Friday
July 25, 2014

Posts by DrBob222


Total # Posts: 43,173

PLEASE HELP D:
Personally, I think that will result in nothing getting done. I suspect there must be a central coordinating agency. At first glance the federal gov might be the obvious choice but I shudder at the thought of another federal czar, more gov red tape, more cost overruns, and all...

Chemistry
The assumption for my response was years.

Chemistry
k = 0.693/t1/2 = approx 4.95E-11 Rate at time zero = k*N and for 1 mol Th, N will be 6.02E23 atoms. Solve for R, which will be in disintegrations/year . Convert tht to d/hour.

Chemistry
With regard to H^+. You added 0.9375 mols H^+ to the buffer. ALL of it will react with the 15.0 mmols NH3 (H^+ is the limiting reagent so there won't be any of it left). With regard to the NH4+ you should add and my ICE chart shows that; however, I said subtract in my inst...

Chemistry
millimols NH3 = 50 mL x 0.3M = 15.0 (NH3) = mmols/mL = 15.0/100 = 0.15M initially. millimols NH4Cl = 50 x 0.3 = 15.0 (NH4Cl) = 15.0/100 = 0.15M initially millimols HCl = 7.50 x 0.125 = 0.9375 pKb NH3 = 4.74; pKa = 14-4.74 = 9.26 I prefer to work with this equilibrium in mmols....

Chemistry
delta T (increase in b.p.) = i*Kb*m All are the same m so that is a constant. kb is a constant. Threfore, it all depends upon i, the van't Hoff factor. i = 1 for urea i = 2 for NaCl i = 3 for MgCl2 i = 5 for Al2(SO4)3. So which will cause the SMALLEST CHANGE?

Chemistry
What's the problem with these? I assume they are in solution. 3Ag^+(aq) + PO4^3-(aq) ==> Ag3PO4(s)

Chemistry Equilibrium
(H2O( = 0.0860 mol/2.00L = approx 0.043M ............2H2O --> 2H2 + O2 I..........0.043......0.....0 C...........-2x...... 2x....x E..........0.043-2x...2x....x Substitute the E line into the Kc expression and solve for x.

chemistry
1g x (5/450) = ?

Chemistry
1.4E10 what? What is mil?

chemistry
0.64 mol/dm^3 x ? dm^3 = 0.320 Solve for ? dm^3

Chemistry
q = mass H2O x specific heat H2O x (Tfinal-Tnitial)

Chemistry
q = mass H2O x specific heat H2O x (Tfinal-Tintial) If you use specific heat as 1 cal/g*C then q will be in cal. Convert to kcal by dividing by 1000.

Chemistry help plzzzzz!!!!!
Have you tried making that -55.1 kJ/mol. It must be negative since it is exothermic. It's time for me to go to bed. Let me know quickly if that is right.

Chemistry
Subscripts multiply the atom for which it's a subscript. Coefficients multiply everything that follows. 3NaCl. 3Na and 3Cl H2SO4 2H 1S 4O 4H2SO4 8H, 4S, 16O

Chemistry
You need to tell us more about what you are doing.

Chem Help!
..........Fe(OH)3 -->Fe^3+ + 3OH^- Ksp = (Fe^3+))OH^-)^3 You know Ksp (or can look it up) (Fe^3+) = 0.2M from the problem. Substitute and solve for OH^-, then convert to pH.

chemistry
I'm not an organic chemist but I would name this as isopropyl-1-butanamine. I clicked on Google and typed in naming amines and came up with an IUPAC page in pdf format. That's the name I came away with.

chemistry
P1V1 = P2V2

Chemistry
mols NaOH = M x L = approx 0.0860 molw CH3COOH = approx 0.05 = HAc ........NaOH + HAc ==> NaAc + H2O I....0.0860.....0.......0.......0 Add...........0.050.............. C.....-0.050.-0.050....0.050...0.050 E......0.036....0......0.050 So you have 0.0360 mols NaOH 0 mols HAc...

