Wednesday
April 1, 2015

Posts by DrBob222


Total # Posts: 48,030

Are there even any physics tutors here???
You may be right but I think Ms. Sue and I were simply pointing out that at least two profs were around in the last couple of hours. You are right, however, that many question, many of them physics and math, go unanswered.
February 2, 2015

Are there even any physics tutors here???
Reiny answered one at 10:20 P.M.
February 2, 2015

chemistry
Use the HH equation.
February 2, 2015

chemistry
Why don't you show your work and let us find the error? M = 0.85 mols/2L = 0.425M ........Br2 + Cl2 ==> 2BrCl I.....0.425..0.425.....0 C.......-x.....-x......2x E.....0.425-x.0.425-x..2x Go from there.
February 2, 2015

chemistry
Thanks for showing your work. Your work looks ok and the substitutions look ok. I think the trouble may be the number of s.f.. If I round a to 1.6E3 (2 s.f.) and add to b rounded to 3 s.f. of 6.96E3 and add to c rounded to 2 s.f. of 1.1E3, I get 9.66E3 which rounded gives 9....
February 2, 2015

physical science
To produce what?
February 2, 2015

chm
I might make that 3.38 M to 3 s.f.
February 2, 2015

chm
I disagree with Damon's answer. 1.105 g/mL x 1000 mL x 0.30 x (1 mol/98g) = 3.4 M
February 2, 2015

chemistry
You must be trying to measure the volume of a Pb cube but it isn't clear to me how you're doing it.
February 2, 2015

Chemistry
Use the Arrhenius equation. Remember to convert kJ/mol to J/mol Use k1 for k1 and 6.5*k1 for k2. That way k1 cancels and have just the ratio.
February 2, 2015

Chemistry
Fe2O3 + 3CO--> 2Fe + 3CO2
February 2, 2015

Chemistry
Convert 14.56 inches to meters. Convert 10.92 inches to meters. Then meters x meters = square meters.
February 2, 2015

Chemistry
mass = volume x density
February 2, 2015

Organic Chemistry
This makes absolutely no sense to me.
February 2, 2015

Inorganic Chemistry
I may have missed something here but it appears this site has all of the rules. It may be painstaking to apply the rules but I don't think I need to do it for you. http://en.wikipedia.org/wiki/Slater%27s_rules
February 2, 2015

Chemistry
I expect that is diprotic acid. The problem doesn't say but I assume the phenolphthalein end point will titrate BOTH H ions. mL x N x mew = grams where mew is milliequivalent weight. Substitute and solve for mew. Convert to equivalent weight. Then equivalent weight = molar...
February 2, 2015

chemistry
Is that 1.489 g/cc? Because the solid has a higher density that 1.489 g/cc.
February 2, 2015

chemistry
I showed you how to do this last night. What's the problem? Show your work if you want help in getting through it.
February 2, 2015

chemistry
A straight solubility product problem and one almost the same as the TlCl problem.
February 2, 2015

chemistry
Ag2CrO4/BaSO4/TlCl. All of the problems are done the same way. I won't work these for you but I shall be happy to help you through them if you tell us exactly what is troubling you with this type problem.
February 2, 2015

Chemistry- sig figs
The rule I follow is to round the 0.2748 to 0.2750 and the 5 rule that says to round to the even number which rounds to 0.28 to two s.f. However, I don't know if the mathematicians agree with this. I see examples all over the net that would round this to 0.27. Perhaps a ...
February 2, 2015

chemistry
Your best bet is to google it. You will find more information about Cu than you ever wanted to know. It is a solid with "copper" color.
February 2, 2015

science
I suppose #3 is considered the right answer but many people have little faith in those regulations and the ability of the nuclear industry to carry out those regulations.
February 2, 2015

Chemistry
Write and balance the equation. Then dHrxn = (n*dHf products) - (n*dHf reactants)
February 2, 2015

oragnic chemistry
92.0g x (1 lb/453.6g) = ? Note g unit cancels with g unit (one in the numerator and one in the denominator thus getting rid of the unit you don't want) and this leaves only the one unit of lb which is what you want.
February 2, 2015

chemistry
mols = grams/molar mass
February 2, 2015

Chemistry
You need to do better than this. I can't tell the difference between questions and answers. In fact, I'm not sure of the question. With regard to the last one, the KClO3 is the decomposition. The Zn and HCl is a single replacement and the Fe and S rxn is synthesis.
February 2, 2015

