Monday
March 30, 2015

Posts by DrBob222


Total # Posts: 48,001

Science
Probably. If no air pressure, no air and if the "animal" breathes s/he is in trouble.
February 5, 2015

chemistry
............Bi2S3 --> 2Bi^2+ + 3S^2- Initial.....solid......0........0 Change......solid......2x.......3x equilibrium.solid......2x........3x Ksp = (Bi^3+)^2(S^2-)^3 Substitute the E line into the Ksp equation and solve for x. x will give you the solubility in mols/L. ...
February 5, 2015

CHEMISTRY
You would do well to post just one problem to the post. This one is done just the reverse of the Ag2SO4. .........Cr(OH)3 ==> Cr^3+ + 3OH^- Initial..solid........0.......0 change...solid........x.......3x equilibrium solid.....x........3x Ksp = (Cr^3+))(OH^-)^3 Substitute ...
February 5, 2015

CHEMISTRY
........Ag2SO4 ==> 2Ag^2+ + SO4^2- I.......solid.......0..........0 C.......solid.....2*3.85E-9..3.85E-9 E.......solid.....7.7E-9.....3.85E-9 Ksp = (Ag^+)^2(SO4^2-) Ksp = (7.7E-9)^2(3.85E-9) Ksp = ? You were right to calculate solubility in mols/L as you did and you have ...
February 5, 2015

Chemistry
M = mols/L. You want 0.073M HClO and you want 0.250 L so that is 0.073 = mols/0.250 so mols = approx 0.01825 (I am using more significant figures than allowd---a few guard digits). Basically you want 18.25 mmols HClO in the solution. For the base, you want mmols 250 x 0.046 = ...
February 5, 2015

Chemistry
The buffer capacity = mols acid/base needed to change the pH of a L of the buffer by 1 unit. molos added = 0.00419L x 0.24M = ? Then ?/25 mL x (1000/25) = mols to change 1L by 1 units = ? You can put this into equatio form with mL as mLacid x Macid/mL buffer = 4.19 x 0.24/25....
February 5, 2015

chemistry
Why can't you use the same screen names. It's confusing to us and we could help better if you kept the same screen name. Cole; Antonette; Luke; et al. It took awhile but here it is. For pH = 0.91,you have 0.91 = 1.26 + log (base)/(acid) B/A = approx 0.447 but you need ...
February 5, 2015

Chemistry
Probably none. I'm sure you meant FLUORINE and not fluoride. Just set up a proportion. (1.55/1.10) = (2.42/x) and solve for x
February 5, 2015

chemistry
The first thing you need to do is write and balance the equation. then I can help.
February 5, 2015

chemistry
dG = dH - TdS Remember to convert dS in J/K to kJ. Also remember T must be in kelvin.
February 5, 2015

Chemistry
What's the problem with #2? Just take equal amount of A and B (it doesn't mattr how many g you take as long as the amounts are equal). Calculate X of each and from there solve for p of each. I can help you if you get stuck.
February 4, 2015

Chemistry
pi = iMRT Solve for i (use 0.08206 for R). Then effective M = i*0.15 = ? Then HF ==> H^+ + F^- (H^+)=(F^-) = x (HF = 0.15-x Then x+x+0.15-x = i*0.15 Solve for x = (H^+) and %ion = (H^+)/0.15)*100 =
February 4, 2015

Chemistry
And changing your names makes things harder for us to do a good job for you.
February 4, 2015

Chemistry
I have a Ph.D. in chemistry. That Dr in front of Bob222 is real. Why would I answer a question in which I wasn't sure of the answer (but yes, I sometimes makae mistakes)? You are answer shopping. What you are doing is taking a vote on which is the best answer? Basically ...
February 4, 2015

Chemistry
I answered both of these below. If you don't like those answers you need to be more specific about what you want in the answer.
February 4, 2015

chem
I've been out more than 50. I know how he feels.
February 4, 2015

chem
Probably it isn't a trick question. p1v1 = p2v2 You know p1 and v1 and p2, solve for v2.
February 4, 2015

Chemistry
Don't overload the column
February 4, 2015

Chemistry
The packing material cracks (gooves/channels form) and this results in poor separation of the mixture.
February 4, 2015

Chemistry
IO3^- + 6H^+ + 5I^- ==> 3I2 + 3H2O C6H8O6 + I2 ==> C6H6O6 + 2I^- | 2H^+ mmols KIO3 = mL x M = ? Use the coefficients in the balanced equations to convert mmols KIO3 to mmols ascorbic acid. ?mmol KIO3 x (3 mol I2/1 mol KIO3) x (1 mol I2/1 mol C6H8O6) = ?
February 4, 2015

Science
It won't stay hot forever but the reason it may not cool off as fast is that the foam cup is a better insulator than a glass cup.
February 4, 2015

chemistry
Convert 39.8m 28.2m and 4.9 ft to cm. Calculate volume = l x w x d = ? cc Convert mass using density to get mass in grams and convert to kg.
February 4, 2015

science
The water (and presumably the container too if thermal equilibrium has been attained) is hotter than the object.
February 4, 2015

