Wednesday
April 16, 2014

Posts by DrBob222


Total # Posts: 41,733

Energy question
This is my personal opinion but I don't think they are. My experience is that the new fluorescent bulbs don't live up to the hype on the box. Supposedly those incandescent bulbs burn out faster and it takes several to last as long as the newer fluorescent bulbs. In add...

Science help!!!!
These fill in the blanks are hard to do because more than one work/phrase often fits. A____solar panel__________________ is a tool used to capture the energy in sunlight. Recycling aluminum cans and taking shorter showers are two ways to practice the ___conservation___________...

Chemistry
q = -192 kJ since that is evolving heat. w = pdV = 125*(2) an that is - since it is expanding; i.e., it is doing work against the atmosphere while expanding. Note that w is in L*atm and need to be changed to J. Do that by x 101.325 then convert to kJ. Note: work is given in te...

chemistry
delta H at constant pressure is q. Or perhaps I should say it another way,k q at constant pressure is delta H. So delta H in this case is +252 kJ.

chemistry
q = 252 kJ and it's + so is endothermic w = 105 kJ and it's - since it is doing the work. delta E = q+w delta E = +252 kJ + (-105 kJ)

chemistry
a. pH = 4.74 + log(base)/(acid) = approx 5.00 b. millimoles NaAc = mL x M = 500 mL x 0.030M = = 15 mmoles. 5.00 = 4.74 + lot (15/x) Solve for x = millimoles acetic acid and convert that to grams in 500 mL solution.

Chemistry
John, did you read the post I left for you? If you will show your work we can spot the problem. Otherwise we're working in the dark.

Chemistry
See your other post above.

Chemistry
I gave you the formula for doing this yesterday. If you still have problems show your work so I can spot the error.

chemistry
.......Mg(OH)2 ==> Mg^2+ + 2OH^- I......solid........0........0 C......solid........x........2x E......solid........x........2x So Ksp = 1.2E-10 You want solubility Mg(OH)2 to be 2.51E-8M = (Mg^2+) = x in the above equation. Plug those values into Ksp expression and solve f...

water chemistry
millimoles HAc = mL x M = 35.0 x 0.150 = approx 5.25 mmols NaOH = 17.5 x 0.150 = 2.625 ..........HAc + NaOH ==> NaAc + H2O I........5.25....0........0......0 add.............2.625............... C.......-2.625..-2.625...+2.625..+2.625 E.......2.625.....0.....2.625.....2.625...

Chemistry
q = [mass ice x specific heat solid ice x [0-(-12)] + [mass ice x heat fusion] + [mass melted ice x specific heat liquid H2O x (29.6-0)]

chemistry
..........A --> 2B I.......1.60.....0 C........-x......2x E......1.60-x....2x Assuming Kc listed is at 500K, substitute the E line into Kc expression and solve for x and 1.60-x.

chemistry
H2SO4 + 2NaOH ==> 2H2O + Na2SO4 mols NaOH = M x L = 0.1896 x 0.01109 = ? mols H2SO4 = mols NaOH/2 M H2SO4 = mols H2SO4/L H2SO4. You have mols H2SO4, L H2SO4 = 10 mL(0.010L), solve for M H2SO4. That's the (H2SO4) in the 10 mL. That solution came from 1:10 dilution so the...

Chemistry
dGo = -RTlnK dGo = -nFE

chemistry
John, what's the problem here. It's just a matter of looking up the half reaction and adding one to the other after reversing one of them.

