Wednesday
April 23, 2014

Posts by DrBob222


Total # Posts: 41,895

chemistry
I don't know if that 1.85 atm is absolute or not; I assume this is to be worked the "easier" way. Use (p1/t1) = (p2/t2) Don't forget T must be in kelvin.

SCIENCE
1. I don't know that I believe it is uncommon to draw Lewis diagrams of ionic compounds. If we go with that assumption, however, I would go with d. 2. food? oil? 3. Doesn't it all depend upon what kind of mixture we have? For example, we separate oil (petroleum) at ref...

Chemistry
For the reaction A + B ==> C + D Q = (C)(D)/(A)(B) which looks like Keq but isn't. I suppose the simple answer is yes. You have two components of equal magnitude on the right and those are the products.

Chemistry
Two comments. Shouldn't that Q be (5.69E-5)^2/(1.34)? Can you add dGo (in kJ) and RTlnQ (which I believe is in J) without convert one or the other?

Chemisty
a. (Ca^2+) = 0.05 x (100/200) = ? b. (SO4^2-) = 0.10M x (100/200) = ? c. You can't do this? d. Calculate Krxn quotient. A ppt will form if Krxn quot > Ksp.

Chemistry HELP PLEASE!!
Mg^2+ + 2e ==> Mg(s) 2Cl^- ==> Cl2 + 2e Oxidation is the loss of electrons so which half rxn is that? Then oxidation occurs at the anode. Reduction occurs at the cathode (which is the gain of electrons).

Chem Check Please!!!
This looks ok to me.

Chemistry
Approx means I've estimated. You should go through yourself and get good answers. pKa = approx 2.4 mols HNO2 = 0.5L x 0.4M = 0.2 = acid pH = pKa + log (base)/(acid) 2.10 = 2.40 + log (x/0.2) Solve for x = mols KNO2 = about 0.1 mol = ? grams. b. millimols HNO2 = 500 mL x 0....

Chemistry
Is that C60O<suh>3 or what? And I thought Arrhenius equation had to do with k1 and k2 at T1 and T2 and T1 and T2 are tempeataures, not time.

chemistry
If that's mols = grams/molar mass, yes.

oops--CHEMISTRY
https://www.google.com/search?q=H+spectrum+diagram&client=firefox-a&hs=DDB&rls=org.mozilla:en-US:official&channel=sb&tbm=isch&imgil=i479Ed5rU636WM%253A%253Bhttps%253A%252F%252Fencrypted-tbn1.gstatic.com%252Fimages%253Fq%253Dtbn%253AANd9GcS-sEHCsm82sKFlff4b8s_5ileY8WxQCKWoliKnz...

CHEMISTRY
Here is a diagram that should help answer this question.

TO: DrBob222 science help
ALL compounds are neutral. I don't understand what you mean by ion count; water has no ions other than the small concns of H^+ and OH^-. Both of those are 1E-7 M in pure H2O; perhaps that's what you mean by ion count but those exactly neutralize each other and the coun...

CHEMISTRY
CaCO3(s)+2HCl(aq)>CaCl2(aq)+H2O(l)+CO2(g) I will estimate all of these numbers; you need to go through and recalculate each. mols CaCO3 = grams/molar mass = approx 0.30 mols HCl = grams/molar mass = approx 0.36 Convert mols CaCO3 to mols CaCl2 using the coefficients in the ...

General Chemistry
work = -p*delta V work = 7*0.52 = -3.64 L*atm Multiply by 101.325 if you want the answer in joules.

chemistry
2SO2 + O2 ==> 2SO3 mols SO2 = grams/molar mass mols O2 = grams/molar mass = ? Using the coefficients in the balanced equation, convert mols SO2 to mols SO3 Do the same for mols O2 to mols SO3. It is likely these values will be different which means one of them is wrong. The...

Chemistry
(amount recovered/amt you should recover)*100 = %yield

Science
You need to know the density of the HCl solution (the 33%) and you need to know how much of the 0.1M you wish to prepare.

Chemistry
Didn't I do this for you earlier?

chemistry
Take a 100 g sample which gives you 75.2g N2 and 24.8g Kr. mols N2 = grams/molar mass mols Kr = grams/molar mass Then X = mol fraction XN2 = nH2/total mols XKr = nKr/total mols pN2 = XN2*total P pKr = XKr*total P

Chemistry
See your other post. Worked the same way. Just take a 100 g sample.

Chemistry
I think what you have to understand is that on the flat portion, the temperature is constant because the phase change is occurring and the temperature cannot go up (if melting) or down(if crystallizing) until all of the molecules have melted or crystallized. At that exact poin...

Chemistry
If I could draw a diagram but I can't. Let me try to use periods as spaces. E = k/N2 .....1.....2.....3.....4.....inf E = -21...-9....-4....-3......0 In going from n = 1 to n = 2 we have dE = 13 Going from 1 to 3 we have dE = 17 Going from 1 to 4 we have dE = 18 Going form...

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?

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