Saturday
April 25, 2015

Posts by DrBob222


Total # Posts: 48,509

Chemistry
HNO3 + KOH ==> KNO3 + H2O mols HNO3 = M x L = 0.06 pH = 2.5 means you want (H^+) to be 0.00316 or mols (H^+) = 0.00316 x 0.4L = 0.00126. That's mols (H^+) remaining which means you must neutralize the difference; i.e., 0.06 - 0.00126 = ? Convert that to grams KOH.
March 17, 2015

Chemistry
All of these hydrolyze (actually NaCl does not) like this. ..........A^- + HOH ==> HA + OH^- I.......0.1..............0....0 C........-x..............x....x E......0.1-x.............x....x Kb for base = (Kw/Ka for HA) = (HA)(OH^-)/(A^-) Substitute Kw, you have pH, I would ...
March 17, 2015

Chemistry
PV = nRT; solve for n = number mols Ar + Ne in the 2L vessel at the conditions listed. PV = nRT in container B; solve for n = number of mols Ne. Subtract total mols - mols Ne to give you mols Ar. Then PV = nRT in container A; You have P, n, R, T; solve for V at the conditions ...
March 16, 2015

Chemistry
Not much else to do than to work the problem. The point you are missing is that it's a strong acid. Strong acids ionize 100% so ALL of the HCl molecules end up as ions and NONE are in the form of HCl molecules. It isn't necessary to do an ICE chart but that might help ...
March 16, 2015

chemistry
Ksp = (Pb^2+)(I^-)^2 Substitute Ksp and I (I^- = 1.1E-4M) and solve for (Pb^2+)
March 16, 2015

chemistry
Hformation = sub + IE + EA + 1/2*BE + Ecryst Solve for Ecrystal, then lattice energy is - of Ecrystal.
March 16, 2015

Physical Chemistry
[mass ice x specific heat ice x (Tfinal-Tinitial)] + [mass ice x heat fusion] + [mass ice x specific heat H2O x (Tfinal-Tinitial)] + [mass H2O x specific heat H2O x (Tfinal-Tinitial)] = 0 The first Tf is 0 and the first Ti is -5 so that term is 0-(-5) = _5. The second Tf is ...
March 16, 2015

chm
a. repeat from the previous post. b. Kp = Kc*(RT)^delta n
March 16, 2015

chm
a. Calculate (H2)&(CH3OH) from M = mols/L. Then substitute these values into K expression and solve for the missing CO in M b. I assume the K of 1.1E-3 is Kc and not Kp. .........Br2(g) ==> 2Br(g) I.....0.0310.......0.210 C........-x..........+2x E....0.0310-x.......0.210+...
March 16, 2015

Chemistry
q1 = heat needed to raise T of ic from -14C to 0C. q1 = mass ice x specific heat ice x (Tfinal-Tinitial) q2 = heat needed to melt ice at zero C to liquid H2O at zero C. q2 = mass ice x heat fusion q3 = heat needed to raise T of liquid water from zero C to 24.0C q3 = mass ...
March 16, 2015

Science
a metal?
March 16, 2015

Chemistry
I thought you did a super job.
March 16, 2015

chemistry
0.685 mol/L x (10/300) = ?
March 16, 2015

chemistry
How much? It makes a difference if you want 1 mL or 1000 mL. mols you need = M x L Substitute M and L and solve for mols. Then mols = grams/molar mass. You know mola rmass and mols, solve for grams. Add some water to the size flask you have chosen, add the grams H2SO4 SLOWLY ...
March 16, 2015

CHEMISTRY
PV = nRT
March 16, 2015

chemistry
How many mols H2O were formed? That's 50 x 0.1 = 5.0 millimols or 0.005 mols. q = heat released = mass H2O x specific heat H2O x (Tfinal-Tinitial) That is q for 0.05 mols. Convert to J/1 mol and to kJ/mol.
March 16, 2015

chemistry
When you post a problem like this you should tell us what you are using for pKa or pKb; otherwise we can come up with the same answers you may have since tables containing those pK values are not consistent from text to text. You have 0.445 x 150 mL = approx 67 millimols of ...
March 16, 2015

chemistry
dGrxn = (n*dGf products) - (n*dGf reactants) You need to look up the dGf in tables. They should be in your text/notes or on the Internet.
March 16, 2015

