with no equations.
  32. Chem -Bob Pursley Please Help!

    a and d are right. The other two are wrong.

    Yes, in that case it still applies. If reactants ar given and zero produccts are given common sense tells you that it MUST go the right and the reactant(s) lose and the product(s) gain. The second possibility is that you have zero reactants but you start with the product. In ...
  34. Chemistry

    See your other post.
  35. Chemistry

    dHorxn = (n*dHo products) - (n*dHo reactants) Post your work if you get stuck.
  36. Chemistry

    Yes, either of those indicators would be suitable for a pH of 7.0, that is, titration of strong acid with strong base.
  37. Chemistry

    Are you sure you are using the same chemical equation I used; i.e., 2NaN3 ==> 2Na + 3N2. If so you haven't done anything wrong. 0.65 gives you the mols N2. Now you convert mols N2 to mols NaN3. That is 0.65 mols N2 x (2 mols NaN3/3 mols N2 = ? Then grams NaN3 = mols ...
  38. Chemistry

    2000 N/m^2 = 2000 pascals. Convert to atmospheres 2000/101325 = approx 0.02 but that's an estimate. Then pi = MRT You know pi, R, T, solve for M = molarity. Then M = mols/L. You know M and L, solve for mols. Then mol = grams/molar mass. You know mols and grams, solve for ...
  39. Chemistry

    Were you given an equation for the decomposition? If so, make sure it agrees with what I've written; otherwise I will use this one. 2NaN3 ==> 2Na + 3N2 volume of bag is 25 x 25 x 20 = approx approx 13,000 cc or about 13 L but you need a better answer than this estimate...

    See your other post.
  41. Chemistry

    (IBr) = 0.5 mol/K = 0.5M ...........I2 + Br2 ==> 2IBr I..........0.....0.......0.5 C..........x.....x........-2x E..........x.....x......0.5-2x Write the Kc expression, substitute the E line, solve for x and evaluate 0.5-2x and x. Post your work if you get stuck.
  42. Chemistry

    Didn't I just do that for you below?
  43. Chemistry

    It looks OK to me but I don't know exactly what you're trying to do. I would add a couple of commas as shown, a period at the end, and change the spelling of synthesized like this. I question if you need the dash in the name but, again, I don't know what you're...
  44. Chemistry

    XA = mols A/total mols = ? = estimated 0.3 XB = mols B/total mols = estimated 0.7 Ptotal = XA*PoA + XB*PoB. You know Ptotal, XA, XB, and PoA. Solve for PoB. Post your work if you get stuck.
  45. Science

    You need to repost this question using proper sentence construction. With no periods at the end and no caps at the beginning of a sentence, I can't understand what you've written.
  46. Chemistry

    2NaOH + H2SO4 ==> Na2SO4 + 2H2O mols H2SO4 = M x L = 0.102 x 0.02615 = ? Using the coefficients in the balanced equation, convert mols H2SO4 to mols NaOH. That is 2 mol NaOH to 1 mol H2SO4; therefore, mols NaOH = 2 x mols H2SO4. Then M NaOH = mols NaOH/L NaOH. You know M ...
  47. Chemistry

    k = 0.693/t1/2 = ? Then ln(No/N) - kt No = 16.0 N = 3.34 k from above Solve for t in years.
  48. Chemistry

    1. mols NH4Cl - grams/molar mass = ? 2. M = molarity = mols/L 3. M = mols/L. You know M and you know mols, substitute and solve for L. Convert to mL if you wish. Post yowr work if you get stuck.
  49. Chemistry

    0.0200 M CaCl2. So you have 0.0200 M Ca^2+ and 2*0.0200 M Cl^- and the total is 0.0200 + 0.0400 = 0.0600 M total. You do the other two the same way. Post your work if you get stuck.
  50. Science

    (P1V1/T1) = (P2V2/T2) Remember T must be in kelvin. Also you must decide what room T is.
  51. @Onye--Chemistry

    You should make a separate post for another question. Piggy backed onto a previous post is likely to get it overlooked. MnO4^- + 3e + 2H2O ==> MnO2 + 4OH^- HO2^- + OH- ==> O2 + 2e + H2O The two balanced half equations are written above. Multiply equation 1 by 2 and ...
  52. Chemistry

    Yes, the problem says lactic acid is a monoprotic acid so we write H for the acid part and A for the rest of the large molecule. It makes typing easier. The molar mass of lactic acid is 90.08. mols HA = grams/molar mas = 0.578/90.08 = approx 0.006 but you should use a more ...
  53. oops typo--Chemistry

    Hope this helps a little.
  54. Chemistry

    OK. Let's forget about oxygen and ozone for the moment and do another one. Let's make fizzy water. Carbon dioxide + water ==> carbonic acid. CO2 + H2O ==> H2CO3 So if we have 1 mol CO2, we could convert it to 1 mol H2CO3. Right. Or if we had 4 mols CO2, we could ...
  55. Chemistry

