Sunday
November 23, 2014

Posts by DrBob222


Total # Posts: 45,555

Chemistry
I don't agree with 12,13,14,15
November 2, 2014

Chemistry
11 is ok.
November 2, 2014

Chemistry
The answers to 16 don't make sense. A and C appear to be the same but with a typo I disagree with answers to 17 and 18.
November 2, 2014

Chemistry
20 is ok. I don't agree with 19
November 2, 2014

Chemistry
I don't agree with 8 and 10. 6,7,9 are ok.
November 2, 2014

Chemistry
1,2,3,4,5 are correct.
November 2, 2014

Chemistry
Why don't you put your answer at the end of EACH question? That way we can look at the question and the answer. As you've done it we must read the question, scroll to the end to find the answer, scroll back to the top for the other choices, back to the bottom to ...
November 2, 2014

chemistry
2C2H2 + 3O2 ==> 2CO2 + 2H2O dH = 1300 kJ/mol C2H2 How many mols C2H2 do we have? That's mols g/molar mass = 1.0/26 = approx 0.038 but you should redo that since it is an estimate. The q = dH = mass H2O x specific heat H2O x delta T. Solved for dT.
November 2, 2014

chemistry
This is a limiting reagent (LR) problem and you know that because amounts are given for BOTH reactants. 4NO2 + 6H2O ==> 4NH3 + 7O2 mols NO2 = grams/molar mass = ? mols H2O = use PV = nRT and solve for n. Using the coefficients in the balanced equation, convert mols NO2 to ...
November 2, 2014

chemistry
fraction by volume = mols fraction. 2.6E-6 = fraction by volume. 2.6E-6 x 106 = ppm = 2.6 but wikipedia shows it as 18 ppm.
November 2, 2014

Chemistry
Use PV = nRT, solve for n. Then n = grams/molar mass. Yu know molar mass and n, solve for grams.
November 2, 2014

chemistry
Equivalent weight calculations depend upon the reaction. If you have a reaction it is molar mass/1 if one NaOH is used; it is molar mass/2 if 2 NaOH are used.
November 2, 2014

Chemistry
P1V1 = P2V2
November 2, 2014

Chemistry
The question is too general because the energy levels flip flop at certain points; however, here are some guidelines for a specific elements. For the second part first. For oxygen: Look at the atomic number. The AN is 8; therefore, it has 8 protons and that means 8 electrons ...
November 2, 2014

chemistry
q = mass Al x specific heat Al x (Tfinal-Tinitial)
November 2, 2014

Chem
That is partly right. For 2s: N = 2 l = 0 ml = 0 ms = +/- 1/2 for each electron For 2p: N = 2 l = 1 ml = -1,0,+1 ms = +/- 1/2 for each electron
November 2, 2014

Chem
In every orbital there CAN be two electrons (no more than two but they may have only one). How are they related: They are the negative of each other; i.e., one has a spin of +1/2 and the other (if there is another) has a spin of -1/2. Not to confuse you but most freshman texts...
November 2, 2014

chemistry
mols Li2O = 1000 g/molar mass Li2O mols CO2 = mols Li2O (from the coefficients in the balanced equation) Then use PV = nRT and convert mols CO2 to volume at the conditions listed..
November 2, 2014

chemistry
One thing you need to learn in chemistry: A MUST. Locate the caps key on your computer and USE it. m is not M. I assume you meant molarity (M) and not molality(m). If it is m you can't work the problem with the information provided. If it is M, then mL1 x M1 = mL2 x M2 mL1...
November 2, 2014

chemistry
6535 kJ/2 mol C6H6 = ? kJ/1 mol C2H6. mols C2H6 in 16.0g = grams/molar mass Then kJ heat released = kJ/mol x # mols in 16.0g = ?
November 2, 2014

