Saturday
September 20, 2014

Posts by DrBob222


Total # Posts: 43,887

College Algebra I
I don't see a question here.
July 6, 2014

chemistry step by step thank a lot
Is that m or M (molality or molarity) M is molarity m is molality Did you make a typo? Is that question for molarity of the H^+. That is 0.888M (not m). Total molarity, however, is much more than 0.888M.
July 6, 2014

Chemistry
pi = MRT pi = 869/760 = ? M solve for this R = 0.08205 L*atm/mol*k T = 273 + 21 = ? M gives you part b. Then M = mols/L solution, you know L solution and M, solve for mols and that is part c. Part a is mol = grams/molar mass. You know grams and mols, solve for molar mass.
July 6, 2014

Soil Chemistry
I don't get it. There are no carbon-halogen bonds in any of those molecules.
July 6, 2014

chemistry
wavelength = h/mv Convert 1A to m.
July 6, 2014

CHEMISTRY
dG = dH - TdS 0 = 8000 - 298(dS)
July 6, 2014

CHEMISTRY
q = mass In x specific heat In x (Tfinal-Tintial) q = 23J mass = atomic mass In solve for sp.h.
July 6, 2014

chemistry
CO2 is the gas evolved. It is colorless and odorless but will extinguish a burning flame.
July 6, 2014

chemistry step for step thank a lot
1. Why do you think 1000 ppm is the correct answer for #1? 2. Balance the redox part. The other parts of the equation (H2O, H^+, SO4^2-, etc) do not need to be balanced. a. KMnO4 + 5FeSO4 ==> Mn^2+ + 5Fe^3+ (Mn changes from +7 on the left to +2 on the right for the gain of ...
July 5, 2014

uos
universal optimum science? university optional science? university optimal services? unrealized optical scans?
July 5, 2014

chemistry
The easy way to do these is to assume some convenient number for the rate of effusion. The number 1 is an easy one to use. unknown gas rate = 1L/min oxygen gas rate = 2.5*1L/min = 2.5 L/min (rate O2/rate unk) = swrt(MMunk/MMO2) (2.5/1) = sqrt(MMunk/32) Solve for molar mass (MM...
July 5, 2014

Chemistry
This is just like the HBr problem. Just follow the format.
July 5, 2014

Chemistry
As in the HCl problem, start with the definition. m = mols/kg solvent mass of 1 L = 1000 mL x 1.38 g/mL = 1380 g. Not all of that is HBr. HBr present is 40% so 1380 x 0.40 = 552g. mols in 552g HBr is mols = grams/molar mass = 552/about 81 (but you need to do it more accurately...
July 5, 2014

Soil Chemistry
I presume it's just like any other hydrocarbon; i.e., products are CO2 and H2O
July 5, 2014

Chemistry
M = mols/L so you want to know how many moles HCl there are in 1 L. 1000 mL weighs how much? That's 1000 mL x 1.19 g/mL = 1190 g How much of that is HCl? Only 36%; therefore, g HCl = 1190 x 0.36 = estimated 428g How many mols is that? mol = g/molar mass mols = 428/36.5 = ...
July 5, 2014

chemistry
There is some information here but you must assimilate your knowledge of chemistry to be useful. http://en.wikipedia.org/wiki/Polyethylene
July 5, 2014

chemistry
How about one of each? We're supposed to help with your homework, not do all of your homework. silt in water--suspension colloidal gold in water--colloid http://chemistry.about.com/od/lecturenotesl3/a/colloids.htm
July 5, 2014

chemistry
Do you have an equation you want to use?
July 4, 2014

chemistry Step for step for me thank a lot
Ken, I did step by step and explained every step as I went. Step by step what do you not understand?
July 4, 2014

Chemistry Step by step for me Thank a lot
See your post below.
July 4, 2014

chemistry step by step for me Bob
Saponification number is the number of mg KOH required to react with 1g fat (in this case peanut oil). mols KOH initially added to 2g oil = M x L = 0.4M x 0.025L = 0.0100 mols. Then H2SO4 is added to neutralize the excess amount of KOH. H2SO4 + 2KOH ==> K2SO4 + 2H2O mols ...
July 4, 2014

