Monday
October 20, 2014

Posts by DrBob222


Total # Posts: 44,571

chemistry
HAc + NaOH ==> NaAc + H2O mols NaOH = M x L = estimated 0.008 but you need a more accurate answer for this and all of the other estimates that follow. From the equation. 0.008 mols NaOH = 0.008 mols HAc M = mols/L = 0.008/0.010L = about 0.8M g HAc = mols x molar mass = ...
September 30, 2014

Chemistry
When you say you're given the peaks I assume you mean the frequency or wavelength of each peak. Then you get a book that gives the peaks by element. Peaks for elements different in number, intensity, etc but generally there are 2-5 strong "lines"(peaks) in the ...
September 30, 2014

solution making/ chemistry/biotech
First determine how many mols you have. The molar mass is about 100 so 340g/100 = 3.40 mols. Then mols = M x L. You know mols and M, solve for L That wll be 3.40 = 2M x L M = 3.40/2 - 1.20L or 1200 mL. Yes, you start by 340 x (1/100) = ? which I've done above.
September 30, 2014

Chemistry
A limiting reagent (LR) problem. You know that when you are given amounts for BOTH reactants. mols C = 20/12 = approx 1.7 but you need a more accurate answer for this and all of the estimates that follow. mols Si = g/atomic mass = 65/60 = about 1 mols SiC formed if you had 1.7...
September 30, 2014

Science 1 quick question
Yes, IF they needed N in a form other than N2 gas.
September 30, 2014

Science 1 quick question
If they needed nitrogen they would die without finding some other pathway
September 30, 2014

chemistry
28Si = 92.23% and 27.9769 amu 29Si = X% and 28.9865 amu 30Si = 100%-92.23%-X% = 7.77%-X and 29.9838 amu ----------------------------------- (0.9223*27.9769)+(X)(28.9865)+(0.0777)(29.9838 = 28.0955 Solve for X and 7.77-X
September 30, 2014

oops--Chemistry II
I have a 5-valent carbon below which i need to get rid of. This should take care of it. CH2 || C-C2H5 | CH2 | CH2 | CH2 | CH3
September 30, 2014

chem
This is about the best I can draw it on this forum but I think you get the idea CH2 || HC-C2H5 | CH2 | CH2 | CH2 | CH3 or you can view this site. http://www.chemspider.com/Chemical-Structure.14663.html
September 30, 2014

oops--Chemistry II
I have a problem with the answer. Most is right but the equation should be K2SO4(aq) + BaBr2(aq) ==> 2KBr(aq) + BaSO4(s). Note: KBr is soluble; BaSO4 is not. Next question is how do you know when a solid is formed. The answer is you memorize a set of solubility tables. Here...
September 30, 2014

chemistry
Mg^2+ + Na2CO3 ==> MgCO3 + 2Na^+ Convert mols Na2CO3 to mols Mg^2+ using the coefficients in the balanced equation. mol Na2CO3 x (1 mol Na2CO3/1 mol Mg^2+) = mols Na2CO3 x 1/1 = ? Then grams Mg = mols Mg x atomic mass Mg.
September 30, 2014

Chemistry
I don't see a question here.
September 30, 2014

chemistry
So 100 g/m^3 = 100 g/1000 L = 0.100 g/L. No2 convert 0.100 g phenol to mols. mols = grams/molar mass
September 30, 2014

college chemistry
heat lost by metal + heat gained by water = 0 [mass metal x specific heat metal x (Tfinal-Tinitial)] | [mass H2O x specific heat H2O x (Tfinal-Tinitial)] = 0 Plug in the numbers and solve for Tf. That's the only unknown.
September 30, 2014

Chemistry
What's the molarity of the H2SO4 you have? That's 1.83 g/mL x 1000 mL x 0.85 x (1 mol/98g) = approx 16 M but you need a more accurate answer. Then c1v1 = c2v2 16M*v = 1.35M x 1000mL Solve for v in mL but remember to get a better answer for that 16M.
September 30, 2014

