Monday
August 31, 2015

Posts by drbob222


Total # Posts: 49,827

Chemistry
Doesn't that mean the electron is ionized? Calculate the energy for an electron moving from n = infinity to n = 1. dE = 2.178E-18(1/1 - 0) dE = 2.178E-18
August 30, 2015

Chemistry
7) 14 carat gold has a purity of 58.3%. How many moles of gold are in 163 grams of 14 carat gold? Answer in units of moles. g Au = 163 x 0.583 = ? mols Au = g/atomic mass = ? 8) A 15.9 g sample of iron ore is treated as follows. The iron in the sample is all converted by a ...
August 30, 2015

chemistry
Pb(NO3)2 + 2KI ==> PbI2 + 2KNO3 Convert each to mols product. The smaller value will be the mols PbI2 produced. 1.37 mols Pb(NO3)2 x [1 mol PbI2/1 mol Pb(NO3)2] = 1.37 mols PbI2 produced. 2.56 mols KI x (1 mol PbI2/2 mols KI) = 1.28 mols PbI2 produced. This is a limiting ...
August 30, 2015

science
delta T = 0-(-.201) = ? delta T = Kf*m You know delta T and Kf, solve for m = molality. m = mols/kg solvent. You know kg solvent and m, solve for mols. mols = grams/molar mass. You know grams and mols, solve for molar mass.
August 30, 2015

Chemistry
Do it as you would for dimensional work. That way you can't fail. 0.3333 mol CO2 x (3 mols atoms CO2/1 mol CO2) x (6.022E23 atoms/mol) = ?
August 30, 2015

Chemistry
The first part of what you did is confusing. Here is what you do. Take 100 g sample which gives you 78.8 g Sn 21.2 g O Convert to mols 78.8/118.71 = about 0.66 21.2/16 = about 1.32 Now find the ratio of the two to each other with the smaller number being no less than 1.00. The...
August 30, 2015

Chemistry
Note the correct spelling of celsius. psoln = Xbenzene*Pobenzene You need Xbenzene. Get that from nbiphenyl = grams/molar mass = ? nbenzene = grams/molar mass = ? Xbenzene = nbenzene/total mols. Then substitute Xbenzene in first equation above and solve for p solution.
August 29, 2015

Science
I think 1-4 are answered correctly although in real life I don't agree with #2; however, that is a personal opinion and your answer is correct. I'm on the fence about the squirrel. Your answer probably is correct but my problem is with the word "about" in ...
August 29, 2015

chemistry
Is there a question here?
August 29, 2015

chemistry
% HCl means grams HCl/100 g solution. 24.8% HCl = 24.8 g HCl/(24.8g HCl + 75.2 g H2O) n HCl = g HCl/molar mass = ? n H2O = g H2O/molar mass = ? XHCl = nHCl/total mols.
August 28, 2015

CHEMISTRY
https://www.google.com/search?q=molar+mass&ie=utf-8&oe=utf-8 https://en.wikipedia.org/wiki/Avogadro_constant
August 28, 2015

SCIENCE!
1 and 3 look ok. 2. I don't think your answer will fly. I would go with perhaps there is a tree outside the window at the new location that is blocking parts of the sky/stars.
August 28, 2015

chemistry
And your problem is? Just plug in the numbers.
August 28, 2015

chemistry
I would not go that way. When dealing with ppm I remember one very nice factor to keep in mind; i.e., 1 ppm = 1 mg/L. So 750 ppm = 750 mg/L. You want 50 mL so that is 750 x 50 mL/1000 mL = 37.5 mg Fe = 0.0375 g Fe you want. Convert that to the oxalate trihydrate and you have ...
August 27, 2015

chemistry
Paul gave it to you straight.
August 27, 2015

Chemistry
There is nothing wrong with Steve's answer but here is a systematic way to solve the problem in case the percentages are not the same. Take 100 g sample, that gives you 50.05 g S and 49.95 g O. Convert to mols mols S = 50.05/32.06 = 1.561 mols O = 49.95/16 = 3.121 Now find...
August 27, 2015

Thermodynamics
a. Use PV = nRT and solve for n. Remember T must be in kelvin. b. Can't be done without knowing more information. If the gas is monatomic then b is the same as a. If the gas is diatomic, then b is 1/2 a. If it is triatomic, then b is 1/3 a.
August 27, 2015

Science
baloney
August 27, 2015

Chemistry
L1 x M1 = L2 x M2 L1 x 5.337M = 1.669L x 0.063M Solve for L1.
August 26, 2015

