Saturday
August 29, 2015

Posts by DrBob222


Total # Posts: 49,818

physics
momentum before = momentum after 4*10 = 4*5 + 10*x
May 17, 2015

chemistry
dG = dH - TdS Substitute and solve for dG. Then dG = -RTlnK Substitute and solve for K.
May 17, 2015

College Chemistry
I don't mind helping you through it but tell me what you know about this. Just working the problem won't help you. I assume part a means the equation for the SPONTANEOUS REACTION or is it the reaction for the way the cell is set up (and that could be spontaneous). So ...
May 17, 2015

Chemistry - PLEASE HELP!!!
M = mols/L (that's the definition--start with that). Then mols = grams/molar mass = ? and I'll estimate that at approx 25/40 = about 0.5 mol (remember this is only close so yo need to redo the math to obtain a more accurate answer). M = mols/L. You know mols and you ...
May 17, 2015

Chemistry - Equilibrium
I tried to find some graphs; here is the best I could do.http://en.wikipedia.org/wiki/Reaction_coordinate You're right with your statement about catalysts and I agree that the last two change. I am ambivalent about c because of the wording. Adding a catalyst certainly ...
May 17, 2015

Chemistry
The approximate concentration of the HCl solution that you have on hand is 0.5M. Therefore, if you transfer 10.00 mL of that HCl solution to an Erlenmeyer flask, the concentration of the HCl still is approximately 0.5M. Since HCl is a strong acid and ionizes 100%, the ...
May 17, 2015

Math (Solving Equations)
I think what "you do from here" is to expand and factor the terms; however, can you subtract 2x/3 from X^2/6. Those are not like terms. I don't believe you can do that, at least not legally. Therefore, I don't agree with the "getting here" part. ...
May 17, 2015

Chemistry
Look up the redox potential of each and note that the problem SHOULD have specified acid or basic conditions.
May 17, 2015

science
q = 1000 g x heat vaporization at 37 C in cal/g. Convert to kcal.
May 17, 2015

chemistry
(P1V1/T1) = (P2V2/T2) Remember BOTH temperatures must be in kelvin
May 16, 2015

chemistry help
Can you describe the diagram. Is there a way of reading the diagram for concentration, mols, mL, etc.
May 16, 2015

chemistry help
Can't be done with no concentrations listed. If you have the concentrations use the Henderson-Hasselbalch equation. Post your work if you get stuck but show what the the concentrations you are using.
May 16, 2015

chemistry help
I don't know the rest of the problem but a Zn/Al galvanic cell the Al is the anode and Zn is the cathode.
May 16, 2015

To Mahlako---biology
You need to do this right. Co2 is not CO2 and the equation is not balanced. It's 6CO2 + 6H2O ==> C6H12O6 + 6O2 An equation not balanced is correct only when noted that it is unbalanced.
May 16, 2015

science (percentage yield)
OK. You know how to get mols. mols = grams Fe/atomic mass Fe = 100 g Fe/55.85 = ?. That is estimated 1.9. To convert mols use the coefficients in the balanced equation. To convert from mols Fe to mols Fe2O3 that's 1.9 mols Fe x (2 mol Fe2O3/4 mols Fe) = 1.9 mols x (2/4) = ...
May 16, 2015

science (percentage yield)
Rust is a number of oxides of iron(III); technically, we can't calculate how much rust will form since it can take more than one form. If we call rust Fe2O3 it is done as follows. 4Fe + 3O2 --> 2Fe2O3 mols Fe = grams/atomic mass = ? Use the coefficients in the balanced ...
May 16, 2015

Science
I agree.
May 15, 2015

Science
I agree.
May 15, 2015

Science
I agree, at least part of the sound wave is absorbed. What is left over still can be transmitted or reflected.
May 15, 2015

Chemistry
You want it balanced? You want it corrected? You have a question? Corrected as as follows: 2Li + Cu(NO3)2 > 2LiNO3 + Cu If you really meant CuNO3, then Li + CuNO3 ==> LiNO3 + Cu but copper(I) nitrate is not that common.
May 15, 2015

Chem
If you're worked this several times with no luck I assume that means you are checking with a database. Why not show your work and let us find the error? It's much easier that way instead of us guessing what you have done right and what you have done wrong.
May 15, 2015

