Thursday
April 17, 2014

Posts by DrBob222


Total # Posts: 41,772

chemistry
I don't think so. 1.6E-6/0.5 = ?

AP Chemistry
I think Ag comes out first followed by H2, then Fe if ever.

Organic Chemistry
Lauren, I'm sorry but we can't draw structures on this forum. You might try Google but that sounds so specific I don't know how much luck you will have.

Chemistry
If your equation is right use 2 mol e. However, I'm somewhat surprised In doesn't go to In^3+.

Chemistry
It starts at 0.01/2 = 0.005 and you want it to go to 1E-4 ln(5E-3/1E-4) = 2E10*t Solve for t.

Chemistry
The b part is a common ion problem; i.e., F^- is the ion common to both KF and MgF2. For part b, Ksp = (Mg^2+)(F^-)^2 The common ion shifts the solubility to the left. MgF2 ==> Mg^2+ + 2F^- because of Le Chatlier's Principle. The new solubility will = new (Mg^2+) and yo...

Chemistry
Use the Henderson-Hasselbalch equation.

Chem
pH = -log(H3O^+) = 7.38 (H3O^+) = 4.16E-8 b. (H3O^+)(OH^-) = 1E-14 c. mols = M x L = ?

chemistry
Johnny said he didn't have a calculator and wants someone to do his work. I did one problem. Then Danny says his calculator returns the wrong answer so it may be broke(n). Then I find Danny and Johnny are the same computer. :-(. Do we have an answer moocher?

science
6*300

science help pleasee
Mostly covalent

chemistry
So you get 1418 kJ for every 2*61 g nitromethane. How much will you get for 6900 g. 1418 kJ x (6900/2*61) = ?

incomplete--planning. and leadership

chemistry
p1v1 = p2v2

chemistry
I don't know the answer because it varies with what kind of concentration you have. g/L, M, m,% w/v, %w/w, % v/v. Frankly I think this is a poor question.

Chemistry
You've done part A. Amount in part A/0.83 = amount you need at 83% efficiency.

Chem.
Kp = Kc(RT)^delta n where delta n = n products - n reactants.

chemistry
2C4H10 + 13O2 ==> 8CO2 + 10H2O mols butane = grams/molar mass = ? Using the coefficients in the balanced equation, convert mols butane to mols O2. Use PV = nRT and solve for V O2 at the conditions listed.

Chemistry [back-titration] - please check my sol'n
One mistake is the 1:1 ratio for Fe^2+ vs Cr2O7^2-. The partially balanced equation is 6Fe^2+ + Cr2O7^2- ==> 2Cr^3+ + 6Fe^3+ A second error is I have the molar mass TeO2 as 159.6 I worked the problem and 13.09% TeO2 is correct. I didn't go through the rest of your work ...

Chemistry
2KClO3 = KClO4 + KCl a. The equation isn't balanced. b. I don't see any potassium chlorite.

Chemistry
This may come as a shock to you but m and M don't mean the same thing. m stands for molality and M stands for molarity. I ASSUME you meant M and not m. mols = M x L = ? You might find the caps key on your keyboard and use it. K2CrO4 means something to me. k2cro4 doesn't.

Chemistry
mols N2 = 57.5/22,400 = ? mols Li = 6x that (from the coefficients in the balanced equation). Then g Li = mols Li x atomic mass Li = ?

Chem
I'm assuming Ca3(BO3)2 has no Ksp. I couldn't find one. a. mols = M x L = ? b. mols = M x L = ? c. mols K = 3 x mols K3BO3 and (K^+) = mols K/total L d. mol BO3^3- from K3BO3 = mols K3BO3 mols BO3^3- from Ca3(BO3)2 = 2 x mols Ca3(NO3)2. Then (BO3^3-) = total mols BO3^3...

Chem
You really don't know because volumes are not additive; however, you can get a very close estimate. Use c1v1 = c2v2 c = concn v = volume 4.3M x 140 mL = 3.3M x mL Solve for mL (which is the total volume). The calculation so far is accurate. To find how much H2O was added y...

Chemistry
It isn't and I don't. The surface area of liquid in a beaker would be done this way. Measure the diameter of the beaker. Then pi*r^2 = area. Yes, you can vary the surface area by changing the size of the beaker. That will work for any cylindrical container. It would be...

Chemistry
Yes BUT you need the heat of combustion of CH4 to know howmuch heat it produces. How much heat do you need? (1 qt H2O = 0.946 L and if the density of H2O is 1.00 g/mL that is 946 g)That's q = 946 g H2O x specific heat H2O x (Tfinal-Tinitial). Let's suppose this is y jo...

Chemistry
You have everything here except the heat of combustion of CH4.