chemistry
See my response above.
November 2, 2014

Chemistry- Reacting Masses Calculations
CaCO3 ==> CaO + CO2 The process looks ok at first glance but the numbers are wrong. You should have used 14 kg = 14,000 g Then 14,000/56 = 250 250 mols CaO (I would have used 56.1 for molar mass CaO) Then 25o mols CaO = 250 mols CaCO3 Then mass CaCO3 = mols CaCO3 x molar ...
November 2, 2014

chemical
See your other posts.
November 2, 2014

chemistry
mols (NH4)3PO4 = grams/molar mass = ? mols NH4^+ = 3x that. mols PO4^3- = 1x that. mols K3PO4 = grams/molar mass = ? mols PO4^3- = 1x that. volume is 0.505L M NH4^+ = mols NH4^+/L solution M PO4^3- = total mols PO4^3-/L solution. Note: total mols PO4^3- = mols PO4^3- from (NH4...
November 2, 2014

Clinical Chemistry
How in the world do you make a 200% solution.
November 2, 2014

chemistry
1107 kJ/2 mol Ba = (1107/2) kJ/mol (1107/2) kJ/mol x 5.75g/atomic mass Ba = ?
November 1, 2014

chemistry
This is a limiting regent (LR) problem because amounts are given for BOTH reactants. Mg + 2HCl ==> MgCl2 + H2 mols Mg = 1.00 mol mol HCl = 0.5M mols H2 produced from 1. mol Mg + 1 mol mols H2 produced from 0.5 mol HCl = 1 mol So this isn't a LR problem after all but the...
November 1, 2014

Chemistry
q = heat gained = mass x specific heat x delta T.
November 1, 2014

chemistry
The general gas law can be modified for density and molar mass by PM = dRT and since P, R, and T are remaining constant we can rewrite that as M/d = RT/P = k molar mass CFCl3 is 137.4; d is 5.58. 137.4/5.58 = 24.62 = k; apply that to the unknown. M/4.38 = 24.62 M = molar mass...
November 1, 2014

Thermodynamic
I don't see a question.
November 1, 2014

chemistry
Ca(HCO3)2 + 2HCl ==> CaCl2 + 2H2O + 2CO2 Use PV = nRT. Substitute and solve for n. mols x molar mass = grams CO2. Convert g CO2 to g Ca(HCO3)2 (g Ca(HCO3)2/mass sample)*100 = % Ca(HCO3)2
November 1, 2014

chemistry
Na2CO3 + heat ==> Na2O + CO2 Therefore, 1 mol Na2CO3 = 1 mol CO2 Therefore, this apparatus has an efficiency of 0.9/0.96 = 0.9375. The mols 0.376/molar mass = ? mols CO2 = the same Use PV = nRT and solve for volume, then v x 0.9375 since the process is not 100% efficient.
November 1, 2014

To Damon---College Chemistry
I think that 13 was a typo. The correct molar mass Fe2O3 is 159.69 and 370g/159.60 = 2.317 which rounds to 2.32 and the remaining part of the math is correct.
November 1, 2014

College Chemistry
My educated guess is that you didn't put in the correct molar mass Fe2O3. It should be [(2*55.85 + 3*(16)] = about 159.69 or so but that may be a typo since your answer of 2.32 mols is correct (although I obtained 2.317 and I always carry an extra place and round at the ...
November 1, 2014

Chemistry
Does that mean you saw my response? Do you have additional question on this problem?
November 1, 2014

physical science
q = heat absorbed = mass Au x specific heat Au x (Tfinal-Tinitial)
November 1, 2014

Math/I'm an adult
Use ratio/proportion. (14W/5R) = (16W/?R) and solve ?R = 5R*16W/14W = 5.71R OR 14W = 5R; therefore, W = 5R/14W, then 16W will be 16W*5R/14W 16W = 5.71R
November 1, 2014

chemistry
A. Pb(NO3)2 + CuSO4 ==> ... B. C6H12O6 + 6O2 --> 6CO2 + 6H2O C. 2AgNO3 + CuCl2 ==> 2AgCl + Cu(NO3)2
November 1, 2014

chemistry
This can't be drawn on this forum but here is a link. http://en.wikipedia.org/wiki/Isopentane
November 1, 2014

