Tuesday
October 21, 2014

Posts by DrBob222


Total # Posts: 44,616

chemistry
Did you give up on me? a + b = 0.02 b/a = 0.158 or b = 0158a So a + b = 0.02 and we substitute 0.158 for b to read a + 0.158a = 0.02 1a + 0.158a = 0.02 1.158a = 0.02 a = 0.02/1.158 = about 0.0173 M. Substitute this value for a into a + b = 0.02 and b = 0.02-0.0173 = 0.00273 M ...
September 12, 2014

chemistry
close. I don't know where you got the 1. 10^-0.8 = 0.158. Now, that's equation 1. We can save some typing if we just call (acid) as a and (base) as b. So b/a - 0.158 and b = 0.158a Now equation 2 I gave you in my original response as a + b = 0.02 M (that's 20 mM). ...
September 12, 2014

chemistry
For whatever it's worth, the pKa of acetic acid is 4.76 according to a text I have so I suspect the author of your problem just rounded it to 4.8. And acetic acid has only one pKa value, not two.
September 12, 2014

chemistry
OK. Forget about the video and follow my instructions. There are only 5 or 6 steps. One equation you need is that last one I wrote. 4.0 is the pH you want the buffer to be. 4.8 is the pKa given to you in the problem. Substitute into the HH equation to obtain 4.0 = 4.8 + log(...
September 12, 2014

chemistry
Saraly, I think you have misread the problem. The pH is 4.0 and the pKa (there is only one listed) is 4.8 So 4.0 = 4.8 + log base/acid and base/acid = ?
September 12, 2014

chemistry
No. You can work out the problem and pick the answer that's the closest. Show your work if you have trouble and I can help you through it. Post your work up to where you don't know what to do then explain in detail why you're stuck.
September 12, 2014

chemistry
Use the Henderson-Hasselbalch equation. 1. pH = pKa + lg (base)/(acid) Substitute the numbers and solve for base/acid ratio. That's equation 1. 2. The second equation is acid + base = 0.020M 3. Solve equations 1 and 2 simultaneously to obtain (acid) and (base) 4a. You know...
September 12, 2014

Chem Help Please Urgent!!!!!!
Yes. Now to find the new boiling point just add delta T to the normal boiling point given in the problem.
September 12, 2014

Chem Help Please Urgent!!!!!!
nope. I didn't work it through but that's way too large an amount. If I divide 0.515/154 = about 0.00334 and that divided by 0.015 = about 0.223. I don't know why you threw two perfectly numbers away (the 23 of the 0.223) but that's in the ball park. So your ...
September 12, 2014

Chem Help Please Urgent!!!!!!
mols C12H10 = grams/molar mass. Solve for mols. m = molality = mols/kg solvent. Solve for m delta T = Kb*m Solve for delta T. Add delta T to the normal boiling point to find the new boiling point.
September 12, 2014

Organic-Chem Help
There are no "steps" per se except to set up a vacuum distillation apparatus. We can't draw structures on this forum but you can Google "vacuum distillation apparatus image" and obtain several nice pictures. I can find some if you can't.
September 12, 2014

Chem Help
I answered this question earlier.
September 12, 2014

Chemicals of Life/Chemistry
Look up the density of water at 20 C and the density at 80 C and use mass = volume x density to calculate the mass of 1000 mL at those two temperatures. You can type "table density H2O versus temperature" into Google and find a table. If you have trouble locating it ...
September 12, 2014

nutrition
Frankly, I don't think the answer to either question will help you eat better.
September 12, 2014

nutrition
These are questions for you to answer. The question wants YOUR opinion, not ours.
September 12, 2014

chemistry
You have a 45 typing question here. If you will explain what you don't understand about this problem perhaps we can help you straighten things out. And please not that we can not draw pictures/structures on this forum. C has 6 protons, 8 neutrons, and 6 electrons. You know...
September 12, 2014

