Sunday
July 5, 2015

Posts by DrBob222


Total # Posts: 49,397

chemistry
How many doesn Au element have? That's the same as the number of protons and that's the atomic number in the periodic table. To make it +1 ion you must lose 1 electron.
April 15, 2015

Chemistry
Why can't you do this? It's just like the last problem. After you see a problem worked you should be able to use that as a template and work similar problems.
April 15, 2015

chemistry
Why are you having trouble with equations?
April 14, 2015

Chemistry
If you had posted your work I wouldn't have to guess what you did. M HCl = 2.7E-4 pH = -log(HCl) since HCl is a strong acid and ionizes 100%. Then (H^+)(OH^-) = Kw = 1E-14
April 14, 2015

Chemistry
PV = nRT. Remember the units. Also T must be in kelvin.
April 14, 2015

Chemistry
2HNO3 + Ca(OH)2 ==> Ca(NO3)2 + 2H2O mols Ca(OH)2 = M x L = ? Using the coefficients in the balanced equation, convert mols Ca(OH)2 to mols HNO3. Then M HNO3 = mols HNO3/LHNO3. You have mols and M, solve for L.
April 14, 2015

Chemistry
Is this 2% w/v. I'll assume so. [(g solute/mL solution)]*100 = % Substitute and solve for g solute.
April 14, 2015

Chemistry
XN2 = 0.745 pN2 = XN2*Ptotal pN2 = 0.745*1 atm = 0.746 atm or 0.745*760 = ? mm = pN2
April 14, 2015

chemistry
2HClO4 + Li2CO3 --> 2LiClO4 + H2O + CO2
April 14, 2015

Chemistry: Potentiometric Anyalysis
Sorry to get back so late but here is what I think based on what you wrote. IF (and only IF) you used the titration CURVE to determine the equivalence point on the computer (that is you determined the eq pt graphically on the computer), then mols acid comes from mols NaOH and ...
April 14, 2015

Chemistry: Potentiometric Anyalysis
I don't know what lab you did. Did you place a weak acid or base in solution, measure the pH, calculate what? what else do you know?
April 14, 2015

chemistry
First, calculate the M of the initial solution. mols CuSO4.5H2O = grams/molar mass = ? Then mols/L = M So the diluted solution is M of first x (13.6/500) = ? For the last part. How many mols do you have in the second solution? That's mols = M x L = ? Then mols = grams/...
April 14, 2015

Chemistry
See your other post under Tim.
April 14, 2015

Chemistry
1. mols = M x L = ? Then mols = grams/molar mass. Substitute mols and molar mass and solve for grams. 2. Just like 1 but in reverse. mols Na2SO4 = grams/molar mass = ? Then M x L = mols. You know mols and M, solve for L. 3. I think this is just #1 again. I'll check you ...
April 14, 2015

Chemistry
Tim, this is just like the problem you posted below which Jundy answered incorrectly but I followed up. What is it you don't understand about limiting reagent problems? We need to get you so you can work all of these yourself.
April 14, 2015

chemistry
I don't understand the problem. Can you give an example or two for n and A.
April 14, 2015

Chemistry
NaOH + H2SO4 ==> NaHSO4 + H2O You have 0.1M x 50 mL = 5 millimols H2SO4. Therefore, to reach the first equivalence point you must titrate 5 millimols (another 5 millimols will be needed to titrate the second H). So you will need 50 mL of 0.1M NaOH to titrate that first H ...
April 14, 2015

Science
momentum is mass x velocity. The wrecking ball is MUCH heavier than the tennis ball; therefore, it does much more damage when it hits the wall.
April 14, 2015

chemistry
PV = nRT and solve for n = number of mols. Then n = grams/molar mass. You know molar mass and n, solve for grams.
April 14, 2015

Chemistry
I don't believe Junday into account the 85 grams of each reactant. mols SO2 = 85/64 = about about 1.3 mols H2S = 85/34 = about about 2.5 Calculate LR from that and I believe the LR is H2S. Check it out.
April 14, 2015

Chemistry
Many thanks for showing your work. It helps me spot the problem right off. BTW, I assume this is a monoprotic acid. Your error is in step 2. 1.78 mmols NaOH is correct. That means mmols HA is 1.78. You took 25 mL for that titration and M = mmols/mL; therefore, 1.78 mmols/25 mL...
April 14, 2015

Chemistry
q = mass metal x heat fusion. You know q and heat fusion, solve for mass metal.
April 14, 2015

Science
E = 2.18E-18*Z^2(1/16 - 1/36) Note this goes from 4 to 6 so energy must be absorbed.
April 14, 2015

Science
See your last post. Also, just what do you mean by value? size, length, width, energy, just what kind of value?
April 14, 2015