Chemistry
The monoprotic acid is HA. HA + NaOH ==> NaA + H2O mols NaOH = M x L = ? (note: volume NaOH = 13.41-2.19 = ? mL and convert to L). Then mols HA = mols NaOH M HA = mols HA/L HA.
August 26, 2015

chemistry
volume = l x w x h = ? cc mass = 1.5 kg = ? g density g/cc = mass/volume
August 26, 2015

chemistry
See what great help you get on Jiskha. You get a means of identification PHYSICALLY and well as CHEMICALLY.
August 26, 2015

chemistry
Add Br2 IN THE DARK. Cyclopropane will add Br2 in the dark to form the bromopropane. Propane will do this but ONLY with UV (or sunlight) and not in the dark.
August 26, 2015

chmistry
This is a limiting reagent problem and you know that when amounts are given for BOTH reactants. Convert 2.50 g CuO to mols. mols = grams/molar mass = ? Convert 0.5 L NO gas to mols (n) using PV = nRT Using the coefficients in the balanced equation, convert mols CuO to mols of ...
August 26, 2015

science
I agree
August 26, 2015

science
duplicate post
August 26, 2015

science
A poorly worded question. No amount of electricity will deposit AgNO3 solution. It will deposit Ag (metal) but not AgNO3 solution. 96,485 Coulombs will deposit 107.9 g Ag. How many C were involved? That's 96,485 x (0.54/107.9) = ? That will liberate 1 g H2. Convert 1 g H2 ...
August 26, 2015

math
See your other post.
August 25, 2015

chemistry
Surely you made a typo. I think that is I2(s) + Na2S2O3(aq)=>Na2S4O6(aq) + NaI(aq). The net ionic equation for my revised equation is I2 + 2S2O3^2- --> S4O6^2- + 2I^-
August 25, 2015

math grade 7
Does 5-(-3)^2 -6 5-(+9)-6 = (because -3*-3 = +9 5-9-6 = -10
August 25, 2015

Science
Isn't that distance = rate x time. You know distance and time, solve for rate.
August 25, 2015

math
2E6 people x $/person = 1.5E9 Solve for $/person
August 25, 2015

math
4.5-10-2(1-2)+5 = 4.5-10-2(-1)+5 = 4.5-10+2+5 = ?
August 25, 2015

Physical Science
Plane mirrors (I assume that's what you are talking about) produce virtual images in which the object distane equals the image distance. For B, see https://answers.yahoo.com/question/index?qid=20110330202945AA1tAfT
August 25, 2015

Chemistry
I don't know if this is readable or not but I typed this up as a set of directions. If it looks too black to read you may click and highlight and the letters show up as black against a white background.
August 25, 2015

inorganic
4 to 3 4 to 2 4 to 1 3 to 2 3 to 1 2 to 1 6 total
August 25, 2015

chemistry
Here is how you do one of the half reactions. Let's take NO3^- --> NO 1. Oxidation state N on left is +5; on right is +2 2. Add electrons on appropriate side to balance change of oxidation state. NO3^- + 3e ==> NO 3. Count charge on left and right. I see -4 on left ...
August 24, 2015

Chemistry
See your post above with a different screen name. You get better results using the same screen name.
August 24, 2015

chem
I think the question means that B will have 1s2 2s1 2p2 and that's how you get BF3, BH3, etc but I must confess the wording is confusing.
August 24, 2015

Chem
You need to read your post and note it doesn't make any sense. "Volume changing to 78 degrees celsius"? Use (P1V1/T1) = (P2V2/T2)
August 24, 2015

chemistry
See your other post.
August 24, 2015

chemistry
Very good but I don't see any answers. If you will post your work I shall be happy to check it.
August 24, 2015

chemistry
Mike--How can I help you with this assignment? I see 40 questions (20 here and 20 on the next one) and I'm not inclined to spend the rest of the day doing those when you've shown no effort on your part. If you will pick them out one at a time and tell me what you don&#...
August 24, 2015

chemisrty
See your other posts. These make 60.
August 24, 2015

Biochemistry
What's the pKa for acetic acid. I think it's about 4.74. Acetic acid/acetate buffer will work best at 4.74 +/- 1 pH unit and 8 is far removed from that. It would not buffer at that pH. But thanks for the "QUOTE". I haven't heard that one before.
August 24, 2015

@ Steve--Word problems
At 40 mph doesn't it take the truck 110/40 = 2.75 hours to cover that distance?
August 23, 2015

Word problems
Midville.........................Carmine distance = X truck..............|...............Car truck moves 40 mph*1.25 hrs = 50 miles The car moves from carmine to 110 miles out(55 mph x 2 hrs = 110 miles) Therefore, the truck moves from 50 miles out of Midville while the car ...
August 23, 2015

Chemistry
k = 0.693/t1/2 Then ln(No/N) = kt No = 18/- N = 2.25 k from above. Solve for t.
August 23, 2015

Science
John, I posted a response to your question under your other screen names of Sarah. I've told you before that it is better to use the same screen name. We can help you better if you don't change screen names with every post; apparently you don't believe that since ...
August 22, 2015