Chemistry
q needed to heat the water is q in Joules = mass H2O x specific heat H2O x (Tfinal-Tinitial) Then convert to 255 watts and q in Joules to time.
September 12, 2014

chemistry
heat gained by water + heat lost by ethanol = 0 [mass H2O x specific heat H2O x (Tfinal-Tinitial)] + [mass ethanol x specific heat ethanol x (Tfinal-Tinitial)] = 0. You will look up the specific heats ethanol and H2O.
September 12, 2014

chemistry
q needed to heat the air is q = mass air x specific heat air x (Tfinal-Tinitial) Then 1 watt*s = J Convert J to watt and then to kW and kW-hr.
September 12, 2014

chemistry
q = mass ethanol x specific heat ethanol x (Tfinal-Tinitial)
September 12, 2014

Chemistry 1300
1. mols Al = grams/molar mass = ? Using the coefficients in the balanced equation, convert mols Al to mols Cl2. Now convert mols Cl2 to g Cl2. g = mols x molar mass. 2. Do what I did above several times; ie. as follows: mols Mg = ? mols Fe = ? Using the coefficients in the ...
September 12, 2014

Chemistry
Increase pressure which shifts the equilibrium to the right. Increase concns N2 and H2 which drives the reaction to the right. Decrease the volume which drives the reaction to the right. I don't think increasing T or adding a catalyst (both which are done in commercial ...
September 12, 2014

Chemistryyy
HCl + NaOH ==> NaCl + H2O mols NaOH = M x L = ? From the equation you can see mols HCl \= mols NaOH Then M HCl = mols HCl/L HCl 2. 0.150M = 0.150 mols/L = (0.150*molar mass NaCl)/L = about 8.9 g NaCl/L but that's an approx and you should redo this problem more ...
September 12, 2014

Chemistry, Help!
1. (P1V1/T1) = (P2V2/T2) 2. mols = grams/molar mass
September 12, 2014

Chem2
(PbSO4) = 7.9E-4M in a saturated solution. That is 7.9E-4 mols/L. Convert to g PbSO4 = mols x molar mass = approx 0.240 but you should do it more accurately. Therefore, a saturated soltuion contains 0.240 g PbSO4 in 1000 mL solution. 0.240g/1000 mL x ?mL = 1.0g. Solve for ?mL.
September 12, 2014

organic chemistry
How about reading your post and taking appropriate action?
September 12, 2014

organic chemistry
I couldn't find a website selling it. Only information about it.
September 12, 2014

example
You need to make sense of your post. Lower case won't get it. Do you want 5m or 5M? What quantity of what?
September 12, 2014

chemistry
If some O2 remains unreacted, then C is the limiting reagent. mols C = grams/atomic mass = ? Using the coefficients in the balanced equation, convert mols C to mols CO2. Now convert mols CO2 to grams. g = mols x molar mass
September 12, 2014

CHEMISTRY
Do you mean how to calculate the pH at the equivalence point or how they look? Here is how they look; i.e., its' the mid-point of the almost vertical part of the curve. https://www.google.com/search?q=titration+curves+images&client=firefox-a&hs=PS0&rls=org.mozilla:en-US:...
September 12, 2014

physical science
Discounting friction, momentum lost by one is momentum gained by the other. Therefore, the pins gained the momentum lost by te ball.
September 11, 2014

Math (2nd time posting this)!
http://en.wikipedia.org/wiki/Order_of_magnitude
September 11, 2014

Chemistry please help
a. You are allowed to the hundredths place so the answer should be 8.73. b. 1.1421E5. In mult and division, you are allowed as many places in the answer as you have the smallest number that has been mult or divided. You have 2 s.f. in 2.7E2 and 3 in 4.23E2 so you are allowed 2...
September 11, 2014

Science
I suggest you Google those.
September 11, 2014

chemistry
pH = pKa + log (base)/(acid) Substitue and solve for pKa, then convert pKa to pKb, then to Kb pKa + pKb = pKw = 14. and pKb = -logKb
September 11, 2014

Chemistry
Convert 5 oz to grams. There are 28.4 g in an oz. Convert 10.0 lb H2O to grams. There are 453.6 g in a lb. q = mass H2O x specific heat H2O x (Tfinal-Tinitial) You know Tf and Ti as well as mass H2O and specific heat H2O = 1 cal/g. When q is calculated the unit will be ...
September 11, 2014

