Saturday
August 2, 2014

Posts by DrBob222


Total # Posts: 43,229

college chem
(P1V1/T1) = (P2V2/T2)

college chem
P1V1 = P2V2

chemistry
It takes 96,485 coulombs to plate out 1 equivalent weight of Mg which is 24.3/2 = 12.15g Mg. You want 29 g so it will take 96,485 x 29/12.15 = ? coulombs amperes x seconds = coulombs. You know amperes and coulombs, solve for seconds and convert to minutes.

chemistry
H2SO4 + 2NaOH --> Na2SO4 + 2H2O mols H2SO4 = M x L mols NaOH = 2 x mols H2SO4 (look at the coefficients) M NaOH = mols NaOH/L NaOH Convert L to mL.

science
I think the answer is D.

Chemistry
This is too much like doing all of you homework for you. I'm glad to help but help is the operative word. What do you not understand about this.

Chemistry
Look in your text/notes. If the acid or base is listed in the table of ionization constants it is weak. It it isn't listed it is strong. If it has an ionizable H it is and acid. Look for bases to have OH groups. It it isn't an acid or base it is a salt.

Chemistry URGENT
1 is ok. 2 and 3 are not. 2. M = mols/L not mols/mL. M = 0.5mol/0.5L = 1 M 3. % w/w = (mass solute/100 g solution)*100. Should be [10 g KCl/(90+10)]*100 = [10g KCl/100 g solution]*100 = 10%

Chem
How many mols do you want? That's M x L = mols Then mols = grams/molar mass. You know mols and molar mass, solve for grams.

Chem.
Yes, but it should be 2NaNO3

Chemistry
(H3O^+)(OH^-) = Kw = 1E-14 Substitute and solve.

Cheměstry
millimols Fe(NO3)3 = mL x M = 150 x 3.5 = 525 mmols NO3^- from Fe(NO3)3 = 3*525 = approx 1500 but you need it more accurately. mmols Mg(NO3)2 = 760 x 1.6 = 1216 mmols NO3^- from Mg(NO3)2 = 2*1216 = approx 2400 Total NO3^- = approx 2400 + 1500 = approx 3900 mmols. Total volume ...

Chemistry
See your other post.

Chemistry
yes

Chemistry
6CO2 + 6H2O ==> C6H12O6 + 6O2 mols CO2 = grams/molar mass mols H2O = grams/molar mass You need to redo the math because these are only approx but I obtained approx. About 2 mols CO2; about 3.5 Convert 2 mols CO2 to mols glucose; that's 2 x (1 mol glucose/6 mol CO2) = ab...

Chemistry
Surely you have more information than this. A table you can use? A graph? Something.

Chemistry
dE = q+w. If q = 0, then dE = w If work is done on it by the surroundings then w is + and that makes dE +. Wouldn't that be d?

Chemistry
a. oxidizing agent H2O2 + 2e + 2H^+ ==> 2H2O b. reducing agent H2O2 ==> O2 + 2e + 2H^+ c. disproportionation. One O goes from -1 to zero; the other O goes from -1 to -2. -1 to zero is loss of electrons; -1 to -2 is gain of electrons. Therefore, one O atom is oxidized and...

Homework helpline?
I can't give specific information and know that's what you want; however, I know that most colleges/universities have study sites/special lectures/study sessions/and that kind of thing. Talk to a counselor at the school and ask. Most of the chemistry profs where I taug...

chemistry
I assume that 18.0 is 18mm Hg. 2KClO3 ==> 2KCl + 3O2 Calculate mols O2 from PV = nRT Since the pressure is listed in kPa and the vapor pressure in mm Hg you must convert one of them. I would convert 18.0 mm to kPa. 18.0 mm Hg x (1 atm/760 mm Hg) x (101.325 kPa/1 atm) = 2.39...

Chemistry: Please check my work!I am stumped
I didn't check the oxidation numbers and electron change but the coefficients appear to be ok. To continue, convert 239 g nitro into mols. mol = grams/molar mass Use the coefficients in the balanced equation to convert mols nitro to mols N2, mols H2O, mols CO2, mols NO. Th...

Science chemistry
A word to the wise. mgs I read as milligrams. The cap key is there for a reason. Use it. This is a limiting reagent (LR) problem. You know that because amounts are given for BOTH reactants. Mg + S ==> MgS Convert 20 g Mg to mols. mol g= grams/molar mass. Do the same for 20 ...