Science
I thought we went over this a day or so ago. Remember momentum is conserved (in an isolated system).
February 4, 2015

Chemistry
Unbalanced. CH4(g) + O2(g) ==> CO2(g) + H2O(l) C6H12O6(s) + O2(g) ==> CO2(g) + H2O(l) Fe2O3(s) + CO(g) ==> CO2(g) + Fe(s) Fe3O4(s) + Al(s) ==> Al2O3(s) + Fe(s) CO + O2 ==> CO2 I wonder what your trouble is in predicting the products. In some cases here they told...
February 4, 2015

Chemistry
I believe #3 is wrong. The others are ok. C is a combustion reaction. D is the double displacement.
February 4, 2015

Chemistry
3 half lives in 1 hour. or about 0.333 hours.
February 4, 2015

Chemistry
2CO + O2 ==> 2CO2 When using gases one may take a shortcut and use L directly as if they were mols. 3.0 L O2 x (2 mols CO2/1 mol O2) = 3 x 2/1 = 6 L CO2 produced.
February 4, 2015

Science
I don't think so. Probably C fits better.
February 4, 2015

Chemistry
Use the Arrhenius equation and solve for Ea.
February 4, 2015

chemistry
6 definitely is true. I don't know what molecular choices they are talking about so I don't know about that.
February 4, 2015

chemistry
What's in Table I? Erxn = mass x specific heat x dT. If you assume density of the solution is the same as H2O you use 200 g for mass; otherwise if Table I contains the density use that to calculate mass of the 200 mL solution. Probably Table 1 contains specific heat; use ...
February 4, 2015

Chemistry
millimols Ce^3+ = mL x M = 60 x 0.025 = 1.5 mmols IO3^- = 40 x 0.045 = 1.8 Qsp = (Ce^3+)(IO3^-)^3 = approx 9E-8 but you can do the more exact number. Note that M = mmols/mL. which means Ksp will be exceeded and a ppt will form. Now we must find the limiting reagent. Ce^3+ + ...
February 4, 2015

chemistry
It will form Ca3N2. Determine %Ca and %N and calculate the empirical formula.
February 3, 2015

chemistry
See your other post.
February 3, 2015

Science
Why not calculate the momentum of each answer and compare with the momentum of the cheetah instead of guessing?
February 3, 2015

Science
Yes, for every action there is an equal and opposite reaction. Water goes one way, jelly fish goes the other. Same way jet airplanes fly except they don't use water but the blast of hot gases from the engines.
February 3, 2015

chemistry
You may be just a 9th grade student but from what you wrote above you know a good bit of the chemistry involved. You determine the percent composition (meaning determine %Ca and %N) and use those numbers to calculate the empirical formula. 9th grade chemistry does that all the...
February 3, 2015

chemistry
Close and I thought of that at the beginning; however, I don't think that PROVES it is Ca3N2. It gives some strong hints but I don't think it proves it. For example, Mg3N2 will do all of what you describe, too. Mg3N2 reacts with H2O to form Mg(OH)2 which is highly ...
February 3, 2015

chemistry
How advanced is this course? I don't think any of the following answers will do because I assume this is a beginning course; however, 1. Determine the crystal structure by x-ray crystallography. 2. Some information can be obtained by infrared spectroscopy. 3. Determine the...
February 3, 2015

Chemistry
I agree it is a little confusing as to exactly what they want. In particular the pH range of the average range is confusing but I would go with the average percent or (0.057+0.084)/2 = about 0.0705%. I would start with 100 mL of solution and that will contain 100 x 0.000705 = ...
February 3, 2015

Acidity of different concentrations
Yes and yes. Yes, the concentration affects the pH and the pH of a stronger acid will have a lower pH.
February 3, 2015

Chemistry
q = mass ethanol x specific heat ethanol x (Tfinal-Tinitial)
February 3, 2015

Organic Chemistry TLC Chromatography
I don't know how this fits into TLC chromatography but here is what I would do. 5.6 mL x 0.95% = mL x 85% mL = 6.2588 mL is what you can make. So you take 5.6 mL 95:5 ethyl acetate and add pure ethyl acetate to make 6.2588 mL total. Check it. You have 5.6 mL x 0.95 = 5.32 ...
February 3, 2015

Chem Uni. Urgent!!!
I re-iterate that the percent recovery is not 50%.
February 3, 2015

Chem Uni. Urgent!!!
So you had in that 1g of stuff you started with 1 x 0.85 = 0.85g acetanilide; 1 x 0.14 = 0.14g NaCl; 1 x 0.01 = 0.01 g charcoal. Wouldn't the theoretical yield = 0.85 g acetanilide. That's what you would get if you had 100% yield? right? I might argue that percent ...
February 3, 2015