chemistry
The dilution formula is c1v1 = c2v2 c = concn v = volume 12.0M x 60mL = 1.85M x ?mL Solve for ? mL Actually, I think it is easier to remember mL x M = mL x M

chemistry
I suspect for reasons of solubility. According to this web site the solubility is 12.78 mg/mL at 20C which is quite soluble. http://en.wikipedia.org/wiki/Paracetamol

chemistry
Of course 9M is more concentrated than 3M if both are H2SO4. M = mols solute/L solution. So 3M = 3 mols/L = 3*98g/1000 mL = 294g/L and 9M = 9 mols/L = 9*98g/1000 mL=882g/L

chemistry
(P1V1/T1) = (P2V2/T2)

chemistry
1 is ok 2 is ok 3 is chemical. If it combines with other elements that makes it a chemical reaction just like burning it in oxygen. 4 is physical. It isn't combining with anything. H2 is still H2; it's just dissolved H2. 5 is ok. 6 is ok.

Chemistry
I don't want that post to stick around on the web so I'm deleting it. But this response will stay so as to answer your question. I don't know why I answered that way because as I was posting I kept thinking things just weren't right. This ranks up there among t...

chem090
This is a limiting reagent (LR) problem. You know that because amounts are give for BOTH of the reactants. mols BaCl2 = grams/molar mass = approx 0.48 but you should confirm this and all of the calculations that follow and you should carry all of them to at least three places....

chemistry
Use the dilution formula of c1v1 = c2v2 c = concn v = volume 0.4M x ? = 8M x 50 mL Solve for ? mL By the way, I think the accepted IUPAC name for HBr is hydrogen bromide. The mono is unnecessary.

Chemistry lab
You need to correct this post. 0.9 mM of what?

Chemistry
eqn 1 CaF2 ==> Ca^2+ + 2F^- eqn 2 Ca^2+ + SO4^2- ==> CaSO4 ------------------------------- sum 1+2 CaF2 + SO4^2- ==> (F^-)^2 + CaSO4 since CaF2 and CaSO4 are solids we can cancel them since they are not involved in the Keq. You note that eqn 1 is Ksp for CaF2 and eqn ...

Chemistry
This is a long (but not particularly complicated) calculation to do on the web. Do you have a specific question that is troubling you?

Chemistry
From what I can read you don't have sufficient information here to calculate a LSI. pH alkalinity T etc.

Chemistry
1 mol contains 6.02 E23 molecules.

Chemistry Help Please!!!
The equation you want is (1/2^t/4)= x amount remaining which in this case is (1/2^30/4) = (1/2^7.5)= x Solve that equation for the amount remaining after 30 days. Using that equation you should be able to do the others. For example c is [(1/2^(t/4)] = 1 and solve for t.

Science
https://answers.yahoo.com/question/index?qid=20070731113316AADwmqF

Science
I agree.

Science
ok. I agree.

Science
What's the question?

Chemistry
If p is same and T is same then mols is proportional to volume. If you have 1/3 the volume you must have 1/3 the mols.

Chemistry
ptotal = pN2 + pO2

Chemistry
First note the correct spelling of celsius. Calculate n = number of mols from PV = nRT. Then n = grams/molar mass. You have n and grams, solve for molar mass. Don't forget to convert mm Hg to atm and T to kelvin.

Science
See your other post.

chemistry
For the freon see your other post. For this other problem the pressure has changed. p1/t1 = p1/t2 t1 and t2 must be in kelvin.

Chemistry
I assume we are to ignore the calorimeter constant. [mass metal x specific heat metal x (Tfinal-Tinitial)] + [mass H2O x secific heat H2O x (Tfinal-Tinitial)] = 0. Substitute and solve for s.h. metal.