Chemistry
The Ag^+ and the CrO4^2- react to form Ag2CrO4 but the NO3^- is not involved in the reaction (it is a spectator ion); therefore, it's concentration is not affected. It will be diluted, of course, due to the added volume from the Na2CrO4. 2.15 M x [(125/(125+75)] = ? M.
August 22, 2015

science`
I recommend you read your lab manual safety section thoroughly before going into your lab. If you have questions about any one of them please talk to your laboratory instructor for further instructions.
August 21, 2015

Science
#1. photosynthesis #2. Several will fit but I go with "organic fertilizers". Surely you have this in your notes or text. #3. oxidation
August 21, 2015

chemistry
How strong is the acetic acid?
August 21, 2015

math
Let X = amount Enid deposited on May 15. and Y = amount Jim deposited on May 15. ================================== May 15 = X...........Y June 1...4...........3 July 1...4...........3 Aug 1....4...........3 Sept 1...4...........3 Oct 1....4...........3 Nov 1....4...........3 ...
August 21, 2015

@ arti--science cbse school
You should post the question or answer it at the original post. I looked for the original question and it is not on the first page. Also as a hint, your question is about physics. Biological science, chemistry, biochemistry, astronomy, geology, psychology, etc are science ...
August 21, 2015

@ just a dad---science cbse school
I never would have figured that out.
August 21, 2015

science cbse school
I don't see a question.
August 21, 2015

cheistry
Can't draw diagrams on this forum. The process works largely because of the fractionating column. Here is a picture. Google fractional distillation for a discussion. https://en.wikipedia.org/wiki/Fractionating_column
August 21, 2015

organic chem
No, since there is no chance for resonance in formaldehyde.
August 21, 2015

Algebra 1
Let B = brother's age and C = cousins agae ==================== B+8 = C 2(B-3) = C-3 Solve those two equations simultaneously for B and C.
August 21, 2015

Algebra
1/3
August 20, 2015

Algebra
Right! It is somewhat confusing.
August 20, 2015

typo==Algebra
I think Ms.Sue meant 12/5 and not 12/25.
August 20, 2015

Chemistry
That's what I would do.
August 20, 2015

Chemistry
yes. #2 is like this. 8E-4 = k*(0.2)(0.4)^2 and solve for k or 2E-4 = k*(0.2)(0.2)^2 and solve for k or 1.6E-3 = k*(0.4)(0.4)^2. Note that all of them give the same value for k. For #3, the rate of disappearance of A = rate of appearance of C since the coefficient of each = 1.
August 20, 2015

Chemistry
Your rate = k(A)(B)^2 is correct(that's #1). For #2 plug rate for any ONE of the trials, plug (A) and (B) for that trial and solve for k. #3. You now know k, plug in 0.3 and 0.3 and solve for rate but I would feel better if I saw an equation for the reaction of A and B to ...
August 20, 2015

Chem
Look up the toxicity of some of those chemicals in tobacco smoke and compare it with the amount that is supposed to be in tobacco smoke.
August 20, 2015

Chemistry
This is a limiting reagent problem. You know that when amounts are given for BOTH reactants. 3Mg + N2 ==> Mg3N2 a. Convert mols Mg to mols product. b. Convert mols N2 to mols product. These answers are likely to be different; if so then both can't be right. The correct ...
August 20, 2015

CHEMISTRY URGENT HELP
Soft drinks are pressurized (to make gas more soluble) and cooled (to make gas more soluble). If you pop the top of a cola and leave it open to the air it will go flat in a short time since all of the dissolved CO2 will be gone.
August 20, 2015

Life Science
I think Andrea wants us to do her assignment.
August 20, 2015

physical science
Zn + Pb(NO3)2 ==> Zn(NO3)2 + Pb
August 20, 2015

Chemistry
Of course since it is white it could be reflecting some light also.
August 20, 2015

Chemistry
You don't understand why placing an opaque substance in the solution cuts down on the light getting through? Look at a light. Now place your hand in front of your eyes. Can you see the light? Why not? Because your hand is in the way; i.e., it absorbs all of the light ...
August 20, 2015

Chemistry
millimols HAc (CH3COOH) = mL x M = 25 mmols NaAc(CH3COONa) = 15 mmols NaOH = mg/molar mass = 12.5 ---------------------------- .......HAc + OH^- ==> Ac^- + H2O I......25....0.......15........ add.........12.5................... C...-12.5..-12.5.....12.5......... E.....12.5...
August 19, 2015

