Thursday
December 18, 2014

Posts by drbob222


Total # Posts: 46,131

Chemistry
Not yet. You're right that mols CO2 = mols CO since that is the limiting reagent and 2 mol CO2 are formed for 2 mols CO initially. Next you calculate mols O2 used by that 1.44 mols CO, subtract from th 3.03 mols O2 you started with (3.03 is what I calculated but you need ...
December 18, 2014

Chemistry
You will need a balanced equation. Use PV = nRT and 1.14 atm to calculate n for mols CO to start. Then use PV = nRT and total P to solve for total mols. Total mols minus CO mols = mols O2 added. I suspect this is a limiting reagent problem but regardless you check that as a ...
December 18, 2014

Science Please Check!
I agree with your choice.
December 18, 2014

incomplete--science

December 18, 2014

Chem
See my response below. It's better to keep the thread going; otherwise we must scroll back and forth to keep up with the numbers.
December 18, 2014

Chemistry
You're welcome.
December 17, 2014

Chemistry
I would convert torr to atm (torr/760) and use 0.08206 for R.
December 17, 2014

Chemistry
22.4 L/mol is the volume at STP and you don't have STP conditions. Balance the equation, find n O2, then use PV = nRT and substitute the conditions of P and T listed (remember T must be in kelvin) and solve for V in L.
December 17, 2014

Chem
PV = nRT If you use P in kPa, R is 8.314 or if you use P in atm (627 kPa/101.325) then R is 0.08206. Solve for n.
December 17, 2014

Chem
P1 = 1.035 atm and T1 is 273.15 + 28 = 301.15 P2 = ? and T2 = -15 + 273.15 = 258.15 (1.035/301.15) = (P2/258.15) P2 = 1.035*258.15/301.15 = 0.887 You must have made an error in solve that proportion. My answer seems to agree.
December 17, 2014

Chem
(P1/T1) = (P2/T2) Don't forget T must be in kelvin.
December 17, 2014

Chemistry
In one step it is 1.09 g/mL x 1000 mL x 0.18 x (1/36.5) = ? mass of 1000 mL solution is 1.09 x 1000 mL = and let's call that y. Only 18% is HCl. How many grams is that? That's y g x 0.18 = ? and that is z grams HCl. Since 1 mol has a mass of 36.5 g, how many mols is ...
December 17, 2014

chemistry
Is that 5.25% w/w (m/m)? (X g/500)*100 = 5.25%
December 17, 2014

chemistry 11
Follow up if need be. You want 0.3 mol of Ac^-. That will be 1/2 that or 0.15 mol of Ca(Ac)2 since 1 mol Ca(Ac)2 contains 2 Ac^- ions. Then M = mols/L M = 0.5M mols = 0.15 L = ? Let me try to do this the way you started. Start with what you have and convert stepwise to end up ...
December 17, 2014

Science
Do you mean you hav 16M KOH but you need 15 mL of 2.5M? Then c1v1 = c2v2 2.5*15 = 16*v2 v2 = ? You want (2.5*15/16) mL of the 16 M stuff and add water to a total of 15 mL.
December 17, 2014

chemisty
M CuBr2 = 1.25. There is 1 Cu atom in 1 molecule CuBr2; therefore, M Cu^2+ ion is 1.25. There are 2 Br atoms in 1 molecule CuBr2; therefore, M Br^- = 2*1.25 = ? mols ion = M x L = ? Convert to g; g = mols x ionic mass
December 17, 2014

Chemistry
6.00 M means 6.00 mols H2SO4/L solution. 1 mol H2SO4 = 98 g; 6 mols approx 600 g but you need to do it more accurately. That's 600 g/L. Use density to convert to ?g/?g solution, then convert that to g solute/100 g solution.
December 17, 2014

chemistry
https://www.google.com/search?q=how+to+make+a+smoke+bomb.&ie=utf-8&oe=utf-8
December 17, 2014

chem
I strongly suggest you find the caps key and use it. If you are working on equilibrium problems SURELY you've had enough chemistry to know that lower case and upper case mean something different. See CO, Co, co. You have used m; I assume that should be M since you didn'...
December 17, 2014

science
1 J/s = 1 watt so 50,000 J/7s = ? watt
December 17, 2014

chemistry
It is true; equilibria are not static.
December 17, 2014

Chemistry
Frankly I never did much with alloys; however, I know interstitial means "in between" atoms while substitutional must be one atom replacing another; therefore, I go with B.
December 16, 2014