Chem
I think you've missed the boat with regard to conjugate acids/bases. I think students make this much harder than it is. Here is the simple scoop. From whatever you have, if you want the BASE you take away a H. If you want the ACID you add a H. HSO4. The conjugate base is S...

Chemistry
Look up mascaline on the web like I did. Here it is. http://en.wikipedia.org/wiki/Mescaline I don't see an alcohol or an acid but I do see an amine group. Also three ether groups.

Chemistry
1000 J = 1 kJ is the factor so 220 J x (1 kJ/1000 J) = ? You see you multiply the value you start with by the factor. You can place the factor as 1000/1 or as 1/1000. Only one way is right. The right way will ALWAYS cancel the unit you don't want and keep the unit you want...

Chemistry
I've never done this but I would guess it would be Cr4O3; i.e., for every 4 mols Cr you use 3 mol O2 for #1 with Cr as the limiting reagent. For #2, O2 is the LR. 2.5 O2 x 4 mol Cr/3 mol O2 = 3.33 so the formula is Cr3.33O2.5. Convert to whole numbers and that is Cr10O7.5 ...

Chemistry
2.) For the reaction, calculate how many grams of the product form when 18.4g of Br2 completely reacts. Assume that there is more than enough of the other reactant. 2K(s)+Br2(l)→2KBr(s) mols Br2 = grams/molar mass = estimated 0.1 but you should be more accurate than that...

chemistry
And what is your problem? a. pOH = -log(OH^-). Substitute and solve. b. Use pH + pOH = pKw = 14 and solve for pH, then use pH = -log(H3O^+). c. See b. pH + pOH = pKw = 14

chemistry
HCl + KOH ==> KCl + H2O Note the ratio is 1 mol KOH = 1 mol HCl. mols KOH = M x L = ? mols HCl = mols KOH MHCl = mols HCl/L HCl Done.

chemistry
pKa = -log Ka

Chemistry
Actually nothing happens. You now have a mixture of Na^+, Cl^-, OH^-, H^+, all mixed in with water.

General Chemistry
Ag2SO4 will begin to ppt when Ksp = (Ag^+)^2(SO4^2-) is exceeded. (SO4^2-) = Ksp/(Ag^+)^2 (SO4^2-) = Ksp/(0.290)^2 Solve for SO4^2- and substitute into Ksp for CaSO4. Solve for Ca^2+

General Chemistry
Do you have the corresponding Ksp values?

chemistry
I guess d. The others are not.

Chemistry
............Sn(OH)2 ==> Sn^2+ + 2OH^- I............solid.......0........0 C............solid.......x........2x E............solid.......x........2x Ksp = (Sn^2+)(OH^-)^2 5.45E-27 = (x)(2x)^2 Solve for x = solubility in mols/L. Then grams = mols x molar mass

chemistry
When gases are used you may use volumes as if it were mols. 560 L CO2 x (2 mol O2/1 mol CO2) = 560 x 2/1 = ?

Chemistry
It is difficult to write the subscripts and superscripts on this board so here is the way I will do it. 20X50. 20 is the atomic number, X is the element, and 50 is the mass number. With that in mind here is how the Fm looks. 100Fm258 ==> 3 2He4 + 2 on1 + 94X244 The subscrip...

Chemistry
To bad I missed out on that (or those). :-) And while I'm here let me correct an error above in one of my posts. In one of them I gave dG = -2.303RTlnK as the correct formula and it isn't. The correct formula is either dG = -2.303RTlogK OR dG = -RTlnK

Chemistry
I understand. I leave those intermediate answers in the calculator; writing them down and re-entering often leads to rounding errors. I think 63.8985 which I would round to 64.0 is the correct answer.

oops--Chemistry
Excuse me. I re-read everything and you have all of that info at the beginning. If you use dG = -2.303RTlnK and your numbers you come out with about 60 which is what I obtained with dG = -RTlnK. You must be pushing the wrong buttons somewhere.

Chemistry
I don't know what you're doing, and it would help if you showed your work so we could find the error, but I get something like 60 or so for K. Are you using dG = 10310 J? You may be using kJ or cal or Kcal. Are you using 8.314 for R?

Chemistry
I think your problem is the wrong formula. I believe that's dG = -2.303RT*log K

Chemistry
Chilling reduces the rate of the reaction. Boiling removes the enzyme. Oxygen reacts with both the enzyme and the citric acid but it reacts with citric acid first and will keep the browning away as long as the lemon juice is in excess.

Chemistry
%N = (1.094/2.500)*100 = 43.76 Now find %N in NH4NO3 and NH4NO2 and compare.

chem
mols NH3 = grams/molar mass = estimated 1.0 mols CuO = g/molar mass = estimated 1.1 Convert mols each to mols product. N2 is the easiest. 1 mol NH3 x (1 mol N2/2 mol NH3) = 1 x 1/2 = estimated 1/2 mol N2. 1.1 mol CuO x (1 mol N2/3 mol CuO) = estimated 1.1 x 1/3 = about 0.4 So ...