Chemistry
I think it's nice that you can get someone to do your work for you but I don't understand why you can't look up these definitions in your text/notes and if you don't have text/notes use Google.
March 16, 2015

Chemisty
Mg + 2HCl = H2 + MgCl2 mols HCl = M x L = ? mols H2 = 1/2 that (from the coefficients)
March 16, 2015

Chemistry - Solubility
CuS not only is considered a solid it IS a solid. It is not considered part of the K. I usually leave that in the equation and assign it a value of x (even though I don't use it) BECAUSE x = (S^2-) and that's the same as CuS so x gives the solubility of CuS. The ...
March 16, 2015

Chemistry - Solubility
Yes, this is a complex ion problem. The CuS has a solubility of its own; the complex with CN^- increases the solubility. I would do this. CuS ==> Cu^2+ + S^2- Ksp = ? Cu^2+ + 4CN^- ==> [Cu(CN)4]^2- Kf = ? ------------------------------ Add the two equations ...CuS + 4CN...
March 16, 2015

chemistry
2KClO3 ==> 2KCl + 3O2 mols KClO3 = grams/molar mass = ? Use the coefficients in the balanced equation to convert mols KClO3 to mols O2. Now convert mols O2 to grams. g = mols x molar mass.
March 15, 2015

chemistry
Isn't that e^(-dG/RT). If dG is -332,000 then the rxn should be spontaneous and K should be a large number and not a small number. dGo = -RTlnK -dGo = RTlnK (332000/8.314*298)= lnK
March 15, 2015

chemistry
A common student error is to use kJ for dGo. You must use dGo in J (unless of course you change R).
March 15, 2015

chemistry
From your description I can't tell what you did wrong. If you post your work I will find the error.
March 15, 2015

Chemistry
The pH at the equivalence point is determined by the hydrolysis of the salt (you don't have an acid and a base at the equivalence point so you can't use the HH equation). You can calculate the concn of the salt at the eq point but let's call it z. ...........ClO...
March 15, 2015

Chemistry
I think you're on the wrong track. I posted the work for that at your other post. I left the z for you to do but it is HOCl+ NaOH ==> NaOCl + H2O You have 10 x 0.4 = 4 millimols HClO initially. The equivalence point will come at mL x M = mL x M = 10 x 0.4 = mL x 0.5 mL ...
March 15, 2015

Chemistry
I think you converted Ka to pKa wrong.
March 15, 2015

Chemistry
Show your work so I can see what you did.
March 15, 2015

Chemistry
First determine the molarity of the concentrated HCl. That's 1.19 g/mL x 1000 mL x (38/100) x (1 mol/36.5 g) = ?M HCl Then use the dilution formula of mL1 x M1 = mL2 x M2
March 15, 2015

chemistry
So what do you want for a? b. A = log 1/T (or 100/%T) What do you calculate for %T? c. write the orbital notation for Zn and you will see the answer.
March 15, 2015

Chemistry
Le Chatelier's Principle reworded in easier to understand language. When a system in equilibrium is subjected to a stress, it will shift so as to undo what we've done to it. That means when we add a reagent it shift to get rid of the added stuff. When we increase P it ...
March 15, 2015

chemistry
Where are you stuck on this problem? mols CaSiO3 = grams/molar mass = ? Use PV = nRT to find mols HF = ? Find limiting reagent.
March 15, 2015

Chem
Where are you stuck on this problem. You know to find the limiting reagent.
March 15, 2015

chemistry
See this and respond here. http://www.jiskha.com/display.cgi?id=1426441081
March 15, 2015