Chemistry
Two equations to be solved simultaneously. Let X = g C3H8 and Y = g C2H2 ============== X + Y = 2.5 (equation 1) mols CO2 from C3H8 + mols CO2 from C2H2 = 1.5*(mols H2O from C3H8 + mols H2O from C2H2). Turning that into a second equation (4X/44) + (3X/44) = 1.5[(Y/26) + (2Y/26...
August 19, 2015

science
I'm somewhat confused with the language so here is a link for you to read to reach your own conclusion. D certainly is not right. B sounds right to me BUT it talks about concepts (and the question is about hypotheses) so I rule that out. https://en.wikipedia.org/wiki/...
August 19, 2015

science
right. https://answers.yahoo.com/question/index?qid=20081204143123AAiwNG1
August 19, 2015

Chemistry
I don't know the instructions given. If the instructions suggest an explanation then you should giver one; otherwise, I would just write spontaneous or non-spontaneous.
August 18, 2015

Chemistry
That is right about delta H. The problem is that no data are given for delta S. You can guess about delta S, however, and be close usually. For example, #1: you have solids on the left (reactants) and gas on the right so delta S must be + (more disorder in gases than solids) ...
August 18, 2015

Science
On the gold medals that outside layer is gold plated and oxygen will have little effect on it. For the silver medals, oxygen will tarnish silver over time forming either silver oxide or silver sulfide or both (think household silverware made with silver or silver plate--the ...
August 18, 2015

Science
http://chemistry.about.com/od/metalsalloys/f/what_are_olympic_medals_made_of.htm
August 18, 2015

science
Why would they want to do that?
August 18, 2015

Chemistry
The Henderson-Hasselbalch equation is the one to use. pH = pKa + log (base)/(acid) If the aicd/base ratio is 2:1, then the base/acid ratio is 1/2; therefore, pH = 7.2 + log (1/2)
August 18, 2015

chemistry
If this is a web site I can't access it. Please post the question.
August 18, 2015

Chemistry
Thanks for showing your work. These two look ok to me.
August 18, 2015

Chemistry
2C2H6 + 7O2 ==> 4CO2 + 6H2O mols H2o formed = grams/molar mass = ? Using the coefficients in the balanced equation, convert mols H2O to mols ethane. Now convert mols ethane to grams; grams = mols ethane x molar mass ethane.
August 18, 2015

G.J.PUC
Let me point out that the total adds up to 99.99; it should add to 100 but that probably won't make any difference in the answer. Take 100 g sample which gives you 18.6 g C 1.55 g H 55.04 g Cl 24.8 g O Convert to mols and I will estimate; you should recalculate each. 18.6/...
August 18, 2015

chemistry
Put the product in a drying oven at 105 C and leave it for a couple of hours.
August 17, 2015

chemistry
2C2H6 + 7O2 ==> 4CO2 + 6H2O
August 17, 2015

math help
Is that 5x[(2x^2)^2]?
August 17, 2015

math help
You are right.
August 17, 2015

science
And you are right. While I'm at it let me expand on one of the answers. HCl is a gas. As a gas it is properly called hydrogen chloride gas. When it is dissolved in water to form an aqueous solution it is called hydrochloric acid and written as HCl(aq).
August 17, 2015

chemistry
P4 + 16H2O ==> 4H3PO4 + 20e + 20H^+ 1H^+ + 1e + HNO3 ==> NO2 + H2O Multiply to keep the electrons equal and add the equations together. Finally, cancel ions/molecules common to both sides.
August 17, 2015

org chem
Since Cl is so electronegativity, it is an electron withdrawing agent. That means it is pulling, through the inductive effect, electrons from elsewhere which makes the the carbonyl more positive and that helps release the proton.
August 17, 2015

Chemistry
Something else in the filtrate that is absorbing at the same wavelength could lead to it but there must be half a dozen other possibilities.
August 16, 2015

Chemistry
I don't agree with those numbers. 2.54*2*2.54*3*0.065*8.96 = 22.54 g/board and that x 5000 is 1.1127E5 g Cu. That means you redo amount removed and remaining. Convert g Cu to mols. mols Cu = grams Cu/atomic mass Cu. Cu + Cu(NH3)4Cl2 + 4NH3 -> 2Cu(NH3)4Cl For every 1 mol...
August 16, 2015

Chemistry H
A little short on specifics but I suppose you separated the steel wool by pulling (a physical process which doesn't change the mass) but heat it (I suppose it caught on fire) and this caused oxidation so it changed mass because oxygen was added.
August 15, 2015

Chemistry
Sydney, I think I answer this for you yesterday. Rachel, I answered this above.
August 15, 2015

Chemistry
2C3H7OH + 9O2 ==> 6CO2 + 8H2O mols C3H7OH = grams/molar mass = ? Using the coefficients in the blanced equation, convert mols C3H7OH to mols CO2. Now convert mols CO2 to L by PV = nRT using the conditions of the problem.
August 15, 2015

Algebra 1
You don't need a calculator for this one. You KNOW it can't be 0 or 1803 since it MUST be more than 2300. And for 8 hours it is unreasonable to think it will grow only by 24 so the answer must be B; i.e., 2914.
August 14, 2015

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