Tuesday
March 3, 2015

Posts by DrBob222


Total # Posts: 47,384

general chemistry
Two ways to do this. The long way, but easier to explain, and the short way but harder to explain. The long way first: The general gas formula can be modifed to P*M = dRT where M is molar mass and d is density in g/L. Substitute into that and solve for M. Then use the same ...
December 16, 2014

chemistry
It all depends upon what concentration the chemist wants the stock solution. If we call that M, it will be c1v1 = c2v2 M*5.00L = 18M x v2 substitute M from your problem, which you didn't post, and solve for v2 of the 18.0 M.
December 16, 2014

Chemistry
Use PV = nRT Ptotal = 760 mm pH2O = 23.8 ptotal = pH2O + pO2. Solve for pO2 then pO2 in atm = pO2 in mm Hg/760 = ? V you know R you know (0.08206 L*atm/mol*K) T = 298 Solve for n = number mols O2 at these conditions. You don't need the 7.65g KClO3 since the problem gave ...
December 16, 2014

chemistry
http://en.wikipedia.org/wiki/X-ray_photoelectron_spectroscopy Here is a little about XPS, AES, ESCA, UPS http://www.lasurface.com/accueil/index.php
December 15, 2014

Chemistry
I believe this is it. https://www.google.com/search?q=hybridization+SF6&tbm=isch&tbo=u&source=univ&sa=X&ei=d8OPVOSGGoOqgwTLtoToDg&ved=0CCIQsAQ&biw=1010&bih=601#facrc=_&imgdii=_&imgrc=owk5ZhMm30lXAM%253A%3BSSSnTNuBuuCOCM%3Bhttp%253A%252F%252Fi.ytimg.com%252Fvi%252FX6NLcNqqwOo%...
December 15, 2014

Chemistry
ln(No/N) = kt No = 40g N = 5 k = ? t = 90 min Solve for k Then k = 0.693/t1/2 Solve for half life in minutes. Another way to do it is (40/2*x) = 5 solve for x Then 90 minutes/x = time for 1 half life. You should get the same answer both ways.
December 15, 2014

Chemistry
Because Pb(NO3)2 is a salt and PbCl2 is a ppt. This is a double displacement reaction which is spontaneous because PbCl2 is insoluble. The insoluble ppt of PbCl2 drives the reaction forward (Le Chatelier's Principle) and the reaction proceeds to completion. Other reasons ...
December 15, 2014

Science
We have cold fronts and warm fronts. Cold air weighs more than warm air (technically that isn't right--I should say cold air has a higher density than warm air) so the air pressure varies. Why as we go up do our ears pop. As we ascend, the column of air at higher altitudes...
December 15, 2014

general chemistry
How do these things ionize? NaCl ==> Na^+ + Cl^-. Two ions produced NH4Cl ==> NH4^+ + Cl^-. Two ions. You do the others. I'll be glad to check your work.
December 15, 2014

general chemistry
%H2O for Li(OH)2.H2O = (18/60)*100 = ? Find %H2O in all of them, the ones with the most percent water will lose the most mass for a 1.0 g sample.
December 15, 2014

Chemistry
I think your problem may be that you simply must recognize that there are SEVERAL definitions. An acid/base pair by the Arrhenius definition may not be an acid/base pair by the Lewis definition which may not be an acid/base pair by the Bronsted-Lowry definition, which may...
December 15, 2014

Chemistry
The easy way is to say I used good old fashioned reasoning but that's not the kind of answer you're looking for. I think q comes out to be approx 115 kJ; let's just say that that's the answer for q = mcdT. Then here is what we have. The molar mass of ethane (...
December 15, 2014