    I showed you how to do this before I went to bed last night. What's the problem?
  56. Chemistry (mol)

    1 mol of anything contains 6.022E23 particles of whatever those things are; i.e., 1 mol x (6.022E23 particles/mol) = ? 2 mol x (6.022E23 particles/mol) = ? etc. Post your work if you still don't get it.
  57. Chemistry

    I don't understand. You have the formula and all of the numbers. What's your problem?
  58. Chemistry (mol)

    See your other post of O3 and O2 to see how to set it up. You can see that you ca convert mols of anything to mols of anyy other thing in the equation by using the coefficients.
  59. Chemistry

    Oxygen is O2 and not O. 4.26E16 mol x (2 mol O3/3 mols O2) - 4.2E16 x 2/3 = ? That 4.25E16 is a huge number; I'm wondering if you intended to write molecules and not mols.
  60. Chemistry (mol)

    Use PV = nRT and solve for n. Remember T must be in kelvin. I must point out that nitrogen monoxide is NO and not N2.
  61. Chemistry

    1.3 g - 0.8g =
  62. Chemistry

    We do our best. It would be nice if you would tell us what you don't understand about the problem and/or what you know or don't understand about it. That we can refine our answer to suit you.
  63. Chemistry

    SiO2 + 4HF ==> SiF4 + 2H2O
  64. Chemistry

    My experience is that the C-H bending at 1454 cm^-1 is not all that strong nor all that sharp; however, these are personal calls and it varies, I suppose, with both the amount of sample and the operator so you call it like it is. I would say ......v = 1454 cm^-1 due to C-H ...
  65. Chemistry

    And I have no idea what you did. Perhaps we can help if you post how the solutions were prepared.
  66. Chemistry

    (1) 2A + B ---> C K1=x (2) 2B ==> D k2 (3) 2C --> 4A + D k3 Reverse (2) D --> 2B k = 1/k2 add to (3) 2C ==> 4A + + D k3 _________________ sum.(4).2C ==> 4A + 2B k = (1/k2)*k3 or k3/k2 Reverse (4) 4A + 2B -> 2C k = 1/k3/k2 or k2/k3 but that is just twice ...
  67. chemistry

    #1 on 1 #1 on 2. Actually, both of the two last ones are balanced but the second one is just twice the first one. The correct one ALWAYS will be the smallersmallest set of coefficients.
  68. Jiskha

    To supplement what Ms. Sue has said let me add a line or two. Students are banned from the site for spamming and posting what are obviously test questions or where it is obvious that someone is posting test questions and/or answers. Logging onto the site and reading what is ...
  69. Chemistry

    I believe my friend made a couple of typos. I think the Kc expression should be 4x^2/(0.2-2x)(.8-6x)^3 where I have bolded the numbers I think it should be.
  70. Chemistry

    This is a problem involving Le Chatelier's Principle. dH is negative which means the process is exothermic. I like to rewrite the equation this way. CO(g) + 2H2(g) <==> CH3OH(g) + heat Le Chatelier's Principle says that a system at equilibrium, when subjected to ...
  71. Chemistry

    mols MgCl2 = grams/molar mass = approx 0.02. There are 2 mols chloride ions per 1 mol MgCl2 so you have approx 0.04 mols Cl^-. There are 6.02E23 chloride ions in 1 mol so there must be ????? total chloride ions in 0.04 mols chloride ions. I estimated the numbers; you should go...
  72. To Scott---Chemistry

    Would you see if you can help this student.
  73. Chemistry

    I am not an organic chemist but I found this. Perhaps this will help.
  74. Chem

    No. I may be mistaken but I think you are changing the subscripts to make the equation balance. That is not allowed. YOu may change ONLY the coefficients. You do form BaSO4 and NaNO3. The valence of Ba is +2 and valence of sulfate is -2 so the formula is BaSO4. For NaNO3 the ...
  75. chemistry

    Carbonates, when heated, usually decompose to CO2 and the metal oxide so ZnCO3 ==> ZnO + CO2. Also you know there is a CO and a CO2 but no CO3 (although the [CO3]^2-) exists--as in ZnCO3, Na2CO3, etc).
  76. chemistry

    2MgO ==> 2Mg + O2
  77. Chemistry

    It depends on the mol ratios.
  78. Chemistry

    First I didn't say cyclohexene was the LR. You may have calculated that and if that's the result you get you go with it. It is important for you to realize that if you are calculating this in two consecutive steps that the second step depends upon how much B2H6 is ...
  79. Chemistry

    The first part is right; i.e., the BF3.Et2O is the limiting reagent (LR). I don't know about the last part of that with the cyclohexene. What you must do for that part is to determine how much of the B2H6 is available for the cyclohexene reaction. But don't forget you ...
  80. Chemistry

