Friday
September 30, 2016

Posts by DrBob222

Total # Posts: 53,189

chemistry
I think of molecular compounds as being made up of molecules with covalent bonds. CO2 for example. NaCl is an ionic compound and consists of discrete Na^+ and Cl^- so it is not molecular while CO2 exists as discrete CO2 molecules. SO2 and SO3 are other molecular compounds.
June 8, 2016

chemistry
So far you are good. So Q = 1E-40 < K = 1.4E-37 which lets you know c and d can't be right. The answer must be a or b. Now write the Keq expression. Keq (which is really Ksp) = Cu3(PO4)2 = (Cu^2+)^3(PO4^3-)^2 = 1.4E-37 Q must be larger. How can it get larger? No way ...
June 7, 2016

chemistry
Reverse eqn 1(change sign of dH), add to eqn 2 and 2 x eqn 3.
June 7, 2016

chemistry
By the way, the Ka value has no units and don't let anyone tell you they do. When they are used, most of the time they are called just units, but often they are called "tentative units". "temporary units", "trial units", or
June 7, 2016

chemistry
You can get the definition of an acid from you text/notes/google. For the HA problem. For pH = 3.50 convert to (H^+). I obtained approx 3E-4 but you need to confirm since that's an estimate. .......HA ==> H^+ + A^- E......x....3E-4...3E-4 Substitute the E line into the ...
June 7, 2016

chemistry
Your text or notes contain all of these definitions. YOu don't need us to do your homework for that. As the for Lewis structure, we can't draw structures on this forum.
June 7, 2016

Chemistry
If the 35 is a superscript and the 15 is a subscript, then C is correct.
June 7, 2016

Chemistry
I think you can heat K2CO3 up to 110 C without decomposition. Spread crystals out on a watch glass and heat at 110 for 2 Hrs. Cool in a desiccator.
June 6, 2016

chemistry
Al ==> Al^+ + 3e Eo ox = ? Ag^+ + e ==> Ag Eo red = 0.8 ----------------------- Al + 3Ag^+ ==> 3 Ag + Al^3+ E=2.46 ? + 0.8 = 2.46 ? in this set up is the oxidation potential. Change the sign to make it the reduction potential.
June 6, 2016

Chemistry
When AgNO3 is added drop wise to the solution, the one with Qsp greater than Ksp will ppt first. You're correct, that is AgI. More drops of AgNO3 results in AgI continuing to ppt until Ksp for AgCl is met. What is (Ag^+) then? Ksp = (Ag^+)(Cl^-). You know Ksp and you know ...
June 5, 2016

Chemistry
mols needed = M x L = ? Then grams = mols x molar mass = ?
June 5, 2016

Analytical Chemistry
Here is a very detailed document. Read through that and see if it helps. I've not seen one this detailed in some time. All of the reactions are there although it is a little light on the stoichiometry part. http://www.lasalle.edu/~prushan/Experiment8-redox%20titration.pdf
June 5, 2016

chem
........CO(g) + Cl2(g)⇌ COCl2(g) E.....1.9E-6...9.3E-7.....x Substitute the E line into the Keq expression and solve for x = (COCL2) in mols/L. Then mols/L x 5.89 L = mols COCl2. Grams COCl2 = mols COCl2 x molar mass COCl2.
June 5, 2016

quimica
millimols NaOH = mL*M = 20*0.175 = 3.5 If pH = 12.55, then pOH = 1.45 and (OH^-) = 0.03548 M so mmols at the end will be 0.03548*(20+xmL) where x mL is the volume of the 0.2M HCl added. .....OH^- + H^+ ==> H2O I...3.5.....0 add.......0.2x.......... C...-x...-0.2x.........s ...
June 4, 2016

chemistry
aluminum sulfide reacts with water to form aluminum hydroxide and hydrogen sulfide a. balance the chem eqn for this rxn Al2S3+6H2O = 2Al(OH)3+3H2S right. b.how many g of water are needed in the rxn to produce al(oh)3? what is the formula i use here?? You can't do without ...
June 4, 2016

Chemistry Homework
No. Your first line is in error and I quit reading there. 2.45 dL = 245 cc.
June 3, 2016