Chem
Why don't you help by looking up delta Ho formation for the products and reactants. That way we'll be using the same set of numbers.

chemistry help~Please!!!
I found this table of Ka values. Zn = 2.5E-10 Cl^- is not hydrolyzed. http://bilbo.chm.uri.edu/CHM112/tables/KaTable.htm

orgo chem
fn = [(1+Kd*(Vo/Va)]-n where fn = fraction solute REMAINING in aq layer after n extractions. Vo = volume organic layer Va = volume aqueous layer Kd = distribution constant for organic/aqueous

chemistry
mols NH4NO3 = grams/molar mass Use the coefficients in the baalanaced equation to convert mols NH4NO3 to mols H2O. Now convert mols H2O to grams H2O. g = mols x molar mass

chemistry
See your other post.

chemistry
Use the coefficients in the balanced equation to convert mols NH3 to mols H2O. Now convert mols H2O to grams. g = mols x molar mass

Ap Chem
Ecell = Eocell - (0.05916/n)log[(Fe^2+/Cu2+)]

Chemistry
Use Ecell = EoCell - (0.05916/n)log(M^x+) Eocell is the reduction potential you look up in the table in your text/notes. M^x+ is the concentration of the ion in the problem. (You will note that if you substitute 1 for the ion the log M is 0 and Ecell = Eocell from the tables)....

Chemistry
And you don't understand exactly what?

Chemistry
I worked this below.

Chemistry
Coulombs = amperes x seconds Convert 48 hr to seconds and that x 7500. That number is close to 173,000 but you should get a better number and that x 7500 = about 1.3E9 C. 96,485 coulombs will plate out 40/2 = 20 g Ca. So you should be able to plate 20 x 1.3E9/96,485 = g Ca at ...

chemistry
Ksp Ag2SO4 = 1.2E-5 = (Ag^+)^2(SO4^2-) Ksp CaSO4 = 4.93E-5 = (Ca^2+)(SO4^2-) So CaSO4 ppts first. How do you know that. Calculate the (SO4^2-) when each bgins to ppt. Ag2SO4. (SO4^2-) = Ksp/(Ag^+)^2 (SO4^2-) = you do it. I get approx 2.7E-2M CaSO4. (SO4^2-) = Ksp/(Ca^2+) = you...

CHEMISTRY
Do you mean at equilibrium (NH3) = 1.23E-4M? and (H2) at equilibrium = 2.75E-3M? that is, is that M? ........N2 + 3H2 ==> 2NH3 E.......x....2.75E-3....1.23E-4M Keq = (NH3)^2/(x)(H2)^3 Substitute and solve for x

Chemistry
I'm glad you corrected that. I was scratching my head trying to figure out your last post. Good luck in your studies.

Chemistry
You didn't waste my valuable time as much as you wasted your valuable time. But I would round my answer to 1.0E-7M.

a note--Chemistry
Note that 1.01E-7 is too many significant figures.

Chemistry
How about 1.01E-7? You should have 3.9E-26/1.4E-6 and that = 3(X)^3 I suspect your error is in the next step. You should divide by 27 and take the cube root of the what is left. But note that if you had shown what you did at the beginning I would have already seen the found th...

Chemistry
And I can't read the brain waves to know what you obtained as an answer.

Chemistry
....Ag3Co(CN)6 ==> 3Ag^3+ + [Co(CN)6]^-3 I..solid............0.........0 C.....solid.........3x........x E.....solid.........3x........x Ksp = 3.9E-26 x (3x)^3(x) Solve for x. (Ag^+) = 3x

Chemistry
I obtained this reaction from Wikipedia. Compare with the reaction in your text/notes. If not the same you will need to adjust my post. Zn(s) + 2MnO2(s) is in equilibrium with ZnO(s) + Mn2O3(s) [e° = 1.43 V] molsZn = grams Zn/atomic mass Zn Using the coefficients in the ba...

CHEMISTRY
I answered this for you below.

CHEMISTRY
You didn't show an equilibrium but the reverse Kreverse is 1/Kforward.

Chemistry
........Fe(OH)3 ==> Fe^3+ + 3OH^- I.......solid........0........0 C.......solid........x........3x E.......solid........x........3x Ksp = (F^3+)(OH^-)^3 Substitute the E line into Ksp expression and solve for x, = [Fe(OH)3] in mols/L. That x molar mass = grams.

chemistry
I assume you mean 73.9% complete. N2 + O2 ==> 2NO This is a limiting reagent (LR) problem. First we determine the LR. atm NO formed if we used all of the N2 and an unlimited supply of O2. 0.352 atm N2 x (2 mols NO/1 mol N2) = 0.352 x 2/1 = 0.704 atm NO produced. atm NO form...