Chemistry
(P1V1/T1) = (P2V2/T2) Remember T must be in kelvin.
November 1, 2014

Chemistry
(V1/T1) = (V2/T2) T must be in kelvin
November 1, 2014

chemistry
possibilities not listed. Note the correct spelling of chemistry.
November 1, 2014

Chem
I'm a little unsure of what you want. I assume that "box" I see and can't read is lamda. lambda = h/mv So you plug in h, you have m right for the electron, and you have v listed, solve for wavelength. If you want KE use KE = 1/2 mv^2 and units will be in J. ...
November 1, 2014

Chem
I can't read the funny blocks before E and after and. If you are asking if there is easier way to solve for lambda, yes you can use 1/lambda = R(1/4-1/9) with R the Rydberg constant of 1.0973E7 m^-1. Those places you have 10^19 should be 10^-19. For lambda I obtain 6.56E-7...
November 1, 2014

Chemistry
I assume you meant moles and not miles. Ca + 2HCl ==> CaCl2 + H2 mols Ca = grams/atomic mass = ? mols H2 = mols H2 (look at the equation. 1 mol Ca produces 1 mol H2)
November 1, 2014

Chemistry
I assume mean KCl and not KCl2. Note the correct spelling of celsius. 10g KCl/20g H2O converted to L of water (assuming density H2O is 1.00 g/L) is 10 g KCl x (1000/20) = 500 g KCl Then mols = grams/molar mass =?
November 1, 2014

Chemistry
density = mass/volume
October 31, 2014

chemistry
PV = nRT
October 31, 2014

chemistry
(P1V1/T1) = (P2V2/T2)
October 31, 2014

chem
You would do better to write your equations in a left to right line (horizontal) rather than a vertical line. 2M + 6HCl>>> 2MCl3 + 3H2 Use PV = nRT and solve for n H2 gas. Using the coefficients in the balanced equation, convert mols H2 to mols M. Then mols = grams/...
October 31, 2014

chemistry
n1 = 0.126 n2 = 0.126+0.07 = ? (V1/n1) = (V2/n2)
October 31, 2014

chemistry
There is no P listed and the formula is not PV = PV. However the answer is correct. It is (V1/T1) = (V2/T2) (813/452) = (356/T2) T2 = 813*452/356
October 31, 2014

chemistry
P1V1 = P2V2
October 31, 2014

chemistry
Look on the periodic table and add them up.
October 31, 2014

chemistry
C = 12.01 O2 = 16*2 = 32 Total = 44.01 g
October 31, 2014

chemistry
(V1/n1) = (V2/n2)
October 31, 2014

Chemistry
a. correct b. mols OH^- = mols H^+ c. mols = grams/molar mass. you have mols and grams, solve for molar mass. Technically you must know if this is a monoprotic, diprotic or triprotic acid.
October 31, 2014

Chemistry
dE = hc/lambda = ? KE = dE-threshold
October 31, 2014

Chemistry
dHcomb = (n*dHformation products) - (n*dHformation products) I ran through this and estimate about 802.5 kJ/mol so the heat emitted by 0.01 mol CH4 will be 8.025 kJ or 8,025 J. I would do the rest of it in pieces. It will take q1 = heat to raise T of solid ice from -11.9 to ...
October 31, 2014

chemistry
Do this steps. q1 = energy to raise T from zero for liquid H2O to 9.9 liquid water. q1 = (mass H2O x specific heat H2o x (Tfinal-Tinitial). You have all of these numbers but mass H2O. q2 = heat to convert solid ice to liquid water at zero C is q2 = mass ice x heat fusion. You ...
October 31, 2014

Organic Chemistry
http://www.jiskha.com/display.cgi?id=1414729583
October 31, 2014

chemistry
mols = grams/molar mass = ? Remember to convert kg to g first.
October 31, 2014

chemistry
mols sugar = grams/molar mass = ? Then 1 mol of anything contains 6.02E23 molecules.
October 31, 2014