Chemistry
The question is a little confusing to me but I would answer that they have different number of protons, different number of neutrons, and different number of electrons. But your question MAY means copper arsenide, germanium arsenide, silicon arsenide etc.
July 4, 2014

chemistry Ben step by step for me
What's the question? 1000 ppm is 1000 mg/L.
July 4, 2014

chemistry please step by step for me
I did it step by step. Here it is again with more explanation. Write and balance the equation. Zn + 2HCl ==> H2 + ZnCl2 How many mols H2 do you want to generate. mols = grams/molar mass g H2 = 4g. molar mass H2 = 1*2 = 2 g/mol. mol H2 = 4g/2 = 2 mols H2 in 4g H2. Now ...
July 4, 2014

chemistry
What is the molarity of the HCl solution? That's 1000 mL x 1.2 g/mL x 0.0365 x (1 mol/36.5g) = 12M Zn + 2HCl ==> ZnCl2 + H2 How many mols is 4g H2. mol = grams/molar mass = 4/2 = 2 2 mols H2 = 2*2 = 4mols HCl M HCl = mols HCl/L HCl. You know M HCl from above and mols ...
July 4, 2014

CHEMISTRY
I don't understand the question. 1 is the conjugate base of HPO4^2-. 2 is the conjugate base of H3O^+. 3 is the conjugate acid of H2PO4^- 4 is the conjugate acid of HPO4^2- and the conjugate base of H3PO4.
July 4, 2014

Science
I don't understand the question. A 2% isotonic solution seems to be an oxymoron to me. An isotonic solution is about 0.9% NaCl/100 mL solution.
July 4, 2014

CHEMISTRY
See your post above.
July 4, 2014

CHEMISTRY
I think you meant to say that the freezing point of the pure water as read on your thermometer was 0.25. Therefore, the freezing point of the original solution KNO2 was -1.40. Then 1.40 = i*Kf*m 1.40 = 2*1.86*m m = about 0.376 0.415g KNO3 = 0.415/101.1 = about 0.0041 mols. m...
July 4, 2014

Chemistry
See your earlier post. I'll explain something here if you don't understand it but I'm not about to rework four problems just for the fun of it.
July 3, 2014

Chemistry
See your other posts.
July 3, 2014

Chemistry
See your earlier post.
July 3, 2014

Chemistry
Brett, I worked these problems for you earlier.
July 3, 2014

Chemistry
http://www.jiskha.com/display.cgi?id=1404360366
July 3, 2014

CHEMISTRY
At 60C 200 g H2O will hold 18 x 200/100 = 36g and that is a saturated solution. At 20C it will hold 12 x 200/100 = 24. Difference is 36-24 = ?g
July 3, 2014

Cattle ranching
I disagree. http://animals.pawnation.com/country-introduced-cattle-us-7162.html
July 3, 2014

Chemistry
I worked this a couple of days ago but that problem didn't included the water washing as described here. There is so much superfluous information here it makes the problem a little confusing. Here is what I will work with. Calculate theoretical yield of Ba(IO3)2 using 30....
July 3, 2014

Chemistry
See your other post above.
July 3, 2014

Chemistry
See you last post. dHrxn = (n*dHf products) - (n*dHf reactants)
July 3, 2014

Chemistry
dHrxn = (n*dHf products) - (n*dHf reactants)
July 3, 2014

Chemistry
multiply equation 1 by 2 and dH x 2. Reverse equation 2 and change sign dH. Balance equation 3(it isn't balanced now). Add the three equations and add dHs. This will get 2NO2 + 2N2O ==> 6NO which is twice what you want. So divide the final equation by 2 and divide sum ...
July 3, 2014

Chemistryq
Use PV = nRT and solve for P. n for O2 = grams O2/molar mass O2
July 3, 2014

Chemistry
mols KMnO4 = M x L = ? Use the coefficients in the balanced equation to convert mols KMnO4 to mols H2O2. Then M H2O2 = mols H2O2/L H2O2 I'll be glad to check your answer.
July 3, 2014

chemistry
heat loss by Cu + heat gained by H2O = 0 heat loss by Cu is [(mass Cu x specific heat Cu x (Tfinal-Tinitial)] heat gain by H2O is [mass H2O x specific heat H2O x (Tfinal-Tinitial)] Add those and set to zero as follows: [mass Cu x specific heat Cu x (Tfinal-Tintial)] + [mass ...
July 2, 2014

chemistry
Ptotal = pHe + pN2 + pAr You know all but one unknown. Be careful with the units. Ptotal is in atm and the gases are given in torr (and mm but 1 mm = 1 torr)
July 2, 2014

Chemistry: Conversion
Of course that does all of the work for you and you don't learn to go through the various factors to get from yard^2 to m^2.
July 2, 2014