Chemistry
1a. mols needed = M x L Then mols = grams/molar mass. You know molar mass and mols, solve for grams. Same concepts for 2 but not worked same way.

Chemistry
Look up the vapor pressure of H2O at 20 C. This is pH2O. Then Ptotal = pO2 + pH2O You know Ptotal and pH2O, solve for pO2.

chemistry
Convert Kb to Ka by KaKb = Kw and change that to pKa; then Use the Henderson-Hasselbalch equation.

Chemistry
Two equations in two unknowns; solve simultaneously. Let X = mass NaCl and Y = mass K2SO4 ------------------- eqn 1 is X + Y = 10.0 eqn 2 is mass PbCl2 (from NaCl) + mass PbSO4(from K2SO4) = 21.75g. eqn 2 in terms of X and Y is this (X*MMPbCl2/2*MMNaCl) + (Y*MMPbSO4/MMK2SO4) =...

Chemistry
mols Cl2 = grams/molar mass Use density to convert mL acetone to grams then to kg. Then m = mols Cl2/kg solvent

Chemistry
What's with the "same air bag"?

chemistry
This is a bear of a problem but I will get you started.First you must determine the limiting reagent(LR). Start by using PV = nRT and calculating mols of each material. Find the LR from that and determine how much of each product is formed. Then multiply by 0.9 to correct for ...

Chem Check Please!!!
I think your work is sloppy. It's delta G and not G (yes I know what you mean) and you've omitted all of the negative signs (yes I could see what you did). I think you put the 103 in the wrong place but calculated as if you had it in the right place. At any rate I obta...

Chemistry Check Please!!!
I think Eox = -0.771 and Ered = +1.36 Then 1.36 + (-0.771) = ? Your answer is right; I don't agree with what you called Eox. The anode is oxidized, yes, and that is an oxidation, yes. But the potential for that electrode is -0.771. The reduction potential is 0.771; the oxi...

chemistry
33.01 g CO2 27.04 g H2O mols CO2 = 33.01/44 = ? = mols C. mols H2O = 27.04/18 = ? and that x 2 = mols H. Now find the ratio of C to H with C being no larger than 1.0

Chem
c) work = -p*delta v d) q = mass x specific heat x (Tfinal-Tinitial) e) qp = delta H

Chemistry
mols = grams/molar mass. Substitute and solve for mols. m = molality = mol/kg solvent Substitute and solve for m. delta T = Kf*m Substitute and solve for delta T. Then subtract delta T from the normal freezing point of camphor.

chem
ammonium phosphate is (NH4)3PO4 I see 20 atoms per molecule. aluminum carbonate is Al2(CO3)3 I see 14 atoms per molecule. iron cyanide is Fe3CN. I see 5 atoms per molecule

Chemistry
(0.75g/20) = (x g/105.4) Solve for x.

Chemistry
Is that a typo first line. Perhaps should be CaCl2.6H2O. If so just add the two equations to obtain CaCl2(s) ==> CaCl2(aq) about -82 kJ/mol but that isn't exact.

Chemistry
See your other post.

Chemistry
3m = 3 mols KCl/1 kg solvent 1 mol KCl = estimated 74.5 but you should be more accurate than that. 3*74.5 = about 223g. So that is about 223g/223+1000 = 223g/1223 g solution % KCl w/w = (223/1223)*100 = >

chemistry
See your post below.

chemistry
C = p*k C = 2.5*0.037 Solve for C in M. M = mol/L. You know L and M, solve for mol. mol = grams/molar mass. You know molar mass and mol, solve for grams.

Chemistry HELP URGENT PLEASE!!!
yes

Chem.
mols KHP = grams/molar mass = ? mols NaOH = mols KHP M NaOH = mols NaOH/L NaOH

chemistry
q = mass x specific heat x (Tfinal-Tinitial)

chemistry
Ag^+ + Cl^- ==> AgCl(s) Ba^2+ + SO4^2- ==> BaSO4(s) Cu^2+ + 2OH^- ==> Cu(OH)2(s) Add Cl^-, filter AgCl. Treat with Na2SO4 and filter BaSO4. Add NaOH. Filter Cu(OH)2.

chemistry
See your post below.

chemistry
3Cl2 => 2CHCl3 mols CHCl3 = 7.20 Convert to mols Cl2. 7.20 mols CHCl3 x (3 mols Cl2/2 mols CHCl3) = ? Then ? mols Cl2 x molar mass Cl2 = grams.

chmistry
density = 1.19 g/mL. mass of 1000 mL is 1.19 g/mL x 1000 = 1190g How much of that is HCl. 37% so 1190 g x 0.37 = about 440g but that is an estimate. How many mols is that? 440/36.46 = about 12 mols. 12 mols/1000 mL = about 12 M.

chemistry
Is there a question here?

