Thursday
May 28, 2015

Posts by DrBob222


Total # Posts: 49,058

Chemistry
H2O(l) ==> H2O(s) delta S rxn = S(solid) - S(liquid) delta S will be in J/mol. Convert that to 5.00 grams. That gives you dS for the system. dS surrounds = - dHfusion/T (and T is 273, not zero). dS total = dSsystem + dSsurroundings. reactions are spontaneous is dS total is +.
March 20, 2015

Chemistry- Electrochemistry
Ecell = Eocell -0.059/n*log Q
March 20, 2015

Chemistry
p1v1 = p2v2
March 19, 2015

Chemistry
I don' know what the question is. What does "Both A and D above are correct" mean.
March 19, 2015

chemistry
Use PV = nRT, substitute the conditions and solve for n = number of mols. Then n = grmas/molar mass. You know mols and grams, solve for molar mass. Look on the periodic table and identify the gas.
March 19, 2015

To Cortney---Chemistry
I see you answered your own question and that's ok with me; however, it is not ethical to type in my name as the author of that answer. I didn't answer that question. My computer shows you used the same computer to type the question and answer. Shame on you for trying ...
March 19, 2015

chemistry
The answer is a
March 19, 2015

chemistry
The one most likely to be a gas at room T is F2 LiF is likly to be soluble in water because both are polar; polar solutes dissolve in polar solvents. LiF is polar; PCl3 is polar. F2, BeF2, CCl4 are not polar.
March 19, 2015

chemistry
Do you know which are ionic and which covalent? That is the secret to answering this question. LiF is ionic, it dissolves in H2O and because the ions are in solution it conducts electricity.
March 19, 2015

Chemistry
I believe I is true. I think II is true. III is true sometimes but not always. I would agree if it said attracted to other polar molecules. It doesn't say that so I would rule III out. IV is not true.
March 18, 2015

chemistry
mols CaCl2.2H2O = grams/molar mass = ? There is 1 mol of CaCl2 in 1 mol CaCl2.2H2O
March 18, 2015

chemistry
What's the reaction?
March 18, 2015

Chemistry
1. You can convert any mole in an equation to another in the same equation just by using the coefficients in the balanced equation. 0.45 mols N2 x (2 mols NH3/1 mol N2) = 0.45 x 2/1 = ?. This will always work. The numberator is what you want to convert to and the denominator ...
March 18, 2015

chemistry
Take a 100 g sample to give you 63.9 g CuSO4 and 36.1 g H2O Convert to mols. mols CuSO4 = grams/molar mass = ? mols H2O = grams/molar mass = ? Now find the ratio of the two with the smaller number no less than 1.00. The easy way to do that is to divide the smaller number by ...
March 18, 2015

Chemistry I
M = mols ethanol/L solution. What else do you need to know?
March 18, 2015

Chemistry
Use k1 and solve for (H^+) = (H2AsO4^-) Use k2 to solve for (HAsO4^2-) Use k3 and your numbers from 1 and 2 to solve for AsO4^3-. Note: you may need to use a quadratic for the first part (k1). Post any work if you get stuck.
March 18, 2015

Chemistry
You shouldn't find this that hard. Look at your original data. How did you determine mols initially. Wouldn't you think that if you doubled the vinegar at the start you would have double the mols? b. Wouldn't you think it you took x mL to tirate the 25 that it ...
March 18, 2015

chemistry
Calculate %H2O in CaSO4.2H2O by (2*molar mass H2O/molar mass CaSO4.2H2O)*100 = ? 8.60g sample x %H20/100 = grams H2O driven off. Convert to mols. Then use PV = nRT and the conditions listed and solve for V in Liters.
March 18, 2015

rate law chem
I wouldn't think so. The order may be different, the coefficients may be different.
March 18, 2015

CHEM
I assume you titrated the acetic acid with a base such as NaOH or KOH. If that is the case, moles acetic acid = mols NaOH and mols NaOH = M x L = ?
March 18, 2015

Chemistry1412
To solve for x do (0.110)(x^3)(9.6) = (0.134)^2 x^3 = (0.134)^2/9.6*0.110 = ? Then x = cube root of ?
March 18, 2015

Chemistry1412
If these are equibrium concentrations that is right.
March 18, 2015

Chemistry1412
136.54 looks ok but that's too many significant figures. I would round it to 136. As to your other what if question, you can do (CH3OH) but only if you have Kc (unless someone tells you that the reactions goes to completion). In that case it becomes a regular stoichiometry...
March 18, 2015

