Tuesday
October 21, 2014

Posts by DrBob222


Total # Posts: 44,623

Organic
High density sinks. Low density floats.
September 29, 2014

Chemistry
2Na3PO4 + 3Pb(NO3)2 ==> 6NaNO3 + Pb3(PO4)2 mols Na3PO4 = M x L Using the coefficients in the balanced equation, convert mols Na3PO4 to mols Pb3(PO4)2. Then convert mols ppt to grams. g = mols x molar mass.
September 28, 2014

Chemistry
See your post below.
September 28, 2014

Chemistyr
mols Ba(OH)2 = grams/molar mass = approx 0.3 but you need to be more accurate. M Ba(OH)2 = about 0.3/1.20L = approx 0.31 or so. Then use c1v1 = c2v2 0.31 x v = 0.100 x 1.00 Solve for v.
September 28, 2014

Chemistry
https://answers.yahoo.com/question/index?qid=20061013095505AAe2Uvf
September 28, 2014

Chemistry
2Mg + O2 ==> 2MgO mols MgO = grams/molar mass = approx 0.25 but you need a more accurate answer. Then convert mols MgO to mols O2 using the coefficients in the balanced equation. That is 0.25 mols MgO x (1 mol O2/2 mols MgO) = 0.25 x 1/2 = 0.125 mols O2. g O2 = mols O2 x ...
September 28, 2014

chemistry
mols KOH = grams/molar mass = 18.3/approx 56 = approx 0.33 but you need a more accurate number. Then M = mols/L solution. You know M and mols, solve for L.
September 28, 2014

chem
2-ethylhexane
September 28, 2014

Chemistry
Note the correct spelling of celsius. NH4NO3 --->N2O + 2H2O Use PV = nRT and solve for n = number mols N2O at the conditions listed. Use the coefficients in the balanced equation to convert mols N2O from the previous calculation to mols NH4NO3. Then convert mols NH4NO3 to ...
September 28, 2014

Chem
No sweat.
September 28, 2014

Chem
I gave you the two half cells with a note to add them. What more do you want? If you don't understand something I wrote let me know in detail what it is.
September 28, 2014

Chem
I answered this for you about noon.
September 28, 2014

Science
m1v1 = m2v2 technically isn't the one to use but it will work in this case. The REAL problem is that you don't have the concentration of the HCl. Without that you're dead in the water. You work the problem this way IF you had the molarity of the HCl. mols HCl = M x...
September 28, 2014

Chemistry
Al2(SO4)3 + 3Ca(OH)2 ==> 2Al(OH)3 + 3CaSO4
September 28, 2014

Chemistry
mols Fe = 3.01E22/6.022E23 = ? Then grams = mols x atomic mass.
September 28, 2014

Chemistry
Third time is the charm. H | C=C-H |....| C=C-H | H Again, ignore the four periods I've put in to try and make that bond between the two right most carbon atoms.
September 28, 2014

Chemistry
Let me try that again. We just can't draw structures on this forum but here's another try. H | C=C-H |...| C=C-H | H Again, ignore the three periods I've put in to try and make that bond between the two right most carbon atoms.
September 28, 2014

Chemistry
I went through the math and ended up withy 52.04 for the molar mass of the hydrocarbon; I expect that small difference is in what we used for the units and I wouldn't worry about that. How to do the remainder which is to determine the empirical formula. CxHy ==> xCO2 + ...
September 28, 2014

chemistry
I agree
September 28, 2014

chemistry
dHrxn = (n*dHf products) - (n*dHf reactants) dHformation can be found in yuor text, usually at the end of the book in the appendix.
September 28, 2014

chemistry
See your post above
September 28, 2014

chemistry
I see you've typed my response to an earlier question but no question here.
September 28, 2014

chemistry
I see my response to one of your earlier question but no question
September 28, 2014

chemisrt
Thanks for showing your work.
September 28, 2014

chemisrt
15.4 and not 15.4 You don't have the 6L blood . I get 3.4E22
September 28, 2014

chemistry
Cl2(g) + Al(s) --> Al3+(aq) + Cl- Cl2 + 2e --> 2Cl^- Al ===> Al^3+ + 3e Multiply equation 1 by 3 and equation 21 by 2 and add. Cancel the electrons. Here is MnO4^- from part c done this way in detail MnO4^- ==> Mn^2+ 1. The oxidation state Mn on the left is +7; on...
September 28, 2014

