Wednesday
September 2, 2015

Posts by DrBob222


Total # Posts: 49,866

Chemistry/reading
It's trying to tell you (and not doing a great job of it) that the He atom must contain something not in the H atom. The H atom has 1 proton and the He atom has 2. Since the He atom weighs 4 times as much as the H atom, it must contain something else that contributes to ...
July 1, 2015

Chemistry
The only way I can answer this question is to write your paper for you and I don't want to do that. I suggest you Google and find the material. I think you can find all you want from three Googles; i.e., "discovery of electrons", "discovery of protons" ...
July 1, 2015

Chemistry
If you draw it out as a 2,2-diethylpent-3-ene but show one of the ethyl groups as -CH2CH3 instead of C2H5, it adds another C to make the longest chain a hexene. From there you add the substituents.
July 1, 2015

chemistry
See your other post.
July 1, 2015

chemistry
3.18 mol H x (4 mols O/12 mol H) = ?
July 1, 2015

Science
The main difference is that the OH group in an alcohol is attached to an aliphatic (straight/branched chain) group while the OH in phenol is attached to an aromatic ring.
July 1, 2015

math 0310
I would let x = speed of train B and x + 20 = speed of train A You know the times are equal for the two trains so distance = rate x time or time = distance/rate [270/(x+20)] = (230/x) Solve for x and x + 20.
June 30, 2015

chemistry
First, the law, which I copied verbatim from Wikipedia. "If two elements form more than one compound between them, then the ratios of the masses of the second element which combine with a fixed mass of the first element will be ratios of small whole numbers." Note ...
June 30, 2015

Science
A pH of 0 is quite possible. If pH = 0 then (H^+) = 1M and that is common. Your book SHOULD SAY pH<7 is acidic and pH>7 is basic. A pH of 1 to 7 being acidic is not right; pH = 7 is not acidic although 1 TO (not through) 7 will be acidic.
June 30, 2015

oops--Chemistry
What you have written is correct; however, I don't think it covers the subject that well. I would consider modifying what you have written. Also, I think it would be great to add what it does and I don't think that strays from the subject at all. Here is a link from ...
June 30, 2015

Science
Use (P1V1/T1) = (P2V2/T2) You have T1 = 273, make T2 1/5 larger. You have 760 for P1, make P2 1-1/2 times that.
June 30, 2015

Utlwanang Barolong secondary school
A weird question; i.e., all of that information about vinegar but the pH of the NaOH has nothing to do with it. However, pOH = -log(OH^-) = -log(0.5M) = ? Then pH + pOH = pKw = 14. You know pOH and pKw, solve for pH. I get about 13.7.
June 30, 2015

Chemistry
mols = M x L = ? There are 6.02E23 sulfate ions in 1 mol. So 6.0E23 x # mols = ?
June 30, 2015

nope--Chemistry
ChuLbuLi has erred. mass N is 14. mass N2 is 28; therefore, n = 5.25/28 = ? P must be in atmosphere if you use R as 0.08206 L*atm/mol*K. P = 74.6 cm/76.0 cm = ? atm.
June 30, 2015

Chemistry
PV = nRT
June 30, 2015

Chemistry
This seems like an odd question to me. All of that information about B but no question about it. mols HCl = grams/molar mass = ? Since that is g/dm^3 that gives you mols/dm^3
June 29, 2015

Chemistry Subatomic particles
This may provide some help. https://sites.google.com/site/daltonsatomictheorysite/home/changes-in-dalton-s-atomic-theory
June 29, 2015

Chemistry Subatomic particles
I think for the first, yes. Just a short summary of the work. For the second I would make the following observations: The question isn't clear as to WHAT you are to calculate. Is it the number of p, n, e, or the charge, or the mass or just what. I assume it is the number ...
June 29, 2015

Chemistry Subatomic particles
Here is a good link for neutrons. Experimental data came in about 1932 from scattering experiments in which Be metal was bombarded with alpha particles. http://hyperphysics.phy-astr.gsu.edu/hbase/particles/neutrondis.html You can get dates for the other discoveries by Googling...
June 29, 2015

Organic Chemistry
CH3OH + NaNH2 ==> CH3ONa + NH3
June 29, 2015

Chemistry
Bob Pursley answered this question for another student. Here is a link. Ignore my answer (except the pictures may help). Mr. Pursley's answer is better than mine. http://www.jiskha.com/display.cgi?id=1435608279
June 29, 2015

