Saturday
August 30, 2014

Posts by DrBob222


Total # Posts: 43,405

Chem
You don't give enough information to know if you want the Eocell for a spontaneous or non-spontaneous cell. I assume you want the spontaneous reaction. Al(s) ==> Al^3+ + 3e Eo = +1.66 Fe^2+ + 2e ==> Fe(s) Eo = -0.440 -------------------- 2Al + 3Fe^2+ ==> 2Al^3+ + ...
May 18, 2014

Chemistry
dGorxn = (n*dGo formation products) = (n*dGo formation reactants)
May 18, 2014

Chemistry
mols AgNO3 = grams/molar mass = approx 0.06 but that's only an estimate as are all of the other calculations I do here. mols NaCl = M x L = approx 5E-4 .......NaCl + AgNO3 ==> AgCl + NaNO3 I......5E-4......0........0......0 add...........0.06.................. C.....-5E...
May 18, 2014

Chemistry
You want 15 g CaCl2. You will need 15 g CaCl2 x [(molar mass CaCl2.2H2O/molar mass CaCl2)] = ? g CaCl2.
May 18, 2014

chemistry
It may be possible depending upon how many other metals have specific heats close to the unknown metal. In any case, however, you probably can narrow the choice to one of a few and more importantly you can eliminate many metals.
May 18, 2014

Chemistry
I see a problem below that has been answered by Mathmate that isn't the same problem as this one. This one doesn't allow water to be added and both of the solutions available are more concentrated than the final desired one. I don't think this one is possible.
May 18, 2014

Chemistry
This can be done?? If you use 2L of the weaker solution of 150g/L and zero L of the more concentrated solution, then you have 300g/2L and that is too concentrated.
May 18, 2014

Chemistry
I don't believe this can be done with the data listed. I think at least one equation is missing.
May 18, 2014

chemistry
A catalyst lowers the activation energy
May 18, 2014

Chemistry
2.07L, yes.
May 17, 2014

Chemistry
(V1/T1) = (V2/T2) Remember T must be in kelvin.
May 17, 2014

Chemistry
To find pH for each equivalence point. For HNO3 + NaOH ==> NaNO3 + H2O That is a strong acid vs a strong base. Neither Na^+ nor NO3^- is hydrolyzed; therefore, the pH at the equivalence point is just that of pure H2O which is 7.0. For NaOH + HCN ==> NaCN + H2O The CN^- ...
May 17, 2014

add on--Chemistry
Don't forget to make that 107 g.
May 17, 2014

Chemistry
Print these steps. 1. Write and balance the equation. NH3 + HCl ==> NH4Cl (The problem doesn't say it reacts with HCl and you only need to know that 1 mol NH3 is in 1 mol NH4Cl but I think an equation makes it more obvious.) 2. Convert what you have, in this case NH3, ...
May 17, 2014

AB Chemistry4
Yes, that's the only way to find the number of mols in 36.0 g H2O then to convert mols MnCl2 to g MnCl2.
May 17, 2014

chemistry
This 4-step procedure will work all simple stoichiometry problems. Limiting reagent problems take an addition one or two steps. 1. Write and balance the equation. You have that. 2. Convert what you have (in this case H2O) to mols. mol = g/molar mass = 133.6/18 = approx 7.5 but...
May 17, 2014

chemistry
This is a buffer problem. Use the buffer equation. Use the Henderson-Hasselbalch equation.
May 17, 2014

Simple question about music
Here is an article you may want t read. I don't know how accurate the figures are. I googled "number copies Thriller sold" and came up with many web sites to read. This is just one of them. http://www.newyorker.com/online/blogs/culture/2013/01/did-michael-...
May 16, 2014

Chemistry
For a. eqn 1. mols NaOH = M NaOH x L NaOH eqn 2. mols acid = mols NaOH eqn 3. M acid = mols acid/L acid You're right, the NaOH is diluted which means you will add MORE NaOH when you titrate the acid. Look at eqn 1, If you add more volume you THINK you have more mols NaOH, ...
May 16, 2014