Science
You have posted many questions in the last week or so but never any thoughts about the answer. You need to start telling us what you think the answer is or exactly what you don't understand.
April 14, 2015

chemistry
Volume of 1 atm? I might believe 1 L but not 1 atm for volume.
April 14, 2015

Science
d although I don't like the word decay following gamma. Gamma rays are the result of decay of the parent atom.
April 14, 2015

Chemistry
mass in grams = volume x density Then convert grams to pounds. There are 453.6 grams in one pound.
April 14, 2015

Science
1/wavelength = R(1/9 - 1/25) Then E = hc/wavelength. OR E = 2.18E-18(1/9 - 1/25)
April 14, 2015

Science
Convert amu to kg, then E = mc^2
April 14, 2015

Science
How many days in a month? Use 30? 50/30 = 1.67 months in 50 days k = 0.693/t1/2 and substitute k into the below equation. I used 1.67 months. ln(No/N) = kt. No = 100 mg N = ? solve for this k from above. t = 5 months
April 14, 2015

Chemistry
5500 kJ. 40.6 kJ/mol x # mol = 5500 kJ. Solve for mols H2O Convert mols H2O to grams. Convert, using density, grams H2O to L H2O.
April 14, 2015

chemistry
0.25 x ((5/2/3/2) = 0.25 x (2.5/1.5)= ?
April 14, 2015

Chemistry
I note that many of these are the same type. Learn to work one and you know how to work all. If you will kindly start over with the first one of your choice, tell us exactly what you don't understand about it, perhaps we can help you through it. Then we can proceed to the ...
April 14, 2015

Chemistry
PV = nRT and solve for n = number of mols. Then n = grams/molar mass. You know n and grams, solve for molar mass. Identify the gas from that. Remember some gases are diatomic.
April 14, 2015

Chemistry
You need to work on this post. It's willy nilly. No sense.
April 14, 2015

Chemistry
pKa = -log Ka. Solve for Ka. Then..........HA ==> H^+ + A^- I.............1.......0.....0 C...........-.375...0.375..0.375 E...........0.625...0.375..0.375 Substitute the E line into the Henderson-Hasselback equation and solve for pH.
April 14, 2015

chemistry
(V1/T1) = (V2/T2) Remember all Ts must be in kelvin.
April 13, 2015

science
http://en.wikipedia.org/wiki/Agonist
April 13, 2015

chemistry
q1 = heat to raise ice from -14.3 to zero. q1 = mass ice x specific heat ice x (Tfinal-T(initial) q2 = heat to melt ice q2 = mass ice x heat fusion q3 = heat to raise T liquid H2O from zero to 24.8 q3 = mass water x specific heat H2o x (Tfinal-Tinitial) Then q1 + q2 + q3 = 4....
April 13, 2015

AP Chem
The reaction, if it occurs, is Pb + 2HCl ==> PbCl2 + H2 dGrxn = (n*dGo products) - (dGo reactants) Then dG = -nEcell*Faraday Post your work if you get stuck. F = 96,485. n = 2 electrons.
April 13, 2015

CHM
I see a lot of information here but no question.
April 13, 2015

chemistry
Write the balanced equation and follow that last post.
April 13, 2015

chemistry
I showed you how to do this. You do this on your own and post your work. I'll check it. However, first you need the equation; otherwise, you won't know what the limiting reagent is.
April 13, 2015

Chem
You can convert mols of anything in an equation to mols of anything else in that equation by using the coefficients in the balanced equation. It works just like dimensional analysis. 3.27 mols CO2 x (3 mols O2/4 mols CO2) = 3.27 x 3/4 = ?
April 13, 2015

Chemistry
Zn + 2HCl ==> H2 + ZnCl2 mols HCl = M x L = ? Using the coefficients in the balanced equation, convert mols HCl to mols Zn. Now convert mols Zn to grams. g = mols Zn x atomic mass Zn.
April 13, 2015

chemistry
reaction of nitromethane with what? Do you have an equation?
April 13, 2015

chemistry
mL1 x M1 = mL2 x M2
April 13, 2015

chemistry
Your answer is correct but you have too many significant figures listed. You're allowed only 2. That means to round your answer to 29 g.
April 13, 2015

chemistry
The 625 should be in the denominator. It should be 12.5 g NaOH x (1 mol NaOH/40 g NaOH) x (1/625 mL) x (1000 mL/L) = ?
April 13, 2015

Chemistry
Thanks for letting me know before I had to look up those numbers.
April 12, 2015

