Sunday
April 26, 2015

Posts by DrBob222


Total # Posts: 48,521

science
It is transferring from particle to particle and travels that way. But each transfer is not 100% and it gradually dies out.
February 21, 2015

chemistry
You should find the arrow key on your computer and use it. When using gases at the same T and P one can use a shortcut procedure in which the volume (in L) is used directly as if it were mols. So all you need to do is to convert 120 L H2S to SO2. 120 L SO2 x (2 mols SO2/2 mols...
February 21, 2015

chemistry
First, note the correct spelling of celsius. Ptotal = pdry ethene + pH2O@17 Ptotal = 680 mm + 14.0 = ? mm
February 21, 2015

chemistry
Do you know how to determine the oxidation number for N in these compounds? I'll do the first two for you. #1 rule. Compounds or elements have a charge of zero. #2 rule.The oxidation state of all of the elements in the material must add to zero (if it's a compound) or ...
February 21, 2015

chemistry
Fe2O3 + 3CO ==> 3CO2 + 2Fe mols Fe2O3 = grams/molar mass = ? Use the coefficients in the balanced equation to convert mols Fe2O3 to mols CO. Now convert mols CO to grams. grams CO = mols CO x molar mass CO
February 21, 2015

science
C isn't right. The best answer you have is B but I wouldn't stick my neck out until you finish the sentence for D. Heat capacity is an extensive property which means it depends upon HOW MUCH of the material is present. So it obviously takes more heat to raise the T of ...
February 21, 2015

Chemistry
I think you're there if you correct the typo in your next to last step. That 8.20M should be 8.10 M so you get a slightly different factor and that x 124 mL will give you the right answer.
February 21, 2015

chemistry
My best guess is no but I can't calculate that no answer without Ksp values for the two materials at whatever temperature you mean by "cold".
February 21, 2015

chemistry
w = nRTln(V2/V1) and since work is being done on the gas the sign of w is +.
February 21, 2015

Chemistry
1. mols = grams/molar mass = ? 2. Convert 6.0 mg to grams. Then mols cisplatin = grams/molar mass = ? # molecules cisplatin = mols x 6.02E23 = ? # Cl atoms will be twice that since there are two Cl atoms/molecule of cisplatin.
February 20, 2015

Chemistry AP
Thanks for the reminder. I don't think you have approached the problem right (at least not completely right). I'll redo some of what you've described. You have the mmols right. .......NH3 + HCl ==> NH4Cl I......1.5....0.......0 add...........4............ C...
February 20, 2015

Chemistry
delta T = i*Kf*m delta T = 4.37 C. You might want to make that 4.38 to add just a wee bit more. i for NaCl = 2 Kf for water = 1.86 Substitute and solve for m = molality Then m = mols/kg solvent You know m and kg (30) solvent. Solve for mols. Then mol = grams/molar mass You ...
February 20, 2015

Chemistry
volume = mass/density Look up the density of brass, substitute and solve for volume. mass is 100 g. The add the volume of the brass to the volume of the water (50 mL) and that will be the new reading of the water level. I don't know what height that is; I'm assuming ...
February 20, 2015

Chemistry
What are you doing wrong? You're using gauge pressure (psig) and not "real" pressure (psia). What you want to do is to convert gauge pressure to absolute (real) pressure, use P1V1/T1 = P2V2/T2, solve for new P2, convert back to gauge. pgauge + 14.7 = pabsolute ...
February 20, 2015

chemistry
Al2(SO4)3 + 6NaOH ==>3Na2SO4 + 2Al(OH)3 mols Al2(SO4)3 = grams/molar mass = ? mols NaOH = grams/molar mass Using the coefficients in the balanced equation, convert mols Al2(SO4)3 to mols Al(OH)3. Do the same and convert mols NaOH to mols Al(OH)3. It is likely that the two ...
February 20, 2015