Science help PWEASEEEE
I would pick c.
May 16, 2014

Choosing Courses
I would think it would be ok, especially if you did well in algebra I.
May 16, 2014

chemistry
Look up the reduction potentials and calculate Ecell. If Ecell is positive the reaction is spontaneous. The element oxidized is the element that lost electrons. Reduction is the gain of electrons.
May 16, 2014

chemistry
There are 33+18+2 atoms in 1 mol of C33H18O2. How many moles do you have? That's 33g/molar mass C33H18O2
May 16, 2014

chemistry
http://wiki.answers.com/Q/What_is_the_difference_between_biochemical_pharmaceutical_and_diagnostic_chemical_reactions_in_health_care?#slide=1
May 16, 2014

chemistry
You are absolutely correct and I goofed. I didn't do what I preach so much about making sure the units come out right. I should have written it as 4.7 L/s x ? sec = L to be pumped. Solve or ? sec.
May 15, 2014

chemistry
This is a math problem, not a chemistry problem. I would convert everything to cm. 50 m = 5000 cm 25 m = 2500 cm 2 m = 200 cm Volume of pool is width x length x depth = ? cc. Convert to L. 1000 cc = 1L = initial volume of pool in L. You want to lower by 5 cm so now the ...
May 15, 2014

analytical
Google them. You can get their formula and their properties.
May 15, 2014

chemistry
Nope. You didn't substitute. And you know the answer can't be right. You start with 0.343 mol, it decomposes and you have more than you started with after 43 mn. I don't think so.
May 15, 2014

chemistry
The units of min^-1 tell you that the reaction is first order. So ln(No/N) = kt. No is starting. N is end k from problem t = 42 min
May 15, 2014

chem
looks ok to me.
May 15, 2014

chem
7.42E-5 kg x (1000g/1 kg) x (1000 mg/g) = ?
May 15, 2014

chemistry
yes. You reversed the sign because the reaction is reversed. So that makes it positive. Then double that for e.
May 15, 2014

chemistry
You have the reaction as shown. You want the reverse reaction and double that. So take dH that you have, change the sign (because of the reversal) and double it.
May 15, 2014

Math 2
I would ask 1/4 what of fabric?
May 15, 2014

chemistry
Read and correct your post. Clarify. It makes no sense as is. delta T in kJ?
May 14, 2014

chemistry
You can see from your previous ost how this is done. I'll be glad to check your numbers.
May 14, 2014

chemistry
Calculate mg morphine in each of the choices. a. 20% w/v means 20 g morphine/100 mL. I wouldn't recommend this choice (if you want the patient to live). b. 2M solution. How many mols is that. mols = M x L = 2M x 0.050 L = 0.1. g = mols x molar mass = 0.1 x 283 = 28.3 g or ...
May 14, 2014

Chemistry
The two half reactions are 2Al ==> 2Al^3+ + 6e Eo = 1.66 3Fe^2+ + 6e ==> 3Fe Eo = -0.44 -------------------- Add half cells to obtain rxn. Add Eo to obtain Eocell.
May 14, 2014

Chem
dGorxn = (n*dGo products) - (n*dGo reactants)
May 14, 2014

Chemistry
n stands for number of mols. It is 1 for CaO, 1 for CaCO3, and 1 for CO2. Look up dHo formation CO2, CaO, and CaCO3. Calculate dHo reaction. Look up dSo for CO2, CaO, and CaCO3. Calculate dSo reaction. Then dGorxn = dHorxn - TdSorxn
May 14, 2014

Chemistry
dHorxn = (n*dHoformation producs) - (n*dHoreactants) dSo rxn = (n*dSo formation products( - (n*dSo formation reactants) dGrxn = dHrxn - TdSrxn dG<0 spontaneous dG=0 equilibrium dG>0 not spontaneous.
May 14, 2014