Chem help
:NH3 + Na. Here is the best I can do for Lewis structure of NH3. H .. :N:H + Na. .. H Let's pick on the right most H. It leaves and takes its electron with it as H. The Na. donates its electron to make ionic bond and one molecule of NaNH2 with Na^+ charge and NH2^- with H...
September 28, 2014

CHM
I would suggest you look on a can of soda and read the ingredients. That will list the preservative(s).
September 28, 2014

Chemistry
a. k = 0.693/t1/2 Substitute k into the below ln(No/N) = kt No = 5E10 N = ? k from above t = 1 month but change that to days if you use half life in days. b. Basically you don't want to get bombarded with radioactive rays longer than necessary.
September 28, 2014

chemistry
(V1/T1) = (V2/T2) Remember T must be in kelvin.
September 28, 2014

Chem
For the 20 mL of 1.00 M NaOH you have mols = M x L = 0.020 x 1.00 = 0.020 mols and grams = mols x molar mass. diluted solution (0.25M) you have the same, don't you? You added 20 mL of 1.00 M NaOH to 60 mL H2O so you added 0.02 mols for that dilution. Yes the concentration ...
September 28, 2014

Chem
Looks ok to me for the dilution but mols and grams you didn't do.
September 28, 2014

Chemistry
You want to write half reactions but I think you made a typo with FeBr. Should it have been FeBr2 Fe^2+ 2e --> Fe Mg --> Mg^2+ + 2e ------------------- Then add the equations.
September 28, 2014

Chemistry
mass = volume x density or volume = mass/density Look up the density and substitute; solve for volume. If you call the length of the side s, then V = s^3. Solve for s.
September 28, 2014

Redox equation
I have news for you; there is no redox here. Prove it? Let me rewrite it because you've omitted parentheses. Zn(OH)4^2- ==> ZnO2^2- + 2H2O Zn(OH)4^2. Zn = +2 O = 4*-2 = -8 H = 4*+1 = +4 +2-8+4 = -2 which = charge on the complex ion. ZnO2^2- Zn = +2 O = 2*-2 = -4 +2-4= -...
September 28, 2014

Need help badly, Science
What about 0.87 kW/m^2 x 104 m^2 = ?kW. Change that to J/s = x J/s Hvap in J/g x ?g = x J/s Solve for ?g and that will be grams H2O lost/second. Check that.
September 28, 2014

chemistry
21.90 kJ/g x 0.1182 g = ?q = energy obtained by combusting salicylic acid. Then calculate the heat capacity of the calorimeter. That is q from above = C/degree c x 2.84 and solve for C, the heat capacity of the calorimeter. q = heat capacity x delta T q = Cfrom above x 3.50 ...
September 27, 2014

chemistry
I don't agree with the 22 (22 what?) so I didn't bother with the 54; I assume is wrong also.
September 27, 2014

chemistry
a. Ptotal = pH2 + pH2O. Use PV = nRT and solve for n = number of mols. 2Al + 6H^+ ==> Al^3+ + 3H2 Convert mols H2 to mols Al and to grams.
September 27, 2014

chemistry
KHP + NaOH ==> NaKP + H2O mols KHP = grams/molar mass mols NaOH = mols KHP since 1 mol KHP = 1 mol NaOH. M NaOH = mols NaOH/L NaOH Note: You would do well to start sentences with a capital letter. It makes it easier to read the question.
September 27, 2014