Chemistry
How many mols do you need? That's mols = M x L = 0.48 x 0.1235 L = ? Then M = mols/L soln. Substitute. Solve. You know M = 5.00 and you know mols from above. Solve for L and convert to mL.

chemistry
Those are conversion factors that I posted. Let's work with the first one. A conversion factor converts anything you have into anything you want (if you have the right factor and use it correctly). So the factor is 1 atm/101.325 kPa and of course it can also be 101.325 kPa...

chemistry
1 atm = 101.325 kPa. 1 atm = 14.7 psi

Chemistry
P1V1 = P2V2 Substitute and solve for the one unknown. Change atm to mm Hg. 1 atm = 760 mm Hg.

chem HARD
Li is in group I; therefore, it has 1 electron in its outside shell and can give it away to a receptor, such as chlorine, bromine etc to make LiCl or LiBr. But when making lithium carbonate, it needs to give away TWO electrons because carbonate takes TWO electrons. Thus TWO Li...

chem
M = mols/L mol = 36.0/58.5 volume = mass/density = 136/(1.13*1000) So M = (36.0/58.5)/[136/(1.13*1000] Check me out on this. This would make it (36.0/58.5) x (1.13*1000/136) = (36.0 x 1.13 x 1000/136 x 58.5 = ?

chemistry
millimols C2H5NH2 = mL x M = 25 x 0.5 = 12.5 mmols HCl = 5 mL x 0.5M = 2.5 HCl. .......C2H5NH2 + HCl --> C2H5NH3^+ + Cl^- I.......12.5.......0.........0......0 added............2.5................ C.......-2.5....-2.5........+2.5....2.5 E.......10.0......0..........2.5....2...

chemistry
Three equations and three unknowns but the way they are set up makes it as if it were two equations and two unknowns. Let X = mass NaX and Y = mass NaI and Z = mass NaNO3 (mm stands for molar mass) --------------------------- eqn 1 is Z + Y + Z = 0.8612g eqn 2 is mass AgBr fro...

Chemistry
Here is a copy of the activity series of metals. Any metal ion below Ag should oxidized Ag metal to Ag +1 ion. So Pt and Au ions should do it https://www.google.com/search?q=activity+series+metals&client=firefox-a&hs=dwv&rls=org.mozilla:en-US:official&channel=sb&tbm=isch&imgil...

Chemistry
Ag(s) ==> Ag^+ + e Eo = -0.799 Hg^2+ + 2e ==> Hg..Eo = +0.789 ------------------------ 2Ag(s) + Hg2^2+ => 2Ag^+ + Hg E = -0.01 If it would oxidize it yes, that would be the reaction; however, you can see that the Eo value is -0.01 so it isn't spontaneous. K for th...

Chemistry
Use the Clausius-Clapeyron equation. Don't forget to substitute dHvap in J/mol.

Chemistry
(mass ice x heat fusion) + [mass ice x specific heat water x (Tfinal-Tinitial)] [mass H2O x specific heat H2O x (Tfinal-Tionitial)] = 0 Substitute and solve for mass ice. Tfinal is 4, Tinitial is 26, mass H2O (that's the 26 C H2O) is 355. Massice is the only unknown.

Chemistry
Now you need dHof fpr H2O gas. dHrxn = (n*dH products) - (n*dH reactants)

chemistry
It's in the last sentence.

chemistry
q(v) = Ccal in kJ/C x delta T That gives you q = dE in kJ for 0.451g That x molar mass gives dE in kJ/mol.

Chemistry
Insects and animals use the odor as sex attractants, as ways to find food, and nature to do its thing. For example, bees are attracted to flowers and in that process they pollinate grasses, flowers, fruits, etc.

Chemistry
Use PV = nRT and solve for n = number of mols of gas. Then n = grams/molar mass. YOu know n and grams, solve for molar mass.

Chemistry
Cl2(gas) ==> 2NaCl which isn't balanced but the Cl is balanced and that's what the question is about. mols NaCl = grams/molar mass NaCl Using the coefficients in the balanced equation above to convert mols NaCl to mols Cl2. Then use PV = nRT and solve for V Cl2 in L.

Chemistry
dGo = -RTlnK Solve it. See if dGo is + or -

College Chemistry (DrBob222)
Yes, if you follow my directions above that will calculate Fe^2+. You have Eocell and Ecell which allows you to calculate Q. Then Q has the definition I gave and that has the concentrations in it. Q = (Fe^2+)/(Cu^2+). You know Q and Cu^2+, solve for Fe^2+. If you need help in ...

College Chemistry (DrBob222)
I presume you meant 25C and not 35. If you meant 35 then replace the 0.0592 below by (RT/2*F) Ecell = Eocell -(0.0592/2)log Q You have Ecell. Eocell = Eo for Cu^2+ + 2e --> Cu and add to Eo for Fe(s) ==> Fe^2+ + 2e That leaves Q. Q in this case is Q = (Fe^2+)/(Cu^2+) Sub...

