Sunday
March 29, 2015

Posts by DrBob222


Total # Posts: 47,990

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

chemistry
2LiOH + H2SO4 ==> Li2SO4 + 2H2O mols LiOH = M x L = ? Using the coefficients to convert mols LiOH to mols H2SO4. Now M H2SO4 = mols H2SO4/L H2SO4
February 17, 2015

science
http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/grnhse.html
February 17, 2015

PNU
I would convert 288 pm to cm, then cube that to obtain the volume in cc. Next, mass = volume x density = ? Next, (atoms/unit cell)x molar mass/6.02E23 = mass from previous step. Solve for molar mass. Then mols = 208g/molar mass 1 mol contains 6.02E23 atoms; how many atoms in ...
February 17, 2015

Chemistry and physics
I think it is two fold. First the Fe filings are heated to an incandescent point, then the combination of Fe and S to produce Fes is an exothermic reaction and that produces the red orange glow with Fe until the all of the reaction has taken place.
February 17, 2015

Chemistry
You haven't worded the question very well; I assume that 6.843 g/mL is the density. Therefore, you have the density and volume and you want to calculate the mass. mass = volume x density You have volume and density, substitute and calculate mass.
February 17, 2015

science
mols HCl = M x L = ? mols HNO3 = M x L = ? M final = total mols/total L (H^+) = final M pH = -log(H^+) (H^+)(OH^-) = Kw = 1E-14
February 17, 2015

Chem
You did an experiment? What did you observe.What pairs of ions did you use?
February 17, 2015

chemistry
Convert 0.88 g CO2 to CaCO3. That's 0.88 x (molar mass CaCO3/molar mass CO2) = ?g CaCO3 Then % CaCO3 in sample = (?g CaCO3/mass sample)*100 = ?
February 17, 2015

chemistry
Intermolecular forces, primarily dispersion forces and induced dipole-induced dipole forces increase as the atomic mass and size increases.
February 16, 2015

Chemistry
Suppose we (you and I) are making hamburgers. You're cooking the meat and I'm toasting the buns. I can toast buns at the rate of 1 whole buns/min. You can cook a pattie in 10 minutes. What determines the number of hamburgers we can make in an hour. You of course. You ...
February 16, 2015

chemistry
heat to water = q = mass H2O x specific heat H2O x (Tfinal-Tinitial). You don't know q or Tfinal. But you can calculate q this way, then solve for Tfinal. The problem tells you that burning 1 mol carbon to produce CO2 gas gives 393.5 kJ of heat. How many mols do you have? ...
February 16, 2015

chemistry - dilution factor
I don't think so and that's one reason I don't use the factor. I'm never sure we're all on the same page with dilution factor. If the graph you are reading from gives you the concn in the SAMPLE BEING MEASURED, then you KNOW that the concn in the undiluted ...
February 16, 2015

chemistry - dilution factor
Yes, the dilution factor is 4 in 5 or 0.8. Frankly, I don't use the factor as such but read the quantity from the graph of A vs conc, which gives you the concn in the diluted sample. Then concn in diluted sample x 5/4 = concn in original sample
February 16, 2015

chemistry
Yes and if that's all the question wants you're ok. However, most questions like this want kJ/mol or kJ/gram (in this case mol or g of NaOH).
February 16, 2015

Chemistry
Noble gases are non-metals; however, astatine is not a noble gas. It is a halogen. Most articles I have read emphasize that there is some evidence for it to be a metal, some as a non-metal, and some as a metalloid. Most also emphasize that with such limited data we can only ...
February 16, 2015

Chemistry
You're right but I don't quite understand why you ask such a question. Halogens are non-metals (all of them are non-metals) Non-metals must be non-metals (or they wouldn't be called that).
February 16, 2015

science
d = rt or r = d/t speed one way = 5000/15.5 = ? speed other way = 5000/14.5 = ? average speeds and round to three significant figures. I get 333.7 which I would round to 334 m/s. 344.83 = sound with wind -322.58 = sound against wind 22.25 = 2w wind = 22.25/2 = 11.1 m/s
February 16, 2015

chemistry
mass H2O = last weighing - first weighing volume = 60 mL density = mass/volume
February 16, 2015

Science
c = f*w So as f goes up, w goes down. Yes, c is the correct answer.
February 16, 2015

Science
right again.
February 16, 2015

Science
Mrs. Sue and Ms. Sue are not the same person according to their IP addresses.
February 16, 2015

chemistry
mols C = grams/molar mass = ? Using the coefficients in the balanced equation, convert mols C to mols CH4. ?C x (1 mol CH4/2 mols C) = ? mols CH4. Convert mols CH4 to grams by g = mols CH4 x molar mass CH4 = ? g CH4. This is for 100% yield. But you will get only 83.0% of that ...
February 16, 2015

Chemistry
Use the coefficients in the balanced equation to convert anything to anything. 17.7 g H2O x (1 mol C3H8/4 mols H2O) = 17.7 x 1/4 = ? mols C3H8. Then g propane = mols propane x molar mass propane.
February 16, 2015

I am so lost
delta T = Kf*m Substitute delta T (6.60-3.98), Kf (20.00) and solve for m = molality m = mols/kg solvent. You know m and kg solvent (0.005818); solve for mols mols = grams/molar mass. You know mols and grams, solve for molar mass.
February 16, 2015

science
You need to clean up your post. Does she drop the stone or throw the stone.
February 16, 2015

Chemistry
Is that 3% w/w or 3% w/v. I will assume 3% w/v 3% w/v means 3g KCl in 100 mL solution. You want 1500 so 3 x 1500/100 = 45 g and you're right.
February 16, 2015

chemistry
pi = MRT Substitute and solve for M = molarity Then M = mols/L. You know M and L, solve for mols Then mols = grams/molar mass. You know grams and mols, solve for molar mass
February 16, 2015

I am so lost
See your post above.
February 16, 2015

Chemistry
The way I read the problem it is a hydrolysis problem. NH4^+ + H2O ==> NH3 + H3O^+ and you want the NH3 (ammonia, not ammonium) to be 5 ppm. Note that 5 ppm is 5E-3g/L and convert to mol/L and work the problem to see M NH4Cl. Then convert that to g NH4Cl in 300 gallons. The...
February 16, 2015

chemistry
http://www.jiskha.com/index.cgi?
February 16, 2015

chemistry
Ptotal = pCO2 + pH2O Ptotal is what you want. You know pCO2 is 740. Look in your text/notes and find the vapor pressure of H2O at 25 c. That is the pH2O. Calculate Ptotal.
February 15, 2015

chemistry
...........Sr(OH)2 --> Sr^2+ + 2OH^- I..........solid........0........0 C..........solid........x........2x E..........solid........x........2x Substitute the E line into the Ksp expression and solve for x = (OH^-), then convert that to pOH then to pH.
February 15, 2015

Chemistry
And what's that got to do with Kc?
February 15, 2015

chemistry
mols HNO3 = grams/molar mass M HNO3 = mols HNO3/L solution pH = -log(HNO3)
February 15, 2015

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