chemistry
It means you did something wrong. Post your work and I'll find the error BUT first, did you change 4052 nm to m?
September 27, 2014

chemistry
R = Rydberg constant = 1.0973E7 m^-1
September 27, 2014

chemistry
1/wavelength = R(1/n^2 - 1/25) Remember to convert wavelength to m In the above n^2 is n1 squared and 1/25 is 1/n2 with n2 squared.
September 27, 2014

chemistry
This answer differs from the other answer you have. I will estimate for the following: mols of each = grams/ATOMIC MASS or 53.31/12 = 4.44 35.51/16 = 2.22 11.18/1 = 11.2 To find the empirical formula you want the ratio of the elements to each other with the smallest number ...
September 27, 2014

chemistry
AlCl3.6H2O ==> AlCl3 + 6H2O mols AlCl3 = 8.5g/molar mass AlCl3 = approx 0.06 but you need a more accurate number. Convert mols AlCl3 mols H2O using the coefficients in the balanced equation. That's about 6 x 0.06 = about 0.36. Then plug that into for n in PV = nRT and ...
September 27, 2014

chemistry
0.781 x molar mass N2 = ? 0.209 x molar mass O2 = ? 0.934 x molar mass Ar = ? (sum/22.4L) = density in g/L
September 27, 2014

chemistry
A or himesh or whatever, Why not work this the same way as steam out of AlCl3.62O
September 27, 2014

chem
its a hexane theres a double bond in position 1-2 with two ch3 methyls attached one methyl on top one on bottom but where are the methyls attached? To carbon 1 or another place? If both are attached to c1 then it is a heptene. So it's (CH3)2C=CHCH2CH2CH2CH3 This would be ...
September 27, 2014

chem
I can't tell from your drawing anything about this. Is it supposed to be a cyclic compound? I hope you received my note about the earlier diiodide compound being trans and not cis.
September 27, 2014

chemistry
Convert 0.0125 mol NiS2 to mols NiO. That is 0.0125 mol NiS2 x (2 mol NiO/2 mol NiS2) = 0.0125 mol NiS2 x 2/2 = 0.0125 mol NiO. Then g = mols NiO x molar mass NiO= ? For part b convert g NiS2 to mols, convert that to mols O2 and that to grams O2. Follow the steps from part a.
September 27, 2014

chem
1/wavelength = R(1/1^2 - 1/n^2) Remember to use wavelength in m. R is 1.0973E7 The 1/1^2 in the above is 1/n1 and n1 is squared. The 1/n^2 in the above is 1/n2 and the n2 is squared. Solve for n. This 121.6 nm line is the first line of the Lyman series and has a value for n of...
September 27, 2014

Chemistry
That's just another stoichiometric problem isn't it? You have mols Fe, use the coefficients in the balanced equation to convert mols Fe to mols Fe2O3 and convert that to grams. OR since you already have mols H2, you can use mols H2 and convert using coefficients to ...
September 27, 2014

Chemistry
2Fe + 3H2O ==> 3H2 + Fe2O3 mols Fe = grams/molar mass = approx 9 but that's an estimate. You need a more accurate number than that. Using the coefficients in the balanced equation, convert mols Fe to mols H2. That's approx 9 mols Fe x (3 mols H2/2 mols Fe) = approx ...
September 27, 2014

Check my answers? Math help.
I don't agree that the answer to #4 is -3.
September 27, 2014

TO M--urgent
I named that compound as cis and it should be trans. The I atoms are on opposite sides and that's trans, not cis.
September 27, 2014

CHEM
Please note on the earlier question and on the note I wrote above to you that the diiodo compound I named is trans and not cis. Trans is named when the groups are on opposite sides; cis is used when they are on the same side. On this and related question why don't you ...
September 27, 2014

chemistry
k = 0.693/t1/2 Substitute k into the below. ln(No/N) = kt No = 4800 N = 600 k from above Solve for t(which will be in seconds) and convert to minutes.
September 27, 2014