Organic Chemistry
You don't say but I assume these numbers you give are the solubility of caffeine in the two solvents. Ko/a = 10.3/2.04 = 5.049 fn = [(1+K(Vo/Va)^-n fn is the fraction of the solute REMAINING in the aq phase after n extractions. NOTE: I don't see any number for the ...
October 31, 2014

Organic Chemistry
I assume you know K for this. K = (x/21)/(0.5-x)/125] x = g in methylene chloride 0.5-x = g caffeine in water layer.
October 31, 2014

chemistry
My comment? Don't believe everything you read. http://www.ehow.com/list_6532902_advantages-potentiometric-titration.html
October 31, 2014

chemistry
Wouldn't you think that the number of collisions would decrease if you increased the size of the container. Remember pressure is caused by the collision of molecules on a surface.
October 30, 2014

Chemistry
20,800 J = mass H2O x specific heat H2O x (Tfinal-Tinitial)
October 30, 2014

Chemistry
C is correct. By the way, that should be Na2C2O4 for sodium oxalate.
October 30, 2014

Chemistry
number
October 30, 2014

Chemistry
Be has two electrons to give away. F need to gain one electron so it takes two F atoms to take those two electrons. By the way, you get faster and better help if you use the same screen name.
October 30, 2014

chemistry
B. dHrxn = (n*dHformation products) - (n*dH formation reactants) C. Use density to convert 1L to grams. Then You know from part B the dH for 1 mol. Convert the mass in grams of 1L CH3OH to mols, the dH/mol x # mols = ? D. From part B you know #kJ/2 mol CH3OH and that's the...
October 30, 2014

Chemistry urgent
See your other post. It isn't necessary to post under different screen names and it doesn't get you an answer any faster. It does clutter the board.
October 30, 2014

chemistry
mols H2O = grams/molar mass = ? #molecules = ?mols H2O x 6.02E23 # mols H atms = 2x that.
October 30, 2014

Chemistry
q = mass sand x specific heat sand x (Tfinal-Tinitial)
October 30, 2014

chemistry
Isotonic means at the same pressure. Since NaCl ionizes to two particles and glucose doesn't ionize, you must have twice as much glucose to do the same job; therefore, you will need 0.30M glucose. 0.30M is 0.30 mols/L solution and that is 0.30 mols is 180 x 0.3 = 54 g/L ...
October 30, 2014

chemistry
NaCl ionizes to two particles. Same as NH4Cl. 0.89% NaCl is 8.90g/L So 8.9 g NaCl x (molar mass NH4Cl/molar mass NaCl) = ? g NH4Cl in 1 L solution.
October 30, 2014

chemistry
mols BaCl2 = grams/molar mass = ? molality = m = mols/kg solvent delta T = i*Kb*m i = 3 for BaCl2 Solve for delta T and add to the normal boiling point of water for the final b.p.
October 30, 2014

Chemistry
First since it is constant P you don't need the P1 and P2 so the equation can be modified to T2 = V2T1/T2 although you could use your formula and just use 729 for P1 and 729 for P2. V2 is 3.78L V1 is 4.39L T1 is 44 C which is (273+44) = 317 Kelvin. Substitute into the ...
October 30, 2014

Chemistry
N2 + 3H2 ==> 2NH3 mols H2 = grams/molar mass Using the coefficients in the balanced equation, convert mols H2 to mols N2. Now convert mols N2 to grams. g = mols x molar mass = ?
October 30, 2014

chemistry
A. Why not keep the same screen name? It help us and doesn't help you.
October 30, 2014

chemistry
A. 2Al + 6HCl ==> 2AlCl3 + 3H2 Look up vapor pressure H2O @ 22 C = and I've estimated 22 mm Use PV = nRT to solve for mols H2 evolved. For P you have Ptotal = pH2 + pH2O 751 mm = pH2 + 22 Therefore, estimated pH2 = 751-22 = approx 729. Use that for P in the PV = nRT ...
October 30, 2014