Chemistry
It would help if I knew what you don't understand about this. Also it would help if you found and used the arrow key(s) To write the net ionic equation you balance the molecular equation (which happens to be A) as step 1, for step 2 convert the molecular equation into a ...
February 20, 2015

chemistry
M = mols/L You want 1 L of 0.5M so you want 1 x 0.5 = 0.5 mols. grams for 0.5 mol = mols x molar mass = ? Weigh that many grams CoCl2.6H2O, add to a 1 L volumetric flask, add some water, swirl to dissolve the solute, add DI water to the mark on the flask, mix thoroughly, stopper.
February 20, 2015

Chemistry
C3H8 + 5O2 ==> 3CO2 + 4H2O When using gases at the same T and P, one can take a shortcut and use liters as if they were mols. For the problem we simply convert L of one thing into L of the other. 0.7L C3H8 x (5 mols O2/1 mol C3H8) = ? L O2 required. The other parts are done...
February 20, 2015

chem
mols nicotine = grams/molar mass = ? mols C6H12 = grams/molar mass Find total mols. XC6H12 = nC6H12/total mols. M C6H12 = mols C6H12/L solution = ?
February 20, 2015

chemistry
LiClO4 --> LiCl + 2O2 mols LiClO4 = grams/molar mass Using the coefficients in the balanced equation, convert mols LiClO4 to mols O2. Now use PV = nRT and convert mols O2 to L at the conditions listed. Remember T must be in kelvin. If you use kPa for P you must use 8.314 ...
February 20, 2015

Chemistry
dG = dH - TdS. You know dH is - You know dS is + (because there are 6 mols gas on the left and 10 on the right; an increase in mols of gas is an increase in S.) From the above equation if dH is - and dS is +, the term -TdS will be - no matter what T is used so dG will be - at ...
February 20, 2015

Chemistry
I disagree also.
February 20, 2015

science
Can you see it burn?
February 20, 2015

chemistry
http://en.wikipedia.org/wiki/Naphthalene http://en.wikipedia.org/wiki/Benzoic_acid
February 20, 2015

chemistry
Ba(OH)2 + 2HCl ==> 2H2O + BaCl2 q = mass H2O x specific heat H2O x (Tfinal-Tinitial) = delta H. mols HCl = 0.065 x 0.660 = 0.0429 mols delta H in J/mol = q/0.0429 = ?
February 20, 2015

chemistry
E = hc/wavelength
February 20, 2015

chemistry
I think Bob Pursley answered this for you earlier. My answer is slightly different; i.e., subtract the electronegativity of each element. The difference is a measure of the polarity of the bond. For H2S, for example, 2.5- 2.1 = 0.4. For AlH3 2.1 = 1.5 = 0.6 From these data, ...
February 19, 2015

Chemistry
You do this in steps. q1 = heat to raise T of solid ice at -15 C to zero C. q2 = heat to melt ice q3 = heat to raise T of liquid H2O from zero C to 100 C q4 = heat to vaporize liquid H2O at 100 C to steam at 100 c. q5 = heat to raise T of steam from 100 c to 120 C. Total is ...
February 19, 2015

Chemistry
q extracted from the water is q = mass H2O x specific heat H2O x (Tfinal-Tinitial) That gives you q for 1.50g sample. The 1.5g sample is how many mols? That's 1.5/molar mass NH4NO3. Then q from above/#mols = q in J/mol. Convert to kJ/mol.
February 19, 2015

Chemistry
Yes you need to melt the ice. You may or may not need to convert to mols. Why didn't you type your work and I could find the problem almost instantly. As it is we're well into 2-3 hours for this. I agree with your 72,360 J for heat to move T from -10 to zero c. Where (...
February 19, 2015

Chemistry
No. The 72,360 J is right for the q1 part. I don't know where the 21,573 came from.
February 19, 2015

Chemistry
q1 = heat to raise T from -10 to zero. q1 = mass ice in grams x specific heat solid ice x 10 q2 = heat to melt ice q2 = mass ice x heat fusion. Add q1 + q2 = total q.
February 19, 2015