Chemistry
mols ZnO = grams ZnO/molar mass ZnO Using the coefficients in the balanced equation, convert mols ZnO to mols Au. Now convert mols Au to grams. g = mols x atomic mass.

CHEMISTRY
See your other post. Same process but you must correct for concns that are not 1M. Use the Nernst equation for that. Post your work if you get stuck.

Chem HELP !!!
Look up Eo values for Fe^3+ + e ==> Fe^2+ and change the sign. Look up Cl2(g) ==> 2Cl^-(aq) Add the two for Eocell.

Chemistry Help Please
See your other post.

Chem Check Please!!!
Follow these directions. Look up the delta Go f (that's delta Gof of each of the products and each of the reactants. Pure elements like H2 are zero but the others are not. Then calculate dGo f for the reaction by dGofrxn = (n*dGf products) - (n*dGf reactants) Finally, dG =...

math help--Please help!

Chemistry
Reason your way through it. I assume A2B is a solid. .........A2B --> 2A^+ + B^2- .....4.35E-4M....x......x For every molecule of A2B that dissolves, you must have two (2) ions of A^+ and one (1) ion of B^2-; therefore, for every 4.35E-4 mols A2B that dissolve, you must hav...

chemistry
There must be a question in here somewhere.

chemstry
267.2 WHAT?

To Nina
I think you transposed the numbers for mass proton on your post yesterday which may be the reason you had trouble getting the answer in the book. I've posted a response at the original post which can be found here. http://www.jiskha.com/display.cgi?id=1394937578

Chemistry
Actually it makes little difference which we call the solute and which the solvent; however, usually we assign the solute to the smaller quantity and the solvent to the larger number. Or if solid/liquid, we usually call the solute the solid and the solvent the liquid. In the c...

Chemistry
6.44% by mass means 6.44 g glucose/100 g solution. What is the volume of the solution? That is mass = volume x density. You know d and you know mass; solve for volume in mL and convert to L. Then find mols solute. That is 6.44g/molar mass glucose. Finally, M = mols/L solution....

Chemistry 151
Use the dilution formula for these. c1v1 = c2v2 c = concn v = volume for a. 100 mL x 0.1M = ? mL x 1M Solve for ?mL of the 1M. b. 250 mL x 0.5M = ? mL x 1 M Solve for ?mL of 1 M.

Chemistry
These are limiting reagent problems. I solve these the long way. Starting with one of the reactants, calculate how much of one of the products will be formed. Do the same for the other reactant and the same product. If both answers are the same everything is in the right propo...

Chemistry
How many mols Cu(OH)2 do you need? That's mols = g/molar mass = 100/97.56 = approx 1 mol but you need to do it more accurately. Convert mols Cu(OH)2 to mols NaOH = twice that = about 2 mol (again, do it more accurately). M NaOH = mols/L. You know mols NaOH and M NaOH, solv...

Chemistry
I think it's your math. I obtained the same equation as you and it looks ok to me. I went through the math and obtained two values for x of 0.0631 (which can't be right since 0.110-2x gives a negative number) and 0.0471. That value plugged back into Kp expression gives...

chemistry
q = mass EtOH x specific heat EtOH x (Tfinal-Tinitial) Substitute and solve for Tf.

Chemistry
(1/A) - (1/Ao) = kt Substitute and solve for k. Second part. rate = delta A/delta T = -0.01/200

chemistry
mol NH4NO3 = grams/molar mass Then M = mols/L solution. You know mols and L soln, solve for M.

I don't get it--Chemistry

Chemistry (titrations)
Yes they are in the 1:1 ratio. 1.8E-4 mols EDTA = 1.8E-4 mols Fe 1.8E-4 mols Fe x atomic mass Fe = grams Fe. Thus you have that many grams Fe in 50 g (50 mL solution) = 2.01E-4 g/g or 201 g/1 million grams = 201 ppm.

Chemistry
I get close to that answer if we neglect the fact that an extra electron produced is ignored, AND I think you transposed numbers for the mass of the proton. I think (2.0141 - 2*1.00728) = ? amu Change to kg. ?amu x (1/6.022E23*1000) = kg E = kg*c^2 and that gives me 6.86E-14 p...

chemistry
This is just another stoichiometry problem but since everything is a gas and measured at the same conditions, it allows us to use a shortcut. C3H8 + 5O2 ==> 3CO2 + 4H2O We may use volume in liters as if L = mols. Simply convert L C3H8 to L CO2 using the coefficients in the ...

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