Chemistry
Calculate %N in NH4NO3. Calculate %N in urea. Those are done (mass N/molar mass compound)*100 = %N. Then amount N in 50 lbs NH4NO3 = 50 lbs x (percent N/100) = ? And 38/?amount N = cost/lb N. Amount N in urea = 50 x (percent N/100) = ? And X/?amount N = cost/lb N.
March 15, 2015

Chemistry
Oil is non-polar.
March 14, 2015

H Chemistry
At constant T, use the following. P1V1 = P2V2
March 14, 2015

Chemistry
How much buffer do you want? The problem doesn't say; if you can choose a volume, say choose 500 mL. Then let x = mL base and 500-x = mL acid, then in the HH equation it becomes 4.0 = pKa + log (0.1*x)/[(500-x)*0.1] and solve for x = volume of the NaF and 500-x is volume ...
March 14, 2015

Chemistry
Hexagonal structure of what?
March 14, 2015

Chemistry
Al2S3 + 6H2O ==> 2Al(OH)3 + 3H2S mols Al2S3 = grams/molar mass = ? Use the coefficients in the balanced equation to convert mols Al2S3 to mols Al(OH)3. now convert mols Al(OH)3 to grams Al(OH)3. That's g = mols x molar mass = ?
March 14, 2015

Chemistry
What's the definition of M? It's molarity = mols/L. You know L and M; you don't know mols so solve for mols you need. How do you get grams from mols? That's mols = grams/molar mass. You know molar mass and mols, solve for grams. Place that many grams KMnO4 in a...
March 14, 2015

Chemistry
Convert grams to mols. mols S = grams/atomic mass = ? mols Cu = grams/atomic mass = ? Now you want to find the ratio of the elements to each other with the smallest number being 1.00. The easy way to do this is to divide the smaller number by itself (thereby assuring 1.00 for ...
March 14, 2015

chemistry
I have no idea what you're talking about. "Islamic values"?
March 14, 2015

Chemistry help
Cr2(CN)6 ? Al4(SO4)6 ?
March 14, 2015

Chemistry help
Na2CO3.xH2O ==> Na2CO3 + xH2O 2.714g.........1.006g.....xg Now how do you think you can find x g H2O? Then where do you go for the empirical formula.
March 14, 2015

chemistry
1/wavelegth = RZ^2(1/1^2 - 1/2^2) is the first line of the Lyman series. 1/wavelength = RZ^2(1/2^2 - 1/4^2) is the second line of the Balmer series. You know R and Z for H, solve for wavelength. Plug this wavelength into the Balmer series and solve for Z. Identify the element ...
March 14, 2015

SCIENCE(CHEMISTRY)
Convert 70 min to seconds. coulombs = C = Amps x seconds. C = approx 1E4 C but you need to do it more accurately than that. Then 96,500 C will deposit 108.1 g (are you sure about the atomic mass Ag???. More like 107.9 I thought). So 108.1 x (1E4/96,500) = ? g Ag deposited.
March 14, 2015

chemistry
Answered below.
March 14, 2015

chemistry
No problem posted. You may be referring to the problem below; if so I've stated you. I'll be glad to help you through any trouble spots.
March 13, 2015

chemistry
You're quite welcome!
March 13, 2015

chemistry
I agree with all of your numbers. a is right; b is right. I obtained 3.8E4 L but that's probably because we didn't use the same molar mass for AgBr. When you ask us to check answers you should tell us what you used for molar mass and atomic masses if we are to get the ...
March 13, 2015

chemistry
You are supposed to use Ksp but not for the solid. Ksp = (Ag^+)(Br^-). Remember that solids and pure liquid are not part of equilibrium constant equations. There must be at least the tiniest crystal but as long as there is SOME solid there then equilibrium can be established.
March 13, 2015

chemistry
Here is how you do a part. That should get you started. .........AgBr ==> Ag^+ + Br^- I........solid.....0......0 C........solid.....x......x E........solid.....x......x Substitute the E line into the Ksp expression and solve for x = (Ag^+) = (Br^-) My presumption is that ...
March 13, 2015

chemistry
Is this a practice problem to check your answers? If so show your work and I'll check for you. If not, please explain what you don't understand about the problem and I'll help you through it.
March 13, 2015

