Friday
July 25, 2014

Posts by DrBob222


Total # Posts: 43,171

Chemistry 104
Instead of us guessing, why don't you show your work so we can find the error.

Chemistry
See your earlier post.

Chemistry
See your others posts. And please stop changing screen names. It won't help and in fact keeps us from helping as much as we might if you used the same name.

Chemistry
Eo is zero, right? :-) The SHE under standard condition is always 0.

Chemistry
I assume that's 3.8 atm. 2H^+ + 2e ==> H2 E = Eo - (0.0592/2)log[(pH2/(H^+)^2]

Chemistry
Ecell = Eocell - (0.0592/n)log[(Cr^2+)/(Ni^2+)] and you get Eocell by adding the OXIDATION for Cr to the REDUCTION of Ni^2+. I would do it here but the values in your text won't agree with the values in my OLD text.

Chemistry
Then you must be in the same room using the same computer so just talk to each other; you don't need to talk via computer.

Chemistry
Janu, Ladoo, et al. It helps us help you better if you use the same screen name. Look up the potentials, add the oxidation half to the reduction half to obtain Eocell. Then dG = -nFE

oops--Chemistry 104
Note that there are two mols of electrons and you must take that into account. A minor problem is that you will not plate out Ni(NO3)2 but Ni metal.

College Chemistry
Ptotal = pN2 + pAr

math lit ,geography,history,life science,LO
You need to provide some other information. What career choices do yo have? Which subjects are you taking? The first thing that come to my mind is that in grade 10 you aren't forced to make a career choice today; you still have a few years to think it over.

Chemistry
I don't understand your confusion. Silicon dioxide is SiO2. That's how you're supposed to write it.

Chemistry
SiO2 is THE formula for silicon dioxide. That's it. That's the only formula for silicon dioxide.

Chemistry
For some, such as silicon dioxide, the name tells you. Write the symbols. Si and O. The name says DI oxide so put 2 for O as a subscript and the formula is SiO2.

Chemistry
delta T = Kf*molality Substitute and solve for m m = mols/kg solvent Substitute and solve for mols. mols = grams/molar mass. You know grams and mols, solve for molar mass

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

Chemistry - Science (Dr. Bob222)
Thermodynamics is not my field. I would go with C but get a second opinion. I don't think A is right because for a diatomic gas Cp is 7/2R. B. B can't be right because at constant P there will be pdV work. C. The difference between Cv and Cp is 8.3 and that is about 28...

(12)Chemistry - Science (Dr. Bob222)
The problem here is in your assumptions. You KNOW the volume will change if the pressure is constant AND the temperature decreases from 165 to 65. Volume is proportional to T; therefore, volume decreases with decreasing T. dE = q + w You've made the assumption that w is ze...

(23.Chemistry - Science (Dr. Bob222)
Devron is right but I want to add a point or two. First, Ana is right. It PROBABLY isn't possible unless the reaction is carried out in under other than standard conditions; i.e., basic solution, complexing materials added to the basic mix, etc. Devron is right that none o...

(19) Chemistry - Science (Dr. Bob222)
RTlnK = nFEo

Chemistry
Calculate the molarity of the concentrated HCl. You made a typo and omitted the % after 37. M HCl = 1000mL x 1.20g/mL x 0.37 x (1 mol/36.5g) = about 12.2M Then mL1 x M1 = mL2 x M2 mL1 x 12.2M = 2850 mL x 0.500 Solve for mL 1 you need. Take mL you've calculated, add to a 50...

chemistry
mols = grams/molar mass

chemistry
I don't know and we can't find out. mols NaOH = M x L = approx 0.0042 IF the unknown acid is a monoprotic acid, then mols acid = mols base and mols acid = grams/molar mass You know mols acid and grams acid, calculate molar mass acid. However, the problem doesn't sa...

chemistry
See your other post under Harley.

chemistry
See your other posts. Just one is all ou need to see how to do these.

(11) Chemistry - Science (Dr. Bob222)
I'm sticking my neck out but go through this reasoning and see if you agree. reactants --> products k = P/R For k to be < 1, reactants must be favored. Just try A; if dH is - the reaction would be R ==> P + heat If we increase T the reaction will be shifted to the...

Chemistry - Science (Dr. Bob222)
A. dG has nothing to do with speed of a reaction. Carbon is the more stable form of diamond but all the girls getting diamond rings today need not worry about that ring crumbling tomorrow. :-). B. All reactions occur to some extent no matter how small. So this has an extremely...

science
I know very little about biology but that's what I think.

science
https://answers.yahoo.com/question/index?qid=20110503190756AADMkC7

CHEMISTRY HELP !!!!
OK. I told you how to do it. Do you need more assistance or do you have the right answer now?