Chemistry
3 mols CO2 x (5 mols O2/3 mols CO2) = 3 x (5/3) = ?
June 3, 2016

Chemistry/- Dr.Bob222
Zn + Ni^++ ==> Zn^++ + Ni Ecell = Eocell - (0.05916/n)*Log Q where Q (I didn't have space to write it is) (Zn^2+)(Ni)/(Ni^2+)(Zn) You know of course that (Ni) and (Zn) = 1 since they are solids. Initially (Ni^2+) = 1.5*(Zn^2+) so at the end, since both are divalent, ...
June 2, 2016

chemistry
Did you make a typo and you meant to type in that the teacher obtained 0.30 N? Technically, you can't say. Both could be right but I disagree with Scott as to why that is so. You must know the equation involved. For example, if you titrate one(1) H then mL x N x ...
June 2, 2016

Chemistry
Actually, you don't need any of this other information since Kb for HPO4- = Kw/Ka for H2PO4^-
June 2, 2016

Chemistry
You didn't read my earlier response? I guess it's just easier to repost and hope someone will work the problem for you.
June 2, 2016

chemistry
The question isn't clear. Decomposed to what? KNO2 + O2? K _ N2 + O2, K2O + NO2? I suspect to KNO2 + O2 but I don't know that and, in my opinion, that isn't completely decomposed.
June 2, 2016

Chemistry
I think you should review your notes and answers. I question 64, 66, 67, 69 and I quit reading.
June 2, 2016

Chemistry
Bobby, what do you not understand about this? In detail, please. Make an ICE chart using mols and substitute into the Henderson-Hasselbalch equation.
June 2, 2016

chemistry
Have you used the Arrhenius equation? Show your work; perhaps we can find the error.
June 2, 2016

Chemistry
I believe the original definition for an Arrhenius base was that a base material contained the OH ion. LiOH would be the answer for this question. I believe the definition was expanded somewhat, later, to include anything that produced an OH ion in aqueous solution. As such, ...
June 1, 2016

Chemistry - Dr.Bob
You don't get Na and S and O. You get H2 gas at one electrode and O2 at the other.
June 1, 2016

Chemistry
I think your answer is right but actually it depends upon the energy of the gamma ray.
June 1, 2016

Chemistry
(V1/T1) = (V2/T2) Remember T must be in kelvin
May 31, 2016

Chemistry
Wouldn't it have been better to show your work instead of leading us around to the back of the barn? No you don't need the formula mas of MgCl2.6H2O. If you can change pounds into liters you're a better chemist than I am. Pounds is a weight. L is a volume. Change ...
May 31, 2016

Chemistry
Something is wrong with the Zn/Cu question above. You have answered it correctly but the computer won't show my answer when I try to post it.
May 31, 2016

Chemistry
Did you leave off the electrons? What you have check is the reduction reaction but that isn't right because the electrons have been omitted. Oxidation is the loss of eletrons. Fe^2+ ==> Fe^3+ + e is the oxidation half reaction. Also note that neither A nor D are ...
May 31, 2016

Chemistry
right
May 31, 2016

chemistry
q = m * c * (change in temperature) q = 20.5 * 2.05 * (0+24.3) = 1021.2 J right and I would make that 1.02 kJ. Then you need to melt the ice. q = (20.5/18)*6.02 = ? q = 20.5 * 4.184 * (100-0) = 8577.2 J right and I would make that 8.68 kJ. Then you need to vaporize the water...
May 31, 2016

Chemistry
I wonder why you don't call that silver nitrate? 2AgNO3 + Cu --> Cu(NO3)2 + 2Ag mols Cu = grams/atomic mass = ? Then you get 2 mols Ag for every mol of Cu.
May 31, 2016

Chemistry
.......H2O2 ==> H^+ + HO2^- I.....0.86......0......0 C......-x.......x......x E...0.86-x......x......x Substitute the E line into the Ka expression and solve for x = (H3O^+).
May 31, 2016

Chemistry
(Na^+) = 0.10 M (OH^-) = 0.10 M (H^+) = Kw/(OH^-) = ?
May 31, 2016

Chemistry!!! PLZ PLZ HELP!!
You can't work this problem without knowing the volume. If we assume a volume of 1L, then (H2) initial is 0.1 M and (I2) initial is 0.2 M. .......H2 + I2 ==> 2HI I.....0.1M..0.2M....0 C.....-x.....-x.....2x E...0.1-x...0.2-x...2x Substitute the E line into the Keq ...
May 30, 2016

@ Mayra---Chemistry
The primary reason I said M was not possible is because that definition is mols/L SOLUTION. Your problem gives 400 mL water which is not the same as 400 mL solution. 25 g NaOH + 400 mL water is not 400 mL solution but more than that. By what volume who knows. So you may ...
May 30, 2016

Chemistry
In what? % w/w; % w/v, mole fraction, M, m......? If you want it in m, then mols = grams/molar mass = ? Then m = mols NaOH/kg solvent. You can't do % w/v or M.
May 30, 2016

