Thursday
September 18, 2014

Posts by DrBob222


Total # Posts: 43,856

Science--Myanswer Plz, plz
1, 3, 6 wrong. 7 is A.
May 23, 2014

chemistry
https://www.google.com/search?q=monomer+structure+DNA&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:en-US:official&client=firefox-a&channel=sb
May 23, 2014

chemistry
https://www.google.com/search?q=polymer+structure+DNA&client=firefox-a&hs=f9G&rls=org.mozilla:en-US:official&channel=sb&tbm=isch&tbo=u&source=univ&sa=X&ei=nJt_U7GKAeiqsQTh84HoCg&ved=0CDkQsAQ&biw=1143&bih=688&dpr=0.9https://www.google.com/search?q=monomer+structure+DNA&client=...
May 23, 2014

Chemistry
IO3^- ==> I2 First balance the I so we are working with apples and apples and not apples and oranges. I on left is +10; on right is 0 add 10 e to left side 2IO3^- + 10e ==> I2 charge on left is -12; right is zero. Add H^+ to left and H2O to the right. 2IO3^- + 10e + 12H...
May 22, 2014

chemistry
right about what? What is unsaturated?
May 22, 2014

chemistry
I don't know. Few people have the tables/graphs of solubility vs temperature memorized. If you will post the solubility from you graphs/tables I can agree or disagree with you.
May 22, 2014

Chemistry
plasma etching, wet etching, oxidation, vapor deposition, alloys, should get you started.
May 22, 2014

SCIENCE HELP !!
1. Fe can lose either two or three electrons to form iron(II) or iron(III). 2. One element loses electrons to form + ions; one element gains those electrons to form - ions.
May 22, 2014

Chemistry
nope. A is true. B. The bp is higher. C. The fp is lower D. Since B and C are not true D can't be right. "When a non-volatile solute is dissolved in a volatile solvent, three things happen. A. The vapor pressure is lowered. B. The freezing point is lowered. C. The ...
May 22, 2014

Chemistry
What is your hang up on this question?
May 22, 2014

Chemistry
I worked this problem earlier; if you can't find it I will give you a link.
May 22, 2014

Science(chemistry) please help me fast
You should expand on this but basically the heat from the room gives energy to the molecules, they move faster and faster with increasing heat and at some point in time the molecules begin to slip and slide over and around each other and it becomes soft enough to spread.
May 22, 2014

Science(chemistry)
See your other post.
May 22, 2014

analytical chemistry
First use the Henderson-Hasselbalch equation and solve for pKa. pH = pKa + log (base)/(acid) 10.30 = pKa + log [0.4/0.2] pKa = ? mmols B initially = 0.4 x 250 = 100 mmols BH^+ initially = 0.2 x 250 = 50 ..........B + H^+ ==> BH^+ I........100...0......50 add............25...
May 22, 2014

chemistry
Yes you would; however, you have expanded the (0.1-x)(0.1-x) unnecessarily. I would have done it this way. It's less work. Keq = (x)(x)/(0.1-x)(0.1-x) Keq = x^2/(0.1-x)^2 sqrt (Keq) = x/0.1-x and go from there.
May 22, 2014

chemistry
You need to locate the caps key on yur keyboard and use it. The concn is 1mol/10 L = 0.1M ........CO2 + H2 --> CO + H2O I.......0.1...0.1....0.....0 C.......-x....-x.....x.....x E......0.1-x..0.1-x..x.....x Substitute the E line into the K expression and solve for x, then ...
May 22, 2014

chemistry
15g of what in 2 hrs?
May 21, 2014

Chemistry
The specific heat of H2O should be listed in your text but I think it is 4.184 J/g*c. Tfinal is listed in the problem as 100 C. Tinitial is listed in the problem as 25 C. Note that if you use specific heat in J/g*c you must change q from the first part of the problem from kJ ...
May 21, 2014