CHEMISTRY HELP !!!!
What does either B or E mean? To me it means you don't know and you're guessing because they aren't close to each other. How many coulombs did you use. That's amperes x seconds = coulombs. Then you know that 27/3 = 9 g Al will be deposited for every 96,485 coul...

CHEMISTRY HELP !!!!
ok Now we can do something. Make the top numbers add up and the bottom numbers add up. on the left. top...1 + 235 = 236 bottom 0 + 92 = 92 which does nothing more than show that 236/92U is right. Now to the next part of the reaction. top: 236 = 137 + ? + (2*1) and solve for ?....

CHEMISTRY HELP !!!!
What's with the 1/2n? neutrons are 1/0n

CHEMISTRY HELP !!!!
Either you've made a typo or this is a screwed up question. 236/92 can't be Te. It MUST be U. And what is 2(1/2)n? neutrons are 1/0.

CHEMISTRY HELP !!!!
nope. And example for element X and I'll make up numbers. 24/12X ==>beta + Y 24/12 X ==> 0/-1 e + zYw and you want to know what z and w are. The upper numbers add up on both sides. The lower numbers add up on both sides. upper number first. 24 = 24 + ? so w must be 0...

Chemistry
22% w/w means 22 g solute Z in 100 g solution. mols in 22 g = 22/215.2 = ? Use density to convert 100 g to mL and convert to L. Then M = mols/L

Chemistry
mols K2SO4 = grams/molar mass Then M = mols/L solution.

Chemistry
The position of the metal and metal ion in the activity series.

chemistry
Probably none. Fe2O3 is not soluble. Sr3(PO4)2 is insoluble. No reaction.

chemistry
A. mols soln A = mol/dm3 x dm3 =? mols soln B = same thing. Bi. total mols HCl = mols of A + mols B Bii. NH3 + HCl ==> NH4Cl mols HCl you have. From the coefficients in the balanced equation, you know mols NH3 = mols HCl Then mols NH3 = mol/dm3 x dm3. You know mols and mol/...

chemistry
2Al(OH)3 + 3H2SO4 --> Al2(SO4)3 + 6H2O 1) How many mols Al(OH)3 do you want? That's M x L = 0.672 x 0.500 = approx 0.3 but you should be more accurate than that. mols Al(OH)3 = grams/molar mass. You know mols and molar mass; solve for grams. 2)How many mols H2SO4 did yo...

chemistry pls help me asap
3NaOH + H3PO4 ==> Na3PO4 + 3H2O mols NaOH = grams/molar mass = 4.0/40 = 0.1 mol. a) M NaOH = mols/dm3 = 0.1mol/0.1 dm3 = 1M b) From the equation, 3 mol NaOH = 1 mol H3PO4; therefore, 40 cc (0.04 dm3) of NaOH x 1 M = 0.04 mols NaOH. mols H3PO4 = 1/3 of that or 0.04/3 = about...

chemistry
This is done by the same procedure as the NaOH/H3PO4 problem above.

chemistry
mols Al2(SO4)3 = M x dm3 = ? mols Al = twice that mols sulfate = thrice that

CHEMISTRY HELP !!!!
It's D isn't it? That's the equivalent of my response.

CHEMISTRY HELP !!!!
(CN)2(en)2Zr(IV)NO3 which I wrote just following your words. Then I would rearrange this to [Zr(en)2(CN)2](NO3)2 Check me out on this.

Chemistry
2C4H10(g)+13O2(g)→8CO2(g)+10H2O(l) mols butane = grams/molar mass Using the coefficients in the balanced equation, convert mols butane to mols CO2. Now use PV = nRT and solve for V in liters. n = number of mols calculated in step 2.

Chemistry
Here is how you do ionic equation but I've gone a step further to show how to obtain the net ionic equation which I suspect may be your next question. Write the full molecular equation and balance it. HNO3(aq)+ KOH(aq) => KNO3(aq) + H2O(l) Next step is to write those ma...

Chemistry
yes

chemistry
#3 is an alkene. I don't know how you've been taught to do this but I do it this way. CnH2n+2 = alkane CnH2n = alkene (this is C20H40 and C5H10 as well as C3H6) CnH2n-2 = alkyne

CHEMISTRY HELP !!!!
I think 3 is right so it can't be D.

chemistry
heat lost by Ag + heat gained by water = 0 [mass Ag x specific heat Ag x (Tfinal-Tinitial)] + [mass H2O x specific heat H2O x (Tfinal-Tinitial)] = 0 Substitute and solve for Tf, the only unknown.

check---chemistry
Please read and correct so it makes sense.