Chemistry- Dr.Bob222
Look at the activity series of metals here and pick a metal below Mn but above Cr. https://www.google.com/search?q=activity+series&ie=utf-8&oe=utf-8 The other part of your question makes no sense. Read it and see.
May 30, 2016

Chemistry
https://www.google.com/search?q=sigma+and+pi+bonds&ie=utf-8&oe=utf-8
May 30, 2016

Chemistry
Boiling points, melting point, solubility, color, solid/liquid/gas, etc are physical properties. YOu can find them here. https://en.wikipedia.org/wiki/Benzene
May 30, 2016

Chemistry
Look in your text or notes for the definition. Look on the web for examples.
May 30, 2016

chemistry
a. mols H2 = g/molar mass = ? mols N2 = g/molar mass = ? XH2 = mols H2/total mols XN2 = mols N2/total mols b. PV = nRT where n is total mols. P will be in kPa if R is 8.314 and that should be J/mol.K c. pH2 = XH2*Ptotal pN2 = XN2*Ptotal
May 30, 2016

Chemistry
No, propoate is not correct.
May 29, 2016

Chemistry
CH3CH2COOH + HOCH2CH2CH2CH2CH3 --> CH3CH2COOCH2CH2CH2CH2CH3 + H2O The ester is pentyl propanoate
May 29, 2016

chemistry
(KOH) in the 250 mL volumetric flask is 1.5 M x 9.6/250 = approx 0.06 but that's an estimate. mols KOH used = M x L = approx 0.06 x 0.0315 = approx 0.0018 Using the coefficients in the balanced equation, convert mols KOH to mols H3PO4. That's 0.0018 x (1 mol H3PO4/3 ...
May 29, 2016

Chemistry- Dr.Bob222
I read your earlier post but fail to understand what you've written. Is E = E*cell = ---- or should that be E = Eocell - (0.0592/n)*log Q?
May 28, 2016

Chemistry
Acetic acid = HAc .........HAc ==> H^+ + Ac^- I........0.05....0......0 C........-x......x......x E......0.05-x...x......x You know x = 0.05 x 0.02 = ? = (H^+). Then pH = -log(H^+) = ?
May 28, 2016

Chemistry- Dr.Bob222
see above
May 28, 2016

chemistry
The easy way of doing this is to assume a mass(any number will do as long as you make mass C2H6 the same as mass of CH8) for mass C2H6 and C3H8 and calculate XC2H6. To do this you have mols C2H6 and mols C3H8. Then XC2H6 - mols C2H6/total mols. That becomes XH2 (the same ...
May 28, 2016

chemistry
Jess, I worked this yesterday for you.
May 27, 2016

a P.S.---Chemistry
Forgot to mention that if you try to put that answer back into the Ksp equation (as DrRebel points out)you can't get Ksp of 5E-6 which is the fault of the author of the problem. S/he didn't put in the right number for the red herring.
May 27, 2016

Chemistry
I'm going to butt in here. There isn't anything wrong with the problem. Jess, I told you how to do this yesterday. I also told you that the 125 mL of 0.005M Cr^3+ was a red herring. Ignore that extra information. You work this as a saturated solution of Cr(IO3)3 and ...
May 27, 2016

Math
How to do what? You haven't asked a question. I see information only.
May 27, 2016

Chemistry
.....AgI ==> Ag^+ + I^- I....solid...0......0 C....solid...x......x E....solid...x......x ....KI ==> K^+ + I^- (100% ionized) I..0.186...0.....0 C.-0.186..0.186..0.186 E...0.....0.186..0.186 Ksp = (Ag^+)(I^-) Ksp = look up (Ag^+) = x from above (I^-) = 0.186 + x. 0.186 ...
May 27, 2016

Chemistry
It increases because H^+ of the acid reacts with the OH^- of the Ca(OH)2 and that shifts the equilibrium to the right which is to be more soluble. Ca(OH)2 ==> Ca^2+ + 2OH^- but 2OH + 2H^+ ==> 2H2O so the OH^- is decreased and the reaction (which is solubility) must shift...
May 27, 2016