Chemistry
It would help if you wrote questions that could be interpreted. You might try looking at the post to see how it is shown. What you have makes no sense; I have hit the enter button to try and separate your one reaction into three separate reactions. I hope I hit the enter key ...
September 27, 2014

oops--oops--CHEM
I have no idea why I named this cis because the I atoms are on opposite side and it should be named trans. I just had cis on my mind when I typed it in and typed in cis--Sorry about that.
September 27, 2014

CHEM
I didn't know what to do with that so I didn't number them. They are cis-1,2-diiodoethene BUT cis IMPLIES they must be on different carbons. If we had 1,1-diiodoethene (we wouldn't name it 2,2-diiodoethene because 1,1 uses smaller numbers) there is no need for cis ...
September 27, 2014

CHEM
This forum doesn't allow spaces. The spaces after the first space is ignored. I would name this cis-diiodoethene
September 27, 2014

chem
Is that ClCH2CH2C(triplebond)CCH3? How about 5-chloro-2-pentyne?
September 27, 2014

CHEMISTRY
Some do both. Gaseous HCl, for example, is a molecular compound (and polar covalent). When added to water HCl + H2O ==> H3O^+ + Cl^- In this case we show the H^+ as being hydrated. Although we hardly ever show it the Cl^- is hydrated, also. Compounds like glucose dissolve ...
September 27, 2014

chemistry
mols base = mols acid M x L base = M x L acid M x (add all the L base) = M x L (add on the L acid) The only unknown is M acid.
September 27, 2014

chemistry
What you have doesn't make sense to me; please clarify it. I think the first part is 230/90Th + 4/2He but I don't know if the ________ are arrows or not. Is that a Po +2 ion? Are those 2 H^+ (as in hydrogen ions). Perhaps you intend 2H^+ to be 2 protons. And what's...
September 27, 2014

chemistry
You won't have trouble with this if you just look at the formula. You have 4.70 mol H2O There are two H atoms in 1 molecule H2O. Therefore, there must be 2*4.70 = 9.40 mols H in 4.70 mols H2O. How many mols O in 4.70 mols H2O? That's 4.70 mols, of course. Said another ...
September 27, 2014

Math--1 question
I think the answer is supposed to be A but if I interpret that correctly it would not be right. I think A is saying 3*(d+5) and that is 3d + 15 which isn't the initial equation. One of the math guru's will set us straight.
September 26, 2014

ordering decimals from least to greatest
Then -1.4555555..... -1.455 -1.45 -1.4
September 26, 2014

ordering decimals from least to greatest
Least to greatest what? From least positive to most positive? And did you intend to have two number the same value? -1.455 is the least positive (most negative) -1.45/-1.45 -1.4 most positive (least negative)
September 26, 2014

Chemistry
Refer to your post below.
September 26, 2014

Organic chemistry
To have a comparison with the Rf value of each.
September 26, 2014

Anthropology
See your post below.
September 26, 2014

biology
Here is some information. I suggest you Google this subject. http://www.aaanet.org/stmts/evolution.htm
September 26, 2014

Chemistry
John, Mandi, whomever-- You should go back and look at your other posts. I answered this below an hour ago. Here is a link. http://www.jiskha.com/display.cgi?id=1411784311
September 26, 2014

Microbiology
What does your book say? What do your notes say?
September 26, 2014

Microbiology
I would think someone here would be happy to read and critique your paper but few of us will write this ten page (or more) report for you.
September 26, 2014

CHEM
weight % = (grams solute/100 g solution)*100 = ? %impure NaCl w/w = (1.522/51.522)*100 =
September 26, 2014

Microbiology
Soaps are made to clean and they do a good job (they wash the germs away) of that but they do not sterilize (they get rid of the germs but they don't kill the germs).
September 26, 2014