Chemistry: please help, I am stumped
See your post above.

chemistry
dGrxn = dG products - dG reactants Then dG = -RTlnK

chemistry
1.00 what? grams? molar? L?

chemistry
delta T = Kb*m Solve for delta T and add to 100 C to find the new boiling point.

chemistry
total mols = mols toluene + mols cholesterol mol fraction toluene = X = mols toluene/total mols. The ptoluene = Xtoluene * Potoluene

chemistry
Balance the equation. N2 + 3H2 ==> 2NH3 Using the coefficients in the balanced equation, convert mols N2 to mols H2. Then convert mols H2 to g. g = mols x molar mass.

Chemistry
I wonder if that is [UO2]^2+? U^4+ ==> UO2^+ Here is how I do it which is not the short way. Oxidation state of U on left is +4. On right is +5. Balance the change in oxidation state by adding electrons to the appropriate side. U^4+ ==> UO2^+ + e Count the charge on the ...

Chemistry
The half reactions are Cu(s) ==> Cu^2+ + 2e (you had 1+ for Cu) O2(g) + 4e ==> 2O^2- (you can see how this differs from what you had). The Cu is the oxidation half; O2 is the reduction half.

Chemistry
I don't think it will but it might be wise to try it on a small scale in the lab before taking a chance on a large scale.

Chemistry
2C2H6 + 7O2 --> 4CO2 + 6H2O dGrxn = (n*dGo products) - (n*dGo reactants)

Simple Chemistry
a. How many mols do you want? That's M x L = 0.150 x 0.250 = ? Then mols = grams/molar mass. You know molar mass and mols, solve for grams CoCl2. Add that many g CoCl2 to a 250 mL volumetric flask, add a little water, swirl until dissolved, make to the mark with distilled ...

Chem
See your other post.

Chemistry
I don't get 5.04 for K but you're on the right track. -4010 = 8.413*298*lnK K = ? I obtained approx 0.2 Then ...........A + B ==> C I.......0.30.0.40...0.0 C.........-x...-x....x E.....0.30-x..0.40-x..x Substitute the E line into Kc expression and solve for x, then ...

Chemistry URGENT/DR BOB
See your other post.

Chemistry URGENT
mass soln = mass solvent + mass solute unless it is a density problem and that is mass = volume x density

Chemistry URGENT
I will make some assumptions for #2. That the 85.5 g solubility you quote later is 85.5g BaCl2/100 g water @ 60 C. If that's so then you will be able to dissolve 85.5g x (150gH2O/100 gH2O) = approx 128 g BaCl2 that can be dissolved at 60 C. The only piece of information ne...

Chemistry URGENT
#1. Take the solubility at 30 and subtract solubility at 20 and divide by 10. That gives you an average solubility per degree C. You have it at 20, then add 3*solubility/degree and you will have it at 23 c. #2. Surely you have a solubility curve or a graph that will tell you t...

Chemistry
You mean name three? There are literally hundreds. Solutions of NaOH, HCl, NaCl, Na2CO3, Na2SO4 etc etc and all of these are STRONG electrolytes (not weak electrolytes).

problem solving
If the picture is square then it must be sqr6 3600 = 60 cm each edge. If the picture frame is 5cm wide, and assuming no overlap between the picture and the frame, the total length of frame + picture is 60 + left side frame + right side frame = 70 cm. The perimeter is the dista...

Chemistry
Andrea, Luke, you want a secnod opinion?

Chemistry
Both are effective as far as neutralization of acids but NaHCO3 is mild enough that humans can tolerate it; NaOH will cause serious issues with the body especially in stronger doses.

chemistry
Aren't these the same problem? You didn't look to see your old post? http://www.jiskha.com/display.cgi?id=1398649923

chemistry
HCl + NaOH ==> NaCl + H2O mols NaOH = M x L =? Using the coefficients in the balanced equation, convert mols NaOH to mols HCl. Then M HCl = mols HCl/L HCl. Solve for M HCl.

Chemistry
Use PV = nRT P in kPa V in L n = grams/molar mass R = 8.314 T = kelvin = 273+C

Chemistry
I would assume a convenient number for the rate of Xe, say something like 5 L/min. Then rate unknown gas, x, is 1.86*5. (rate x/rate Xe) = (MM Xe/MM X) Solve for MM = molar mass X.

Chemistry
Use PV = nRT and solve for n = number of mols. Then n = grams/molar mass. You know n and grams, solve for molar mass. Don't forget P is in atm, V in L and T in kelvin

science/ ms. sue
The oil reduces the friction between the two metal pieces.

Chemistry
q = mass x specific heat x (Tfinal-Tinitial)

Chemistry
Use PV = nRT and solve for n = number of mols in the cylinder. Do the same and solve for n in the smaller balloons. Then determine how many can be filled.

chemistry
A. It isn't a stupid website. B. They aren't stupid questions. C. You see by looking. Use your eyes, not your keyboard.