Chemistry
1. mols NH4NO3 = grams/molar mass = ? 2. Using the coefficients in the balanced equation, convert mols NH4NO3 to mols H2O. 3. Now use PV = nRT, substitute mols from above for n, use the conditions of P and T in the problem, solve for V in liters. Remember to change 350 C to ...
June 29, 2015

Chemistry
I think your explanation is good. Perhaps these images will help. That's all I could find. https://www.google.com/search?q=image+cross+section+copper+particle&tbm=isch&imgil=HL-PiOq6PSpFpM%253A%253Bb1KlgfLW3DflMM%253Bhttp%25253A%25252F%25252Fnewsoffice.mit.edu%25252F2011%...
June 29, 2015

Chemistry
The way the problem is stated makes it appear there is a lot of information that isn't used. Most of these problems want to know the pressure of the dry H2 gas at STP; however, this one just asks for pressure of dry H2 gas so I assume that is pressure at 25 C but dry gas ...
June 29, 2015

Chemistry
Let HB = benzoic acid I will use pKa 4.2 but you should use the value from your text/notes. You have 50 mL x 0.1M HB = 5 millimols. First calculate millmoles acid and base needed. pH = pKa + log (base)/(acid) 4.5 = 4.2 + log b/a 0.3 = log b/a b/a = 2 or base = 2*acid. This is ...
June 29, 2015

Chemistry
When you post a problem like this in the future you should include the pKa; otherwise, the answer I get won't be the same as the answer you get since texts differ in tabular values for Ka, Ksp, etc.
June 29, 2015

Chemistry
I don't know how moral these solution are, probably not moral at all. Do you mean molarity or molality? I assume you want molality since you gave no density of the solution. XEtOH = 0.05; therefore, XH2O = 0.95 Take 1 mol of solution; it will contain 0.05 mols EtOH and 0....
June 29, 2015

Chemistry
See your other post above.
June 29, 2015

Chemistry
This question (and the duplicate just before) makes no sense to me. There is no Keq given because the equilibrium lies far to the right; i.e., it essentially goes to completion. Another problem is that concentration of a solid makes no sense either. A third problem is that ...
June 29, 2015

Chemistry
See your other post.
June 29, 2015

chemistry
q = mass x specific heat x (Tfinal-Tinitial) q = 150 J; m = 10.5 g; sp.h. = 0.38 J/g*C; Ti = 25 C; Tf = ?
June 29, 2015

Science
Read this and put the answer in your own words. http://www.citycollegiate.com/daltons_lawXI.htm
June 28, 2015

Chemistry
You included numbers as an example. Personally, I think another example would be redundant but I don't know that it would do any harm if you think it would help.
June 28, 2015

Chemistry
I think you have written a very good explanation; however, please read over it before you submit it for your class since there are some repeated words (it helps it helps). Also I would place a period after proportions and start a new sentence with In other words, he used .....
June 28, 2015

Chemistry
The easiest answer is that there has been a chemical change and the properties of the products are not the same as the reactants. One atom of the element Na has lost an electron to become a sodium ion (a cation) and one atom of the element Cl has gained an electron to become a...
June 28, 2015

chemistry
Yes, Cl atom forms an anion by adding an electron. Cl + e ==> Cl^- or if you want the entire equation it is 2Na + Cl2 ==> 2Na^+ + 2Cl^-
June 28, 2015

chemistry
Reason through this. 1. You have 1620 cc gas at 15 C (273 + 15 = 288 K) and you want to know what it will be at 273. You know that T is getting smaller, you know V will get smaller so you multiply by a factor using temperature that will give you a smaller number; i.e., 1620 x...
June 28, 2015

chemistry
I notice the percents don't add up to 100%. Take a 100 g sample which gives you 15.12 g P, 6.841 g N 78.03g Br Convert to mols. 15.12/31 = mols P 6.841/14 = mols N 78.03/80 = mols Br Now find the ratio of those mols to each other with no number being less than 1.00. The ...
June 28, 2015

Science
1.5 what? You can work this a couple of ways. Use PV = nRT and solve for P and plug this back into PV = nRT with n = 1.2, P from above and all others being the same. A second way is to use ratio/proportion. (v1/n1) = (v2/n2) A third way is to use PV = nRT but modify that so ...
June 28, 2015