Chemistry
1.5(9) + 14(4) + 11(4) = ? kcal
September 11, 2014

Chemistry
The correct answer is 35.6. You are allowed 3 s.f. since there are three in 155, 3 in 18.5 and 3 in 0.235. If you round to the nearest even number then 35.65 will be rounded to 35.6. Some may round to 35.7. I suspect either will be counted as correct by your database.
September 11, 2014

Chemistry
q = mass Ag x specific heat Ag x delta T Solve for delta T.
September 11, 2014

Chemistry
Do them both. q = mass metal x specific heat x delta T. q iw 50,000 The smaller heat capacity increases more.
September 11, 2014

Chemistry
See your post under Mary above. It is good if you use the same screen name with your posts. It helps us help you AND you get answers faster.
September 11, 2014

science
It means that 1 sigma (1 standard deviation) or 68% of the students will fall within +/- 17 cm of 205 cm and 95% of the students will fall within 2 sigma or +/- 34 cm of 205 cm. (And 99% will fall with 3 sigma or 205 +/- 3*17 cm.
September 11, 2014

chemistry :)
NO3^- is nitrate ion. CO3^2- is carbonate ion. HCO3^- is bicarbonate (or hydrogen carbonate ion. You get the idea.
September 11, 2014

Science
It would help if you told us what to look for. Clothes, furniture, food, spices, cleaners, what?
September 11, 2014

college chemistry
0.0620M is 0.0620 mols/L solution. g = mols x molar mass = 0.0620 x 19 = 1.18 g/L mass% = (g solute/g solution)*100 = (1.18/1000)*100 = ? = about 0.12 mass %. A ppm is 1 mg/L so if we have 1.18g/L that is 1180 mg/L and that is 1180 ppm. What the number of significant figures ...
September 11, 2014

Science
http://www.answers.com/Q/What_is_difference_between_apparent_brightness_and_absolute_brightness
September 11, 2014

chemistry
A is a true statement. B is not true. C I think is true because chemists with experience can predict most of them; however, I believe the spirit of the question is to call it not true. Since there are multiple oxidation states a plethora of compounds are possible. D is far ...
September 11, 2014

Biochemistry
Right. Up to a + 0.87a = 0.5 but then you went in the wrong direction. If a + 0.87a = 0.5 then 1.87a = 0.5 and (acid) - 0.5/1.87 = 0.267 M and (base) = 0.5-0.267 = 0.233 M. So M acid = 0.267 = mol/L. You know L and M, solve for mols and convert to grams. Do the same for M base.
September 11, 2014

science
I agree. There are chemical reactions taking place in volcanoes and plants and animals but the sytems/communities themselves are physical in nature.
September 11, 2014

Science!
Many theories go down in flames because of new evidence that is contradictory.
September 11, 2014

Music
Is the answer a whole note? Here is a note tree. https://www.google.com/search?q=note+tree&client=firefox-a&hs=9jr&rls=org.mozilla:en-US:official&channel=sb&tbm=isch&imgil=kxe2MvN9QkmVEM%253A%253B0n0Qqxw9S0aUrM%253Bhttp%25253A%25252F%25252Fwww.personal.kent.edu%25252F~jrex2%...
September 11, 2014

biology
See your other post.
September 11, 2014

biology
Why? Who know? That's just the way they are made. But where does that come from? Onions and potatoes are starchy foods and starch is carbohydrates. Sugar is a carbohydrate.
September 11, 2014

chemistry
mols = grams/molar mass = ?
September 11, 2014

CHEMISTRY
Equivalence point is where the CHEMISTRY tells you when neutralization has occurred. The end point is where the indicator tells you where neutralization occurred. So you want the end point and the eq point to be the same if possible. That usually isn't possible to be EXACT...
September 11, 2014

CHEMISTRY
The equivalence point for #1 is 7; therefore, you want an indicator that turns at about 7 which is b rather than a. #2 I think has a typo. You have bromophenol blue changing differently than for 1. The eq pt for #2 is acidic and methyl orange should do. #3 has a typo too. I ...
September 11, 2014

CHEMISTRY
You generally assign the larger number to the solvent and the smaller number to the solute. 14k Au is 14/24 pure or about 58% Au. It is alloyed with Cu, Ag, or some other metal to make it harder. So I would call Au the solvent and Cu/Ag as the solute. In a pepsi, the CO2 is ...
September 11, 2014