Chemistry
What nitrates did you have? I assume you have list from which to choose. You could have Ni, Co, Mn, Fe, Al, Cr, Zn

Chemistry
OK. Step by step #2 and I'll assume you know how to get from grams to mols. 6.59g CO2 = 0.150 mols CO2 = 0.150 mols C. 2.7 g H2O = 0.150 mols H2O = 0.300 mols H(atoms) So now we have 0.150 g C 0.300 g H We want to find the ratio, in small whole numbers, with no number bein...

Chemistry, Science
Just follow the written statements. 2NaOH(aq) + Pb(NO3)2(aq) --> Pb(OH)2(s) + 2NaNO3(aq) Pb(OH)2(s) + 2NaOH(aq) --> [Pb(OH)4]^2-(aq) + 2Na^+(aq). However, this leaves it in ionic form and I think the problem wants it in molecular form so I would make the product Na2Pb(OH...

Chemistry
C7H12 + 10O2 ==> 7CO2 + 6H2O moles C7H12 = 7.6g/96 = estimated 0.08 mols CO2 = 0.08mols C7H12 x (7 mols CO2/1 molC7H12) = estimated 0.55 Then mass = mols CO2 x molar mass CO2 = ? Do the same for mols C7H12 to mols H2O, convert mols H2O to grams. then add the g CO2 + g H2O =...

chemistry
A confusing problem. Use PV = nRT and solve for n of the 4.70 g gas at STP, the convert n to molar mass. That is n = grams/molar msss. You know n and grams, solve for molar mass. Then use PV = nRT again at the new conditions and solve for n in the new container at the new cond...

chemistry
velocity is a vector quantity; i.e, both speed and a direction. Speed is a scalar quantity. You can read more about it here. http://en.wikipedia.org/wiki/Velocity

chemistry help~~~~ Please!!!
If you intend to do well in chemistry you had better find the caps key. For example, m stands for molality; M stands for molarity. They are different. If you are trying to ask about the difference between the K and the Na salts, there will be none as far as pH is concerned for...

CHEMISTRY HELP !!!! Check
Looks good to me.

chemistry
millimols = mL x M = ? millimols K from K2CO3 = 2*234*1.2 = ? mmols K from K3PO4 = 3*312.5*0.32 = ? (K^+ final) = total K mmols/total mL = ?

CHEMISTRY HELP !!!!
Here is how you do these. ........NH4^+ + H2O ==>H3O^+ + NH3 Ka = (H3O^+)(NH3)/(NH4^+) Ka for NH4^+ = (Kw/Kb for NH3)= ?

PLEASE HELP D:
Personally, I think that will result in nothing getting done. I suspect there must be a central coordinating agency. At first glance the federal gov might be the obvious choice but I shudder at the thought of another federal czar, more gov red tape, more cost overruns, and all...

Chemistry
The assumption for my response was years.

Chemistry
k = 0.693/t1/2 = approx 4.95E-11 Rate at time zero = k*N and for 1 mol Th, N will be 6.02E23 atoms. Solve for R, which will be in disintegrations/year . Convert tht to d/hour.

Chemistry
With regard to H^+. You added 0.9375 mols H^+ to the buffer. ALL of it will react with the 15.0 mmols NH3 (H^+ is the limiting reagent so there won't be any of it left). With regard to the NH4+ you should add and my ICE chart shows that; however, I said subtract in my inst...