Science
0.02 mol urea x (1 mol/60.06) = 1.20 g. mass solution = volume x density = ? %by mass = [mass urea/mass solution]*100 = ? % by volume = [mass urea/250]*100 = ?
June 28, 2015

general chemistry
trigonal bipyramidal and not trigonal planar. Draw the Lewis dot structure. It is a AB5 structure which makes it tbp.
June 28, 2015

chem org
It's a part of chemistry, not necessarily organic chemistry. Organic molecules are both polar ans non-polar as are inorganic molecules. Examples for organic molecules: C2H6 is ethane which is non-polar C2H5OH is ethyl alcohol which is polar. Examples for inorganic ...
June 28, 2015

chemistry
It takes 540 cal to vaporize 1 grams H2O at 100 C to steam at 100 C. 540 cal/g x #g = 540,000 cal. Solve for #g.
June 28, 2015

Science
Many of these questions have no answer but here is a stie that will give some insight. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2596698/
June 28, 2015

organic chemistry
I agree with the answer by "name" but I will go a little further. In general organic chemistry is the study of carbon compounds and inorganic chemistry is the study of all of the other compounds. As for the difference between covalent and ionic bonds, ionic bonds are...
June 27, 2015

Chemistry Stoichiometry
Go back and re-read my original response. I showed you how I did it; i.e., I didn't just pull it out of the air. I derived the equation for you. I started with PV = nRT, substituted grams/molar mass (g/M) for n, rearranged to get P*M = gRT/v, noted that g/v = density = d ...
June 27, 2015

Chemistry Stoichiometry
I don't think that will get it. You can modify the ideal gas law of PV = nRT for density as follows: n = g/M where M is molar mass substitute for n to get PV = gRT/M or PVM = gRT. Then P*M = gRT/v but g/v is density in g/L so P*M = dRT and M = dRT/P M = 1.42*0.08206*298/(...
June 27, 2015

Chemisty
I think you want to focus on the attractive forces between molecules, the space between molecules, and things like that. Here is a good link that talks about the KMT and you should get a lot of ideas from that. http://chemwiki.ucdavis.edu/?title=Textbook_Maps/...
June 27, 2015

Stoichiometry chem
yes. It's two steps. 1. Convert grams you have to mols. 2. Convert mols of what you have to mols of what you want.
June 27, 2015

Stoichiometry chem
What you have done now is mols CaCO3 = g/molar mass = 250/100.09 = 2.498 mols. Then convert from mols CaCO3 to mols C. 2.498 x (1 mol C/1 mol CaCO3) = 2.498 x 1/1 = 2.498 mols C. Suppose the formula for CaCO3 was CaC2O3 (strictly a fictitious compound). Then mols CaC2O3 in 250...
June 27, 2015

Chemisty
You're right. 24.0 is the limiting number so you are allowed only three s.f. Probably I would report -381 kJ since -571.6 x 1/2 x (24.0/18.0) gives -381.066 kJ which rounds to -381 kJ to 3 s.f.
June 26, 2015

Chemisty
I think you are right; however, I don't know that I will go along with the 380 unless that's just a quickie number. The 571.6 has four places in it and if the other numbers have that many you are allowed more than 3 places in the answer. If I leave all of the numbers ...
June 26, 2015

Chemisty
I believe the previous answer is based on that being -571.6 kJ/mol but actually it is -571.6 kJ/2 mol or -285.8 kJ/mol (and it says -571.6 kJ/reaction and that's for 2 mols). Then multiply by 1.33.
June 26, 2015

Chemistry
mols Na ion from NaNO3 is M x L = ? mols Na ion from Na2CO3 is 2*M x L = ? M Na ion is total mols Na ion/total L = ?
June 26, 2015

Chemistry
For e I think you threw away one of the digits. I would have kept it at 1.82 (when taking logs the 1 is there as a decimal placer; therefore, you are allowed two significant figures and 1.82 would be ok. Same thing for e. That would be 14-1.82 = ? a. and f are done the same ...
June 25, 2015

chem
Mg + 2HCl ==> MgCl2 + H2 q = mass H2O x specific heat solution x (Tfinal-Tinitial) q is delta H. This will give you delta H for the reaction. Most of these problems, however, want delta H in kJ/mol and not just joules; i.e., they don't state the problem correctly and ...
June 25, 2015

chemistry
Do you want qualitative tests or quantitative tests? qual--taste. acids sour; bases not. ------feel. bases slick; acids not. quant--use a pH meter. I suggest you Google this and read. You should pick up some other ways.
June 24, 2015