CHEMISTRY
Orange juice (if you can get just the juice) is homogeneous; however, in most cases it has pulp with the juice so it is heterogeneous. Tap water is homogeneous.
September 11, 2014

Chemistry
Didn't I do this for you last night? At your original post? mols NaCl = grams/molar mass Then M = mols/L
September 11, 2014

chemistry
mass = volume x density You know mass (change that to grams) and density in g/mL (same number as specific gravity), solve for mL
September 11, 2014

chemistry
Use the Clausius-Clapeyron equation. p1 = 155 torr T1 = 45.0C p2 = 760 torr T2 = 78 C change dHvap to J/mol
September 11, 2014

chem
-q = mass ice x specific heat ice x (Tfinal=Tinitial) -309 = 10.0 x 2.06 x [Tf -(-5.5)] Solve for Tf.
September 11, 2014

Chemistry - dilutions
5% x (100/109.9) x (10/50) = ?
September 11, 2014

Physical science
Take a 100 g sample which will give you 74 g C 8.65 g H 17.35 g N Now, mols = g/atomic mass. Convert these to mols and you redo these because I will estimate. 74/12 = about 6.2 8.65/1 = 8.65 17.35/14 = 1.24 Now find the ratio of these numbers to one another with the smallest ...
September 11, 2014

Chemistry
Frankly I don't think this problem is workable unless we make some assumptions which probably are not true. The penny has a mass of 2.50g mass Cu = 2.50*0.025 = about 0.06 g mass Zn = 2.50*0.975 = about 2.44 g volume Cu = m/d = 0.06/8.94 = about 0.007 cc volume Zn = m/d = ...
September 11, 2014

Chmistry
First it isn't what I call a cube because the dimensions of each side are not the same. The volume is length x width x height but be sure to change the units so all of them are the same. I would suggest you change all to cm which will be 20.0 cm x 15.2 cm x 45.8 cm = ? ...
September 10, 2014

Science
Calculate the density as d = mass/volume and compare the measured value with that of pure metals.
September 10, 2014

Science
FYI. There are spectral emission lines and spectral absorption lines. If you can describe what you're studying I may be able to guess where you're going with this. Otherwise, here is link that may get you started. http://phet.colorado.edu/en/simulation/blackbody-spectrum
September 10, 2014

Science
I don't think it does. And are you talking emission lines or absorption lines? I strongly suspect (although I've not counted them) that uranium produces more spectral emission lines than you can get from the sun.
September 10, 2014

chemistry
mols NaCl left in the beaker (the same as mols in the original solution) = grams/molar mass = ? Then M = mols/L
September 10, 2014

Science
The composition of the sun.
September 10, 2014

Science
Fluorescent lights contain a small amount of liquid mercury.
September 10, 2014

Chemistry
M = mols/L 0.0013 M = mols/3.50L mols = 0.0013 mols/L x 3.50L = estimated 0.005 mols but you need to do that more accurately. Then substitute for n in PV = nRT with other conditions and solve for volume.
September 10, 2014

chemistry
We would like for you to do some work on your own. I gave you most of b and a you obtained mostly from Bob Pursley. So write up c,d,e, and we will critique them for you.
September 10, 2014

Science
I agree with the answer for #1. Having said that, however, it is my opinion that much of society is hardly scientifically literate.
September 10, 2014

chemistry
M = mols/L = 0.1 mol/10L = 0.01M Qc = (PCl5)/(PCl3)(Cl2) = 0.01/0.01*0.01 = 100. Since Qc>Kc that means the means too much product and too small reactant so the reaction will move to the left to achieve equilibrium. ..........PCl3(g) + Cl2(g) <==> PCl5(g) I.........0....
September 10, 2014

chemistry
See your post above.
September 10, 2014

chemistry
q = mass air x specific heat air x (Tfinal-Tintial) You know q, mass, Tf and Ti. You will need to look up the specific heat of air. Solve for q (in joules) needed. Then 1 watt = 1 joule/second Here is a site that will convert joules to kW-hr. http://www.rapidtables.com/convert...
September 10, 2014

chemistry
q = mass ethanol x specific heat ethanol x (Tfinal-Tinitial) q is 938 J. mass you get from the density and volume. You must look up the specific heat of ethanol. Solve for Tfinal.
September 10, 2014