Chemistry
volume coal = 7.5*7*6.5 = aprox 340 cc mass = volume x density = approx 500g but you should recalculate this number and all of the others that follow because I've estimated all of them. ?kJ = apprx 394 kJ x (500/12) = ? and it is exothermic so it has a - sign. Then +q = [...
May 21, 2014

Chemistry
You were able to get "how far"? I don't see anything but the question and the numbers. I can work the problem for you which won't help you. If you've watched Kahn academy, what do you not understand now. Let's take it from there. How far can you get ...
May 21, 2014

Chemistry
mols N2 = 145.8g/molar mass N2 = ? Convert mols N2 to mols NH3 using the coefficients in the balanced equation. Now convert mols NH3 to g. g = mols x molar mass. This is the theoretical yield. If the actual yield is only 90%, then g NH3 x 0.90 = ?
May 21, 2014

Chemistry
See your other post.
May 21, 2014

Science 1 question
Just to add my two cents' worth, I think the question is not clearly stated. I think it makes a difference WHEN. If this is at the START of the inhalation phase you have one answer or if it is at the END of the inhalation phase you have another answer.
May 21, 2014

Science(chemistry)
physical change
May 21, 2014

Science (A&P)
https://www.google.com/search?q=food+from+mouth+to+large+intestine&client=firefox-a&hs=M6C&rls=org.mozilla:en-US:official&channel=sb&tbm=isch&tbo=u&source=univ&sa=X&ei=H_J8U_2JFPKwsATMw4CIDA&ved=0CEwQsAQ&biw=1143&bih=688&dpr=0.9
May 21, 2014

chemistry
mols HCl = M x L = ? Using the coefficients in the balanced equation, convert mols HCl to mols Mg. Now convert mols Mg to g. g = mols x atomic mass.
May 21, 2014

Chemistry
See your problem above with Mg and HCl. This is the same type of problem. The 80.5% is handled this way. 285g impure iron(II) nitrate x 0.805 = ? g pure iron(II) nitrate
May 21, 2014

Science -Check Answers-
Both are wrong.
May 21, 2014

chemistry
P1V1 = P2V2
May 21, 2014

Science(chemistry)
law of constant proportions.
May 21, 2014

Chemistry
The limiting reagent problems are really just two ordinary stoichiometry problems solved more or less together. Here is how it is done. The first step is to write and balance the equation which you have supplied. CaCl2 + Na2CO3 ==> CaCO3 + 2NaCl Step2a. Convert g CaCl2 to ...
May 21, 2014

Science
http://en.wikipedia.org/wiki/Prepuce http://books.google.com/books?id=5XogAQAAMAAJ&pg=PA19&lpg=PA19&dq=define:preouce&source=bl&ots=CI40WcXkl_&sig=5WQoN85Ehia0eynrI-LJfSKFvpQ&hl=en&sa=X&ei=uRN8U-eKKtHNsQSyqYDAAQ&ved=0CDwQ6AEwBA#v=onepage&q=define%3Apreouce&f=false
May 20, 2014

Science
http://en.wikipedia.org/wiki/Prepuce
May 20, 2014

Chemistry
This isn't so much a normality problem as it is a dilution (concentration) problem. If you take 4 ml and dilute to 20 you have diluted it 5 times, right? Then another 50 times in the 1:50. So the total dilution is 5*50 = 250 times. So if you have 1N solution and it's ...
May 20, 2014

Chemistry
Solubility is 1g aspirin in 300 mL. So how much aspirin is lost with a 10 mL rinse and I use the term rinse lightly which I will comment on later. 1000 mg aspirin x 10mL/300 mL = 33.33 for the first rinse. 33.33 for the second rinse. 33.33 for the third rinse. Total is 100 mg ...
May 20, 2014

chemistry
I would name that 3,4-dimethyl-2-pentene.
May 20, 2014

AP chemistry
I don't like to do it this way because students ALWAYS get confusted so I'll put it together for you. heat lost by Al is mass Al x specific heat Al x (Tfinal-Tintial) heat gained by H2O is mass H2O x specific heat H2O x (Tfinal-Tinitial) So set heat lost + heat gained...
May 20, 2014