Chemistry
You know it can't be air; there was no air to begin with. You know the water didn't decompose so ii can't be right. Same reasoning for why iii can't be right. No reason to think CO2 can be right. So what's left. Wouldn't you think water vapor would be ...
June 24, 2015

Chemistry
pCl2 = pPCl3 = p Ptotal = pCl2 + pPCl3 + pPCl5 0.2 = p + p + pPCl5 0.2-2p = pPCl5 a. Didn't you use 2-2p to arrive at the correct answer of 1.78 for Kp? pCl2 is 0.814. pPCl3 = 0.814. pPCl5 = 0.372 so (0.814)(0.814)/0.372 = 1.78 = Kp. b. Try it with 0.2-p and you get p = 0....
June 24, 2015

Chemistry
I agree with the answers for a1 and a2. Here is b2 and b3. ..........PCl5 ==> PCl3 + Cl2 I.........0.2.......0......0 C........-2p........p......p E........0.2-2p.....p......p Kp = 1.78 = p*p/(0.2-2p) Solve for p. I obtained 0.0973 which is pCl2 for b(3). b(2) is volume...
June 24, 2015

Chemistry
Do you mean you want the formula for sodium sulfate? That's Na2SO4.
June 24, 2015

Chemistry
a. is iii. 100 g H2O + 100 g sugar = 280 g total. That's the law of conservation of mass. 100 + 180 = 280. b. is v. Solid sugar added to the water will dissolve and leave the volume a little more than 100 mL. The only one that fits is v; i.e., a little more than 100 is ...
June 24, 2015

Chemistry
Substitute into the Hednderson-Hasselbalch equation and calculate pH.
June 24, 2015

Chemistry
q = mass ethanol x heat vaporization.
June 24, 2015

Chemistry
No. The answer is 0.038 as you first stated. The error you are making is that you are taking the cube root BEFORE dividing by 4. It's the other way around. Thanks for showing your work; it makes it easy to spot the problem. Ksp = 2.2E-4 = 4z^3 z^3 = 2.2E-4/4 = 5.5E-5 z = ...
June 24, 2015

Chemistry
.........XY2 ==> X^2+ + 2Y^- I........solid...0.......0 C........solid...z.......2z E........solid...z.......2z Ksp = 2.2E-4 = (X^2+)(Y^-)^2 2.2E-4 = (z)(2z)^2 Solve for z.
June 24, 2015

Chemistry
You've done it in the question. Na^+ is the symbol for the sodium ion and SO4^2- is the symbol for the sulfate ion.
June 24, 2015

Chemistry
I don't see a question here.
June 24, 2015

chimistry
q = mass x heat fusion = ? Remember to change 97.0 g to mols.
June 24, 2015

Chemistry
The atomic number of P is 15 which means P has 15 protons; therefore, the number of electrons for a neutral P atom MUST be 15. m being 1 affects the energy level of one or more of the electrons (and of course the P atom) but it doesn't change the number of electrons from 15.
June 23, 2015

Science
http://www.chemteam.info/Redox/Redox-Rules.html
June 23, 2015

Chemistry
You made two errors. The rest is ok. You want grams CaCl2 and not Cl so omit Cl. That's mols needed = M x L = 2.00L x 3.5M = 7.00 mols. Then grams = mols x molar mass = 7.00 x 110.98 = about 777 g. How you obtained 5.55 grams I don't know. YOu must have punched the ...
June 23, 2015

Chemistry
I give up. It posted then. Sorry about all of this but I think I have all of your answers posted. Let me know if I omitted something.
June 23, 2015

Chemistry
(OH^-) is what I can't post.
June 23, 2015

Chemistry
I don't know why I couldn't post all of the answers with one post. 8. Convert OH^- to pH.
June 23, 2015

Chemistry
The last one is to convert OH^- to pH.
June 23, 2015

Chemistry
7. ........B^- + HOH ==> HB + OH^- I.......0.0167.............0....0 C..........-x..............x....x E.......0.0167-x...........x....x Kbase for B^- is (Kw/Ka for HB) = (x)(x)/(0.0167-x) Solve for x = (OH^-).
June 23, 2015

Chemistry
6. When the B^- reacts with H2O it is ............B^- + HOH ==> HB + OH^- so you are looking for OH^- which you let be x.
June 23, 2015