Chemistry
If it's still in that 48.0 L container the volume will be, guess what, 48.0L. I assume you are asking what volume if the gas were allowed to expand freely but the question isn't clear on that. (V1/T1) = (V2/T2) Remember T must be in kelvin.

chem
1 mol C5H11OH contains 12 mol H atoms. Each mol contains 6.02E23 individual atoms so 12 mols will contain ....... atoms.

chemistry
Hi back. If you have a question post it at the top of the page.

chemistry
a. joules H2O absorbed = mass H2O x spcific heat H2O x (Tfinal-Tinitial) b. joules absorbed by H2O = heat gained by metal d. q metal = mass metal x specific heat metal x (Tfinal-Tinitial) c. q = mass metal x delta T

Chemistry
I worked this for you a few days ago. Did you not see it? not understand it? Show your work that you've done and we can go from there. The empirical formula is C8H20Pb

Chemistry
K = (NH3)^2/(N2)(H2)^3 You know N2 and H2, substitute with Kc and find NH3 in M = mols/L. Then to find mols in 10L, that is mols = M x L Then mol = grams/molar mass. You know molar mass and mols, solve for grams.

Chemistry
.........M2X3 ==> 2M^3+ + 3X^-2 I.......solid.....0........0 C.......solid.....2x.......3x E.......solid.....2x.......3x Ksp = (M^3+)^2(X^2-)^3 Ksp = (2x)^2(3x)^3 Substitute and solve for Ksp.

chemistry
Pb^2+ + C2O4^2- ==> PbC2O4 CrO4^2- + Cu^2+ ==> CuCrO4 As^3+ + S^2- ==> As2S3 you balanced

Chemistry
There isn't anything here to be confused about. ............PCl5 --> PCl3 + Cl2 E.........0.00500..0.00680..0.0290 What's K. Kc = (PCl3)(Cl2)/(PCl5) Plug in the equilibrium numbers and solve for Kc.

chemistry
How much of this can you do? A seems easy enough. What do you have for that? B. What's the mol count? C. What's the ideal gas law and what do you plug into it?

Chemistry
Your post isn't clear.

chemistry
I'm glad you understand it. I don't know when I've screwed a simple problem up so badly and it all goes back to writing the equation incorrectly. Let that be a lesson. Make sure the equations you work with are balanced.

sorry about that---chemistry
I typed the wrong equation in so I'm wrong too. Here is how it goes. 2H2 + S2 ==> 2H2S Kc = (H2S)^2/(H2)^2(S2) Kc = (0.24666)^2/(0.2933)^2(0.1333) Kc = 5.3057 You have in the original problem, assuming you typed in all the digits, 4.4, 2.0 and 3.7 and 15.0. That allows ...

oops again---chemistry
Sorry. I shouldn't have type the oops in the first place. The reaction is H2 + S2 ==> 2H2S Kc = (H2S)^2/(H2)(S2) Kc = (0.24666)^2/*0.29333)(0.1333) You square the H2S because the coefficient is 2. You raise (H2) and (S2) to the first place since the coefficient for both...

oops--chemistry
I forgot the square on H2. That should be K = (0.24666)^2/(0.2933)(0.1333)^2

chemistry
So K = (0.24666)^2/(0.2933)(0.1333) = Punch in the top numbers and divide by the bottom numbers WITHOUT copying any numbers; i.e., leave everything in the calculatord come up with an answer. I don't get 39.

chemistry
What numbers do you get for 4.4/15 = ? 2/15 = ? 3.7/15 = ?

chemistry
And your answers were?

chemistry
What numbers did you substitute for concns H2, S2, H2S? That should be (H2) = 4.4/15 = ? (S2) = 2/15 = ? (H2S) = 3.7/15 = ? I suspect that's the problem.

chemistry
M each = mols/L = ? Substitute M of each into the Keq expression for H2 + S2 ==> 2H2S and solve for Keq.

Chemistry 2
You also listed Ka wrong. That's 1.8E-5. acetic acid is HAc = HC2H3O2 millimols HAc = mL x M = 30 x 0.1 = 3 millimols NaOH = 3 ........HAc + NaOH ==> NaAc + H2O I.......3.......0........0.....0 add.............3............. C......-3......-3........3......3 E.......0.....

Chemistry 2
If this is a mixture you didn't post all of the problem.

oops---Chemistry
I might believe 8 days but not 8 min.

Chemsitry
A--> 2B Kc 2B --> A K'c = 1/Kc

Chemistry
Yes but that's too many significant figures.

Chemistry
Several things can change the equilibrium (shift to left or right) but only change in T can change the numberical value of Kp or Kc.

