Posts by DrBob 222

Total # Posts: 58

  1. Chemistry- please check my work

    I think so. Look up Ksp in your set of Ksp tables and see how close that comes. I have an old quant book (about 15 years old) that shows 2.5 x 10^-16.
  2. Chemistry- please check my work

    You didn't square the OH^-
  3. Chemistry

    The sites won't post.
  4. Chemistry

    I will try to post those sites under a new post. Look at the top for them.
  5. Chemistry

    Try something here. Work the problem as (3x)^3(0.476) = 1.3E-20, solve for x, then multiply by 3 and that will be Ag^+. NOW, try letting Ag^+ = x (instead of 3x). How will the equation look then? Will it be (x)^3(0.476) = 1.3E-20. Solve that and see if x the second time is the...
  6. Chemistry

    There is nothing wrong with the equation except that when you solve for x you get what? What did you let x stand for? It looks to me as if you let x stand for the solubility of Ag3PO4 and Ag^+ is then 3x. So when you solve your equation, you will get x THEN YOU MUST MULTIPLY ...
  7. Chemistry

    No. The phosphate ion is 0.4762 (if your prof is a freak about significant digits perhaps this should be 0.48 since only 2 places are shown for the Ksp in the problem. The problem states that x = (Ag^+) [in fact it is repeated in the problem] and what you have is (Ag^+) = 3x.
  8. Chemistry

    Your equation looks great; however, the problem states that x is to equal to (Ag^+). You have it set up so that x = (Ag3PO4) = (PO4^-3) and (Ag^+) = 3x
  9. Chemistry

    Read about the effect of ionic strength on solubility (the activity and the activity coefficient). The activity coefficient is a factor used to correct for non-ideal behavior of solutions. In connection with this, you will see reverence to the Debye-Huckel theory (or equation...
  10. Chemistry

    Yes, it would be larger. Do you know why? It's important that you know why.
  11. Chemistry

    I have tried to post sites but the board isn't posting.
  12. Chemistry

    You misread my response or I misrepresented it---one or the other. Yes, CH3OH is methyl alcohol (the trivial name) or methanol if you name it by the IUPAC system. CH3- is the methyl group> The first part of the name is methyl because 1. its the alcohol (from CH3OH) 2. CH3- ...
  13. Chemistry

    1. What is the name of the ester formed from formic acid and methanol? ( I know formic acid equals methanoic acid(HCOOH) and we need to change "oic acid" to "-oate", but how about methanol? I had no ideas what to do with the alcohol...) The alcohol part is...
  14. Chemistry

    There is no AgI in your final equation(and I'm not suggesting there should be); also, note that AgI as a solid has a molarity of 1 (by definition so the AgI-x has no meaning). (Technically it's the activity that is 1.) Also note that the problem states 150.0 mL and not...
  15. Chemistry

    I think the equations you want are as follows: AgI(s) ==> Ag^+ + I^- Ksp = (Ag^+)(I^-) = look up. Ag^+ + 2CN^- ==> Ag(CN)2^- Kf = [Ag(CN)2^-]/(Ag^+)(CN^-)^2 = look up.
  16. Chemistry

    I don't think an ICE table is needed. You have the solubility at 0.00172 M so 1.72 x 10^-3 M is the # moles in 1 L, then 1.72 x 10^-4 is the # moles in 0.100 L, and grams = moles x molar mass.
  17. Chemistry

    M = moles/L So if the M = 0.00172, then the moles in a liter will be 0.00172. Since the problem tells you it is in 100 mL, then 1/10 that will be the moles that will dissolve in 0.100 L. To convert that to grams, moles = g/molar mass, then convert grams to mg.
  18. Chemistry

    The 1.97 grams is extraneous information. You don't need it (as long as the problem says the solution is saturated AND there is a small amount of solid in the container). The (Pb^+2) IS 1/2 the (OH^-); i.e., 1/2*(OH^-)=(Pb^+2) So you know (OH^-) and you know (Pb^+2); (Pb^+...
  19. Chemistry

    Pb(OH)2 ==> Pb^+2 + 2OH^- Ksp = (Pb^+2)(OH^-)^2. pOH = -log(OH^-). You are given the pH, then 14-pH = pOH, and solve for (OH^-). Note carefully: Won't the (Pb^+2) be just 1/2 the (OH^-)?
  20. chemistry

    The molecules are relatively far apart. In a liquid or a solid the molecules are much closer together. The molecules in a gas are much further apart UNLESS we are talking about LOW LOW temperatures OR HIGH HIGH pressure.
  21. chemistry

    Because the molecules are more randomly positioned.
  22. Chem.

    You name the alcohol group first and the acid group second. The alcohol group in this case is methyl. Then you count the C atoms, including the C attached to the =O and name it as an -oate. So the name is methyl ethanoate (the acid CH3COOH is ethanoic acid)
  23. Chem.

    I must admit that I have never heard of a stoic acid before. Thanks for the explanation. An ester is RCOOR' whereas an acid is RCOOH. What is attached to the RCOO- is the secret. If you attach a H atom, it is an acid. If you attach another R group (CH3 or higher), it is an...
  24. Chem.