Chem Help!
a) Because the Ksp for AgCl is exceeded. b) Ba^2+ + SO4^2- ==> BaSO4(s) c) See answers to a and b above. Put that into words. d) Yes, if dilute HCl were used. e) identity of the material, its solubility and ease of making solutions, its stability, etc. f) AgCl + 2NH3 ==>...

Chem Help
a. Ksp PbCl2 = (Pb^2+)(Cl^-)^2 Qrxn = (0.2)(5E-3)^2 = 5E-6 and this is smaller than Ksp; therefore, no PbCl2 ppts. Ksp AgCl = (Ag^+)(Cl^-) Qrxn = (0.2)(5E-3) = 1E-3 which is larger than Ksp; therefore, AgCl ppts. b. The total chloride is now 3M + 5E-3M. I will ignore the small...

Chem Help
What values do you have for Ksp PbCl2 and AgCl. I can look them up in my text but the numbers probably will not the same as in your text. I would rather use your numbers.

Chemistry
molsKClO3 = 9.50E25/6.02E23 = ? Convert mol KClO3 to mols mols KCl and mols O2 using the coefficients in the balanced equation. Then convert mols KCl to g. g = mols x molar mass Similarly, g O2 = mols x molar mass.

CHEM.
Yes if you have Kb. The problem says "qualitatively" which means make the best educated guess. Qualitative in that sense always means to make the best estimate. If you know Kb (which is 1.8E-5) you can calculate it as follows: ..........NH3 + HOH ==> NH4^+ + OH^- ...

CHEM.
a). NH3, NH4^+, OH^-, H3O^+ b) NH3 is a weak base so you know it will be basic and you might guess pH 10 or so. c) Mn^2+ + 2OH^- ==> Mn(OH)2(s) d) Adding HNO3 would react with the OH^- of Mn(OH)2 to product H2O and the ppt would dissolve because the OH^- has been decreased.

Chemistry URGENT
Li is right as is O. As is not right. As is +5 Here is a good site that explains how to do oxidation numbers. http://www.chemteam.info/Redox/Redox-Rules.html

chemistry
Use PV = nRT and solve for n = number of mols. Then n = grams/molar mass. You know molar mass (or can find it) and n, solve for grams.

chemistry
Use PV = nRT and solve for n = number of mols of the gas. Then n = grams/molar mass. You know grams and n, solve for molar mass.

Chemistry
a. X^- + HOH ==> HX + OH^- The anion hydrolyzes with water producing OH^- ions which is why they are basic. b. .....X^- + HOH ==> HX + OH^-. For 0.3M I...0.3.............0.....0 C....-y.............y.....y E...0.3-y...........y.....y Kb for X,Y, or Z = (Kw/Ka for HX, k2 ...

chemistry
mols = grams/molar mass Then M = mols/L solution

Chemistry
#1. Br2 + 2e ==> 2Br^- written as a reduction. (Reduction is the gain of electrons and this gained e). Look in the table of standard reduction potentials (tabulated I suspect in your text). If Br2 + 2e ==> 2Br^- is more less positive than 1.23 (volts for electrolysis of ...

Chemistry
For #1, I suspect they expect you to calculate dGo which you get from dGo = dHo - TdSo from tables. However, most tables have dGo already tabulated and you need not go through the dH-TdS part. Then dGo = -RTlnK should get it. #2. I'll look at 2 later.

chemistry
Use (P1V1/T1) = (P2V2/T2) P1 = 84.6 kPa for wet gas pH2O = 12.3 kPa P1 = 84.6 kPa - 12.3 kPa = ? kPa for dry gas. P2 = 120 kPa

Chemistry
A cell can deposit atomic mass Al/3 (about 27/3 = approx 9g) Al when 96,485 coulombs is passed through a solution. How many coulombs do you have? That's coulombs = amperes (that's amps) x seconds. So you have C = 5.00 x 5.00 hrs x (60 min/1 hr) x (60 sec/1 min) = about...