Science
Are you looking for a second opinion?
February 19, 2015

Science please help
Why would you pick D? Why would you want smaller amounts of oxygen? I would go with A. There is no way C or D can be correct.
February 19, 2015

Science please help
I think B is a true statement; however, the problem asks about the respiratory system and the heart is not part of the respiratory system. I'm not a biology or anatomy guy but I would not go with B.
February 19, 2015

Science
A molecule is the smallest division of a compound.
February 19, 2015

Chemistry
What are the potentials? I could look them up but I should use numbers from your text/notes.
February 19, 2015

Math
Plug the numbers into d = rt and solve for distance, then redo and calculate r for the second student. Post your work if you get stuck.
February 19, 2015

Science
The temperature of a substance is a measure of the kinetic energy of that material. KE = 1/2 mv^2. As the kinetic energy rises the temperature rises. The thermometer measures the temperature.
February 19, 2015

chemistry
With no numbers and only a general description, there isn't much I can help with.
February 19, 2015

Chemistry
You should use the same screen name. There is no learning, just plug into the formula. Don't forget T is in kelvin and P is in atmosphere if you use R = 0.08206 Use PV = nRT
February 19, 2015

chemistry
Remember to use the same screen name. Use PV = nRT as in your other post and solve for n = number of mols. Then n = grams/molar mass. You know n and molar mass, solve for grams. Post your work if you need further assistance.
February 19, 2015

chemistry
There is a long way and a short way. Here's the long way (the modern way). MgSO4.7H2O ==> MgSO4 + 7H2O mols MgSO4.7H2O = grams/molar mass = approx 0.0101 Convert that to mols H2O. That will be 7x that or 0.0707 which you get from the coefficients in the balanced ...
February 19, 2015

chemistry
http://en.wikipedia.org/wiki/Lidocaine The above is lidocaine. The hydrolysis is shown here. The bond between the NH-C=O is split to leave the ring amine on the left and the carboxylic acid on the right as shown here. http://www2.courses.vcu.edu/ptxed/m2/powerpoint/download/...
February 19, 2015

Chemistry
I don't think it means that. I think the fallacy in your thinking is that you've not taken into account the change in the number of mols during the reaction. I think you must convert pether and pO2 to mols using PV = nRT, determine the limiting reagent (which I think ...
February 19, 2015

Chemistry
rms = sqrt(3RT/M)
February 19, 2015

Chemistry
sit quietly? hide in a corner? Do you have choices? I have no idea what you want.
February 19, 2015

Chemistry
q absorbed by water = mass x specific heat x (Tfinal-Tintial) q lost by metal = heat absorbed by water [mass metal x specific heat metal x (Tfinal-Tintial)] + [mass H2O x specific heat H2O x (Tfinal-Tinitial)] = 0 Substitute and solve for sp. h. metal.
February 19, 2015

Chemistry
H2SO4 + 2NaOH ==> Na2SO4 + 2H2O mols NaOH = M x L = ? mols H2SO4 = 1/2 mols NaOH from the coefficients in the balanced equation. M H2SO4 = mols H2SO4/L H2SO4
February 19, 2015

Science Help Plz
I don't agree with A.
February 19, 2015

Chemistry
2X + Y = X2Y rate = (X)^2(Y) What if (X) = 1 and (Y) = 1 then rate = (1)^2(1) = 1 Now we double X and triple y so rate = (2)^2(3) = 12 So you have changed it from rate of 1 to rate of 12. What factor is that.
February 19, 2015

chemistry
new concn will be 0.8 x (298)/(298+425) = ? This assumes the volumes are additive.
February 19, 2015

P.S.--Chemistry
Many thanks for showing your work. It makes it easy to catch mistakes like this.
February 19, 2015