    Would you explain what a stoic acid is. I don't know. Then I can answer your question.
  25. Chemistry

    a) melting point - increases OK b) vapor pressure-increases As the IM forces increase, it makes it harder for the molecules to escape to the vapor phase (the pressure of the gas over the liquid); therefore, the vapor pressure must decrease. c) boiling point- increases OK d) ...
  26. chemistry

    Divide Ksp of one by the other. [KspPbSO4/KspAg2SO4]=[(Pb^+2)(SO4^=)/(Ag^+)^2(SO4^=)]. Note (SO4^=) cancels and you are left with 2*10^-8/1.2*10^-5 = (Pb^+2)(Ag^+)^2 Plug in (Ag^+)^2 and solve for (Pb^+2), Check my thinking.
  27. Entropy

  28. Chemsitry

    You have the answers mixed up with the number of the question to the point that the whole thing is confusing. The answer to the first question (H2SO4) is correct. The answer for what you have labeled 27A is blarney.
  29. chemistry

    PV = nRT Since n is increased, what must happen to P.
  30. Chemistry

    qH2O = mass water x specific heat water x (Tfinal-Tinitial). Then q/7.5 = heat of solid/gram if you use specific heat of water in joules (4.18 joules/g*C). Note that they tell you Tfinal-Tinitial = 6.2 degrees.
  31. Chemistry

    qH2O + qmetal = 0 qH2O = mass H2O x specific heat water x (Tfinal-Tinitial). qmetal = mass metal x specific heat metal x(Tfinal-Tinitial). Just plug in the numbers and solve for specific heat metal.
  32. Math 116 algebra

    And you think what?
  33. Math 116 algebra

    What do you not understand about collecting like terms?
  34. Math 116 algebra

    Yes, but it would be better if you posted your work. That way, if you have the wrong answer we will know what you did wrong. If you have the right answer we will also check that you came about the correct answer properly.
  35. Math 116 algebra

    Lines are parallel if the slope is the same. They are perpendicular if the slopes multiplied = -1.
  36. Math 116 algebra

    8x-(5x + 7)=17 remove parentheses. 8x - 5x -7 = 17 move -7 to the other side. 8x-5x = 17 + 7 combine terms 3x = 24 divide both sides by 3. 3x/3 = 24/3 x = 8. Check it. 8*8-(5*8+7)=17 64-(40+7)=17 64-(47)=17 64-47 = 17 17 = 17 It checks.
  37. Math 116 algebra

    yes. 80%X = 40 0.8X = 40 X = 40/0.80 = 50
  38. Math 116 algebra

    Is that (-5/6)*x = -7/8 or (-5/6x) = -7/8
  39. chemistry

    GK is correct; the problem could have been worded more correctly. I assumed you were asking for the solution. Also, I note that I made an error in typing. It isn't 11.1 g CaCl2 but 1.11 g CaCl2.
  40. chemistry

    Remember the definitions. Molarity = # mols/L. and # mols = g/molar mass. How many moles CaCl2 do you have in 11.1 g CaCl2. That will be 11.1 g CaCl2/molar mass CaCl2. Then #mols = M x L. You have M and you have mols, calculate L.
  41. algebra 1

    +1/3 ??
  42. algebra 1

    11/12-(1/3+1/4) = 11/12 - 1/3 - 1/4 = get a common denominator which is 12. 11/12 - 4/12 - 3/12 = Add the numerators to obtain 11-4-3 = 4 so the answer is 4/12 which reduces to 1/3 Check my work.
  43. Chemistry

    Shanta, please go to the top of the page and click on post a new question. Post a question in your name instead of an answer to another problem. Since there are three nitrate ion per mole of Al(NO3)3, then the nitrtion concn is ??
  44. Chemistry

    Accuracy is how close the analyst is to the actual value. The precision is how close the repetitive values are to each other.
  45. Gen Chem2

    Sr(s) + NH4CO3(aq) ==> ppt + flammable gas. Wouldn't you expect the ppt to be SrCO3? And Sr + the water in the 1 M NH4CO3 solution must be H2 gas. Can you continue?
  46. math

    (C^2 + 14C + 49)/(C+7)= factor the numerator. [(C+7)(C+7)/(C+7)]= Now you finish.
  47. Math

    Would you add 8 1/2 feet + 2 3/4 feet = ?? feet?
  48. algebra

    I don't know that you did anything wrong. How did you solve the quadratic? Did you use the quadratic formula?
  49. algebra

    I don't get the 0=0 step but your solution is correct for x = 1.5 and x = -0.3333.
  50. Algebra

  51. Chemistry

    Most filter paper has a texture to it and any solid placed on it during the weighing may stick to the surface and not be transferred quantitatively to a vessel of choice. I assume this is the intent of the question. If I have misinterpreted, please clarify.
  52. Chemistry

    Under the beaker with the tip of the inner blue cone of the burner just touching. However, I never like to heat a beaker directly (unless it's made of Vycor). I prefer to place the beaker on top of a wire gauze and heat the wire gauze. Beakers made of Pyrex have been known...
  53. algebra

    Clear the parentheses. r-6s+3+7r+5s+s+5=?? combine like terms.
  54. physical science

    And your question is a little confusing, too. ALL elements in the periodic table have a charge of zero when they are in their elemental state. You may be asking how to tell the charge on the ions. For the B group of elements, ONE of the possible ionic charges (valence) is ...
  55. chemistry

    A buffer is formed from a weak acid and its salt (conjugate base) OR a weak base and its salt (conjugate acid). For examples: acetic acid and sodium acetate (its the acetate that is the conjugate base part so it can be sodium acetate, potassium acetate. etc) ammonia solution ...
  56. math

    All of that multiplied together is zero. (Because of the zero in the sequence)
  57. chemistry

    The flame color will be visible as a reddish violet color. The blue glass, typically a cobalt blue glass, will filter out extraneous colors, such as the intense yellow color of a sodium flame. The intense yellow color of the sodium flame will mask the potassium flame unless ...
  58. chemistry

    First convert 50.6 g CH4 to mols. mols CH4 = 50.6 g CH4 x (1 mol CH4/16 g CH4) = ??