Chemistry
Yes, that approach will get you there, at least that's a good place to start. How much heat do you need to heed the water? That's q = mass H2O x specific heat H2O x (Tfinal-Tinitial) = ? Then 3120.6 kJ/mol x (grams ethanol/2*(molar mass C2H6) = q Solve for grams ...
December 15, 2014

chemistry
I'm pretty sure it can't be b since if the repulsive forces overcome any attractive forces they will NEVER get together. I would go with d although I don't like that answer to describe how bonds are formed. The D answer focuses on the nucleus and omits any ...
December 15, 2014

chemistry
mols KClO3 = grams/molar mass = ? Then M = mols KClO3/L solution = ?M
December 15, 2014

chemistry
Your equation is right and yes all are aq, There are no ppts. However, the equation is not balanced. You need a coefficient 2 for NaOH. Yes 60 mols H2SO4 With the balanced equation that makes 120 mols NaOH Then redo your work from there. If everything else is ok that will make...
December 15, 2014

Chemistry
We did this before and you are right, c is the correct answer. A is correct for 1 molecule (although some are uncomfortable with the word in this sense---I'm not). So 1 + ion and 1 - ion, such as Na^+ + Cl^- gives only 1 formula unit (1 molecule) of NaCl. The question is ...
December 15, 2014

chemistry
1 mg/kg = 1 ppm xmg/2.5 kg = 600 Solve for x mg.
December 15, 2014

chemistry
Yes, but you can check these things by substituting and see if the answer you get is 5%. (1.5/30)*100 = ? Yea! It's 5%.
December 15, 2014

chemistry
(1.5/x)*100 = 5%
December 15, 2014

chemistry
You can't get away with lead2 nitrate. It must be lead(II) nitrate. Pb(NO3)(aq) + 2NaI(aq) ==> PbI2(s) + 2NaNO3(aq)
December 15, 2014

Chemistry
If you carry that out to one more place MAYBE it is (41.74*3.65/4.41) = 34.5467 and if I round that to 34.55 and round that to 34.6 to three significant figures; otherwise, your procedure looks ok to me.
December 15, 2014

chemistry(ppm parts per million)
If the problem is 2.34 mg in 3.5 kg and convert to ppm, that is 2.34/3.5 = 0.666 ppm
December 15, 2014

chemistry(ppm parts per million)
If the problem is 2.34E-6/3.5 = then the answer is 6.68571E-7
December 15, 2014

chemistry(ppm parts per million)
punch in 2.34E-6, hit the divide button, and punch in 3.5. Hit the enter button.
December 15, 2014

chemistry
You left out the 100. It's (50/s)*100 = 58 s = 5000/58 = s = ?
December 15, 2014

chemistry
Close. You can check you answer by plugging in your answer. See if it is. (50/0.86)*100 = ? I get about 586% so 0.86 must not be right. If you will post your work I will find the error. I think it's must a math error.
December 15, 2014

chemistry
(g solute/g solution)*100 = % You have g solute and %, solve for g solution.
December 15, 2014

chemistry(solutions)
% w/v = (g solute/mL solution)*100 = ?
December 15, 2014

Science Help!!!!
You're guessing.
December 15, 2014

Science Help!!!!
I don't think you understand the question or the answer.
December 15, 2014

Chemistry
Please note that you will not get anywhere in chemistry, probably flunk out, it you don't find and use the caps key. You must know where it is for you started sentences with a capital letter and I must congratulate you on ending the sentences properly BUT lower case and ...
December 15, 2014

chemistry
See below.
December 15, 2014

Chemistry
The nomenclature is confusing. The choices could be 1st I.P., 2nd IP etc OR Do 2nd, 1st, etc refer to the number of the electron. If so then the O atom would look like this. O [1,2] [3,4] [5,6,7,8] corresponding to O 1s2....2s2....2p4 I'm guessing it means 1st means IP for...
December 15, 2014

Chem Moles
N2 + 3H2 ==> 2NH3 We have 3.0 mols H2. We can convert that to any thing with the proper factor. The factor is made using the coefficients in the balanced equation. 3.0 mol H2 x factor = mols NH3. 3.0 mols H2 x (2 mol NH3/3 mol H2) = ? See that mol H2 cancel and leaves mol ...
December 15, 2014