Chemistry
Convert 9.25E-3 g/L to mols/L. I will call that x. ....Mg(OH)2 ==> Mg^2+ + 2OH^- I...solid........0.......0 C...solid........x.......2x E...solid........x.......2x Substitute the E line into Ksp expression and solve for Ksp.
May 27, 2016

chemistry
ignore it. It's irrelevant. Ksp = (x)(3x)^3 and solve for x = solubility.
May 27, 2016

chemistry
The easiest way to do this is to work a-d and see if they provide the same thing. Example: What you have. ......H2PO4^- + OH^- ==> HPO4^2- ......0.75................0.6 Or....HPO4^2- + H^+ ==> H2PO4^- .......0.6...............0.75 Now try a,b, etc and see which gives you...
May 27, 2016

chemistry
N2 + 3H2 ==> 2NH3 6 L H2 x (2 mols NH3/3 mols H2) = 6 x 2/3 = ? L NH3.
May 27, 2016

science
no
May 26, 2016

Chemistry
......HNO2 ==> H^+ + NO2^- I.....0.9......0......0 C.....-x.......x......x E....0.9-x.....x......x Substitute the E line into Ka expression for HNO2 and solvle for H^+
May 26, 2016

Chemistry
https://en.wikipedia.org/wiki/Fuel_cell http://www.bluffton.edu/courses/TLC/MontelA/Montel/Alternative_Energy_Website/Fuel_Cell.htm
May 26, 2016

Chemistry
No, magnets won't do it.
May 26, 2016

Chemistry
And what are you stuck on? http://www.chemteam.info/Redox/Redox-Rules.html
May 25, 2016

Chemistry
No. https://www.google.com/search?q=dry+cell+construction&tbm=isch&imgil=AOCAb61wVBt45M%253A%253B3szRgvfh4PcZWM%253Bhttp%25253A%25252F%25252Fwww.rfcafe.com%25252Freferences%25252Felectrical%25252FNEETS-Modules%25252FNEETS-Module-01-2-21-2-29.htm&source=iu&pf=m&fir=...
May 25, 2016

Chemistry
I would go with salt bridge, also.
May 25, 2016

Chemistry
4Al(OH)3 ==> 2Al2O3 + 6H2O 2.23 mols H2O x (2 mols Al2O3/6 mols H2O) = 2.23 x 2/6 = ? Look at the coefficients. They tell you the answer. For part b, how many mols Al(OH)3 must you have started with. That's 2.23 mols H2O x (4 mols Al(OH)3/6 mols H2O). Then convert to ...
May 25, 2016

Chemistry
The two sets of unpaired electrons on the water molecule repel each other making the H-O-H angle less than the 108.29 theoretical value.
May 25, 2016

Chemistry
No. The Zn^2+ is not an electrode. That's a solution. The two electrons are copper and Zinc.
May 25, 2016

Chemistry
No. Look at the activity series. http://antoine.frostburg.edu/chem/senese/101/redox/faq/activity-series.shtml
May 25, 2016

Chemistry
right
May 25, 2016

Chemistry
https://en.wikipedia.org/wiki/Condensation_reaction
May 25, 2016

chem
1 ppm is 1 mg/L 1000 ppm is 1000 mg/L. You want 1000 mg/L for 1 L of 1000 ppm Na. Using NaOH, that will be 1000 ppm Na x (molar mass NaOH/atomic mass Na) = 1000 x 40/23 = ?
May 25, 2016

chemistry
I don't understand the question? What's k1?
May 25, 2016

Chemistry
You need to find the mole fraction of H2O. 1 L of the solution has a mass of 1000 mL x 1.09 g/mL = 1090 grams. There are 1.90 mols MgCl2 in that 1 L and that has a mass of 1.90 x molar mass MgCl2 = approx 170 but you need to do it more accurately. This is just an estimate. ...
May 24, 2016

CHEMISTRY
I'm guessing that the author wants this. H3O^+(aq) + Cl^-(aq) + KOH ==> KCl(aq) + 2H2O(l)
May 24, 2016

Chem
Marie, I'll let you in on a little secret. There aren't many people who have the millions of solubility graphs/tables memorized. If you can read the table/graph and post that with your question, someone here will be able to help.
May 24, 2016

Chemistry
Pb(NO3)2 + 2NaCl ==> PbCl2 + 2NaNO mols NaCl = grams/molar mass = 96/58.45 = approx 1.6 but you should confirm this as well as all other calculations that follow. I've estimated. 1.6 mols/dm3 = 1.6 M mmols NaCl = mL x M = 46 x 1.6 = approx 75. That means the amount of ...
May 24, 2016

chemistry
q = mass metal x specific heat x (Tfinal-Tinitial). q = 175.0. Substitute and solve for specific heat.
May 24, 2016