Chemistry
You do these by noting that the formation constant is huge so that the complex essentially forms at 100%, then turn the reaction around as if it were a weak acid and calculate the (M^2+). ..........M^2+ + 6CN^- ==> M(CN)6^4- I.....0.170M....1.31M........0 C....-0.170...-6*0...

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

(5) Chemistry - Science (Dr. Bob222)
First thanks for sharing that Zn/Cu answer. I was sure that was right and as I posted last night, I might be missing something but if so I didn't see it. My equation for the buffer was 4.99 = 4.74 + log (130+x)/(100-x) 0.25 = log (130+x)/(100-x)see below 1.78 = (130-x)/(10...

(5) Chemistry - Science (Dr. Bob222)
Let HA = CH3COOH millimols HA = mL x M = 1000 x 0.1 = 100 mmols A^- = 1000 x 0.13 = 130 First determine what the pH of the solution is initially using the Henderson-Hasselbalch equation. I obtained 4.85 but you should ocnfirm that. Then you want to increase that by 0.14 by add...

Chemistry - Science (Dr. Bob222)
millimols NH3 = mL x M = 100 x 0.1 = 13 mmols HCl = 87 x 0.15 = 13.05 My best guess is that these are to be considered the same since the 87 has two s.f. and 13 does too. ........NH3 + HCl ---> NH4Cl I.......13....13........0 C......-13...-13.......+13 E........0.....0........

science check answer
I think your first choice was right.

Chemistry - Science (Dr. Bob222)
mmols CH3NH2 - 0.40 x 130 mL = 52 ..........CH3NH2 + HCl ==> CH3NH3^+ I..........52.......0........0 add.................x............. C.........-x.......-x........x E.........52-x......0........x 11.59 = 10.64 + log (52-x)/(x) 8.91 = (52-x)/x 8.91x = 52-x 9.91x = 52 x = 5...

Chemistry - Science (Dr. Bob222)
Did you convert pKb given to pKa?

Chemistry - Science (Dr. Bob222)
This looks almost like the KOH/acetic acid above. If you still have trouble show what you've done and where you're stuck as well as what you don't understand and I can help you through it.

Chem Check Please!!!
I think when the cell is set up as written above (with the diagram) it means Ag + Cl^- ==> AgCl + e E = -0.222 Cu^2+ + 2e --> Cu E = 0.337 So the sum is +0.115 or c.

Chem Check Please!!!
1 is right. 2. I am not familiar with this particular series but you can read about it here. http://en.wikipedia.org/wiki/Spectrochemical_series

Chem Check Please!!!
I don't think the answer is either c or d. If the complex is diamagnetic doesn't that mean all of the electrons are paired. Doesn't that make it low spin. And if they are paired doesn't that make the delta oct difference between t2g and eg large? So I would thi...

Chem Check Please!!!
I agree

CHEMISTRY HELP !!!!
Isn't that e. I think I answered this a day or so ago and for some inexplicable reason I thought it was Cr(IV) but of course Cr(II) is right.

chemistry
29.6% (w/w) is 29.6 g KCl/100 g solution. That is 29.6g KCl in (29.6g KCl + 70.4 g H2O. mols KCl = grams/molar mass = ? kg H2O = 0.0704 molality of the solution is mols/kg solvent Then delta T = i*Kb*m i = 2 for KCl. Solve for delta T and add to 100 C to find new boiling point.

Science
work is -pdV work is -0*dV = 0

chemistry
This problem is a bit confusing to me. If you've collected the H2 over water and you calculate V H2 from PV = nRT why won't the volume of the H2O be the same as the volume of H2 gas? I plugged in the numbers and obtained abou4 31 L for volume H2. Seems to me any other ...

chemistry
.....CH3NH2 + HOH ==> CH3NH3^+ + OH^- I...0.1003............0.........0.1204 C.....-x..............x..........x E...0.1003-x..........x........0.1204+x Kb = (CH3NH3^+)(OH^-)/[CH3NH3^+] Look up Kb and plug in the numbers. Solve for x = (CH3NH3^+)

chemistry
Those formula don't mean anything to me. If you write them in acid/base notation, which I suspect they are, it would be easier. At any rate, look at your post above and see if it isn't worked the same way.