Chem Moles
All of this type question are solved by the factor method using the coefficients as factors. Here is the first one; you see if you can do the second one. 3.00 mols H2 x (2 mols NH3/3 mols H2) = 3.00 x 2/3 = 2.00 mols NH3 produced.
December 15, 2014

chemistry
Nancy, Jessica, anonymous? See my response below under anonymous. You get better service here if you don't change screen names.
December 15, 2014

chemistry
No. We don't do homework for you. We HELP you do your homework. You aren't asking for help; you're asking me to do your homework for you. We are tying to help so you will learn how to do these things yourself. If you need help you've come to the right place. If...
December 15, 2014

chemistry
21.4*x = 1280. Solve for x.
December 15, 2014

chemistry
The balanced equation minus the phases to save typing space. 2C8H18 + 25O2 ==> 16CO2+ 18H2O 21.4 mpg x #gallons = 1280 miles Solve for gallons needed. . Convert gallons octane to L octane. Using density convert L octane to grams octane. Convert g octane to mols octane. mol...
December 15, 2014

chemistry
You wrote the choices but not the question.
December 15, 2014

chemistry
Leo, I can't decipher the symbols. BTW, did you omit the exponent on Ka = 3.5 x 10?
December 15, 2014

chemistry
I would like to know what you don't understand about this. It would help answer the questions. H2A ==> H^+ + HA^- HA^- ==> H^+ + A^2- Surely you know how to write Ka1 and Ka2 expressions. If not explain and I can help you through them. b. (H2A) > (H^+) = (HA^-) &...
December 15, 2014

Chemistry 120
KOH = 1.9E-6 pOH = -log(KOH) Then pH + pOH = pKw = 14 You know pOH and pKw, solve for pH.
December 15, 2014

chemistry
I confirm that.
December 15, 2014

Chemistry
I think I worked this yesterday. Let me know if this is not the same problem. http://www.jiskha.com/display.cgi?id=1418542095
December 15, 2014

chemistry
S is 1s2 2s2 2p6 3s2 3p4. You are right with either c or d. I don't know what your study guide is calling 3p1 and 3p4. The 3p configuration is ud u u where up is the spin one way and d is spin the other way. he least amount to ionize with be the two outside (either of the ...
December 15, 2014

Science Help!!!!
! and 2 are ok now.
December 15, 2014

Science Help!!!!
3 is ok.
December 15, 2014

Science Help!!!!
I don't agree with 1 and 2. You didn't answer 3.
December 15, 2014

Science Help!!!!
I agree with your choices.
December 15, 2014

Chemistry
-1. At should have seven (7) electrons in its outer shell and needs 1 more to make eight (8).
December 15, 2014

Science Help!!!!
yes
December 15, 2014

Physical science
If you want to balance what you've written it is MgSO4 + 2NH4OH ==> (NH4)2SO4 + Mg(OH)2 and you are correct that what you have written is a double replacement reaction. Technically that is not correct because NH4OH does not exist. Ammonia is NH3 gas and if you have a ...
December 15, 2014

Chemistry
It's the number of O atoms in the polyatomic ion. Na2SO4 is sodium sulfATE. Na2SO3 is sodium sulfITE. NaNO3 is sodium nitrATE. NaNO2 is sodium nitrITE Na3PO4 is sodium phosphATE. Na3PO3 is sodium phosphITE There is arsenate and arsenite There is chlorate and chlorite There...
December 14, 2014

Chemistry
b was your first choice a few days ago.
December 14, 2014

Chemistry
I think the statement you have written (I assume a quote from your study guide) is very good and states the concept very plainly; however, I don't think it points the way to any of the choices. The quote also does a good job of repeating what I said before; i.e., that it ...
December 14, 2014

Chemistry
mols NaOH = M x L = ? Convert mols NaOH to mols H3A using the coefficients in the balanced equation. Then M H3A = mols H3A/L H3A. for b. M = mols/L solution. Convert mols to grams. g = mols H3A x molar mass H3A to give you grams/L. You want g/100 so divide grams by 10 to give ...
December 14, 2014

chemistry
H2SO4 + 2KOH ==> K2SO4 + 2H2O mols KOH = M x L = ? Convert mols KOH to mols H2SO4 using the coefficients in the balanced equation. Then M H2SO4 = mols H2SO4/L H2SO4
December 14, 2014