chemistry
I would be much happier if you just called HNO3 as nitric acid and Pb(NO3)2 as lead(II) nitrate. a. HNO3 + NaOH ==> NaNO3 + H2O b. mols NaOH = 4/molar mass NaOH = ? c. M NaOH(soln B) = mols/cm3 = ? cc(HNO3) x M(HNO3) = cc(NaOH)x M(NaOH. Substitute and solve for M HNO3. d. I...
May 24, 2016

chemistry
Almost. Since Mg + 2HCl ==> H2 + MgCl2 then 0.1 mol Mg will form 0.1 mol H2. Now convert that to NTP. STP is 0 degrees C (273 kelvin) and 1 atm pressure. NTP is 20 C (293 kelvin) and 1 atm pressure. Is this a trick question? 0.1 mol Mg metal will produce 0.1 mol dry H2 (or ...
May 23, 2016

Chemistry
2. Propanoic acid + ethanol ---->ethyl propanoate + H2O 3. 3-pentanol --->(oxidized) CO2 H2O
May 23, 2016

Chemistry
To do what?
May 23, 2016

Chemistry
Sidney, I may be missing something but I don't think you can prepare any solution using pure water that contains HCl of any density/percent by mass.
May 22, 2016

Chemistry
Sidney, I don't understand the question. Are you sure you have posted all of the problem?
May 22, 2016

Chemistry
0.93 g/mL x 0.186 = grams NH3/mL
May 22, 2016

Chemistry
I posted this before and I know now to use P1T2=P2T1 but I was wondering what I would plug in as pressure and temp? just an example of one would be so great. A gas at 760 mm Hg pressure and 25 C is heated to 50 C. What is the new pressure? p1 = 760 mm Hg T1 = 25 + 273 = 298 K ...
May 22, 2016

Chemistry
a. Use (p1v1/t1) = (p2v2/t2) p1 = 1 atm v1 = 1 L T1 = 30 + 27 = ?Kelvin P2 = ? V2 = 0.0714 L T2 = 480 + 27 = ?Kelvin. b part is done the same way.
May 22, 2016

Chemistry
There are two problems with this problem. 1. First, you can't convert mass of anything to mols of that without knowing what it is. 2. You symbolism leaves something to be desired. Is that 4.6E5(4.6 x 10^5) or something different. I don't know what to do with the - sign...
May 22, 2016

Chemistry
How many mols do you have? That's mols = grams/molar mass = ? Then M = mols/L. L = 0.127
May 22, 2016

Chemisty-Dr.Bob222
That looks ok to me but I object somewhat to you saying Q = Ksp. For example, Ksp for c is Ksp = [Ag^+][Cl^-]. In my book, (just an expression) Q is used to multiply Ag^+ and Cl^- and use the answer to compare with Ksp to see if a ppt will take place. That is, for c, it's ...
May 21, 2016

Chemistry
What the concn of the HCl you have? that's 1000 mL x 1.18 g/mL x 0.35 x (1/36.5) = approx 11 N. Then mL1 x N1 = mL2 x N2 100 mL x 2N = mL2 x 11N Calculate mL2. That is approx 18 mL. So take 18 mL of the good stuff, add to a 100 mL volumetric flask, add distilled water to ...
May 21, 2016

chem
This question can be interpreted two ways. I will assume you want to know how much NH4I solution must be added to react with ALL of the Pb(NO3)2? Pb^2+ + 2I^- ==> PbI2 millimols Pb^2+ = mL x M = ? millimols I^- necessary to react with all of the Pb^2+ is twice that. Then mL...
May 20, 2016

Chemistry
A lot of reading and most is just a description of the experiment. Don't get distracted by all the verbiage. Ptotal = pH2 + pH2O You know Ptotal and pH2O. Substitute and solve for pH2(dry).
May 20, 2016

Gen Chem
How many mols do you want? That's mols = M x L = ? Then mols = grams/molar mass. You know molar mass and mols,solve for grams. Weigh that many grams salicylic acid, place in a 100 mL volumetric flask, add enough solvent to dissolve it, swirl until dissolved, make to the ...
May 20, 2016

General Chemistry
Wouldn't it make sense that you need the pH of the solution to determine the solubility. You don't have a pH or the amount of the solute. And 10^-39 what
May 20, 2016

Organic Chemistry
I assume the equation is Fe^3+ + SYL ==> Fe(SYL)^3+ You want 50.00 mL x 0.00350M = 0.175 millimols of the complex. So you will need 3x that of SYL and 1x that for Fe^3+. So mL x M = millimols. For Fe you need mL x 0.1M = 0.175 mmol. For SYL you need mL x 0.00250 = 3*0.175 ...
May 20, 2016

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