Chemistry
1. 3O2 --> 2O3 I would call this a synthesis reaction. 2. oxidation reduction 3. synthesis 4. synthesis
September 30, 2014

chemistry 101
Sorry about that. That forms a heptane and the name is 3-methylheptane. You can see that if you draw it out.
September 30, 2014

chemistry 101
2-ethylhexane
September 30, 2014

Chemistry
mols H3PO4 = grams/molar mass Using the coefficients in the balanced equation, convert mols H3PO4 to mols HCl. Now convert mols HCl to grams. That's g = mol HCl x molar mass HCl
September 30, 2014

chemistry
My balanced equation is 4NaClO + 2H2O ==> 4NaOH + 2Cl2 + O2 which is just twice your balanced equation but the ratios are the same. 1.12 g/mL x 15 mL x 0.0585 = 0.982 g NaClO mols = 0.982/74.45 = 0.0132 mols NaClO mols O2 = 0.0132/4 = 0.00330 Then V = nRT/P. I used P = 755/...
September 30, 2014

chemistry
Damon didn't quite balance the equation. There are 3 O atoms on the left and four on the right. What was your balanced equation? I'll look at this later.
September 30, 2014

chem
mols Br in 7.20 mol FeBr2 = 7.2 x 2 = 14.40 Then g Br = mols x atomic mass = 14.40 x 79.9 = ?
September 30, 2014

CHEM
These problems are two equations in two unknowns that are solved simultaneously. Let X = mass As4S4 and Y = mass As4S6 ------------------------ equation 1 is X + Y = 1.000 The second equation comes from the 0.905 g of the As4O6 product formed. The equations are As4S4 + 7O2 ==&...
September 30, 2014

Chemistry
dHrxn = (n*dH BE reactants) - (n*dH BE products) BE = bond energy which you have listed. To get you started C-H is 99 kcal and you have four of them so you must break 4 C-H bonds at 99 each so it costs almost 400 kcal to break those four bonds. Then you put together CO2 and ...
September 30, 2014

Chemistry
IO3^- + 5I^- + 6H^+ ==> 3I2 + 3H2O Then you titrate the liberated I2 with the thiosulfate. 2S2O3^2- + I2 ==> 2I^- + S4O6^2- How much KIO3 did you weigh out? It was supposed to be weighed accurately but weigh out about 1 g. I will assume you weighed out exactly 1.00 g ...
September 30, 2014

CHEM HELP!
I believe I will do the trick. I don't think 2 will work; flowing the gases through the converter faster will result in less time for reaction and that will be a negative effect. If I looked up the 1/2N2 + 1/2O2 --> NO right ( you should confirm this) it was + meaning ...
September 30, 2014

Chemistry 30
(H2O) = 2.5 mol/50 L = 0.05 M ..........C + H2O ==> CO + H2 I.......solid.0.05.....0....0 C.......solid -x.......x....x E......solid.0.05-x....x....x Kc = (CO)(H2)/(H2O) The problem give you H2, CO is the same H2, you plug in Kc and solve for (H2O) You didn't give Kc in...
September 30, 2014

Chemistry 30
In every day language, Le Chatelier's Principle says that an equation in equilibrium will try to undo what we do to it. Adding O2 means it will shift so as to use up O2. So it goes to the right. Reducing H2O means it will try to make more H2O so it will shift to the right...
September 30, 2014

Chemistry- Answer Check
I wouldn't bet on it. When only one molecule in a thousand has enough energy to react the odds are against much of a reaction at all. I think the question is asking what can you do to make more molecules react and I believe the answer is to raise the temperature. That ...
September 29, 2014

Chemistry
So at 11 C the solubility is 5.6g/16cc. Convert that to g/100 cc and you have 5.6 x 100/16 = ? g/100
September 29, 2014

chemestry
You might check out the spelling of chemistry.
September 29, 2014

chemestry
3Li = 1s2 2s1. If you lose the outer electron it leaves 1s2 which is not an octet because there are only two electrons instead of 8 but it's a closed shell none-the-less.
September 29, 2014

oops---chemistry
1.00 cm x 4.00 cm x 7.80 cm is not 54.7 cc is it? more like 31.2 cc.
September 29, 2014

