Sunday
February 1, 2015

Posts by DrBob222


Total # Posts: 46,676

Chem
See my response to your duplicate post above. Since you didn't balance the equation I think all of your work needs to be redone. For openers I don't believe O2 is the LR.
December 30, 2014

science
When I was in school this was explained by "increased molar mass". The explanation these days is "London Forces" or "intermolecular forces".
December 30, 2014

science
CaCO3(s) --> CaO(s) + CO2(g) initial mass = 15.08g final mass...= 9.83 mass CO2 lost = 15.08-9.83 = ? Convert mass CO2 to mass CaCO3 using the coefficients in the balanced equation. %CaCO3 = (mass CaCO3/mass sample)*100 = ?
December 30, 2014

CHEM
This is a limiting reagent (LR) problem and you know that because amounts for BOTH reactants is given. mols Pb(NO3)2 = grams/molar mass = ? mols Al2(SO4)3 = grams/molar mass = ? Using the coefficients in the balanced equation, convert mols Pb(NO3)2 to mols either product. Do ...
December 30, 2014

CHEM
See your CaCO3 problem. Post your work if you get stuck.
December 30, 2014

chemistry
Please clarify this question. I can bring up the site but don't know what you want to do with it. If you have a question, I suggest you post it instead of trying to copy it.
December 30, 2014

science
Damon is absolutely right. The problem is much larger than evolution. For the last 50 years the government has pumped millions into math and science projects aimed at better teaching of these subjects and my opinion is that much of it (most of it?) has failed. Witness the ...
December 29, 2014

chemistry
Use the information in the previous post to see how far you can get in this one. Post your work and I'll help you through if you get stuck.
December 29, 2014

chemistry
(base) = (sodium acetate) = grams/molar mass/0.100 = ?M. (acid) = (acetic acid) = 1.20M x (20/100) = ?M pH = pKa + log (base)/(acid) Substitute and solve for pH. The answer should be about 4.8 or so.
December 29, 2014

chemistry
H2 is a smaller molecule than O2; it effuses through a small hole faster than any other gas. Look up Grahams's Law for further information. The rate of effusion is indirectly proportional to the square root of the molar mass.
December 29, 2014

General Chemistry!!!!
How can we help you? There are many good chemistry books on the market. One I like is "General Chemistry" by Whitten, Davis & Peck although it may be a little dated. It's published by Saunders.
December 29, 2014

science
http://www.flu.gov/pandemic/history/
December 28, 2014

chemistry
You need the equation, Kp or Kc, and the conditions (pressure and temperature). .............PCl5 ==> PCl3 + Cl2 I...........4 mols......0.....0 C..........-2.4........2.4....2.4 E..........1.6.........2.4....2.4 At equilibrium, (PCl5) = 1.6/V (PCl3) = 2.4/V (Cl2) = 2.4/V
December 27, 2014

science
q = mass H2O x specific heat H2O x (Tfinal-Tinitial) mass H2O = 1000 g specific heat H2O = 1 cal/g*c Tfinal = 50 Tinitial = 20
December 26, 2014

Chemistry
Is your prof picky about significant figures. You have too many in some cases.
December 22, 2014

Chemistry
Propanol is higher largely because it is a larger molecule (molar mass is higher) and higher dispersion forces. Are you sure the ionic character is higher in LiI? Li has electronegativity (EN) of about 0.98, K is about 0.82.
December 22, 2014

Science - MIT
You're question isn't clear and you listed only one choice; however, what you have listed is the possible choice for the 4p1 electron added.
December 22, 2014

chemistry
(P1V1/T1) = P2V2/T2)
December 22, 2014

chemistry
What is cao? You won't get far in chemistry unless you find and use the caps key. Note that CO, Co, and co are different. Do you mean CaO? CaO + H2O ==> Ca(OH)2 mols Ca(OH)2 = grams/molar mass = ? mols CaO = mols Ca(OH)2
December 22, 2014

science
KE = 1/2 m*v^2
December 21, 2014

correction--Chemistry!
Ignore the last two lines; i.e., Xa liq = and B = Po of 200. Those were below my screen from earlier attempts and I didn't get them erased. The rest of it looks ok to me.
December 21, 2014