Chemistry
I agree with A.
December 16, 2014

Chemistry
I'm inclined to think c. You already have a cation ad an anion (a + and a - charge) and distance I think is how strong that attraction is. It varies as 1/r^2.
December 16, 2014

chemistry
I think so. Of course few of us use antennas anymore; most of use use cable or a dish company. The cable sends the signal by wires and the dish on top of our house collects the signal from a satellite.
December 16, 2014

chemistry
Here is a fairly well written general explanation. http://www.darvill.clara.net/emag/ Here is one that is a little more complicated. http://en.wikipedia.org/wiki/Electromagnetic_spectrum When Steve answered your question yesterday by asking what did you know that used an ...
December 16, 2014

Chemistry
I agree with c.
December 16, 2014

Thank you
Thanks, you too. Enjoy your time off. :-)
December 16, 2014

science
You need to be more specific with your question.
December 16, 2014

chemistry please help drbob222
25.0 x 0.357 = mL x 0.246 mL = 36.3 mL. If we assume volumes are additive (they aren't) then 36.3-25.0 = ? mL water to be added to make a total of 36.3 mL.
December 16, 2014

CHEM MOLES !@@!
Are you having that much trouble with mols? :-/. Don't sweat it. Almost every problem comes down to mols. There are two ways to calculate mols. 1. When you have a solution of known molarity, then mols = M x L = ? 2. When you have a mass of something, then mols = grams/...
December 16, 2014

Tips Plz
I want to add one more suggestion to what my colleagues have offered. You already know you can't memorize your way through math. The trick is to UNDERSTAND THE CONCEPT, understand the reasoning, understand the procedure. The more you really understand about math the less ...
December 16, 2014

chemistry. please help drboz222
I've always wanted a graphing calculator but never had one. The answer is not 0.7 ppm which may be why you were told it wasn't right. 2.34 mg/3.5 kg = 0.66857 ppm which I would round to 0.669 ppm. My response above does not contain anything about multiplying by 10^6 ...
December 16, 2014

chemistry. please help drboz222
I don't know what kind of calculator you're using but I suggest you get a different one. ;-). Just in my head I can see that 2/3.5 is nowhere near 1.5E12. 2/4 is about 0.5 and 2/3 is about 0.7 so the answer MUST be somewhere in that vicinity.
December 16, 2014

chemistry. please help drboz222
There are two very easy formula to remember for ppm. If I'm dealing with solutions I remember 1 ppm = 1 mg/L If I'm dealing with solids (or at least with kg), I use 1 ppm = 1 mg/kg. So ppm for this is (2.34 mg/3.50 kg) = ? That sure makes it simple doesn't it? What...
December 16, 2014

Chemistry
I'm not a big MO guy but I would look at b as the false statement.
December 16, 2014

chemistry
What's wrong with 52.0*35.7 = c*65.9 and solve for c with units in %.
December 16, 2014

chemistry
I'll do two and show you how. He. Atomic number is 2 from the periodic table, look at the periodic table and round the atomic mass to a whole number. In most cases that will give you at least one of the isotopes with that mass number. For He that will be 4. That would be ...
December 16, 2014

chemistry
The actual yield is 28.5 L according to the problem. Try it. Isn't (28.5/44.8)*100 = 63.62%? Sure is.
December 16, 2014

chemistry
I don't think so but try it and see. Most answers you can check yourself. (L solute/L solution)*100 = % (1.50/22.5)*100 = 6.67% which isn't 5% so 22.5 mL must not be right.
December 16, 2014

chemistry
Allison, I assume you meant the ice cub had a mass of 4.3 g and a volume of 5.0 mL.
December 16, 2014

Chemistry (Solutions)
1500 what? 1500 mg is correct.
December 16, 2014

Chemistry Honors
See your MgSO4 problem below. Same process.
December 16, 2014

Chemistry Honors
mols MgSO4 neded = M x L = 0.20 M x 0.100 L = 0.02 mols. Then M MgSO4 = mols MgSO4/L MgSO4. 0.50 = 0.02/L, solve for L.
December 16, 2014

Chemistry Honors
I guess I would vote for D but I don't see much wrong with A.
December 16, 2014

Chemistry Honors
The correct answer is not listed but the answer you're supposed to pick is c. The reason it isn't the correct answer is because you're assuming the 4mL adds to the 6 mL to make 10.0 mL solution. BUT solutions are not additive. c should say it this way. "He ...
December 16, 2014

Chemistry
Yes, the crystal lattice can be used to calculate the density. The theory is that the density of a unit cell is the same as the density of the macroscopic unit. So the fcc has 4 atoms/unit cell. That's right. The mass of a unit cell then is 4 * 26.98/6.02E23 = mass unit ...
December 16, 2014

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

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