NO SCHOOL
I presume this is a tax, probably Goods and Services Tax in Canada. Your post isn't clear. If you have 100 to spend on an item it will cost you 100 + 10% of 100. Or you may mean that the total cost of an item, including GST, is 100.00. And you want to know the cost without...
May 14, 2014

chemistry
Surely it's in your text. You're right. Bases are proton acceptors according to the Bronsted-Lowry theory of acids/bases.
May 14, 2014

chemistry
This isn't in your text/notes. The first half is According to this theory, acids are proton donors. So bases must be proton ........?
May 14, 2014

chemistry
Metals with a small heat capacity heat faster and cool quicker than metals with a higher heat capacity.
May 14, 2014

chemistry
That's right. % = (mass solute/total mass)*100 = ?
May 14, 2014

chemistry
You have half of it right. The other half you have ignored. q1 = heat needed to raise T of water from 15C to 100 C is what you have calculated. q2 = heat needed to change T of water at 100 C to steam at 100 C. That is q2 = mass H2O x heat vaporization.
May 14, 2014

math
Change meters to cm. 1 meter x (100 cm/1m) = 100 cm 100 cm + 5 cm = ?
May 14, 2014

Chemistry
I would say an oxidizing agent, a reducing agent, and a salt bridge/porous barrier. If you want to get technical I suppose you might add a cell (something to hold the oxidizing agent/reducing agent and the salt bridge).
May 14, 2014

chemistry
H3PO4 + 3NaOH ==> Na3PO4 + 3H2O
May 14, 2014

Chemistry
What does the equation tell you? That 89.3 kJ are absorbed when 1 mol (76.1g CS2) are formed. You have 6.33 g; therefore, 89.3 kJ x (6.33/76.1) = ? kJ
May 14, 2014

science
60 meters in 34 seconds. That is avg velocity of 60m/34s = ? m/s.
May 14, 2014

chemistry
20L propane = 20L x (1 mol/22.4L) = about 0.892 mols propane. You get 2220 kJ for 1 mol; therefore, you will get 2220 x (0.892 mol/1 mol) = ? kJ released.
May 14, 2014

Chemistry
1. Write the equation. 2. Balance it. 3. dHrxn = (n*dHo formation products) - (dHo formation reactants)
May 14, 2014

Chemistry
You're cluttering the board now. Spend your time solving problems instead of typing.
May 13, 2014

Chemistry
Same 'ol same 'ol. See your other posts.
May 13, 2014

Chemistry
I don't see anything new here. See your other posts.
May 13, 2014

Chemistry
See your other posts.
May 13, 2014

Chemistry
Zn^2+ + 2e ==> Zn from the table is -0.76v. Your half cell reaction is Zn ==> Zn^2+ + 2e E = +0.76v Ag^+ + e ==> Ag E = 0.80 v. --------------------------- Add rxnx; add half cell oxidation half to reduction half. Cell rxn is Zn + 2Ag^+ ==> Zn^2+ + 2Ag Ecell = 0....
May 13, 2014

Chemistry
n = 2 and you know that from the equation I wrote earlier of Zn + 2Ag^+ ==> Zn^2+ + 2Ag The term you are talking about is (RT/nF)ln[(Zn^2+)/(Ag^+)] and if you want to substitute R, T, n, and F in there you may. However, if you do all of that AND multiply by 2.303 to convert...
May 13, 2014

Chemistry
It really helps us help you if you use the same screen name. Tom, Tyler, help ASAP etc is not helpful at all. You know from your previous post how to calculate the standard Zn/Ag^+ cell potential. That is Eocell and that is for standard concentrations of 1M Zn^2+ and Ag^+. ...
May 13, 2014

Chemistry ASAP
yes
May 13, 2014

Chemistry ASAP
Look up the reduction potential for Zn^2+ + 2e ==> Zn(s) in your text. Reverse the sign. Add that to the reduction potential for Ag^+ + e ==> Ag(s) That potential will be for the reaction of Zn(s) + 2Ag^+(aq) ==> 2Ag(s) + Zn^2+(aq)
May 13, 2014