AP Chem
And thank you. You're quite welcome.
March 13, 2015

AP Chem
Yes, that's right. Good work. You did all of this; I just got you started. By the way, I would not type in a last name on the net (unless of course it's a phony one). We recommend no identifying information on Jiskha. Just good safe sense.
March 13, 2015

AP Chem
All of that is right except x is 0.192. However, the other numbers are right so that must be just a typo.
March 13, 2015

AP Chem
Assuming your numbers are right the ICE box will just about do them all. ........H2 + Br2 ==> 2HBr I....0.342.0.209.......0 C......-x.....-x.......2x E..0.342-x..0.209-x....2x Read the problem again; it tells you that the Equilibrium concn (H2) = 0.150M. That tells you that...
March 13, 2015

AP Chem
Do the ICE box although that isn't completely necessary. Post your work and I'll be glad to check it.
March 13, 2015

chemistry
I tend to believe A is the answer. CO2 has no dipole moment.
March 13, 2015

Chemistry
I wonder how one knows that Mg(OH)2 will react first and if so it all of it will react before CaCO3 begins to react. We will assume that is so. You know that mL x M = 45 x 0.1M = 4.5 millimols of acid will be used. How much Mg(OH)2 do you have? That's 110 x 2 x (1 g/1000 ...
March 13, 2015

chemistry
Convert pounds to grams = ? Convert grams to mols with mols = grams/molar mass = ? Convert gallons to liters = ? Then mols/L = [NH4^+] = ?
March 13, 2015

Chemistry ( HELP PLEASE!!! )
I showed you how to do this last night. I'll be happy to answer any questions about what you don't understand but asking me to redo all of that is a waste of my time as well as your time.
March 13, 2015

chemistry
A litany of questions. Is there something you don't understand? If so let's get to the heart of the matter and not spend our time working parts of problem not needed.
March 13, 2015

Chemistry
I don't see that this problem differs that much from the previous problem. If you will explain what you don't understand perhaps I can clue you in.
March 13, 2015

Chemistry
In actual practice you try to set these things up so that the amount of excess added is such a small amount (0.01-0.03 mL) that it doesn't affect the results AND if you run a blank at the same time that usually takes care of that problem. Technically, however, you must add...
March 13, 2015

chemistry
1. Calculate the molarity of the commercial HCl. 2. Use the dilution formula of mL1 x M1 = mL2 x M2 3. Solve #2 for mL of the commercial material to take, pipet that amount into a 500 cc volumetric flask, add some water, swirl, add DI to the mark on the flask and mix ...
March 13, 2015

Chemistry
I believe you are right about a. I would choose C.
March 13, 2015

chemistry
0.5 x (20/7) = ?
March 13, 2015

chemistry
Convert 5.90 pH to H^+. Convert 3.70 pH to H^+ = z I would convert 600 gallons to L. It's approx 2E3 L but you should do that exactly. L1 x M1 = L2 x M2 2E3L x 15M = L2(lake)*z Solve for L2. L2 will be the total volume and you should subtract the volume of the 600 gallons ...
March 13, 2015

Science Help Please
I would choose C
March 13, 2015

Science Help Please
I don't agree with 2 or 5. I didn't look at the others. You have too many questions to a post.
March 13, 2015

chemistry
g Cr present = 0.175 x 72.2 = ? Then mols = grams/atomic mass.
March 13, 2015

chemistry
%C = (atomic mass C/molar mass K2CO3) and change that to %.
March 13, 2015