Chemistry
Usually smaller.
February 2, 2015

Science
You don't? Why does the floor hold you up(that is, why don't you sink into the floor?). Because the floor is pushing back with the same force you are pushing(standing) down. When you sit on a chair the chair pushes you up with the same force you are pushing down. If it...
February 2, 2015

Science
For every action and there an equal and opposite reaction.
February 2, 2015

Science
What's doing the aciton? The arms and legs. What is reacting? the water pushes back.
February 2, 2015

Science
See your previous question.
February 1, 2015

Thermodynamics
T final is the same for both. Tinitial for Al is T it started; Tinitial for H2O is T it started.
February 1, 2015

Thermodynamics
heat lost by Al shot + heat gained by H2O = 0 [mass Al x specific heat A x (Tfinal-Tinitial)] + [mass H2O x specific heat H2O x (Tfinal-Tinitial)] = 0 Substitute all of the numbers and solve for Tfinal.
February 1, 2015

Chemistry
By itself you don't. Usually 15% by mass means 15g solute/100 solution. In that case, then 15 g/molar mass solute = mols solute.
February 1, 2015

chemistry
mols TlCl = grams/molar mass = ? mols Then M = mols/L = approx 0.04 but you need to do it more accurately. ........TlCl ==> T.^+ + Cl^- I.......solid....0.......0 C.......solid....x........x E.......solid....x........x Substitute the E line into the Ksp expression and solve...
February 1, 2015

chemistry
No ppt. There are essentially three reasons for a reaction to occur. 1. A ppt is formed 2. A gas is formed. 3. A slightly ionized substance si formed. KCl, Na2SO4, K2SO4 and NaCl all are soluble so #1 will not occur. 2. None of the four possibilities is a gas so #2 will not ...
February 1, 2015

chemistry
If a ppt forms it must be because Ksp is exceeded. The only slightly soluble material is the possibility of CaSO4. Therefore, you must determine Qsp for the solution and see if Ksp is exceeded. (Na2SO4) in final solution is 0.004 x (100/600) = approx 6.67E-4 (CaCl2) in final ...
February 1, 2015

Science
right
February 1, 2015

Science
momentum is mv. The higher mass makes it harder to start or stop.
February 1, 2015

Chemistry
15% w/w = 15 g H2O2/100 g solution. mass = volume x density. You know mass and density, solve for volume in mL and convert to L. mols H2O2 = grams/molar mass, then M = mols/L solution.
February 1, 2015

Chemistry
OK, we'll assume that is m and 0.267 molal KIO3. 0.267m means 0.267 mols KIO3/1000 g solvent. 0.267 mols KIO3 x molar mass KIO3 = grams KIO3 = approx 57 g but you need to that more accurately as well as the calculations that follow. Then total solution is g KIO3+ 1000g ...
February 1, 2015

Chemistry
Is the m or M?
February 1, 2015

Chem
mols solute = grams/molar mass. No molar mass; can't work the problem.
February 1, 2015

Science
Let's let L be long wings; s for short wings. So we have Ls and ss So the combinations are Ls; Ls; ss and ss. The two Ls will be long and the ss will be short wings which looks like 50% to me.
February 1, 2015

chemistry II
acetic acid is HAc HAc + KOH ==> KAc + H2O mols KOH = M x L Look at the coefficients. mols HAc = mols KOH Then M HAc = mols HAc/L HAc
February 1, 2015

chemistry
H2C2O4 + 2NaOH ==> Na2C2O4 + 2H2O mols H2C2O4 = M x L = ? mols NaOH = 2x mols H2C2O4 (look at the coefficients) M NaOH = mols NaOH/L NaOH You know M and mols, solve for L NaoH.
February 1, 2015

Chemistry
I assume you mean M^2+ ions. Also I assume the 0.150 mol M(NO3)2 solid does not change the volume of the solution. You do this in two steps. .....M^2+ + 4CN^- ==> M(CN)4^2- I..0.150...0.840.........0 C..-0.150..-4*0.150......+0.150 E....0......0.240........0.150 What we ...
February 1, 2015

Chemistry
......Ba3(PO4)2 ==> 3Ba^2+ + 2PO4^3- I.....solid..........0..........0 C.....solid..........3x.........2x E.....solid..........3x.........2x Ksp = (Ba^2+)^3(PO4^3-)^2 Substitute the E line into Ksp expression and solvle for x. That gives you the solubility of the solid.
February 1, 2015