Delaware State University
Chemistry is the subject, not Delaware State University. The most complicated has the largest, the least complicated has the least S.
April 12, 2015

chemistry
Frankly, I don't think this question can be answered and be confident the answer is correct. Beaker a COULD be HCl or NH3 and beaker b COULD be NH3 or HCl. And of course they might be thousands of other elements/compounds. And since you don't know what chemical is in ...
April 12, 2015

Chem
1. Write and balanced the equation. 2. Convert 2 lb KClO3 to grams. 3. Convert g KClO3 to mols. mols = grams/molar mass 4. Using the coefficients in the balanced equation, convert mols KClO3 to mols KCL. 5. Convert mols KCl to grams via g = mols KCl x molar mass KCl = ?
April 12, 2015

Chemistry
I think the sign for exponent of Kp is -5 and not +5. Check that out. I think you have too many significant figures in 3.472 but you have rounded correctly in the answer. . I don't understand the dG calculation at all. If I plug in 3.472E+5 I don't get 25.4. If I plug ...
April 12, 2015

Chemistry
Add equation 1 to equation 2 and check to see that gives the equation you want. Then add dGo values.
April 12, 2015

Chemistry
I answeed this for you. All you need to do is to substitute n, Eo, and F(faraday) and solve for dGo. I assume "standard potential" means Eocell for the reaxction.
April 12, 2015

Chemistry
dGo = -nEF
April 12, 2015

Chemistry
Tell me what you don't understand about this. Can you write the two half cells. The overall spontaneous reaction? If so show them and explain what you don't understand about the next step.
April 12, 2015

Chemistry
All compounds are zero. You know Zn and O, solve for Cr and you want it for EACH Cr atom.
April 12, 2015

Chemistry
Liquids < S than gases. higher molar mass >S than lower molar mass
April 12, 2015

chemistry
Your question makes no sense. Cl is not in CH3OH. The molar mass of CH3OH is 32 in round numbers. 12 + 3 + 16 + 1 = about 32.
April 12, 2015

chemistry higher
This is a limiting reagent (LR) problem and we know that because amounts are given for BOTH reactants. I do these the long way. mols Mg = your number is right at 0.247 and that will produce 0.247 mols H2 if you had all of the HCl needed. mols HCl = M x L = 1 x 0.1 = 0.1 0.1 ...
April 12, 2015

Chemical Reactions
Google it.
April 12, 2015

Chemistry - Help
Your equation isn't balanced. I would write the net ionic equation as 2CrO4^2- + 2H^+ ==> Cr2O7^2- + H2O Keq = (Cr2O7^2-)/(H^+)^2(CrO4^2-)^2 If you want to keep your equation molecular I would balance it this way. 2K2CrO4 + 2HCl ==> K2Cr2O7 + H2O + 2KCl
April 12, 2015

Chemistry
molecular equation: Zn(s) + 2AgNO3 ==> Zn(NO3)2 + 2Ag(s) net ionic equation: Zn(s) + 2Ag^+ ==> Zn^2+ + 2Ag(s)
April 12, 2015

Math Please Help Me
3 can be done a couple of ways. The percent way is this. He caught 100 deer and 17 were tagged; that's 17% tagged or 0.17 Then 17% of what number is 66 which is 0.17*number = 66 number = 66/.17 = ? or you can do it this way. Take the number caught, 100, and 100 x 66/17...
April 12, 2015

physics- Space
Some of what you want can be found here. http://science.howstuffworks.com/dictionary/astronomy-terms/dark-matter-dark-energy.htm
April 12, 2015

Chemistry
You didn't list any choices but here is how you work the problem heat lost by metal + heat gained by water = 0 [mass metal x specific heat metal x (Tfinal-Tinitial)] + [mass H2O x specific heat H2O x (Tfinal-Tinitial)] = 0 Substitute and solve for specific heat of the ...
April 12, 2015

Science
HNO3+ KOH= H2O + KNO3 mols KOH = M x L = ? mols HNO3 = mols KOH because of the 1:1 ratio in the balanced equation. Then M HNO3 = mols HNO3/L HNO3. You know mols and L, solve for M.
April 12, 2015

CIRCUIT
All in series, R adds. R = E/I = 10/4 = 2.5 ohms for lamp R motor = E/I = ? ohms R for resisister = 10 ohms Total R = ? Then total voltage = E = IR. I is 4A in the problem.
April 12, 2015

CIRCUIT
Etotal = sum voltage drop across each
April 12, 2015

Circuits
3 ohm R. voltage drop is 6v so I = E/R and that I is the I through the circit. 5 ohm frop = IR 4 ohm drop is IR total voltage is sum of drops across each.
April 12, 2015

chemistry
I don't have all of the solubility tables memorized for all of the salts. There must be thousands. Do you have a graph or a table that will give you the solubility?
April 11, 2015