Chemistry
millimols NH3 = 50 mL x 0.3M = 15.0 (NH3) = mmols/mL = 15.0/100 = 0.15M initially. millimols NH4Cl = 50 x 0.3 = 15.0 (NH4Cl) = 15.0/100 = 0.15M initially millimols HCl = 7.50 x 0.125 = 0.9375 pKb NH3 = 4.74; pKa = 14-4.74 = 9.26 I prefer to work with this equilibrium in mmols....

Chemistry
delta T (increase in b.p.) = i*Kb*m All are the same m so that is a constant. kb is a constant. Threfore, it all depends upon i, the van't Hoff factor. i = 1 for urea i = 2 for NaCl i = 3 for MgCl2 i = 5 for Al2(SO4)3. So which will cause the SMALLEST CHANGE?

Chemistry
What's the problem with these? I assume they are in solution. 3Ag^+(aq) + PO4^3-(aq) ==> Ag3PO4(s)

Chemistry Equilibrium
(H2O( = 0.0860 mol/2.00L = approx 0.043M ............2H2O --> 2H2 + O2 I..........0.043......0.....0 C...........-2x...... 2x....x E..........0.043-2x...2x....x Substitute the E line into the Kc expression and solve for x.

chemistry
1g x (5/450) = ?

Chemistry
1.4E10 what? What is mil?

chemistry
0.64 mol/dm^3 x ? dm^3 = 0.320 Solve for ? dm^3

Chemistry
q = mass H2O x specific heat H2O x (Tfinal-Tnitial)

Chemistry
q = mass H2O x specific heat H2O x (Tfinal-Tintial) If you use specific heat as 1 cal/g*C then q will be in cal. Convert to kcal by dividing by 1000.

Chemistry help plzzzzz!!!!!
Have you tried making that -55.1 kJ/mol. It must be negative since it is exothermic. It's time for me to go to bed. Let me know quickly if that is right.

Chemistry
Subscripts multiply the atom for which it's a subscript. Coefficients multiply everything that follows. 3NaCl. 3Na and 3Cl H2SO4 2H 1S 4O 4H2SO4 8H, 4S, 16O

Chemistry
You need to tell us more about what you are doing.

Chem Help!
..........Fe(OH)3 -->Fe^3+ + 3OH^- Ksp = (Fe^3+))OH^-)^3 You know Ksp (or can look it up) (Fe^3+) = 0.2M from the problem. Substitute and solve for OH^-, then convert to pH.

chemistry
I'm not an organic chemist but I would name this as isopropyl-1-butanamine. I clicked on Google and typed in naming amines and came up with an IUPAC page in pdf format. That's the name I came away with.

chemistry
P1V1 = P2V2

Chemistry
mols NaOH = M x L = approx 0.0860 molw CH3COOH = approx 0.05 = HAc ........NaOH + HAc ==> NaAc + H2O I....0.0860.....0.......0.......0 Add...........0.050.............. C.....-0.050.-0.050....0.050...0.050 E......0.036....0......0.050 So you have 0.0360 mols NaOH 0 mols HAc...

chemistry
The dilution formula is c1v1 = c2v2 c = concn v = volume 12.0M x 60mL = 1.85M x ?mL Solve for ? mL Actually, I think it is easier to remember mL x M = mL x M

chemistry
I suspect for reasons of solubility. According to this web site the solubility is 12.78 mg/mL at 20C which is quite soluble. http://en.wikipedia.org/wiki/Paracetamol

chemistry
Of course 9M is more concentrated than 3M if both are H2SO4. M = mols solute/L solution. So 3M = 3 mols/L = 3*98g/1000 mL = 294g/L and 9M = 9 mols/L = 9*98g/1000 mL=882g/L

chemistry
(P1V1/T1) = (P2V2/T2)

chemistry
1 is ok 2 is ok 3 is chemical. If it combines with other elements that makes it a chemical reaction just like burning it in oxygen. 4 is physical. It isn't combining with anything. H2 is still H2; it's just dissolved H2. 5 is ok. 6 is ok.