chemistry
If the volume decreases (by say a factor of 2) that will double the (PH3) and double (BCl3). For a factor of 1.774 concn will be increased for EACH by 1.774. Remember the solid doesn't appear in Kc. Kc = 1/(PH3)(BCl3) So Kc > Q = 534.8/(1.774)(1.774)

chemistry
Do you mean for this reaction be be written as N2 + O2 ==> 2NO with Kc = 2400. That's the way you have your arrows.

chemistry
Substitute the equilibrium concentrations given in the problem into the Kc expression and solve for K.

chemistry
q = mols H2O x molar heat capacity x (Tfinal-Tinitial)

Chem 130
You need to find the arrow key and use it. mols CaCO3 = grams/molar mass Using the coefficients in the balanced equation, convert mols CaCO3 to mols CO2. Now convert mols CO2 to grams CO2. g = mols x molar mass

Chem 130
You have a 100 L tank and you want to fill it with He to a pressure of 155 atm at 22 C. This problem is two problems in one. One for He and the other for H2. Here is the He one done for you. It's just a matter of substituting into PV = nRT and using n for solve for grams. ...

Chem 130
Use PV = nRT and solve for n in each tank. Then n = grams/molar mass. You know molar mass and n, solve for grams in each tank.

chemistry
Ptotal = pO2 + pH2O You know Ptotal and pH2O, solve for pO2. Note Ptotal and pH2O are not in the same units.

Chem 130
Ptotal = pO2 + pH2O You know Ptotal and pH2O, solve for pO2.

Chemistry
%Z(w/w) = (g Z/total grams)*100 = ? where total grams = gX + gY + gZ

Chemistry
dHsurr = -dH/T

Chemistry
Is that 2.6M HCl? I will assume so. Zn + 2HCl ==> ZnCl2 + H2 How many mols H2 is that? Ptotal = 845 torr pH2O at 65C = approx 190 torr. You need to look up this value in your text/notes because I've estimated it from some tables I have. pH2 = 845-190 = about 655 mm or 6...

Chemistry
See your other post.

Chem 130
mols He = 2.03/molar mass He = n1 mols He = 6.19/molar mass He = n2 (n1/12L) = (n2/xL) Solve for x L.

Chemistry
............MgF2 ==> Mg^2+ + 2F^- I...........solid.....0.......0 C...........solid.....x.......2x E...........solid.....x.......2x Ksp = (x)(2x)^2 You know x = 2.3E-3M.Substitute and solve for Ksp.

Chemistry
Let's call aniline BNH2 ...........BNH2 + HOH ==> BNH3^+ + OH^- I..........0.201...........0........0 C...........-x.............x........x E.........0.201-x..........x........x Kb = (BNH3^+)(OH^-)/(BNH2) You know x. Substitute into Kb expression and solve for Kb.

Chemistry - Science (Dr. Bob222)
I worked through it and came up with 1.09v also. 1.13 seems to be the closest ad I would go with that. Sometimes answer sheets give approximate answers and this could be one of them. If I'm missing something I don't see it.

chemistry
Use PV = nRT and solve for P (in atmospheres) and convert to mm Hg. 1 atm = 760 mm Hg. Don't forget T must be in kelvin.

Organic CHM II
http://lipidlibrary.aocs.org/Lipids/tag2/index.htm

chemistry: please check work
I agree with the procedure as well as the value and the number of significant figures.

Chemistry
http://en.wikipedia.org/wiki/Delocalized_electron

chemistry
What do you need help with? The lower concn will be the increasing and the higher concn will be decreasing until both have the same concn. So you know the lower concn will be oxidized and the higher concn will be reduced.

Chemistry
No, of course you don't know the final T. That's what you're trying to find. It ways that in the problem, "What is the final T if ..." heat lost by Ni + heat gained by H2O = 0 [mass Ni x specific heat Ni x (Tfinal-Tinitial)] + [mass H2O x specific heat H2...

Chemistry
You can but that's the hard way to do it. It is much easier to substitute the individual numbers and work it out by pieces.

Chemistry
heat lost by Ni + heat gained by H2O = 0 [mass Ni x specific heat Ni x (Tfinal-Tinitial)] + [mass H2O x specific heat H2O x (Tfinal-Tinitial)] = 0

Chemistry
You want 1 mol SO3 and not 2 so divide by 2. You want the reverse so change the sign.

Chem Check Please!!!
I disagree with 1. I agree with 2,3,4. I con't see all of the name typed on 5 but e is right if that is chromium IV.

Chemistry
It's twice dHof

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