Chemistry URGENT
#2 is right. #1 I'm unsure exactly what is being asked. I think I responded to this question within the last few days but I interpreted the question then as being one of accuracy/precision of weighing. I thought they were after the precision of balances et al. I don't ...

Chemistry URGENT
I can't believe the numbers are right for all entries. For example, when I look at 23410.2-21789.6 for mass after first heating ( a loss of 1620.7) then loss after second heating of 2116.6 that's 21789.8-2116.6 = that's 19,673.2 which is unbelievable between heatin...

chemistry
2HCl ==> H2--not balanced mols H2 needed = grams/molar mass = 200/2 = 100 mols So you will need 200 mols HCl. g HCl = mols HCl x molar mass HCl

Chemistry URGENT
If things are what you show then mass NaCl is 5.0000 and the extra zeros are necessary to show the number of significant figures. There is no indication for the use of the 8.4 nor the units.

chemistry URGENT
Both student A and student B get a 100 for accuracy. If the correct value is 2.63 and both obtained 2.63 then both are about as accurate as you can get. I would suggest that errors for both are random but I don't think you can tell that from the data. I think random errors...

chemistry URGENT
I think you are right with #1. I can't answer 2 and 3 because I don't know the correct value.

chemistry
I think you meant to say the freezing point depression constant is -1.86 degree C/m for water. (The normal freezing point is 0.00 C) mols Na2SO4 = grams/molar mass = approx 0.035 but you need to do it more accurately. molality = mol/kg solution = approx 0.035/0.045 = approx 0....

Chemisrty
See your other post.

oops--Chem
I did work it; however, I didn't post it. Here is is. http://www.jiskha.com/display.cgi?id=1398473570

Chem
I did work it; however, I didn't post it. Here is is.

Chem
I worked this for you earlier. I'll look for it if you can't find it.

chemistry urgent!
Reactions go to completion for one of just a few reasons. 1. A ppt (insoluble material) is formed. You need to know the solubility rules to know what is soluble and what isn't. Here is a simplified table. http://en.wikipedia.org/wiki/Solubility_chart 2. A gas is formed. (H...

College Chemistry
I worked this earlier today but with different numbers. 3.00 mols NaCl mols AgNO3 = M x L = 0.9L x 0.5M = 0.45 .........AgNO3 + NaCl ==> AgCl I.......0.45..................... add.............3.00............ C.......-0.45..-0.45......+0.45 E.........0.....2.55.......0.45 Y...

Chem
H2A + 2NaOH ==> Na2A + 2H2O mols NaOH = M x L = ? mols H2A = 2 x mols NaOH from the coefficients in the balanced equation. mols H2A = grams H2A/molar mass H2A

Chemistry
Same procedure. mols HCl = grams/molar mass Then M = mols/L solution.

Chemistry
In what units? molarity? 27.08 what? grams? mol = grams/molar mass Then M = mols/L solution.

Chemistry
NH4Cl + Na2SO3 no reaction NH4Cl + NaOH --> NH3 + H2O + NaCl Na2SO3 + BaCl2-->BaSO3 + 2NaCl Na2SO3 + NaOH -->I don't believe this will react. H2SO4 + BaCl2-->2HCl + BaSO4 BaCl2 + 2NaOH -->Ba(OH)2 + 2NaCl

chemistry
You want 315 mL of 0.620M = 0.315*0.620 = mols ethanol needed. mol = g/molar mass to give you grams, then use the density to calculate volume (mL) ethanol. Then to make this solution, you must add H2O to make a total volume of 315 mL.

chemistry
This isn't any chemistry I've seen. You want to make $1000 in sales (Is that in 1 month?). At $100 each you must sell 10 to get the $1000. The machine needs 6 parts for a product so you must have 10*6 = 60 parts. 10 workers can make 39 parts in a month so you need 60 p...

chemistry
AgNO3 + NaCl ==> AgCl(s) + NaNO3 You start with 3.0 mols NaCl. Add 200 mL x 1.5M AgNO3 = 0.300 mols. You will form 0.3 mols AgCl. You will have 2.7 mols NaCl unreacted.

Chemistry
If you added 18.01 mL of 0.1M NaOH you added 0.01801 x 0.1 = ? mols NaOH Then (NaOH) = mols/L = 0.001801/0.02801 = ? You may have added 0.4503 mols for all I know since you posted only part of the experiment, but mols NaOH in that particular part is 0.1 x 0.0180 = ?

Chemistry
You added how may mols NaOH? That's M x L = mols. What final volume do you have. You added 18.01 mL and 10 mL so total volume is 28.01 mL. Convert that to L., then M = mols/L

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