Chemistry: Conversion
The easy way is to Google and type in, without the quotation marks, the following: "7 square yards to m^2" and hit the enter key. Up pops 7 sq yards = 5.85289 square meters
July 2, 2014

chemistry
CH2OHCOOH + NaOH ==> CH2OHCOONa + H2O mols NaOH = M x L = ? Using the coefficients in the balanced equation, convert mols NaOH to mols glycolic acid. That should be 1:1. Then mols glycolic acid = grams/molar mass. You know molar mass and mols, solve for grams.
July 2, 2014

chemistry
millimols HOCl = mL x M = 225 x 0.283 = estimated 64. mmols KOCl = 225 x 0.456 = 103 add 46 mmols HClO4. ..........OCl^- + H^+ ==> HOCl + H2O I.........64......0........103 add..............46............. C........-46....-46.........+46 E.........18......0........149 ...
July 2, 2014

Organic biochemistry
https://www.google.com/search?q=diethylammonium+bromide&client=firefox-a&hs=oWE&rls=org.mozilla:en-US:official&channel=sb&tbm=isch&tbo=u&source=univ&sa=X&ei=m5OzU6ThC9XEsASbp4DwBA&ved=0CCsQsAQ&biw=1143&bih=688&dpr=0.9
July 2, 2014

chemistry
For inorganic strong bases use those that end in OH such as NaOH, KOH, Ca(OH)2, Ba(OH)2, CsOH etc. For organic bases use those that have amine groups; either RNH2 (primary amines) or R2NH (secondary amines).
July 1, 2014

Chemistry
morality? Most H2SO4 solutions are not moral at all. Neither are NaOH solution. H2SO4 + 2NaOH ==> Na2SO4 + 2H2O mols NaOH = M x L = ? mols H2SO4 = 1/2 mols NaOH which you get from the coefficients in the balanced equation. Then M H2SO4 = mols H2SO4/L H2SO4 M is for molarity.
July 1, 2014

Chemistry
I may have interpreted this all wrong but I think you want 1.2 mL of 100 mM solution. If that is true then 100 mM x 1.2 mL = ? mmols or ?/1000 = mols. mols = grams/molar mass. You have molar mass and mols, solve for grams.
July 1, 2014

Chemistry
This problem isn't clear to me at all. Is the drug a liquid? density is needed if we are to make 1.2 mL. How much is the stock solution to be diluted?
July 1, 2014

chemistry
5% glucose means 5 g glucose in 100 mL solution. So in 500 mL there will be 5*5 = 25 g glucose in 500 mL.
July 1, 2014

science
3e5 N/m2 = 3 bar Sea level is 1 bar Pressure increases 1 bar for every 10.06 m so to go from 1 bar to 3 bar would require 3*10.06 m = ?
July 1, 2014

Chemistry 1
1/wavelength in m = R(1/4 - 1/n^2) The 1/4 is 1/2^2. R = 1.0973E7 m^-1
July 1, 2014

Chemistry 1
I don't see a question here. I assume you want to calculate the heat of neutralization (in what units?)
July 1, 2014

Chem
I thought I worked this a couple of days ago. 4H ==> 2H2 So 435 kJ/mol x 2 mol = 870 kJ. 870,000J = mass H2O x specific heat H2O x (Tfinal-Tinitial) Plug and chug. Solve for mass H2O
July 1, 2014

Chemistry
Balance the redox part first. You don't need to write the entire equation, just the redox part. C2O4^2- + Cr2O7^2- ==> 2Cr^3+ + 2CO2 C in C2O4 changes from +6 (for 2C) to +8 (for 2C) which is a change of 2e. Cr in Cr2O7^2- changes from +12 (for 2Cr) to +6(for 2 Cr) ...
July 1, 2014

Chemistry
mols KOH = M x L = ? Since aspirin is a monoprotic acid then mols aspirin = mols KOH. g aspirin = mols aspirin x molar mass aspirin. % aspirin = (mass aspirin/0.534)*100 =
July 1, 2014

Chemistry
(35.9675*0.003365) + (37.9627*0.000632) + (39.9624*0.99600) = ?
July 1, 2014

Chemistry
1 ton = 2000 lbs. 261 tons x (2000 lbs/1 ton) x 0.014 x (molar mass (CH3)2Hg/atomic mass Hg) =
July 1, 2014