Chemistry1412
What's your trouble with this problem? It's just a matter of substituting the values into Kc expressions.
March 18, 2015

chemistry
I don't like any of the answers. The reason a gas exerts pressure is because of collisions of the particles with the walls of the container. I would go with c easily if it added, "Collisions......gas WITH THE WALLS OF THE CONTAINER."
March 18, 2015

Chemistry
Print this out. This 4-step procedure will work all of this type. 1. Write and balance the equation. 2. mols HNO3 = M x L = ? 3. Use the coefficients in the balanced equation to convert mols HNO3 to mols Ba(OH)2. 4. Then M Ba(OH)2 = mols Ba(OH)2/L Ba(OH)2
March 18, 2015

Chemistry1412
Kp for the rxn is 2.26E4 For the reverse it is 1/Kp For 3x the rxn it is (1/Kp)^3
March 18, 2015

chemistry
You made a typo; you have too many zeros in that 226000 don't you? The answers looks ok.
March 18, 2015

chemistry
Answered above.
March 18, 2015

Chemistry
Use P*molar mass = density*RT Solve for molar mass. Then empicical formula mass x x = molar mass Solve for x which is (empirical formula mass)x which is (CH2)x or it can be re-written as CxH2x for the molecular formula.
March 18, 2015

chemistry
Use PV = nRT and solve for n CO2 (mols CO2). Do the same for n H2O. The wording is confusing. Do you want the mass of the reaction as is or do you want it balanced first. I would think balanced first, then the mass of the balanced equation. If so, then balance the equation. ...
March 18, 2015

chemistry
E = 2.180E-18(1/2^2) joules.
March 18, 2015

chem
If you can give us some hints as to what you don't understand about all of these questions someone here may be able to help. You can google most of the answers.
March 18, 2015

Chemistry
nFEocell = RTlnK
March 18, 2015

chemistry
1 and 2 are right. I'm not an internal combustion man but I think the answer is c. The compression stroke is when the piston is at the bottom of it's stroke and it has just pulled in the fuel, then it starts up and compresses the gas so that the gas occupies the ...
March 18, 2015

chemistry
6.02E23 atoms Cr = 52 g. So 1E6 Cr atoms will have a mass of .....?
March 18, 2015

Chemistry
I didn't answer this last night because I really didn't like any of the answers. I,like Jai, think the best answer is c. I would have liked it better if the answer for c had been stated as, The NaCl CRYSTAL is surrounded by water molecules. I thought perhaps the fact ...
March 18, 2015

Chemistry
I think you made a typo with that Cu(NO3)4^2. I assume you meant [Cu(NH3)4]^2. 18.8 g Cu(NO3)2 = ?M. That's mols = grams/molar mass. Let's call that about 0.1 but you should go through and confirm that. ........Cu^2+ + 4NH3 ==> [Cu(NH3)4]^2 I....... 0.1....0.400...
March 17, 2015

chemistry
yes
March 17, 2015

chemistry
I think the easy way to do this is as follows: It reuires 129 kJ to decompose 2 mol NaHCO3 so it should require 129 x 3/2 to decompose 3.5 mols. The difference in where the dH is written is the sign. If you write it as you have above, it means the rxn is endothermic and you ...
March 17, 2015

Physical Science
http://chem-guide.blogspot.com/2010/04/cracking-and-reforming.html
March 17, 2015

Chemistry
I think if you just balance the equation things will work out. 2I^- + O3 ==> 3H2O + I2 I goes from -2 total to 0 for 2 I. O goes from 0 to -6 total for 3 O. Multiply I part by 3 and O part by 1 so equation becomes 6I^- + O3 ==> 3H2O + 3I2 Now balance the charge by ...
March 17, 2015

Chemistry
Yes, D.
March 17, 2015

chemistry
I agree
March 17, 2015

chemistry
XCO2 = mols CO2/total mols. XCO = mols CO/total mols XO2 = mols O2/total mols. pCO2 = XCO2*Ptotal pCO = XCO*Ptotal pO2 = XO2*Ptotal
March 17, 2015

chemistry
First, your equation isn't balanced. Balance it. mols C6H12O6 = grams/molar mass = ? Using the coefficients in the balanced equation convert mols C6H12O6 to mols O2. Then use PV = nRT and convert mols O2 to volume in L at the conditions listed.
March 17, 2015

Chemistry
Which atom are you talking about?
March 17, 2015

chemistry
I don't think that will do it. The Law of Conservation of mass says everything on the left must equal everything on the right. 2.241 + x = 2.852. X = ?
March 17, 2015

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

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