    I don't see a question here.
  81. science

    If I knew what experiment you were doing I might be able to answer the question.
  82. Chemistry

    % yield = (actual yield/theoretical yield)*100 = ? The actual yield is what the problem tells you the reaction produces. The theoretical yield is what you calculate is formed from the stoichiometry.
  83. Chemistry II - Concentrations

    Amy, Dalton, Jamie, et al. You are skirting on not getting help if you can't follow us. You're making it twice as hard t hel you. .......2HOH ==> H3O^+ + OH^- I......liquid..0......0 C......liquid..x......x E......liquid..x......x Kw = 1.46E-14 = (H3O^+)(OH^-) Solve...
  84. Chemistry 2 - pH

    Please don't change screen names. Use any you wish but keep the same one. It makes it much easier to help you. The pH is determined by the hydrolysis of the salt. The proper way to do this is to solve for Kb or Ka and compare but I have an easier way to do. Your prof may ...
  85. Chemistry 2 - Acids and Bases

    hydrazine = BH ......BH + H2O ==> BH2^+ + OH^- I....0.2M...........0.......0 C.....-x............x.......x E....0.2-x..........x.......x Write the Kb expression, plug in the E line and solve for x = OH^- Post your work if you get stuck.
  86. Chemistry

    That looks ok to me. I would make two suggestions. 1. I would write the product in the first equation you have as C5H5NH^+ to make it obvious that the H has been added. At first I thought you had made a typo. 2. I think it is always a good idea to write the K expression in the...
  87. Chemistry

    There is no way without knowing. If you know both are monoprotic it works ok. If both are diprotic it works OK, too. except that there are two H or OH in the excess reagent.
  88. Chemistry

    1/A - 1/Ao = akt
  89. Chemistry

    Here us a site that gives specific instructions how to make slime. At the very end is a small discussion about the polymer and the hydrogen bonds that cross link it.
  90. Chemistry

    mols H2O = grams/molar mass = ? Convert mols H2O to mols O2. 6 mol H2O produces 6 mols O2. 1 mol O2 at stp occupies 22.4 L. Post your work if you get stuck.
  91. Chemistry

    Do you have a formla for this material; i.e., ammonium iron 2 tetraoxomanganate 7? Do you have an equation for the readction with KMnO4.
  92. Chemistry

    10Fe(NH4)2(SO4)2 + 2KMnO4 + 8H2SO4 ==> 10FeNH4(SO4)2 + 2MnSO4 + 8H2O + K2SO4 + 5(NH4)2SO4 Check that.
  93. AP Chem

    Without the reaction, I don't think I can give a good answer. A is not right. B can be right in some cases. C can be right. D may or may not be right depending upon how air is involved in the rxn. My gut feeling is C since that is a "standard" question/answer on ...
  94. Chemistry

    C6H12O6 + 6O2 ==> 6CO2 + 6H2O mols C6H12O6 = grams/molar mass = ? Convert mols glucose to mols O2 using the coefficients in the balanced equation. It takes 6 mols O2 for every mol glucose. Now convert mols O2 to volume. Use PV = nRT at NTP. NTP is 20 C (293.15 K) and 1 atm...
  95. chemistry

    I agree with 0.322 atm and I would round that to 0.32 atm. You have two places in Kc and 2 places in 0.17. There is only 1 place in the 0.4 mol S; however, since that is a solid AND it is in excess, it never enters into the calculation so I wouldn't use that to determine ...
  96. Chemistry

    I assume you want Kc and not Kp. 13.4 mol/3.8 = approx 3 but that's just an estimate. You can recalculate and use a more accurate number. ........2SO3 ==> 2SO2 + O2 I.......3.........0.....0 C......-2x........2x....x E......3-2x.......2x....x You are given mols SO2, ...
  97. more--Chemistry

    For whatever it's worth, here is the calculation to determine the pH of the solution you have made. mols NH4^+ = M x L = 0.1 M x 0.1 L = 0.01 mols NH4^+ from NH4Cl = 1.0 M x 0.08 L = 0.08 mols. Total mols NH4^+ = 0.01 + 0.08 = 0.09 and that in 1 L is 0.09M. The pH of that ...
  98. Chemistry

    How can you have a buffer with NH4^+ and NH4Cl. You have no base. Both NH4^+ by itself and NH4^+ from NH4Cl are acidic. A buffer usually consists of a weak base and a salt of the weak base (NH3 and NH4Cl) or a weak acid and a salt of the weak acid (acetic acid for example and ...
  99. Chemistry

    I would google "pKa table acids/bases" (without the parentheses) and look for pKa values in the 9.15 range. I looked and found: HCN = 9.21 H3BO3 = 9.23 NH4^+ = 9.25 but anything within a + or - 1 will do. I wouldn't use HCN because of the toxicity and since you ...
  100. science

    You don't have enough information,Where's the starting point.
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