Science
Yes.
February 3, 2015

Science
Did you not understand "conserved"? When mass is conserved it is neither gained nor lost. When momentum is conserved it is neither gained nor lost. I copied the following from Wikipedia. "The law of momentum conservation can be stated as follows. For a collision...
February 3, 2015

Science
Isn't momentum conserved? If D is correct then the system gained momentum and it can't do that.
February 3, 2015

Chimstery
1. Write and balanced the equation. 2. Convert mass Fe to mols. mols = grams/molar mass = ? 3. Using the Coefficients in the balanced equation, convert mols Fe to mols CO. 4. Now convert mols CO to g. g = mols x molar mass. Print this page. This four step procedure will work ...
February 3, 2015

chemistry
The problem doesn't say so but implies you want the dH, dS, dG FOR THE REACTION. 1. You have the equation, balanced it. 2. dHrxn = (n*dHf products) - (n*dHf reactants) 3. dSrxn = (n*dSf procuts) - (n*dSf reactants) 4. Then dGrxn = dHrxn - TdSrxn. Substitute and solve for ...
February 3, 2015

Physical Science
Ms. Sue is right. All of these units show up on Google.
February 3, 2015

science subject
We can't draw structures on this forum. Your best bet is to google them.
February 3, 2015

Chemistry
I don't follow everything you've done. There are 4 atoms to the face centered unit cell. mass unit cell = (197 x 4/6.02E23) = ?grams. volume unit cell = mass/density = ? cc cubed root V = ? = a cm Then a(2)^1/2 = 4r and solve for r = ? in cm. I obtained 1.44E-8 cm = 1....
February 3, 2015

science 1 question
Yes, D.
February 3, 2015

Chemistry
Thank you for showing your work. You have done everything exactly right EXCEPT you have one more step to go through. Your answer is ln p1 = 4.613. Find the number for which ln p = 4.613 and it is about 100.7 which rounds to 101 mm. :-)
February 3, 2015

chemistry
Yes, again thanks for showing your work. It really helps spot the problem quickly. I which more students would do that. It would make it easier for them but they don't want to take the time it takes to type it out. Which makes us take the time to type it which means we ...
February 3, 2015

chemistry
Thanks for showing your work. It helps spot the problem which is that you should have substituted 29 for 29%. The 100 is in the formula to convert that 0.29 to 29% or 29 = 100(x/40). You can omit the 100 and use 0.29 = (x/40) In other words, your answer is just 100x to small. ...
February 3, 2015

chemistry
What's the problem? dG = dH-TdS The usual mistake made by students is they don't recognize that dH is in units of kJ/mol BUT dS in in units of J/mol. One of them must be converted to the other.
February 3, 2015

chemistry
core electrons 15-5 = ?
February 3, 2015

chemistry
Test for what? to show what?
February 3, 2015

chm
Like dissolves like. KBr is a polar compound; it won't dissolve in non-polar solvents. And your "think" makes no sense; similar solute???
February 3, 2015

chm
Please don't change screen names. mols glucose = grams/molar mass mols methanol = grams/molar mass Total mols = mols glucose + mols methanol mole fraction methanol = nmethanol/total mols. psoln = Xmethanol*Pomethanol For the difference, what about interactions between ...
February 3, 2015

chm
See your other post with a different screen name. Do you think posting under different screen names will get different answers?
February 3, 2015

chm
Please don't change screen names. m = mols/kg solvent mols = grams/molar mass. 1.143 g/mL x 1000 mL = 1143 g = mass solution 10.0% of that is H2SO4 = 1143 x 0.100 = 114.3 g is H2SO4. mols H2SO4 = grams/molar mass = ? mass H2O = 1143-114.3 = 1028.7 Then m = mols/kg = ? You ...
February 3, 2015

General Chemistry
The first question makes no sense due to typos (and I think parts have been omitted). The second one is ...........SrCO3 ==> Sr^2+ + CO3^2- I..........solid.....0........0 C..........solid.....x........x E..........solid.....x........x Substitute the E line into Ksp ...
February 3, 2015

Chemistry
C = Q/dT C = 3871/44.9 = ? J/C
February 3, 2015

Chemistry
delta T = Kf*m You know delta T (it's 20C), and Kf, solve for m. Then m = mols/kg solvent. You know m and kg solvent (1 kg), solve for mols. Then mols = grams/molar mass You know mols and molar rmass, solve for grams.
February 3, 2015

chem
Can't you use the Clausius-Clapeyron equation. ln(p2/p1) = dHvap(1/T1-1/T2)/R You have p1 = 1 atm with T1 = 373 and you have p2 and listed. Solved for T2 in K. Convert to C is needed.
February 2, 2015

chem
See your other post.
February 2, 2015

science
Yes. Mass doesn't change. The weight changes with the gravitational force.
February 2, 2015

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

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