Science 8th Grade
start, stop, change direction, compression/decompression, etc.
May 15, 2015

chemistry- Check please
I think you need to find a way to clarify the question. As an example of what is missing, Zn ==> Zn^2+ + 2e Eocell = +0.76 Cu^2+ + 2e ==> Cu Eocell = +0.34 -------------------------------- Zn + Cu^2+ ==> Zn^2+ + Cu and Ecell = about 1.1 v BUT it isn't clear that ...
May 15, 2015

chemistry- Check please
I know we've talked about this before. Do you have some reason for knowing your answers are not right. Also, I'm still a little confused about how this is to be done; for example, if I use H2 and Ag (as opposed to Ag and H2) the voltage is -0.8 and that would be lower ...
May 15, 2015

Science
http://en.wikipedia.org/wiki/Evolution
May 14, 2015

chemistry
So it has a mass of 53.0 grams and volume of 51.5 cc (volume of the water = mass/1.00 = 51.5 cc. Density of the saline is ?
May 14, 2015

chemistry
delta T = Kb*molality Substitute and solve for m m = mols/kg solvent Substitute and solve for mols. mols = grams/molar mass. You know grams and mols, solve for molar mass.
May 14, 2015

Chemistry
4.41E-3/11 sec is rate of consumption S2O3^2-. Rate of production I^- is same.
May 14, 2015

Chemistry
To calculate dS for each reaction, it is dSrxn = (n*dSo products) - (n*dSo reactants) You look up the dSo values in your text or notes.
May 14, 2015

Math
I don't believe +2 is right. You should do (y2-y1)/(x2-x1) and see if you obtain 2.
May 14, 2015

For my future, I'm 13.
You were 21 just a few posts below. Are you going back in time?
May 14, 2015

Science
It's density = grams/volume Substitute and solve.
May 14, 2015

Science
find volume of tank in cubic feet. 11 x 18 x 12 = ? cubic feet. Then (62.4 lbs/ft^3) x ? cubic feet = weight water in lbs.
May 14, 2015

Science
See your other fish tank problem. Same formula, Substitute and solve for the only unknown.
May 14, 2015

Chemisty
Bob Pursley is right. More explicitly, it comes from this. If we start with 100 counts and drop to 50 counts (which is 1 half life or t1/2), then ln(No/N) = kt ln(100/50) = kt1/2 ln 2 = kt1/2 0.693 = kt1/2 and k = 0.693/t1/2
May 14, 2015

Chemisty
ln(No/N) = kt No = 3000 N = 2736 k = ? t = 48 hrs. Solve for k. Then k = 0.693/t1/2 Substitute k from above and solve to t1/2
May 14, 2015

Chemistry
How many mols do you want? That's mols = M x L = ? Then mol = g/molar mass. You have mols and molar mass, solve for grams.
May 13, 2015

chemistry
Yea! Go to the top of the class.
May 13, 2015

chemistry
You must read and follow step by step. I'll get you started. Following are my step by step instructions and I'll do the first few steps to show you how it's done. 1. Write and balance the equation. You have that. 4Al(s)+3O2(g)->2Al2O3(s) 2. Convert what you have...
May 13, 2015

chemistry
Your 0.09259 is mols Al. That's the first step. Now you do mols O2 and follows steps 2,3,4.
May 13, 2015

chemistry
I don't get that answer. Post your work and I'll find the error. Follow the steps above.
May 13, 2015

chemistry
2a and 2b above. mols = grams/molar mass For Al that is grams/atomic mass = 2.5 g/ 27 = ?
May 13, 2015

chemistry
This procedure will work almost all of the stoichiometry problems. This one is a limiting reagent problem (LR); you know that because amounts are given for BOTH rectants. I work these the long way. 1. Write and balance the equation. You have that. 4Al(s)+3O2(g)->2Al2O3(s) 2...
May 13, 2015

chemistry
Yes, I can.
May 13, 2015

Organic chemistry
The hydrolysis of phthalic anhydride yields phthalic acid.
May 13, 2015

chemistry
When you blow into the solution you are adding CO2 to the solution. The CO2 reacts with water to form H2CO3 and that ionizes to produce H^+. That lowers the pH of the solution and the phenolphthalein turns the acid color which is colorless. You write the equations.
May 13, 2015

chem
Didn't you ask recently if this is an outer or inner complex? That ALMOST tells you that it is d2sp3. And the fact that oxalate is a bidentate and there are three of them makes the coordination number of six. That almost surely makes it octahedral. And octahedral is d2sp3.
May 13, 2015

chemistry
Single bonds are sigma (s-s or s-p bonds). Pi bonds are double & triple (sp AND p-p).
May 13, 2015

Chemistry
2. You had 5 mL in the tube initially (of KSCN but that's still 5 mL). You add 5 mL of 0.2 M Fe(NO3)3 so the iron nitrate has been diluted from to 10 mL; therefore, its concentration has been halved. That is 0.2 M x (5/10) = ? I'm assuming that the last sentence about ...
May 13, 2015