Chemistry
Electrons are in the 3d (or 4d or 5d) levels and sometimes some of those 3d electrons are involved in bonding.
December 14, 2014

Science Help!!!!
Does solar power require a turbine to generate electricity?
December 14, 2014

Science Help!!!!
Yes, but fossil fuel emissions are not the only ingredient.
December 14, 2014

P.E. help
Callie, you are guessing again. Surely your study guide doesn't suggest that.
December 14, 2014

chemistry
I don't know. One of the problems with a question of this type is that we are trying to compare micro concepts to macro events. I can see how A might be true if we think in terms of a student spending an hour in English, an hour in history class, an hour in algebra class, ...
December 14, 2014

chem
What do you understand and not understand about this. I can balance it but we need to work so you can.
December 14, 2014

Chemistry
H2SO4 + 2NaOH ==> Na2SO4 + 2H2O mols NaOH = M x L = ? Convert mols NaOH to mols H2SO4 using the coefficients in the balanced equation. Finally, M H2SO4 = mols H2SO4/L H2SO4.
December 14, 2014

Chemistry
NiCl2 + 2KOH ==> Ni(OH)2 + 2KCl mols NiCl2 = M x L = approx 0.006 but you need a more accurate answer. mols KOH = M x L = approx 0.07--again you need a more accurate answer. mols Ni(OH)2 formed if all NiCl2 used will be 0.006 x 1 mol (Ni(OH)2/1 mol NiCl2) = approx 0.006 ...
December 14, 2014

Science
If you have tables or graphs showing the solubility, post that information and we can help. I don't know of anyone who has all of that solubility information memorized.
December 14, 2014

Chemistry
I obtained 251.568. I don't know how many significant figures you have on that 773 but everything else you have is 4 places. If you can have 4 s.f. I would round that to 251.6 J.
December 14, 2014

Chemistry
No. Note the problem specifically suggests you pay attention to the units and you didn't do that. If you use 1.977(2.603) that gives you units for work in L*atma and you want J here. You convert L*atm to J by L*atm x 101.325 = J. Your sign of - is correct. The sign for 773...
December 14, 2014

gen chem (already have answer)
How much (pick any product--I'll pick SO3) mols SO2 will be formed from 0.25 mols P4S6 if we had all of the KClO2 we needed to react with all of the P4S6? That's 0.25 mols P4S6 x (6 mols SO2/1 mol P4S6) = 0.25 x 6 = 1.5 mols SO2 formed. Now how many mols SO2 will be ...
December 14, 2014

basic chemistry
I just looked at Damon's response again and I don't see anything wrong with it. The answer I posted is almost the same as the answer he posted. The only difference is he rounded the molar mass of Fe3O4 from 231.54 (which I used) to 232. Other than that there is no ...
December 14, 2014

basic chemistry
Yes, Damon's response, as noted in that response, is he though it was 1.38E3 L (and not mols). Here is the question again. Fe3O4 + 4 H2 -> 3 Fe + 4 H2O What mass (g) of Fe3O4 would be needed to react with 1.38 x 10^3 mol H2? 1.38E3 mols H2 x (1 mol Fe3O4/4 mols H2) = ...
December 14, 2014

basic chemistry
Do you want me to look at it and repost here if needed?
December 14, 2014

basic chemistry
Damon answered your question on your first post and I answered the one on moles below that. What's the problem?
December 14, 2014

Chemistry
I've never fully understood why students have trouble with conjugate acids/bases. If you want the conjugate acid of something, add a H^+ to what you have. If you want the conjugate base of something, take a H^+ away from what you have.
December 14, 2014

chemistry
Fe3O4 + 4H2 ==> 3Fe + 4H2O 115 mols H2 x (3 mols Fe/4 mols H2) = ?
December 14, 2014

chem
So the volume will be area x thickness = 55 cm x 3E-4 cm = ? mass = volume x density = ?
December 14, 2014

chemistry
No. Consider Na^+ and Na and Cl^- vs Cl2.
December 14, 2014

chemistry
[24.3050*(0.7899)] + [24.9858*(0.1000)] + [25.9826*(0.1101)] = ? = atomic mass Mg
December 14, 2014