Chemistry
dSrxn = (n*dSo products) - (n*dSo reactants) Look up the So values in your text/notes. They should be in a table at the end of your text.
April 11, 2015

chemistry
And you don't understand what about this problem?
April 11, 2015

chemistry
You need to use an ICE chart. Post what you can and explain what you don't understand and I can help you through it if you get stuck.
April 11, 2015

Chemistry
It is very very simple. You can convert mols of anything in an equation to mols of anything else in the equation by using the coefficients in the balanced equation. That's why you write and equation for almost everything you do and balance it. So you have 1.2 mols CrCl3 ...
April 11, 2015

science
1600 what? If it isn't years, convert to years. k = 0.693/t1/2 Substitute k into the below equation. ln(No/N) = kt No = 100 N = 25 k from above Solve for t in years.
April 11, 2015

Chemistry: Acids/Bases
Didn't I do this for you yesterday? I think so. http://www.jiskha.com/display.cgi?id=1428706410 If there is something you don't understand follow up with that post instead of posting it all over again. If you didn't get the answer in your database, post your work ...
April 11, 2015

Chemistry (solubility product question)
You're right. (CrO4^2-) = 0.00114M Your c1v1 = c2v2 is ok but you should be solving for c2 and not v. You know volume. c1v1 = c2v2 0.01M*3.00mL = c2*6.00 mL. c2 = 0.005 = [Cu(NO3)2] initially Do the same for K2CrO4. You should get 1/2 * 0.006 = 0.003 = K2CrO4. ...Cu(NO3)2...
April 10, 2015

chemistry
For part II, plug into the HH equation. 5.00 = 4.74 + log (base)/(acid) 5.00 = 4.74 + log (100*0.5)/(x) Solve for x = mmols acetic acid and convert that to grams acetic acid.
April 10, 2015

Chemistry
This is a limiting reagent (LR) problem; we know that because amounts are given for BOTH reactants. I work these the long way because it easier to explain. 2C2H6 + 7O2 ==> 4CO2 + 6H2O mols C2H6 = grams/molar mass = ? mols O2 = grams/molar mass = ? Using the coefficients in ...
April 10, 2015

Chem
dSrxn = (n*dSo products) - (n*dSo reactants) Look the standard So values in tables in your text/notes/web.
April 10, 2015

chemistry
PV = nRT Remember T must be in kelvin.
April 10, 2015

chemistry
You need a distribution coefficient.
April 10, 2015

Chemistry
See the note above.
April 10, 2015

chemistry
Suppose you have 100 millimols HClO and you titrate it with NaOH. So halfway to the equivalence point you will have added 50 millimols NaOH. .........HClO + NaOH ==> NaClO + H2O I........100.....0..........0......0 add ............50.................. C........-50...-50...
April 9, 2015

Chemistry
I think you posted only part of the problem. I assume you have titrated the NaOH with HCl and you want to know the M of the NaOH. mols HCl = M x L = ? mols NaOH = mols HCl from the molar ratio of 1:1. M NaoH = mols NaOH/L NaOH. You know mols NaOH and L NaOH, solve for M NaOH.
April 9, 2015

Chemistry
Brian, I don't understand the problem.
April 9, 2015

chemistry
I don't see a question here.
April 9, 2015

chemistry
2KHP + Ca(OH)2 ==> CaP + K2P + 2H2O mols KHP = grams/molar mass = ? Using the coefficients in the balanced equation, convert mols KHP to mols Ca(OH)2. Then M Ca(OH)2 = mols Ca(OH)2/L Ca(OH)2. YOu know mols and M, solve for L Ca(OH)2 and convert to mL if needed.
April 9, 2015

Science
Some people that that and there are debates about which ones are friendly, both for the planet and for health. Think nuclear power plants.
April 9, 2015

Science
Another part of the debate is about global warming. Fossil fuels produce CO2 and that is the primary cause of the green house effect.
April 9, 2015

chemistry
See your other post and not CaCl2.
April 9, 2015

chemistry
If you are referring to calcium chloride that is CaCl2. How many mols do you want? That's M x L = ? Then mols = grams/molar mass. You know mols and molar mass, solve for grams.
April 9, 2015

chemistry
(P1V1/T1) = (P2V2/T2) Remember T must be in kelvin. You spelled celsius wrong in this post but right in the previous post.
April 9, 2015

chem3A
PV = nRT and solve for n = number of mols. Then n = g/molar mass. You have g and n, solve for molar mass.
April 9, 2015

science
"it's safer for everyone." but a number of correct answers can go there. Do you have choices?
April 9, 2015

science
https://www.google.com/search?q=illness+caused+by+protist&ie=utf-8&oe=utf-8
April 9, 2015

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