CHEMISTRY
I just posted a response at the original site below.

CHEMISTRY
Put that endothermic part into the equation so you can see how it affects the reaction. SO2Cl2 + heat ==> SO2 + Cl2 Le Chatelier's Principle says that when we do something to a reaction that is in equilibrium that the reaction will shift so as to undo what we've don...

CHEMISTRY
You can work this out with numbers or with reasoning. Numbers take longer but may lead to some more confidence. Kc = (B)^5/(A)^6 So if pressure decreases you know the reaction will shift to the left. That means Qc will be too large meaning B is too large and A is too small. Th...

Chemistry
You don't get pH from Ka UNLESS you have the concentration of the acid. In this case you don't have that so you can't get a straight pH. If you are referring to the first question, which is The following questions refer to the following acids and bases. A) Hydrazoi...

Chemistry
Zach, this is about a 20 question post which I've done several times in the last day or so. All of these questions are similar. Can you summarize what it is you don't understand about these. We need to get at the root so you can do these yourself.

CHEMISTRY
Kp = Kc(RT)delta n where delta n = n products - n reactants

CHEMISTRY
P = products R = reactants c = coefficients Kc = (p)^c/(R)^c) I've seen some text where the products are called RHS (right hand side) and the reactants called LHS (left hand side) then Kc is defined as (RHS)/(LHS) with coefficients becoming exponents.

CHEMISTRY
Kp = Kc(RT)delta n

CHEMISTRY
.........A ==> 2B I....0.154.....0 C........-x....2x E...0.154-x....2x Substitute the E line into Kc expression and solve for x and 0.154-x. I don't know if the prof expects you to answer this with math (working out the above equation) or by reason but the math should d...

CHEMISTRY
........H2 + Cl2 ==> 2HCl I...0.1877.0.1432......0 C.......-x....-x.......2x E...0.1877-x.0.1432-x..2x Substitute the E line into Kc expression and solve for x, then evaluate each individual term.

CHEMISTRY
Reactants ==> products K = (products)/(reactants) So a large K means more products and fewer reactants. That's the only way to get a large number for K. A small K means fewer products and more reactants. That's the only way to get a small number for K. So large K me...

CHEMISTRY
.......PCl5 --> PCl3 + Cl2 I...0.1983.......0......0 C.......-x.......x......x E....0.1983-x....x......x Substitute the E line into the Kc expression for PCl5 and solve for x.

CHEMISTRY
Use the Arrhenius equation. Don't forget to convert kJ/mol to J/mol. And K must go into the equation as kelvin.

CHEMISTRY
I hate to be picky but why do I want to answer 10 questions so you can compare answers. It is much more efficient for you to post your answers and let me find any errors. While you're doing all that typing (which I would have had to do) I can be working your other posts.

no one's here to help us!!! -.-
I like Writeacher's comments! I'll second that! I'll add a third. 3. A student who post his/her work and asks us to check it for errors is more likely to get a quick response than one that posts a LOOONG question consisting of many parts and asks us to work the pro...

Chem
I strongly suspect you know how to do some of these and for those it's redundant for me to help. Post your work on what you know and clearly explain what you don't understand about the others and I'll help you through them.

chemistry
delta T = Kb*m delta T = 101.86 - normal boiling point. Substitute and solve for m = molality. m = mols/Kg solvent. You know kg solvent and m, solve for mols.

Chem
5. Which solution will have the highest concentration of Na+ ions? A) Na2CO3 B) NaHCO3 C) NaCl D) NaHSO4 E) All are equal There is no answer for this one BECAUSE there is no concn listed for any of them. For equal concentrations, which probably is what the asker meant, is A be...

Chem
4. Based on my responses above what do you think. A is not right.

Chem
3) Which aqueous solutions are acidic? A) Na2CO3 and NaHCO3 B) NaCl and NH4Cl C) NaHSO4 and NH4Cl D) NaHSO4 and NaHCO3 E) NaHSO4, NaHCO3, and NH4Cl A. If Na2CO3 is very basic and NaHCO3 is slightly basic, then a mixture should be acid or basic....? B. NaCl is neutral; NH4Cl is...

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