Chem
I would rank these Br < P < Na < Ca
December 14, 2014

chemistry
I2 is held together by covalent bond; therefore, you would expect it to dissolve in a non-polar solvent (cyclohexane) and not be very soluble in a polar solvent (H2O).
December 14, 2014

Science Help!!!!
I think A is the answer but I'm not a land manager. I think mining anything from underground, replacing the soil and replacing the plants sounds like land reclamation (reclaiming the land) to me. B is cutting all the timber, not doing anything to the land, and letting it ...
December 13, 2014

Science Help!!!!
Do you know what desertification means?
December 13, 2014

chemistry
If solubility is 39 g/100 mL, how many grams will dissolve in 250 mL? That's 39 g x (250 mL/100 mL) = 97.5 g. The problem states that 83 g has been dissolved; the solution can hold 97.5 so the solution is .......?
December 13, 2014

chem
Mg + 2HCl ==> MgCl2 + H2 mols Mg = grams/molar mass = ? Using the coefficients n the balanced equation, convert mols Mg to mols MgCl2. Now convert mols MgCl2 to grams. g = mols MgCl2 x molar mass Mgcl2.
December 13, 2014

Chemistry
That might work but it's the long way around AND you don't know mols KCl in the mixture, although you can calculate mols KCl but only after you've worked the problem. I would use the equation you have to convert mL O2 gas to mols O2 and convert that to mols KClO3. ...
December 13, 2014

chemistry
Three equations will work most of the heat problems. When you are heating WITHIN a phase (raising a liquid @ one T to liquid at another T; solid at one T to solid at another T; gas at one T to gas at another T) use q = mass x specific heat in that phase x (Tfinal-Tintitial) ...
December 13, 2014

chemistry
I believe the way to approach this problem is through mole fraction. With all materials in the gaseous phase one can use volume as mols; first determine the limiting reagent. 100 mL NO will give you 100 x (2 mol NO2/2 mols NO) = 100 mL NO if we had all of the O2 needed. For ...
December 13, 2014

science
My personal opinion is that orientation make sno difference. Also I think the type of light is relevant. A bright white light vs a yellow light vs a uv light I think would make a huge difference. I don't know about C since I don't know the behavior of young vs old ...
December 13, 2014

Chemistry
Yes, heed Bob P's advice. CO means carbon monoxide, Co means cobalt, co is a abbreviation for company.
December 13, 2014

Chemistry
c1v1 = c2v2 5.2M x v1 = 0.04 x 81.0 Solve for v1.
December 13, 2014

Chemistry
E = h*freqency or E = hc/wavelength in m
December 12, 2014

chemistry
That is correct for those mentioned.
December 12, 2014

To Drbob222
Thank you clarifying that.
December 12, 2014

Chemistry
I think the photoelectric effect shows that A is true. (B) Electrons can be thought of as particles or as waves; certainly they have a wave nature but i wouldn't call them composed of light. C and D are not reasonable.
December 12, 2014

chemistry
(x g solute/150.0)*100 = 1.30% Solve for x grams and subtract from 150. 150-x = grams H2O
December 12, 2014

chemistry
(15g/x g)* 100 = 20.0%
December 12, 2014

L.A. Not really important but want an answer. . .
I Googled "types of poems" and obtained a bunch of hits. Try it.
December 12, 2014

Chemistry
First determine the molarity of the HCl. mols NaOH = M x L = ? mols HCl = mols NaOH M HCl = mols HCl/L solution. You know mols and L(convert mL to L), solve for M. M HCl means mols/L solution Convert mols HCl to grams HCl. mols = grams/molar mass. You know molar mass and mols...
December 12, 2014

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