Saturday
March 28, 2015

Posts by DrBob222


Total # Posts: 47,990

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

Chemistry
grams = mols x molar mass.
March 12, 2015

Chemistry
Convert to mols. mols = grams/molar mass. Then find the ratio of the mols to each other with the smallest number being 1.00. The easy way to do that is to divide the smaller mols by itself and divide the other number by the same small number. Round to the nearest whole number ...
March 12, 2015

Chemistry
USUALLY we call the larger quantity the solvent and the smaller quantity the solute. Also if it's a solid and a liquid we usually call the solid the solute and the liquid the solvent. I would call the methanol the solute and water the solvent. The solution is the methanol ...
March 11, 2015

WHY CANT I POST URL'S?
I see someone should give you a lesson in reasoning. You're assumption is that all of us work at some college. 99% are retired teachers who do this volunteer work for the fun of it and because we want to help students who want help. Good luck to you.
March 11, 2015

WHY CANT I POST URL'S?
I don't believe the answer by Smartie will get it. Writeacher and I gave you the straight scoop.
March 11, 2015

WHY CANT I POST URL'S?
The webmaster gives that ability to those tutors who have passed the test of time with many many right answers and no wrong answers. You're probably new to this site so you don't have that benefit. If you want to keep posting answers and you do a VERY good job (and you...
March 11, 2015

chemistry
It takes 80 calories to melt a grams of ice. Therefore, 5400 cal = mass ice x 80 Solve for mass ice.
March 11, 2015

chemistry
The volume of solid H2O (ice) is higher than the volume of the liquid. Applying pressure will cause the reaction shown to shift to the side that occupies the lower volume. That is the liquid side so the solid melts.
March 11, 2015

Chemistry
........H2O ==> H^+ + OH^- I.......liquid..0......0 C.......liquid..x......x E.......liquid..x......x Substitute the E line into Kw for H2O and solve for x = (H^+) then convert to pH.
March 11, 2015

chemistry
I agree with all of this.
March 11, 2015

chemistry
I disagree with part of the statement but not all of it. It is exactly true that NaCl dissociates into two particles and CaCl2 into three; THEREFORE, it WOULD be more effective to use CaCl2 for the melting of ice. The fact that it raises the boiling point more, which is true, ...
March 11, 2015

chemistry
You need more info than that.
March 11, 2015

CHEMISTRY HELPPPP!!!!!!!!!
a. The one with the lowest Ea. b. k = -Ea/RT. Do that for uncatalyzed. Do that for W surface. Compare the k values.
March 11, 2015

Chemistry 2
Why not show your work for the ICE table and let us see what you need to do. Otherwise we're just guessing what you've done. It appears that you need Kc = (C)/(A)(B)^2 (Note: you don't have the squared term) Then you have x, and I assume the rest of ICE table. If ...
March 11, 2015

chemistry
The colligative property equation is delta T = i*Kf*m where i is the van't Hoff factor. It is the number of particles. NaCl ionizes to two particles. CaCl2 ionizes to three particles. So which will have the greater effect, everything else being the same.
March 11, 2015

Science
I agree
March 11, 2015

Science
I agree.
March 11, 2015

chem
PV = nRT
March 11, 2015

Chemistry
It picks up H2O from the atmosphere and changes to KOH. K2O + H2O --> 2KOH
March 11, 2015

Chemistry HW!!!
Too many questions on one post. 1. 0.50M x (75 mL/375 mL) = ? if you can make a 0.50M CaF2 solution. I didn't think it was that soluble. 2. Use the dilution formula. mL1 x M1 = mL2 x M2
March 11, 2015

chemistry
Right on all except what you do for atoms. You are right that each molecule oxygen contains two atoms of O so doesn't it stand to reason that O atoms will be twice O molecules.
March 11, 2015

Chemistry
The pH is determined by the hydrolysis of the salt. SO3^2- + HOH ==> HSO3^2- + OH^- so it will be basic.
March 11, 2015

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