Chem 130
E= 2.180E-19 J x (1/n^2)
May 13, 2014

Chem 130
[Kr]4d25s2 http://www.webelements.com/zirconium/atoms.html
May 13, 2014

Math 6th Grade
Do you honestly think -15 = -21? How can that be. 2 = 2 and 6 = 6 and -2 = -2 but -15 = -21?
May 13, 2014

chemistry
You have two typos in your equation. The correct equation, balanced, is CaCO3 + 2HCl ==> CaCl2 + H2O + CO2 mols CaCO3 = grams/molar mass mols CO2 = mols CaCO3 from the coefficients in the balanced equation. Now g CO2 = mols CO2 x molar mass CO2.
May 13, 2014

Chemistry
I would first convert 40% HCl into molarity. 40% (I guess that's w/w) HCl means 40g HCl/100 g solution. 40g/36.5 = approx 1.10 mols HCl mass = volume x density so volume = mass/density. That 100 g soln = 100/1.2 = approx 80 mL or 0.08 L; therefore, the molarity is 1.1/0....
May 13, 2014

science
You can add the phases. You have it partly balanced but I am removing the 2 and 3 and start over. First you write the products (and that isn't considered part of the balancing). H3PO4(aq) + CaCl2(aq) ==> Ca3(PO4)2 + HCl You do these by trial and error; basically that ...
May 13, 2014

SIG FIGS
1.75E2
May 13, 2014

college chemistry
To melt ice requires q1 = mass ice x heat fusion. To raise T of melted ice at zero C to Tfinal requires q2 = mass melted ice x specific heat liquid H2O x (Tfinal-Tinitial) To cool the water from 75C to Tfinal requires q3 = mass liquid water x specific heat x (Tfinal-Tinitial...
May 13, 2014

chemisty
q1 = heat needed to raise temperature of liquid water from 15 C to 100 C. q1 = mass x specific heat H2O x (Tfinal-Tinitial) q2 = heat need to convert H2O at 100 C to steam at 100 C. q2 = mass H2O x heat vaporization.
May 13, 2014

college chem
Devron answered this for you below.
May 13, 2014

Physical Science
Just because this may be a little foreign don't let it intimidate you. It's a matter of plugging in the numbers. The formula is q = mass x specific heat x (Tfinal-Tinitial). The numbers are mass = 0.75g from the problem. specific heat = 0.385 J/g*C from the problem. Tf...
May 13, 2014

Science
Just remember that a force always has an equal and opposite force opposing it. If I sit on a chair the chair (and floor) must push back with the same force I exert during sitting. When I was a student in physics class I asked "but how can that be?" and the prof ...
May 13, 2014

End of Year question
Mine would be "awesome". "Great" as a second choice. "Beautiful" as a third choice.
May 13, 2014

chemistry
I don't think so. If the 1000 has no period after it it has only 1 s.f. and the answer 1E3. If it has a period, the answer is 1056.
May 13, 2014

chemistry
I suspect that is because molecular and ionic formulas have flaws in them (or they could be typos--in fact some appear to be typos). NaHCO3 + H2SO4 ==> NaHSO4 + H2O + CO2
May 13, 2014

science
1. I know this is a poor answer but it's the best I can do. The images are reversed and inverted because that's what lenses do. 2. At high power it takes VERY LITTLE movement to take the specimen out of the field of view; therefore, you want to get it centered and you ...
May 13, 2014

Alegbra ck to see if I did it correclty please
I think you have it down cold.
May 13, 2014

chemistry
43.7 has only 3 s.f. Add that to 0.393 for an answer with 3 s.f. and divide by 4 s.f. so you may have only 2 in the answer. 1.741 has 4 which is one too many.
May 13, 2014

chemistry
I would change all of these to km. Note that with no period after the 80,000 mm. that has only one s.f. 0.000035 km 0.0083 km 75.341 km 0.08 km --------- 75.429335 which I would round to 75.43
May 13, 2014