Chemistry
If that is 7.04% N (and not N2), you have 7.04g N in 100 g of the fertilizer. To convert to g urea just multiply by the chemical factor (which usually isn't taught in schools now). 7.04 x (molar mass urea/2*atomic mass N) = ?
July 1, 2014

chemistry
Did you make typo? If Kp is at 160 C then it will be different at 100 C. Assuming you mean Ptotal at 160 C... ....2NaHCO3(s)=>Na2CO3(S)+CO2(g)+H2O(g) I...solid.......solid......0......0 C...solid.......solid......p......p E...solid.......solid......p......p Kp = pCO2 * pH2O...
July 1, 2014

Soil Chemistry
Yes you are, STP means standard temperature and pressure. So P is 1 atm standard, T is 273 K standard and you are to calculate standard V.
July 1, 2014

Soil Chemistry
(P1V1/T1) = (P2V2/T2) Whatever units you use for the left side use the same units for the right side.
July 1, 2014

Soil Chemistry
I don't see a question here.
July 1, 2014

Chemistry
Two rules to follow in chemistry problems. 1. Work in mols. You get mols two ways. The first is when you have grams; that's mols = grams/molar mass. The second is when you have a solution; then mols = M x L. 2. When you have mols you can convert mols of anything in the ...
June 30, 2014

Chemistry
Ba(NO3)2 + 2NaIO3 + H2O ==> Ba(IO3)2*H2O + 2NaNO3 Ba(NO3)2 is the limiting reagent with either number. mols Ba(NO3)2 = M x L = 0.4912 x 0.030 = 0.014736 = mols Ba(IO3)2.H2O g Ba(IO3)2 = mols x molar mass = theoretical yield (TY). Actual yield (AY) = 6.895g in the problem...
June 30, 2014

Chemistry
See you other post.
June 30, 2014

Chemistry
See your post below. Same procedure.
June 30, 2014

Chemistry
See your post below. You calculate mols to calculate grams.
June 30, 2014

Chemistry
See your post below. BTW, you would get faster responses if you didn't change screen names. Joe, Steve, Chris, ?
June 30, 2014

Chemistry
This is a limiting reagent (LR) problem. 2NH4F + Ca(NO3)2 ==> CaF2 + 2NH4NO3 1. Write and balance the equation as above. 2. Convert numbers to mols. mols = M x L = ? mols Ca(NO3)2 = M x L = ? mols NH4F = M x L = ? 3a. Using the coefficients in the balanced equation, convert...
June 30, 2014

chemistry
2AgNO3 + CaCl2 ==> Ca(NO3)2 + 2AgCl mols CaCl2 = grams/molar mass = ? Use the coefficients in the balanced equation to convert mols CaCl2 to mols Ca(NO3)2 (That should be mols CaCl2 x 2 = ?). Then g Ca(NO3)2 = mols Ca(NO3)2 x molar mass Ca(NO3)2 = ?
June 30, 2014

Soil Chemistry
You must pay attention to units no matter what problem you are working. Here, use PV = nRT and solve for n P must be in atm and 755/760 = ? atm. V in L n = number of mols. Solve for this. R = 0.08205 L*atm/mol*K T = 24C + 273 = ?K. T must be in kelvin. Then n = mols = grams/...
June 30, 2014

Soil Chemistry
No big problem. Just remember the definitions. Oxidation is the loss of electrons. Reduction is the gain of electrons. In the problem Mn goes to Mn^2+, so Mn ==> Mn^2+ + 2e is the loss of electrons and is oxidation. A is the only answer that fits for Mn. I don't see the...
June 30, 2014

Chemistry
You need three things: a. What is the change in oxidations state? b. Were electrons lost of gained. c. the definitions: oxidation is the loss of electrons. Reductions is the gain of electrons. Here is a. Zn has an oxidation state of zero on the left and +2 on the right. Loss ...
June 29, 2014

chemistry
http://en.wikipedia.org/wiki/Hard_water
June 29, 2014

Chemistry
q = 4 mol x 435 kJ/mol = ? kJ = ? x 1000 J. q = mass x specific heat x (Tfinal-Tinitial). YOu know Tfinal, Tinitial, specific heat, and q, solve for mass
June 29, 2014

Chemistry
Convert 1 L to gallons. Convert Canadian $ to U. S. $. 0.771 CD/L x (1 USD/1.401 CD) x (1 L/0.264 gallons) = ? USD/gallon.
June 29, 2014