Chemistry
Bitterness in beer is caused by isohumolones (see http://en.wikipedia.org/wiki/Isohumulone). I couldn't find anything on yeast as far as a chemical structure goes. They are microorganisms, of course. Probably you could use either but since the former has so many different ...
September 29, 2014

Chemistry - Titrations
For whatever it's worth I learned something tonight that I wasn't aware of. It makes no difference how many H ions are neutralized. When mL and M are boxed in with the KOH and NH4OH, the volume comes out to be the same number no matter which assumption one makes. When ...
September 29, 2014

Chemistry - Titrations
15.61 mL should be right. By the way, I should point out that NH4OH doesn't exist. Years ago we thought NH3 + H2O ==> NH4OH which then ionized into NH4^+ and OH^- and that made a lot of sense.(and the ions DO exist.) But years of looking for the NH4OH MOLECULE has ...
September 29, 2014

Chemistry - Titrations
I was waiting for your reply to suggest that the best thing to do is just that; i.e., assume all of three H^+ are neutralized. If that is so we have this equation. H3PO4 + 3KOH ==> K3PO4 + 3H2O millimols KOH = mL x M = 35.25 x 0.2300 = ? mmols H3PO4 used = 1/3 of that = x ...
September 29, 2014

Chemistry - Titrations
M stands for molarity and is = mols/L solution N stands for normality and is = equivalents/L of solution. Most schools have stopped teaching normality and I applaud your teacher for including it. I think it's a huge mistake to dismiss normality BUT the IUPAC has spoken, ...
September 29, 2014

Chemistrey: Please check my answer
Everything is ok except for the last step. The question is for % ClO2 and you substituted mass Cl2 and not ClO2. That should be (25.9/26.98)*100 = ? and round to 3 significant figures. Here is a short cut to calculating mols ClO2. You used ratio/proportion and that will work ...
September 29, 2014

CHM
EDTA complexes with almost all elements. By controlling the pH one can control possible interference from other metals than the one being determined.
September 29, 2014

CHM
It isn't necessary to change screen names for different questions. I have most often heard the term free calcium used in connection with the amount of calcium in solution (but not complexed). I have never heard it used in connection to the amount of Ca metal. For example, ...
September 29, 2014

Chemistry
This is a problem with two equations and two unknowns and you solve them simultaneously. But first you didn't carry out the calculation for mols H2; you threw away some. I solved for n and obtained 0.00719879 which I would round to 0.0072 mols H2. Let X = mass Fe and Y = ...
September 29, 2014

chemistry
This is a problem with two equations and two unknowns and they are solved simultaneously. Let X = mass Ag and Y = mass Cu ----------------- equation 1 is X + Y = 3.00 To get the second equation note that mols NO3^- = M x L = 0.650 M x 0.1L = 0.0650 mols. Therefore, mols NO3^- ...
September 29, 2014

chemistry
What's a ff reaction? The driving force is the formation of I2 which is a solid in effect a precipitate.
September 29, 2014

CHM LAB
Are you doing it with EDTA? mols EDTA = M x L mols CaCO3 = mols EDTA mass CaCO3 = grams = mols CaCO3 x molar mass CaCO3
September 29, 2014

possible oops--Chemistry II
I'm not sure about this and I think the best thing to do is to ignore my response until you've cleaned up the problem so I'm sure of the data.
September 29, 2014

Chemistry II
You need to clean up the post. I know you want normal boiling point of PCl3. Is that dHofF S? Is that -288.07 dHo formation PCl3? Is that 311.7 dSo formation PCl3. dGo = dHo-TdSo dGo at boiling point is zero. 0 = dHo - TdSo Plug in dHo and dSo and solve for T if I've ...
September 29, 2014

Chemistry
Both of those formulas are correct for citric acid. They are empirical formulas and you will notice that both are C6H8O no matter how you slice it. The difference. If you are working a problem and citric acid is acting as an acid you want to highlight those H atoms (H ion) ...
September 29, 2014

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

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