Microbiology
1. The time frame it is effective. 2. How long it stays in the environment. 3. It's decomposition products. 4. Toxicity to humans/pets.
September 26, 2014

Chemistry
3CaCl2(aq) + 2K3PO4(aq) ==> Ca3(PO4)2(s) + 6KCl(aq) You add the phases. 3Ca^2+ + 6Cl^- + 6K^+ + 2PO4^3- ==> Ca3(PO4)2(s) + 6K^+ + 6Cl^- You turn that into a net ionic equation by canceling those items that appear on both sides; i.e., the Cl^- and K^+ to leave you with ...
September 26, 2014

CHM 300
You want the pH to be about 9 and Na2CO3 will do that. It aids in preventing decomposition of the thiosulfate.
September 26, 2014

CHM 300
In iodometry, the I2 is released by chemical reaction, then the released I2 is titrated with thiosulfate. I2 is not a good primary standard because it sublimes so easily. That means that the mass will change between the time it is weighed and the time it is used.
September 26, 2014

chemistry
dE = q + w q = +4070 J w = -2442 J dE = ?
September 26, 2014

Math Help.
The suggestion made by Ms. Sue is very good but in addition I suggest you note your answers by EACH question, too. To read an unnumbered question, then scroll down what seems like forever to find your answer is just too confusing. If you placed an asterisk or noted below the ...
September 26, 2014

Science URGENT
1 wave/4s = ?
September 26, 2014

chemistry
I have no idea what this looks like. Use dE = q + w q will be joules of heat. If the arrow goes INTO the object it is +, if OUT OF the object it is -. Same sign convention for work. If the arrow goes INTO the object it is +w; if out of the object it is -w.
September 26, 2014

Science
See your post above.
September 26, 2014

Chemistry
Are these the answers? What's the question?
September 26, 2014

chem
AgNO3 ==> Ag^+ + NO3^-
September 26, 2014

Chemistry of Life
Water molecules move randomly around each other. Without the proper balance of water, chemical reactions in cells could not take place. It enables water molecules to bond to each other.
September 26, 2014

Science
If 757 g is your answer I don't agree. On second thought that looks like another choice for an answer. I don't understand your problem. If D = M/V then mass = volume x density. Just plug and chug.
September 26, 2014

Chemistry
distance = rate x time. d = 55.0 mi/hr x 4.25 hr = ?
September 26, 2014

Chemisty
You work through these things logically. The best advice I have for beginning students is to think "moles". How many mols CF3Cl2 are in 38.0 g. I will estimate all of these numbers; you should do them more accurately. mols = grams/molar mass = 38/121 = approx 0.3 ...
September 26, 2014

Chemistry
mols = grams/atomic mass 11 g Zn sounds high to me but then I'm not an MD. Are you sure that isn't 11 mg?
September 26, 2014

CHEM
ketone CH3COCH3 in which the C and O are CH3 | C=O | CH3
September 26, 2014

oops---CHEMISTRY
I believe the IUPAC name is 2-aminobutane
September 26, 2014

CHEMISTRY
As you can see this forum does not allow spaces. Anything over one space is ignored so drawing structures is almost impossible although with some footwork i can be done as in the next response for you. I thin the easy way to do this kind of question is to write the formula as ...
September 26, 2014

Chemistry
It took 20 minutes to type all of that stuff. :-)
September 26, 2014

Chemistry
18.7% by mass means 18.7 g Ba(NO3)2 in 100 g solution. Use density to calculate the volume. mass = volume x density or volume = mass/density = 100 g/1.09 = approx 91.7 mL. Therefore, you have 18.7 g Ba(NO3)2 in 91.7 mL or 18.7 g Ba(NO3)2 in 9.17 dL. In 87.6 dL you will have 18...
September 26, 2014

chemistry
That's the "ethyl" group.
September 26, 2014

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