Chemistry
Explain your trouble. You set up Ca(s) --> Ca(g) dH = +192 kJ Ca(g) --> Ca^+ + e dH = + 589.5 kJ Ca^+(g) --> Ca^2+ + e dH = + 1146 kJ Cl2(g)--> 2Cl(g) dH = 242.6 kJ 2*Cl(g) + 2e -->2*Cl^-(g) dH =2*-348 kJ Ca^2+(g) + 2Cl^-(g) --> CaCl2 dH = lattice...
June 29, 2014

Chemistry
1/wavelength = R(1/4 - 1/n^2) 1/4 is 1/2^2
June 29, 2014

Chemistry
E for 3.00 mm is E = hc/wavelength. Convert wavelength in mm to m. That gives E for 1 photon which is q/photon q needed to raise T H2O is q = mass H2O x specific heat H2O x delta T = 1.45g x 4.184 x 1 = estimated 6 J Then q/photon x # photons = estimated 6 and solve for # ...
June 29, 2014

Chemistry
You have a typo in the equation. 6HCl + Fe2O3 -> 2FeCl3 + 3H2O g Fe2O3 reacted = 37.5-5.5 = 32.0g mols Fe2O3 = grams/molar mass = estimated 0.2 a. mols HCl used = 0.2 x (6 mol HCl/1 mol Fe2O3) = estimated 1.2. M HCl = mols/L = estd 1.2/0.240 = ? b. mols FeCl3 = mols Fe2O3 x...
June 28, 2014

Chemistry 12
KOH ==> K^+ + OH^- mols KOH = grams/molar mass = ? M KOH = mols KOH/L solution = ? pOH = -log(KOH) Then pH + pOH = pKw = 14. You know pKw and pOH, calculate pH.
June 27, 2014

Chemistry
pi = MRT pi = 0.138 atm M = ? R = 9.08205 L*atm/mol*K T = 273.15 + 28 = ? Solve for M. Then M = mols/L. You know L and M, solve for mols. Then mols = grams/molar mass. You know mols and grams, solve for molar mass.
June 27, 2014

Chemistry 108
mass benzene = volume x density = ? mols benzene = grams/molar mass = ? m benzene = mols benzene/kg solvent For f.p.: delta T = Kf*m, then subtract delta T from 0C to find new f.p. For b.p.: delat T = Kb*m, the add delta T to 100 C to find new b.p.
June 27, 2014

science
I don't see a question here.
June 26, 2014

Chem
CH4 + 2O2 ==> CO2 + 2H2O 16g CH4 releases 802 kJ so 16 x 542 kJ/802 kJ = ?
June 26, 2014

Chem
2Mg + O2 ==> 2MgO + 1203 kJ (although I can't tell if you meant that to be a + or a -). You know from the equation that 2 mol Mg (which is 2*24.3 g Mg) liberates 1203 kJ/ So 1203 kJ x 7.01/(2*24.3) = ? and you place the right sign on it.
June 26, 2014

Chemistry
I looked up the enthalpy of solvation for NH4Cl and CaCl2. I can work this problem for you now. If you still need help, please repost as a new question and I will get to it.
June 26, 2014

Chemistry
Do you have any other data given such as heat solvation etc?
June 26, 2014

Chemistry
Not balanced. MnO4^- + C2O4^2- + H^+ ==> 10CO2 + H2O + Mn^2+
June 26, 2014

chemistry
It depends upon what 1:2 means. There is confusion among even experienced on this. If 1:2 means 1 part NaHCO3 + 2 parts water, then the concn is 0.6M x (1/3) = ? If you mean 1 part NaHCO3 + 1 part (to make 2), then the concn is 0.6M x (1/2) = ? The following is a good web site...
June 26, 2014

math
I think "would be produced" is superfluous wording. I read it as what is the greatest odd number after rounding 660 to the nearest hundreds. 660 rounds to 700 and that's an odd number
June 25, 2014

Chemistry
No idea what the set up was. max P = 1.4094 what? initial P = what unit? atmosphere probably. Did the system gain weight? If so due to what?
June 24, 2014

analytical question
I would call this the near infrared although this is the upper end of that region. E = hc/wavelength in meters. E is J/photon. Multiply by 6.02E23 to convert to J/mol photons and change that to kJ/mol.
June 24, 2014

Analytical chem
If I read this right, you have 3 mg Cu initially, you place it in 250 mL, withdraw 15, add 15 more of something else and take 25 of that 30. So you should have 0.003/63.55 mol = ? initially and at the end it will be (0.003/63.55) x (15/250) x (25/30) = ? and that is in 30 mL ...
June 24, 2014

Pages: <<Prev | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | Next>>

Search
Members