CHEMISTRY
g C = 0.367 x 12.9g = ? mols C = grams/atomic mass atoms C = mols C x 6.02E23 = ?
March 13, 2015

chemistry
0.1 what?
March 13, 2015

chemistry
I thought I did one of these for you a couple of days ago. ...........H2O ==> H^+ + OH^- I.........liquid....0.....0 C.........liquid....x.....x E.........liquid....x.....x Substitute the E line into the Kw expression and solve for x = H^+, then convert to pH.
March 13, 2015

Chemistry
I answered this question for you (or I thought you)yesterday. If you can't find it I will try to find it.
March 13, 2015

chemistry
https://www.google.com/search?q=l%3Bewis+dot+structure+methanol&ie=utf-8&oe=utf-8
March 13, 2015

Chemistry
The density of CO2 at STP is 44g/22.4L = ? g/L.
March 13, 2015

CHEMISTRY PLEASE!!! ( I NEED HELP ASAP)
The first one is a regular stoichiometry problem and I know one was worked for you yesterday. You should need only one worked of each type because you need to learn to do them yourself. Here is a 3/4 step process that will work aboutr 99.9% of all of the stoichiometry problems...
March 12, 2015

chemistry
n = grams/molar mass = ? Then use PV = nRT Note the correct spelling of celsius.
March 12, 2015

chemistry
For 1, I think the requirement to write that much is overkill but I don't think you've said anything wrong. Make sure you clean up the typos and grammar. Perhaps you should add something about Ssysten + Ssurroundings = + the reaction will be favorable (spontaneous). ...
March 12, 2015

chemistry
I don't believe you don't know these. I shall be happy to critique your thoughts.
March 12, 2015

Science Check
I disagree with 1. For 2 I don't believe you have enough information. You have the angle but you also need one of the sides. Or at least a statement that the hypotenuse is constant.
March 12, 2015

chemistry
..........H2 + I2 --> 2HI I........0.3...0.3.....0 C.......-x....-x.......x E.....0.3-x..0.3-x.....x Substitute the E line into the Kp expression and solve for x = p and 0.3-x
March 12, 2015

chemistry
What are the adducts?
March 12, 2015

Chemistry
It appears to me that this is AX4 and tetrahedral.
March 12, 2015

Chemistry
As I see it you have two choices. 1. Start over 2. If you can use another sheet out of the same box weigh it and hope that the sheets weigh about the same.
March 12, 2015

Analytical Chemistry
What are you using for pK2 for H2L? It might help if I knew pK1 also.
March 12, 2015

chemistry
I have no idea what the question is.
March 12, 2015

Chemistry
And you know how to do how much of this? Start by explaining what you don't understand
March 12, 2015

Chemistry
mols in 5.0 g AlCl3 = grams/molar mass = ? Then M = mols/L. You know M and mols, solve for L and convert to whatever unit you want.
March 12, 2015

chemistry
2KOH + Al + 6H2O--> 2KAl(OH)4 + 3H2 mols Al = grams/molar mass = ? Use the coefficients in the balanced equation to convert mols Al to mols H2 Now convert mols H2 to grams. g = mols x molar mass
March 12, 2015

chemistry
Just plug in the numbers. 2.4 mol/L x #L = 2.3 mols.
March 12, 2015

chemistry
3NaOH + H3PO4 ==> Na3PO4 + 3H2O mols NaOH = M x L = ? Use the coefficients in the balanced equation to convert mols NaOH to mols H3PO4. Now M H3PO4 = mols H3PO4/L H3PO4. YOu know mols and M, sole for L and convert to mL.
March 12, 2015

Chemistry
What's the speed of sound in the units you want? I would convert 1 mile to ? meters. Then look up speed of sound at each temperature. Call that m/s. m/s x #s = ?meters Solve for #s.
March 12, 2015

chemistry
CxOy ==> xC + 1/2O2 % C = (3/11)*100 = ? about 27 % O2 = (8/11(*100 = about 73 mols C = about 27/12 = about 2.25 mols O2 = about 73/32 = about 2.28 O2 molecules or about 4.56 mols O atoms. Now find the ratio of the C atoms to the O ATOMS, round to whole numbers and that ...
March 12, 2015

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