Chemistry
post #1. Work with mols. mols NaOH in 8g = grams/molar mass = ? mols NaOH in 599 mL of 0.250M = M x L = ? Total mols NaOH = ? Now total volume is 599 mL + 1.68 gallons. Convert mL to L and convert 1.68 gallons to L. Add to find total L. Then (NaOH) in final solution is mols/L
May 13, 2014

chemistry
I'll be glad to check your work or answer questions on this topic but it does you no good for me to give you the answers.
May 13, 2014

Chemistry
Ma x Va = Mb x Vb Substitute and solve for the unknown.
May 13, 2014

Chemistry
Table salt is NaCl, an ionic compound. It dissolves in water due to the dipoles of H2O attracting the positive Na ions and the negative Cl ions. That plus the energy released when the Na ion and Cl ion form hydrates with the water is enough to break the lattice energy of the ...
May 13, 2014

chemistry
What specifically do you not understand? Basically I have two explanations. The first one I incorrectly assumed that all of the ice would melt. It doesn't and I showed how to work the problem in an earlier post. That I took your work down to the point where you get a ...
May 12, 2014

Chemistry
1. We would expect H2O to have the higher boiling point due to hydrogen bonding. 2. We would CS2 to have the higher boiling point due to dispersion forces.
May 12, 2014

To Drbob222
You have it wrong my friend. Everyone cares but no one with expertise in physics is available to help at this moment. I usually don't help in physics because I may give the wrong answer. Most of the time you can get an answer in 2-3 hours but here it is almost midnight CDT...
May 12, 2014

To Drbob222
I'm sticking to chemistry.
May 12, 2014

chemistry
If you followed your math you ended up with Tf of 15.3. I didn't go through line by line but my explanation was that your work should have produced a negative value for Tf. When that happens we know it can't be right from the data given so we know something is wrong. ...
May 12, 2014

chemistry
All of your work is ok until here. 50*4.18*(Tf-22) 1030+8350+104.5Tf=-(209Tf-4598)( negative since heat lost) 4782=313Tf tf=15.3 Should have been 1030 + 8350 + 104.5Tf + 209Tf + 4598 = 0 Then you get xxxTf = -some number and that makes Tf = -something and you KNOW that can'...
May 12, 2014

chemistry
http://www.jiskha.com/display.cgi?id=1399943202
May 12, 2014

chemistry
That's because I assumed, incorrectly, that all of the ice would melt. It won't. How many J does it take to move T of ice at -20C to OC? That's q = (mass ice x specific heat ice x (Tf-Ti) = [25g x 2.01 J/g x (20)] = 1005 J. How much will that lower the T of the ...
May 12, 2014

chem
The boiling point of a liquid, including water, is the temperature at which the vapor pressure equals atmospheric pressure. So at sea level atmospheric pressure is 760 mm Hg so water boils at 100. On top of Mt Whitney the pressure may be say 700 mm Hg. So the water will boil (...
May 12, 2014

Chemistry
I see only parts A and B, no C nor D. A is the oxidation at the anode of Cr. Cr(s) ==> Cr^3+(aq) + 3e B is the reduction at the cathode. 3Ag^+(aq) + 3e==> 3Ag(s)
May 12, 2014

To Tom1---Chemistry
Read what I wrote. I said 3.7E10 dps = 1 Ci, not that Ci = 1.
May 12, 2014

Chemistry
k = 0.693/t1/2 k = approx 0.09 but you should get a more accurate number. Convert 140 mg to number of atoms initially (at time = 0) Use ln(No/N) = kt to determine N = number of atoms after four hours. The difference between initial and after 4 hours is atoms that decayed in 4 ...
May 12, 2014

Chemistry
dGorxn = (n*dGoproducts) - (n*dGoreactants)
May 12, 2014

Chemistry
Look up dHo formation and dSo formation. Then dHo rxn = (n*dHo products) - (dHo reactants) dSo rxn = (n*dSo products) - (n*dSo reactants) Then dG = dH - TdS for each temperature dG = - number is spontaneous dG = + number is not spontaneous.
May 12, 2014

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