Chemistry
First, you transposed 3.16E-5 to 3.61E-5 to come up with pKa = 4.44. It won't change that much but pKa is 4.5 using 3.16E-5 for Ka. Then working with millimoles, x/(107-x) = 0.347 and x = about 27.5 millimols. That isn't that far from you 30.4 but probably far enough ...
February 19, 2015

chemistry
10% I suppose w/w, means 10 g HNO3/100 g solution 10 g HNO3 is how many mols. That's 10/63 = ? Then mass = volume x density or volume = mass/density = 100/1.051 = ? M HNO3 = mols/L Then pH = -log(HNO3)
February 19, 2015

chemistry
I don't see a question here.
February 19, 2015

Chemistry
I'm assuming that the problem below (which I did in detail) will help you work this one.
February 19, 2015

Chemistry
#1. i. more soluble in HCl because Cu(OH)2 + 2HCl ==> CuCl2 + 2H2O ii. less soluble in Cu(NO3)2 because of the common ion effect of Cu^2+ from the Cu(NO3)2. In pure water, .......Cu(OH)2 ==> Cu^2+ + 2OH^- inital..solid.......0.......0 change..solid.......x.......2x equil...
February 19, 2015

physical science
Can you use KE = 1/2 mv^2
February 18, 2015

chemistry
If BH3 is a trigonal planar molecule then it has no dipole moment which means it isn't polar and with no polarity there is no reason for it to orient itself a particular way in an electric field. Count the electrons around BH3. How many do you see?
February 18, 2015

Science
yes
February 18, 2015

Science
That is correct.
February 18, 2015

Science
I gave you a site to read and there is a section that gives the factors affecting speed of sound. The answer is there for the taking.
February 18, 2015

chemistry
Use the Henderson-Hasselbalch equation.
February 18, 2015

Chemistry
You're trying to solve the problem wrong. Since one is first order and the other is second order, that equation won't work; besides, you have only one concn. What you want to use is the rate equation of rate = k(NO)^2(O2) Plug in k, NO, and O2 and calculate rate. 4.4E-...
February 18, 2015

Chemistry
Use the Arrhenius equation and remember to insert Ea in J/mol and not kJ/mol.
February 18, 2015

science(sound#4)
Flutes CAN play a relatively low pitch but we normally thing of flutes and piccolos as playing high frequencies. Most of the instruments you listr (that's Destinee's list) CAN play high or low and I interpret the question as an instrument that plays ONLY high or low ...
February 18, 2015

science(sound#4)
Pitch is the frequency of the sound. A high pitch means something like a fire siren; a low pitch is like the roar of a hot rod car or motorcycle. Now which instrument has a low pitch (and I guess that means a musical instrument)?
February 18, 2015

science(sound#4)
What do you think? Do you have any choices?
February 18, 2015

science(waves)
energy
February 18, 2015

Quick chemistry help
Ca3(PO4)2 is a white solid.
February 18, 2015

science (sound #2)
Let's see now. We have high temperatures and low temperatures. You know the answer for faster sound travel; doesn't it sound reasonable that the other answer would be for sound to travel slower? Are you thinking about any of these questions/answers or just copying the ...
February 18, 2015

science (sound)
At low temperatures the molecules of the medium are closer together so sound travels faster.
February 18, 2015

science (aka sound)
Isn't sound transported by liquids, solids, gases? and plasma?
February 18, 2015

Physical Science
CaCO3 + 2HCl>CaCl2 + H2O + CO2
February 18, 2015

science
solid? liquid? gas? Plasma?
February 18, 2015

Science
Think about this. c = frequency x wavelength so changing freq or wavelength has no effect on c. Read here. http://www.physicsclassroom.com/class/sound/Lesson-2/The-Speed-of-Sound
February 18, 2015

Science
I think d is correct; however, I don't think that is the only one nor is it the primary one.
February 18, 2015

Science
Not really a tricky question. You go through the answers and c is the only one in air. Have you heard the question, "If a tree falls in a forest and no one is there (implying no living thing is there), is there a sound?" Think about that some, here is a link if you ...
February 18, 2015