Not a subject for course-off topic question
Writeacher gave you the best advice. On this subject of thanking teachers I never thanked some of the best and caring teachers I had and I've regretted it time after time. Some I stayed in contact with and thanked them MANY years later. Some I stayed in contact with but ...
February 1, 2015

chemistry
Yes, that's what it is. Don't forget to include the liquid H2O in the reactants.
February 1, 2015

chemistry
See your sucrose question.
February 1, 2015

chemistry
I can't tell the difference between your answers and those on the question.
February 1, 2015

science answer fast please!
I don't think so. Molecules are a combination of atoms so if it's just one of a kind we call it an atom and not a molecule.
February 1, 2015

chemistry
Do you have a question?
February 1, 2015

science
Technically speaking graphite is not an element. Carbon is an element and graphite is pure carbon. Graphite is just another form of carbon. Graphite is an allotrope of carbon; diamond is another allotrope of carbon. http://en.wikipedia.org/wiki/Allotropes_of_carbon
February 1, 2015

chem
I wonder if your typing is just VERY bad or if you don't know better. amstrong must be Angstrom, spectra line should be spectral line, bama series must be Balmer series and I have no idea what R = 109766rcm is. lander must be lambda and Li2 doesn't exist. Assuming you ...
February 1, 2015

chemistry
ln(No/N) = kt No = 99.8 N = 78.2 k = solve for this t = 25 hours Then k = 0.693/t1/2 Solve for t1/2 You probably do better to write I-131.
February 1, 2015

chemistry
See your other post below.
January 31, 2015

Chem
k = 0.693/t1/2
January 31, 2015

chemistry
dHrxn = (n*dHf products) - (n*dHf reactants)
January 31, 2015

chemistry
Add equation 1 to the reverse of equation 2, then divide the final equation by 2. When reversing an equation change the sign of dH. When dividing an equation by 2 divide dH by 2. When adding equations add dH values for each.
January 31, 2015

chemistry
dHrxn = (n*dHf products) - (n*dHf products) dHrxn = -127 = (n*dHf .....etc) Substitute and solve for dHf CaC2 which is the only unknown in the equation.
January 31, 2015

chemistry
Thank you for showing your work. I don't see anything wrong with your set up or the numbers. Always check to see that you used the correct value from the tables. I suspect the problem is one of significant figures. I think the answer is -2512 kJ. -1.574E3 - 0.4836E3 = -2....
January 31, 2015

To Morgan---Chemistry
If you had shown your work instead of answers we could have seen at a glance what the problem was. As it is you must check your work against mine below. I recognize this as one of the answers I gave you a couple of days ago. You have made errors in q1, q2 and q2*. I didn't...
January 31, 2015

chemistry
Use the HH equation, then convert pH to H^+.
January 31, 2015

chemistry
millimols HCOOH = mL x M = approx 65 but you need to do all of these calculations more accurately. mmols HCOONa = base pH = pKa + log (base)/(acid) Substitute and solve for (base) in millimols. Change to mols, then g = mols x molar mass. You know mols and molar mass
January 31, 2015

chemistry
You have doubled the reaction; wouldn't the new enthalpy change be just twice as much.
January 31, 2015

Chemistry
What's the /\H = 90?
January 31, 2015

Chemistry
mL x N x mew = grams 1000 x 1.5N x (molar mass/1000) = grams if it's 100%. It is only 96.5%; therefore, Then grams/0.965
January 31, 2015

chemistry
q = mass x specific heat x delta T
January 31, 2015

chemistry
q = mass x specific heat H2O x (Tfinal-Tinitial) I would use mass = 17,000 and calculate q in J, then convert to kJ.
January 31, 2015

Science
I agree.
January 30, 2015

chemistry
mols = 4.18E16/5.02E23 = ? Then molar mass = g/mols = ? That "funny" unit you posted must be microgram or 5E-6g.
January 30, 2015

chemistry
1 light year is 9.46 x 10^15 m which converts to 9.46 x 10^12 km. So 4.3 light years is 4.3 x that.
January 30, 2015

chemistry
I don't see a question here. Also check to see that you have entered all of the data.
January 30, 2015

Science
How much pollution. How much energy value. Cost Can it be renewed. Ease/cost of waste disposal.
January 30, 2015