Chemistry
5. I don't know which K you are talking about. K for HB is given in the problem as 6.3E-5. I expect you are talking about the Kb for B^- (benzoate ion) and that is Kb benzoate = (Kw/Ka for HB) = ?
June 23, 2015

Chemistry
4. millimols HB = 0.3 volume NaOH = 6 mL total volume = 18 mL at equivalence point. If we call benzoic acid HB, then .........HB + NaOH ==> NaB + H2O I.......0.3.............0.....0 add...........0.3................ C.......-0.3..-0.3......0.3.....0.3 E........0.....0...
June 23, 2015

Chemistry
I have tried posting the answer but the site won't let me. I'll try posting them as separate problems. The first three are right.
June 23, 2015

pragati s.s.h.s.s
Power is not one of the basic seven SI units. Anything not one of the original seven can be obtained in terms of one or more of the seven basic units. Those are called "derived units".
June 23, 2015

physcial science
c = frequency x wavelength 344 m/s = 25000 Hz x w solve for wavelength in meters. Do the same for 30 Hz
June 23, 2015

chemistry
I did this for you yesterday. Go back and find that work. I can find it for you if you can't.
June 23, 2015

Chemistry
Here is a site you can read. I don't think 86 is the right answer either. I think closer to 0.39 (39%) https://en.wikipedia.org/wiki/Extent_of_reaction
June 23, 2015

chemistry
Convert 1.06 g Ni(OH)2 to g NaOH. That's 1.06 x (2*molar mass NaOH/molar mass Ni(OH)2) = ?. That's the g NaOH in excess. How many g NaOH was in the original? That must be g excess NaOH + g titrated by HCl. How much was titrated by HCl? That's L x M x molar mass ...
June 23, 2015

chemiestry
I did that for you yesterday.
June 23, 2015

chemistry
See your other post.
June 23, 2015

Chemistry
First find the molarity of the concentrated HNO3. 1.42 g/mL x 1000 mL x 0.0704 x (1 mol/63g) = ? M. Then use the dilution formula of mL1 x M1 = mL2 x M2 33.4 x ?M = 2000 mL x M2. Solve for M2.
June 23, 2015

college chemistry
8g NaOH = 8/40 = 0.2 mols 8g HCl = 8/36.5 = 0.22 mol So NaOH is the limiting reagent. q = mass x secific heat H2O x (Tfinal-Tinitial) q = (50+250) x 4.184 x (33.5-25) = ? q is delta H in J (convert to kJ) and that is all the post asks for. Usually these problems want kJ/mol
June 23, 2015

biology
I'm not a biologist and I can't help you with this; however, I would like to point out that BOOKS are written covering this information and you want someone to answer in that kind of detail. I don't think you will get any takers.
June 22, 2015

chemistry
Please rephrase the question. As posted it makes absolutely no sense. You've just jumbled the words.
June 22, 2015

chemistry
I haven't hear solidity used in connection with H2O before; are you trying to say density since density is 1 g/mL. mass H2O = volume x density = 18 mL x 1 g/mL = 18 grams. mols H2O = g/molar mass = 18/18 = 1 mol There are 6.02E23 molecules in 1 mol. There are 16 electrons ...
June 22, 2015

chememistry
(2*H + 1*O) = ? Plug in atomic mass H and atomic mass O and solve for ? That's approx 18.
June 22, 2015

Chem 30
Solubility is 30g/100g H2O at 20C; therefore, how much will 140 g hold? That's 30 x (140/100) = ? Subtract from 60 to find the amount that comes out of solution.
June 22, 2015

Organic Chemistry
That is my take on it.
June 22, 2015

Organic Chemistry
I would go with the bond dissociation energy. Here is a table. Distance, as you suggest, plays a part but so does the polarity of the bond. https://labs.chem.ucsb.edu/zakarian/armen/11---bonddissociationenergy.pdf
June 22, 2015

CHEM
What numbers did you get and how did you get them?
June 22, 2015

chemistry
You want 2 L of 0.50 M. How many mols is that? That's mols = M x L = ? Then mols = grams/molar mass. You know mols and molar mass, solve for grams.
June 21, 2015

Chemistry
millimols HF = mL x M = approx 375 mmols NaF = 1500 x 0.25 = 375 mmols NaOH added = 50 ........HF + OH^- ==> H2O + F^- I......375...0........0.....375 add..........50................ C.....-50...-50.......50.....50 E......325...0...............425 Substitute the E line into...
June 21, 2015

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