AP chemistry
heat lost by aluminum + heat gained by water = 0 heat lost by Al = mass Al x specific heat Al x (Tfinal-Tinitial) heat gained by water = mass H2O x specific heat H2O x (Tfinal-Tinitial) Substitute into the heat lost + heat gained = 0 and solve for Ti.
May 20, 2014

Chemistry
I don't know where you obtained the 85 C? m = 312, right c = unknown, right The problem tells you delta T is 15, where did the 85 come from?
May 20, 2014

Chemistry
I hesitate to answer all of these for you for that way you aren't learning how to do them yourself. I will get you started. For the others show what work you've done, how you think the problem should be solved. and/or exactly what you don't understand about the ...
May 20, 2014

Chemistry
Do you have suggestions for these?
May 20, 2014

Chemistry
.........Ag + ....xN2 --> AgxNy I......344.588.....0........0 add.............15.906......... C.....-344.588.....-x......359.503 So you end up with 359.503 You started with...344.588 How much N2 was added? Then N2 remaining = start-end = ?
May 19, 2014

Chemistry
If we look at this the reverse direction. H2(g) + 1/2O2(g) --> H2O(l) that's the heat formation liquid H2O in kJ/mol and my text shows that as -285.8 kJ/mol Then H2O(l) ==> H2O(s) is another 6.0 kJ/mol to form ice and freezing water to ice is exothermic so that ...
May 19, 2014

chemistry
PV = nRT
May 19, 2014

Chemistry
That's the best choice.
May 19, 2014

Chemistry
delta T = i*Kf*m So you want the highest delta T. i is the van't hoff factor, Kf is constant, molality is constant in this case so it appears to depend upon i. i = 1 for A i = 1 for B i = 2 for C i = 2 for what you have but I suspect you made a typo and that should be ...
May 19, 2014

Chemistry
I don't know. I looked up the numbers in my text. Although they are slightly different I obtained essentially the same values you did; i.e., 128.2, 6.05, and -58.2 all in kJ/mol. I also looked up dGo in the same text and it was 130.4 at T = 298 and using dG = dH - TdS I ...
May 19, 2014

Chemistry
heat gained by cold water + heat lost by warm water = 0 [mass cold H2O x specific heat H2O x (Tfinal-Tinitial)] + [mass warm H2O x specific heat H2O x (Tfinal-Tinitial)] \ 0 Substitute and solve for the only unknown, which is Tf.
May 19, 2014

chemistry
Look up the reduction potentials and add the oxidation half cell to the reductin half cell to obtain the Eocell. If it is + the rxn is spontaneous; if Eocell is - it is not spontaneous.
May 19, 2014

chemistry
What are you starting with?
May 19, 2014

Chem
mols Pb(NO3)2 = M x L = approx 0.28 mols PbCl2 formed = mols Pb(NO3)2 (see the 1:1 ratio for Pb(NO3)2/PbCl2 Then g PbCl2 = mols PbCl2 x molar mass PbCl2.
May 18, 2014

Chemistry
http://www.jiskha.com/display.cgi?id=1400465598
May 18, 2014

Chemistry
If you post your work so we know what you did perhaps we can find the error. Especially important is what are you using for Eo values.
May 18, 2014

chemistry
You should make a habit of looking to see if an earlier post has been answered. I answered this about 5-6 hours ago.
May 18, 2014

science help
For 1 read about tectonic plates. For 2 you didn't list them.
May 18, 2014

Chemistry
Mg^2+ + 2e --> Mg 2Cl^- ==> Cl2 + 2e
May 18, 2014

chemistry
If you are talking about HNO3, nitric acid, a suitable procedure is to bubble gaseous N2O5 into distilled water until saturation is achieved.
May 18, 2014

Chemistry
If you will show what you did perhaps we can find the problem. Other than guessing, however, we don't know what you've done.
May 18, 2014

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

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