Chemistry!
vapor pressure A = X vapor pressure B = Y total p of vapor = Ptotal = Xav + Ybv Xa in vapor = Xav/(Xav + Ybv) = 0.3 Xb in vapor = Ybv/(Xav + Ybv) = 0.7 In liquid Xa liq = Poa liq*0.3/Ptotal vapor = Poa liq/(Xav + Ybv) Similarly for Xb liq = Xb = Pob liq/(Xav + Ybv) I hope this...
December 21, 2014

science
I don't see anything you posted.
December 21, 2014

Chemistry
H bonding occurs when you have N (as amines), O(as in alcohols etc) and F. Alkanes and alkenes have only dispersion forces. You can usually pick out dipole-dipole forces because the molecules are dipoles. (I consider H bonding to be a special case of dipole-dipole bond). Ion-...
December 21, 2014

chemistry
2NH3 ==> N2 + 3H2 When working with gases one can use volume directly as mols and not go through the conversion step of mols = L/22.4. 100 cc NH3 x (3 mols H2/2 mols NH3) = 100 x 3/2 = ? cc H2
December 21, 2014

Do you guys get Christmas off?
I don't believe you will find any of us neglecting our families. We can come and go as we please. Our families usually don't live with us anymore but have families of their own and their children become our grandchildren and great grandchildren.
December 21, 2014

chemistry
Use PV = nRT and solve for n = number of mols. Then n = grams/molar mass. You know grams and moles, solve for molar mass.
December 21, 2014

chemistry
(P1V1/T1) = (P2V2/T2)
December 21, 2014

chemistry
Two points. The number 1 is not the letter l and you DON'T use lower case for all chemical symbols. Potassium chlorate is KClO3. First write and balance the equation. 2KClO3 ==> 2KCl + 3O2 mols KClO3 = grams/molar mass = ? Using the coefficients in the balanced equation...
December 21, 2014

Science
PE = mgh.
December 21, 2014

Chemistry
None unless you react it with something to provide CO2.
December 21, 2014

physical science
I have news for you. MgO and NaCl won't react as solids and they won't react in solution. However, I can write and balance the equation for you. MgO + 2NaCl ==> MgCl2 + Na2O. Aqueous reactions go to completion for one of three reasons. 1. A gas is formed. 2. A ppt ...
December 20, 2014

question on theft
I attended an eight week course (once a week) on "Thinking About Thinking" this last year. We learned about Socrates, Plato, Aristotle, Japanese culture, Islamic culture. etc. According to the prof it is in Islamic culture. Not only justified but the right thing to ...
December 19, 2014

Chemistry
Here is the problem stated differently. You have a solution of 37% HCl, density 1.19 g/mL. You want to use this solution to prepare 250 mL of 2.5 M HCl. First determine the molarity of the concentrated HCl (the 37% material). 1.19 g/mL x 1000 mL x 0.37 x (1/36.5) = ...
December 19, 2014

Ms. Sue
Skye, I thought we answered this correctly last night.
December 18, 2014

Science
Yes but I think the word is osmosis.
December 18, 2014

Chemistry
mols HCl = M x L = ? mols NaOH = the same M NaOH = mols NaoH/L NaOH
December 18, 2014

Chemisty
You didn't say what units. I could say the concn is 6.4/0.125L
December 18, 2014

chemistry
Reverse equation 3 and add to the reverse of equation 2 and add twice equation 3. When you get the final equation it will be 1/2 of what you want; just multiply that by 2. When reversing equations change the sign of dH. When multiplying equations, multiply the dH value by the ...
December 18, 2014

Chemistry
Steve answered your question.
December 18, 2014

science
q = 1500J = mass Au x specific heat Ar x (Tfinal-Tinitial)
December 18, 2014

science
If you wrote the equation right it should be obvious. 2NaOH + H2SO4 ==> Na2SO4 + 2H2O 2 mols NaOH neutralize 1 mol H2SO4.
December 18, 2014

chemistry
dHf rxn = (n*dHf products) - (n*dHf reactants). You have dHf rxn, plug in the dH for the CO2 and the H2O and calculate dHf C2H2.
December 18, 2014

CHEMISTRY
1. Note the correct spelling of celsius. 2. It won't make any difference at all. You're working with this equation. q = mass x specific heat x (Tfinal-Tinitial). As an example, let's say a REAL thermometer reads Tfinal as 50 C and Tinitial as 25 C, then delta T is ...
December 18, 2014

chemistry
AgNO3 + HCl ==> AgCl + HNO3 mols AgNO3 = grams/molar mass Using the coefficients in the balanced equation, convert mols AgNO3 to mols AgCl. Now convert mols AgCl to grams. g = mols x molar mass.
December 18, 2014

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

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
You're right. It's a s.f. thing and I should have caught it. My answer is 0.887216 which I would round to 0.8872
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

Pages: <<Prev | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | Next>>

Members