Chemistry
I assume you mean boiling point as in solutions and not boiling point of the pure material. i is the van't Hoff factor and is the number of particles MnSO4 ==> Mn^2+ + SO4^2- so i = 2
May 13, 2015

Chemistry
Hydrogen is flammable; therefore, no open flames
May 12, 2015

Chemistry Gas Law
Mg + 2HCl ==> H2 + MgCl2 Use PV = nRT and solve for n = mols H2 gas at the conditions of the problem. Use the coefficients in the balanced equation to convert mols H2 to mols Mg. Then g Mg = mols Mg x atomic mass Mg (in grams). Convert to mg. Finally, length of Mg is 1.83 ...
May 12, 2015

chem
I don't know what they are considered to be but they are dimagnetic.
May 12, 2015

science
I don't understand the question. There are all kinds of molecules. Are you talking about air molecules, water molecules, dust molecules, or some other kind? About move, do you mean do they move up, down, horizontally one way or the other?
May 12, 2015

To Kelsey
Your buffer problem has moved down quite a bit but I've responded to your last response with my own response.
May 12, 2015

chem
http://en.wikipedia.org/wiki/Potassium_ferrioxalate See the site above. This is a high spin complex which I believe means it is an outer orbital complex.
May 12, 2015

chem
My crystal ball is hazy today. What are you doing? Which reagents are you using? I assume it's a typo but I'm sure you meant "dihydrate">
May 12, 2015

Chemistry-check answer please
I may have misunderstood the question but I don't agree with your answer. Did you work out the voltage generated by each possible pair? And do you want the highest or lowest voltage, period, or do you that only for cells that are spontaneous? For the low voltage, for ...
May 12, 2015

Chemistry
q = mass oil x specific heat oil x (Tfinal-Tinitial)
May 12, 2015

Chemistry
You are making it far too complicated. pH = pKa + log (base)/(acid) millimols base = 150 x 0.75 = ? millimols acid = 250 x 0.50 = ? Substitute the millimols into acid/base and solve for pH. Tehcnically, one can't substitute millimols; i.e., it is supposed to be ...
May 12, 2015

Chemistry
What's the problem. Use the HH equation. If you want me to check it let me know what you're using for pKa for HF.
May 12, 2015

chemistry
See your other post.
May 12, 2015

chemistry
You CANNOT continue in chemistry and not use the caps key. I will get you started. Cr goes from +6 for each on the left to +3 on the right for each. I on the let is -1 and on the right is zero. Make things easy by making that 2KI on the left. You may need to change it later ...
May 12, 2015

Chemistry
H2CO3 has two ionization constants; i.e., ka1 and ka2. Generally the Ka values for diprotic acids is far apart and you simply treat these as two separate ionizations; the second one contributes little so you ignore it. ..........H2CO3 ==> H^+ + HCO3^- I........0.23.......0...
May 12, 2015

science(check answers)
I don't see anything to check. (No answer)
May 12, 2015

Chemistry
7.2 is right for pK2. And I obtained 6.0g NaH2PO4 which is quite close to your number. The difference is that I used 43.15 mL of 1M NaOH to do that and that's the difference. Do you want to work on that a little or want me to show you what I did.
May 12, 2015

Chemistry
I don't think so. pH = 7.21 + log (0.007/0.007) pH = 7.21 which isn't 8.00 7 mL x 1 M = 7 millmols NaOH = 0.007 mols.
May 12, 2015

Chemistry
If we are to try for the same number I need to know what you used for pK2.
May 12, 2015

Chemistry
I obtained 0.038 for x. So Y is 2x isn't it? ...........XY2 ==> X^2+ + 2Y^- I........solid.....0.......0 C........solid.....z......2z E........solid.....z......2z Note that Y is just twice X. I tried, with different manipulations, to obtain 0.0318 but couldn't do it...
May 12, 2015

Chemistry
No, the answer is 2.0E-5. I've looked at the problem again and it appears not to have any "tricks of the trade" attached to it so I believe if you have a database version or an answer sheet that those are incorrect.
May 12, 2015

Chemistry
.......X2Y(s)<-->2X^+(aq)+Y^(2-)(aq). Ksp = (X^2+)^2(Y^2-) X = 0.02 Y = 0.05 Ksp = (0.02)^2(0.05) = ?
May 12, 2015

chem
N2 + O2 --> 2NO mols N2 = grams/molar mass = 10/28 = approx 0.3 but you need a more accurate answer than that estimate. Use the balanced equation to convert mols N2 to mols NO. That's 0.3 x (2 mols NO/1 mol N2) = approx 0.3 x 2/1 = approx 0.6 mol NO. Then grams NO = ...
May 12, 2015