To Kekmaster
You are loading up the board with useless comments. You can quit now; if you continue I will ban you from posting on this board again.
January 30, 2015

biochemistry
..NH2CH2COOH + NaOH =>NH2CH2CONa + H2O I...0.2.........0..........0 add............0.1............. C...-0.1.......-0.1........+0.1 E....0.1.........0.........0.1 pH = pKa glycine + log (base)/(acid) base = salt = 0.1 acid = glycine = 0.1 pH = pKa + log 0.1/0.1 0.1/0.1 = 1 ...
January 30, 2015

chemistry
I am not familiar with your equation. I would use the Clausius-Clapeyron equation (and please note the correct spelling of celsius). ln(p2/p1) = dHvap/R(1/T1-1/T2) If you let p1 = 92.7 and T1 = 50C+273; then solve for p2 = ? when T2 = 25+273
January 30, 2015

Chemistry
dG = -RTlnK, then convert dG in J to kJ.
January 30, 2015

Chemistry
Is that H or dH? Is that S or dS. Are you sure that is -75 kJ/mol for S? Usually they are measured in J/mol. Is there a T listed?
January 30, 2015

Chemistry
A reaction is favored thermodynamically when delta G < 0.
January 29, 2015

Chemistry
How would you like us to help you short of writing the paper for you?
January 29, 2015

chemistry
q = mass x specific heat x delta T #1. q = 10.0g x 0.897 U/g x 25 = ? Calculate q for each then rank from low to high.
January 29, 2015

Chemistry
Use your numbers for this. Adding NaIO3 dropwise to the solution will continue until the most insoluble material starts pptng. That will be Pb(IO3)2. Pb(IO3)2 will continue to ppt until the IO3^- rises high enough to begin pptn of Cu(IO3)2. At that point, what is the (IO3^-)? ...
January 29, 2015

Chemistry
What Ksp values are you using? The answer depends upon those value you use.
January 29, 2015

Science
I'm having trouble believing 3d is correct. I think A is a better answer.
January 29, 2015

chemistry
Do you want the entropy of the reaction? dSrxn = (n*dSo products) - (n*dSo reactants). Look up the standard S values in your text/notes and plug into the above equation and solve for dSrxn.
January 29, 2015

Chemistry
The equation is delta T = i*Kf*m i = van't Hoff factor which is the number of particles. CoCl3 is 4, K3CO3 is 3, KNO3 is 2. Kf is a constant The problem tells you m is constant, so.....
January 29, 2015

chemistry
2H2 + O2 ==> 2H2O mols H2 = grams/molar mass Using the coefficients in the balanced equation to convert mols H2 to mols O2. Now convert mols O2 to what you meant by "how much". If you want grams O2, g O2 = mols O2 x molar mass O2. If you want volume at STP it is L...
January 29, 2015

Chemistry
If those two substances were the only ones in the solution there will be no reaction. Reactions occur for one of just a few reasons. 1. A ppt is formed. Nothing insoluble here. 2. A gas is formed. No gas can be formed here. 3. A slightly ionized material is formed. Both NaCl ...
January 29, 2015

college chemistry
P1V1 = P2V2
January 29, 2015

Science
I agree
January 29, 2015

Science
I think the correct answer COULD be any of these. I think most cold fronts produce A sometimes if enough humidity is present, I think B if more water vapor is in the air, D is conditions are right. and C if there is not enough moisture in the air.
January 29, 2015

Chemistry
What do you want? The cation is NH4^+ and the anion is Cl^-. Probably that isn't what you want. And you want the molarity of what? the cation? the anion? NH4Cl? The molarity of NH4Cl is mols/L. mols = grams/molar mass Then mols/0.0199 = ?M
January 29, 2015

Science
I only checked those two.
January 29, 2015

Science
I agree with 2 and 4.
January 29, 2015

Chemistry
q1 to melt ice = mass ice x heat fusion. q2 to raise T to 100 C = mass H2O x specific heat H2O x (Tfinal-Tinitial) q2* to torn liquid H2O at 100 C to steam at 100 C = mass H2O x heat vaporization. Total to melt ice = q1 Total to raise T from zero to 100 and turn steam is q2 + ...
January 29, 2015

Chem
I think you have too many minus signs there. I would have done (1/4)*-0.41 = - 0.10 M/s
January 29, 2015

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