Chemistry
To follow up on Bob Pursley's response, you know the Cl2 will be the limiting reagent (unless of course you start with too much P4) but I would think you start with some amount of P4, use stoichiometry to add enough Cl2 to form PCl3 and do a separate calculation to see how...
September 10, 2014

chemistry
I assume the concentrations shown are initial concentrations. ...........N2(g)+ O2(g) <--> 2NO(g) I.........0.025..0.025.......0.0015 C..........+x......+x........-2x E.......0.0025+x..0.025+x....0.0015-2x Kc = (NO)^2/(N2)(O2) Substitute into Kc expression and solve for ...
September 10, 2014

chemistry
With Q>K it means products are too large and reactants too small which means the reaction will move to the product side to achieve equilibrium. You need to show the reaction to know which Kc we are talking about; i.e., the forward or reverse reaction.
September 10, 2014

chemistry
In most cases specific gravity is the same numerical value as density in g/mL. density = mass/volume. You have the mass. When you substitute volume in cc or mL you can calculate density.
September 10, 2014

Physical science
AgCl AgNO3(aq) + KCl(aq) ==> AgCl(s) + KNO3(aq) Ag^+(aq) + Cl^-(aq) ==> AgCl(s)
September 10, 2014

Physical science
precipitation reaction ionization or dissociation cation base
September 10, 2014

Chemistry
a. %w/w = (grams solute/g solution)*100 % = [900,000/(100,000+900,000)] x 100 = ? b. M = mols solution/L solution. mols solute = grams/molar mass = ? L solution = 100 Solve c. m = mols solution/kg solvent m = mols solute same as for part b. kg solvent you don't know and ...
September 10, 2014

chemistry
The easy to do this is to determine the molarity of the concentration HCl. That's 1.20 g/mL x 1000 x 0.37 x (1 mol/36.5g) = approx 12 M but you should be more accurate than that. Then use c1v1 = c2v2 12*v1 = 0.25*100 Solve for v1. That will give you the amount of concd HCl...
September 10, 2014

Algebra!!!! HELP
V = k/t^2
September 10, 2014

Physical science
CaCO3 is insoluble. All of the others are soluble.
September 10, 2014

heat change
q = mass Au x specific heat Au x delta T. Solve for delta T.
September 10, 2014

chemistry
This may be a dimensional analysis problem but you don't have enough information to do a dimensional analysis. kg fuel = 0.803 kg/L x L fuel = ? kg. [That part is dimensional analysis. Note that L in the denominator of kg/L cancels with L in the numerator to leave kg.] But...
September 9, 2014

Chemistry
% anything actually is parts per hundred; i.e., how many somethings you have in 100 total. If we had 6 toys and 3 were wagons. we would have 50% wagons. That is % wagons = (# wagons/total toys)*100 = 50%. Or if there are 75 people in a room and 25 of them are men and 50 are ...
September 9, 2014

Chemistry
That shows a tetrahedral structure; therefore, it must be sp3 if you meant Co and not CO
September 9, 2014

Chemistry
Do you mean [CoCl4]^2- https://www.google.com/search?q=[COCl4[^2-&client=firefox-a&hs=ryD&rls=org.mozilla:en-US:official&channel=sb&tbm=isch&tbo=u&source=univ&sa=X&ei=IqsPVLOsIoPPggSSyYCwCA&ved=0CCcQsAQ&biw=1007&bih=601
September 9, 2014

Math Problem (please help)
e^0 = 1
September 9, 2014

Chm Help Please!!!
m = molality = mols/kg solvent. You know mols and kg solvent, solve for m Then substitute m into the below equation. delta T = Kb*m Solve for delta T and add to the normal boiling point to find the new boiling point.
September 9, 2014

Organic CHM Lab
Look up the boiling points of n-hexane, benzene and toluene. It should be easier to separate the two with the greater boiling point difference.
September 9, 2014

Organic CHM Lab
Scroll down to flooding and read about that.
September 9, 2014

chemistry
Pethyl ether = Xethyl ether*P<aup>oethylether 380 = X*400 Solve for X
September 9, 2014

chemistry
You must not have copied all of the problem. How far is the jet going?
September 9, 2014

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