Chemistry
See your post above.
May 12, 2015

Electronics, Physics
The parallel group has an equivalent resistance of 1/R = 1/R1 + 1/R2 1/R = 1/60 + 1/5 R = ? which I will call Rp Then the total for the circuit is Rtotal = 10 + Rp = ?
May 12, 2015

Math to hard please help
The 4x^2 and 3x^2 are like terms. You can add or subtract like terms but not unlike terms. The 15x is a different terms than x^2 and has no other like term. So 4x^2 - 3x^2 = x^2 +15x has nothing to add or subtract so it remains 15x. -3 and -5 = -8
May 11, 2015

Chemistry
I don't intend to work this problem for you under any name. You take those numbers I gave you earlier and substitute them. Telling me you don't know how to solve for t doesn't help. Substitute the numbers, show me your work, go as far as you can, then tell me what ...
May 11, 2015

Science
http://www.enviropedia.org.uk/Weather/Movement_of_Air.php
May 11, 2015

chemistry B-11
P1V1 = P2V2
May 11, 2015

Chemistry
mols H2 gas = mL/22,400 = ? Using the coefficients in the balanced equation, convert mols H2 gas to mols K. Now convert mols K to grams. g = mols K x atomic mass K = ?
May 11, 2015

Chemistry
.......N2 + 3H2 ==> 2NH3 I.....1.15..1.36......0 C......-x....-3x.....2x E....1.15-x..1.36-3x..2x So if 2x = 0.78 then x = 0.39 The way they get 86.02% is this. (3x)/1.36]*100 = 86.029 but that makes no sense to me. I Googled "extent of reaction" and came up with ...
May 11, 2015

Chemistry
I don't know what you mean by extent of reaction.
May 11, 2015

Math
Yes, D is correct.
May 11, 2015

oops--four typos--Math
If n is supposed to be that series, then you do 5*3^n 5*3^1 = ? 5*3^2 = ? 5*3^3 = ? 5*3^4 = ? etc. What you must do is evaluate the 3^n part and multiply by 5. 5*3^1 = 5*3 = 15. etc.
May 11, 2015

Math
If n is supposed to be that series, then you do 5*3^n 5*3^1 = ? 5*3^2 = ? 5^3^3 = ? 5^3^4 = ? etc. What you must do is evaluate the 3^n part and multiply by 5. 5^3^1 = 5^3 = 15. etc.
May 11, 2015

Math
If you don't know what n is, how did you arrive at A as being the best answer? Guessed, I suppose. I think n is supposed to 1, then 2, then 3, then 4, etc. so that you have a series of answers.
May 11, 2015

Math
If n is supposed to be 1,2,3,4 sequentially, your answer of A is not right.
May 11, 2015

Math
Your question isn't very clear. What's n?
May 11, 2015

Chemistry
Here is the process that will work EVERY ONE of the titration problems. In fact it will work ALL of the stoichiometry problems, bar none. By the way, most of us here use carets to denote an exponent. No caret means it is a coefficient OR a subscript. Placed BEFORE the equation...
May 11, 2015

Math
try 87.532 That's 80 +07 +0.5 +0.03 +0.002 Total is 87.532
May 11, 2015

Science
The amplitude of the two waves add (algebraically) and the new is zero amplitude.
May 11, 2015

Science
The formula for visible light is a new one on me. The speed of light is dictated by the formula C = frequency*wavelength but that works no matter visible or not visible light. When light passes through a medium it bends slightly(is refracted) because it slows down slightly. ...
May 11, 2015

Science
For 1, P = E*I
May 11, 2015

Science
very poor; however, it will burn.
May 11, 2015

oops--typo--chemistry
0.01kg = 10.0 grams water.
May 11, 2015

Chemistry 20
When one has gases one may treat L as if they were moles and not go through the conversion to mols step. 17 L CH4 x (3 mols O2/2 mols CH4) = 17 x 3/2 = ? L O2.
May 11, 2015

Science
7 is correct. 8 is incorrect. Look back at my comments to #1. Henceforth, please make your answers at the point of entry. A letter will do, asterisks will do, almost any notation will do but it takes at least three or four scroll downs and scroll ups to check one question (for...
May 11, 2015

Science
6 is incorrect if you mean 2 N. If you mean answer b (of 3N) 6 is correct.
May 11, 2015

Science
C is not correct for 5. 52 x 10 = 520 for the cheetah. 5000 x 1 = 5000 for the elephant which is not less than 520
May 11, 2015

Science
4 is correct.
May 11, 2015

Science
3 is correct.
May 11, 2015

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