Science
If it's B how does the sound travel through "empty space" (a vacuum). No air, no sound.
February 18, 2015

Science
I don't think so. Sound can't be transported by a vacuum. The question contains the give away answer; i.e., "most likely to travel through AIR". Therefore, no air, no way for sound to get from point A to point B.
February 18, 2015

science
5 and 6 are not right. I think you have the expected answer for 9 but technically I think the first is correct. 10. Evaporating the mixture is correct but I don't know about the last one. I don't know of any filters that will do that. The author of this problem may be ...
February 18, 2015

Chemistry
If I knew the answer to your last response I could have answered it in the first place.
February 18, 2015

Chemistry
Morgan, I've struggled with this question and looked in all of my references + web. Finally I've had to conclude that I simply don't have enough understanding about the answered listed to give an unequivocal response so the safe thing to do is to leave it alone. ...
February 18, 2015

chemistry
specific rot = (alpha)/yl sp. rot. = 45/[(0.400/5)(1)]
February 18, 2015

chemistry
I don't think it's A. A says there are no additional number of shells but Na has another shell not present in Li. Also there ARE additional shielding electrons. Right? I agree that b doesn't sound right. I would bet on D by the process of elimination. A, B, C, E ...
February 18, 2015

chemistry
2Li + 2H2O ==> 2LiOH + H2 mols LiOH = grams/molar mass = ? Look at the coefficients. It takes 2 mols H2O to produce 2 mols LiOH; therefore, mols H2O = mols LiOH
February 18, 2015

Chemistry
Example: CH4 + 2O2 ==> CO2 + 2H2O 16 + 64 = 44 + 36 What do you think? Are atoms conserved? That is, do you have the same number of atoms on each side? Is mass conserved? That is, do you have the same number of grams on each side?
February 18, 2015

chemistry
Probably none. I don't recall H3PO4 decomposing to form H2 gas.
February 18, 2015

science
Use the Henderson-Hasselbalch equation.
February 18, 2015

Organic Chemistry
You want the solubility expressed as g/mL. So 1.0g/300 mL = 0.333 g/100 mL. Right? And 1.0 g/17 mL is 1/17 = about 0.06 g/mL or approx 6 g/100 mL. Then Ko/a = approx 6/0.333 = about ? in which Ko/a is the partition coefficient of organic/aqueous.
February 17, 2015

chemistry
I answered your earlier post below.
February 17, 2015

chemistry
Anytime amounts are given for BOTH reactants you know it is a limiting reagent (LR) problem and the first thing you must do is determine the LR. mols (NH4)2CrO4 = M x L = ? mols Cr(NO3)3 = M x L = ? Using the coefficients in the balanced equation, convert mols EACH one into ...
February 17, 2015

Chemistry
I believe this is 3% w/w which means 3g H2O2/100 g solution. mols H2O2 = 3/molar mass H2O2 in 100 g solution. 2H2O2 ==> 2H2O + O2
February 17, 2015

AP Chemistry
I think 8.72 is the correct answer.
February 17, 2015

chemistry
different radii different charge on ions different volumes among others.
February 17, 2015

AP CHEM
mols Ba(OH)2 = M x L = ? mols OH in Ba(OH)2 = 2x that = ? mols Naoh = m x L = ? final (OH^-) = total (OH^-)/total L
February 17, 2015

chemistry
You would have done well to write the full question. I assume you are mixing 20.00 ml of a 50% saturated solution of BaCO3 (with the given Ksp) with 20.00 mL of 0.0100 M Na2CO3 although you don't say what the solutions are. Next, I understand the first sentence that you ...
February 17, 2015

chemistry
See your other post.
February 17, 2015

chemistry
mols H3PO4 ==> M x L = ? Use the coefficients in the balanced equation to convert mols H3PO4 to mols Ba(OH)2. Now M Ba(OH)2 = mols Ba(OH)2/L Ba(OH)2. You know mols and M, calculate L.
February 17, 2015

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