Chemistry
I don't want that post to stick around on the web so I'm deleting it. But this response will stay so as to answer your question. I don't know why I answered that way because as I was posting I kept thinking things just weren't right. This ranks up there among t...

chem090
This is a limiting reagent (LR) problem. You know that because amounts are give for BOTH of the reactants. mols BaCl2 = grams/molar mass = approx 0.48 but you should confirm this and all of the calculations that follow and you should carry all of them to at least three places....

chemistry
Use the dilution formula of c1v1 = c2v2 c = concn v = volume 0.4M x ? = 8M x 50 mL Solve for ? mL By the way, I think the accepted IUPAC name for HBr is hydrogen bromide. The mono is unnecessary.

Chemistry lab
You need to correct this post. 0.9 mM of what?

Chemistry
eqn 1 CaF2 ==> Ca^2+ + 2F^- eqn 2 Ca^2+ + SO4^2- ==> CaSO4 ------------------------------- sum 1+2 CaF2 + SO4^2- ==> (F^-)^2 + CaSO4 since CaF2 and CaSO4 are solids we can cancel them since they are not involved in the Keq. You note that eqn 1 is Ksp for CaF2 and eqn ...

Chemistry
This is a long (but not particularly complicated) calculation to do on the web. Do you have a specific question that is troubling you?

Chemistry
From what I can read you don't have sufficient information here to calculate a LSI. pH alkalinity T etc.

Chemistry
1 mol contains 6.02 E23 molecules.

Chemistry Help Please!!!
The equation you want is (1/2^t/4)= x amount remaining which in this case is (1/2^30/4) = (1/2^7.5)= x Solve that equation for the amount remaining after 30 days. Using that equation you should be able to do the others. For example c is [(1/2^(t/4)] = 1 and solve for t.

Science
https://answers.yahoo.com/question/index?qid=20070731113316AADwmqF

Science
I agree.

Science
ok. I agree.

Science
What's the question?

Chemistry
If p is same and T is same then mols is proportional to volume. If you have 1/3 the volume you must have 1/3 the mols.

Chemistry
ptotal = pN2 + pO2

Chemistry
First note the correct spelling of celsius. Calculate n = number of mols from PV = nRT. Then n = grams/molar mass. You have n and grams, solve for molar mass. Don't forget to convert mm Hg to atm and T to kelvin.

Science
See your other post.

chemistry
For the freon see your other post. For this other problem the pressure has changed. p1/t1 = p1/t2 t1 and t2 must be in kelvin.

Chemistry
I assume we are to ignore the calorimeter constant. [mass metal x specific heat metal x (Tfinal-Tinitial)] + [mass H2O x secific heat H2O x (Tfinal-Tinitial)] = 0. Substitute and solve for s.h. metal.

Chemistry
How many mols do you need? That's mols = M x L = 0.48 x 0.1235 L = ? Then M = mols/L soln. Substitute. Solve. You know M = 5.00 and you know mols from above. Solve for L and convert to mL.

chemistry
Those are conversion factors that I posted. Let's work with the first one. A conversion factor converts anything you have into anything you want (if you have the right factor and use it correctly). So the factor is 1 atm/101.325 kPa and of course it can also be 101.325 kPa...

chemistry
1 atm = 101.325 kPa. 1 atm = 14.7 psi

Chemistry
P1V1 = P2V2 Substitute and solve for the one unknown. Change atm to mm Hg. 1 atm = 760 mm Hg.

chem HARD
Li is in group I; therefore, it has 1 electron in its outside shell and can give it away to a receptor, such as chlorine, bromine etc to make LiCl or LiBr. But when making lithium carbonate, it needs to give away TWO electrons because carbonate takes TWO electrons. Thus TWO Li...

chem
M = mols/L mol = 36.0/58.5 volume = mass/density = 136/(1.13*1000) So M = (36.0/58.5)/[136/(1.13*1000] Check me out on this. This would make it (36.0/58.5) x (1.13*1000/136) = (36.0 x 1.13 x 1000/136 x 58.5 = ?

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