CHEMISTRY
2Ag + S ==> Ag2S If you started with 10.8 g Ag and ended up with 12.4g Ag2S, that means you must have added 1.6 g S. Convert these masses to mols by mols = grams/atomic mass mols Ag = 10.8/estimated 108 = estimated 0.1 molsl S = 1.6/estimated 32 = 0.05 Now fine the ratio of...
October 30, 2014

chemistry
P1V1 = P2V2
October 30, 2014

Chemistry
There is no better time to learn the solubility rules then now. That's all it takes and a little practice helps of course. Here is a simplified version. See below for an example of how to do these. https://www.google.com/search?q=solubility+rules&client=firefox-a&hs=bg1&...
October 30, 2014

chemistry
KCN is a salt and the pH is determined by the hydrolysis of KCN. (KCN) = mols/L. mols = 100 g/molar mass = estimated 1.5 and 1.5 mols/L = estimated 1.5M. ............CN^- + H2O ==> HCN + OH^- I...........1.5.............0.....0 C............-x.............x.....x E...
October 30, 2014

chemistry
1 mol H2O has a mass of 18.015 grams and you can get this number by adding 2*atomic mass H + 1*atomic mass O. In that 18.015 g there will be 6.022E23 molecules of water in one of several forms. What kind of forms? If we call 1H p for protium, 2H D for deuterium, and O16 and ...
October 30, 2014

chemistry
Do you honestly not know the answer to #1? Why don't you try answering these and let us respond?
October 30, 2014

chemistry
.........SO3^2- + H2O --> HSO3^- + OH^- I........1.22..............0........0 C.........-x...............x........x E.......1.22-x.............x........x Kb1 for SO3^2- = (Kw/Ka2 for H2SO3) = (x)(x)/(1.22-x) Solve for x = OH^- . That gives you SO3^2-, HSO3^- and OH...
October 30, 2014

ap chem
rate = 1/5*(dC/dT) dC/dT = ?
October 30, 2014

chemistry
CH4 + 2O2 ==> CO3 + 2H2O mols CH4 = grams/molar mass Using the coefficients in the balanced equation convert mols CH4 to mols CO2 Now convert mols CO2 to grams. g = mols x molar mass.
October 29, 2014

Chemistry
2.0 L flask: Use PV = nRT and solve for n. 1.00L flask: Use PV = nRT and solve for n. Add to find total mols. Then PV = nRT and use total mols and total volume to find total pressure. Use PV = nRT and EACH n with total volume to find partial pressure of each. I know you don&#...
October 29, 2014

Chemistry
Then M = mols from above/0.1L = ?
October 29, 2014

Chemistry
Note the correct spelling of celsius. mols Al2(SO4)3 = grams/molar mass = ? Then M = mols /L Is that 26.7 g/100 L. That's hard to believe but check that unit before working the problem.
October 29, 2014

Chemistry
How much of this do you not know how to do? It's wasted time for me to go over steps you already know. And if you just want to check your answer, show your work and I'll check it.
October 29, 2014

CHEMISTRY
See your PbI2 problem above.
October 29, 2014

chemistry
mass % H2O = (mass H2O/molar mass compound)*100 = ? %H2O = (108.12/237.93)*100 = ?
October 29, 2014

Chem Help
I haven't heard of that expression either. I can make an educated guess that the question wants you to write up a procedure for converting the one chemical to the other and use 0.2 molar materials at the start. That might not mean exactly 0.2 M but in that vicinity. For ...
October 29, 2014

chemistry
35.7 g x 50/100 = ?
October 29, 2014

Chem 130
4Al + 3O2 ==> 2Al2O3 1. mols Al - grams/atomic mass 2. Using the coefficients in the balanced equation, convert mols Al to mols Al2O3 3. Now convert mols Al2O3 to g. g = mols x molar mass
October 29, 2014

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