Thursday
November 27, 2014

Posts by DrBob222


Total # Posts: 45,634

Chemistry
If you had typed in what you did I could have found the error by now. I don't know what you did wrong either. How do you know 22 is wrong? What are you using for specific heat Cu.
November 4, 2014

Chemistry
The mistake you're making is trying to manipulate the numbers to get answer; i.e., guessing. Reason it out. You know mol = grams/molar mass. mol = grams/molar mass 0.85 mol = 23.8/molar mass molar mass = ? approx 28 Therefore X2 = 28 and X must be 28/2 = ? You should have ...
November 4, 2014

Chem 130
%H2O = [(5*molar mass H2O/molar mass CuSO4.5H2O)]*100 ?
November 4, 2014

chem 2
..........CH3NH2 + HOH --> CH3NH3^+ + OH^- I..........0.025............0..........0 C...........-x..............x..........x E........0.025-x............x..........x You need the Kb for CH3NH2. You can find that in your text/notes/web. Substitute the E line into Kb ...
November 4, 2014

Chemistry
This is a regular stoichiometry problem. All of these are worked with the following steps. 1. Write and balance the equation. You have that. 2. Convert grams of what you have (in this case B2O3) to mols. mols = grams B2O3/molar mass B2O3 = ? I'm estimating mols = approx 0....
November 4, 2014

chemistry
mmols HCl added initially = mL x M = 5.00 mmols NaOH to neutralize = 4.21 x 1.2 = 5.05. Check you numbers. mmols NaOH > mmols HCl which means antacid tablet did not neutralize any of the HCl.
November 4, 2014

chemistry
https://www.google.com/search?q=lewis+structure+N2O5&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:en-US:official&client=firefox-a&channel=sb
November 4, 2014

Chemistry
We can't draw structures on this forum. Do what I do; i.e., Google lewis structure ......and fll in the blank
November 4, 2014

Chemistry
Use the Henderson-Hasselbalch equation and substitute millimols for base and millimols for acid. Solve for pH.
November 4, 2014

Science
The cattle egret does that but other egrets do not.
November 4, 2014

Chemistry pretty urgent!!!!!!!
http://faculty.ncc.edu/LinkClick.aspx?fileticket=L2sV5SDzIhE%3D&tabid=1871
November 4, 2014

chem
pO2 = XO2*Ptotal pO2 = 0.21*760 = approx 160 mm Then pressure remaining is 760-approx160 = approx?
November 4, 2014

chem
4Fe + 3O2 --> 2Fe2O3 mols O2 = 80 mL x (1 mol/22,400 mL) = ? Using the coefficients in the balanced equation, convert mols O2 to mols Fe. Then convert mols Fe to grams. g = mols x atomic mass Fe.
November 4, 2014

Chemistry
I see Bob Pursley ignored the difference in temperature. Is that 23.3 and 23.8 a typo?
November 4, 2014

Chemistry
Is that 50 mL total? How much HCl and how much NaOH? What's the molarity of HCl and NaOH? You need to know mols H2O formed if you are to calculate dH/mol.
November 4, 2014

chemistry
millimols base = 1,500*0.17 = 255 mmols acid = 1,500*0.32 = 480 add 54 mmols HCl .........Bz^- + H^+ ==> HBz I.......255......0.......480 add.............54............... C.......-54....-54......+54 E.......201.....0.......534 Plug these E line values into the HH equation ...
November 4, 2014

Chemistry
Is this what you're looking for? Universal indicator--mixture of two. http://www.all-about-ph.com/ph-indicators.html
November 4, 2014

chemistry
You have two "addeds" in your post. I assume you want to know how much NaOH was ADDED FROM the buret TO the titration solution and not how much was added to the buret initially. 24.8-1.2 = ?
November 4, 2014

Chemistry
CO3^2- + Cu^2+ ==> CuCO3 millimols CuSO4 = mL x M = 23.7*0.167 = approx 4 but that's an estimate so you need to redo all of these calculations. So you will need approx 4 mmols NaCO3 and M Na2CO3 = mmols/mL or mL = mmols/M = approx 4/0.122 = ? mL. g CuCO3 = mols CuCO3 x ...
November 4, 2014

science
If you will look up those values and post them here we may be able to help. Include infor on HgSCN+. Why? My table values may not agree (probably will not) so we can't get the same answer. Show what you know to do also.
November 4, 2014

organic chemistry laboratory
Here is my answer of two days ago. Did you see it? http://www.jiskha.com/display.cgi?id=1414966391
November 4, 2014

Science
How many mols do you want? That's mols = M x L = ? Then mols = grams/molar mass. You know molar mass and mols, solve for grams.
November 4, 2014

To Chandler---chemistry
Remember you get faster service if you don't post piggy back. Go to the top of the page and post your own question all by itself. heat lost by steam + heat lost by 1.3g liquid H2O + heat gained by 31 degree H2O = 0 [mass steam x -heat vap] + [mass steam to H2O x specific ...
November 4, 2014

chemistry
If there is a question here I don't see it.
November 4, 2014

chemistry
Look on the web for drawings of how to do this. Most I have seen ascarite or drierite. We can make drawings on the forum. Textbooks also have drawings showing how to do it.
November 3, 2014

Chemistry Lab
I suppose we are to assume that the volumes are additive. M1V1 = M2V2 0.150*1.5 = M2*(3.5+1.5) M2 = 0.045M Another way. You start with 1.5 mL and end up with 5.0 mL (if the solutions are additive) so 0.150M x (1.5/5.0) = 0.045M
November 3, 2014

chemistry
dE = q + w q1 = mass H2O x specific heat H2O x (Tfinal-Tinitial) to get from 25 C to 100C. q2 = mass H2O x heat vaporization to get from liquid water at 100 to steam at 100 q3 = mass steam x specific heat steam x (Tfinal-Tinitial) to get from steam at 100 C to steam at 111 C. ...
November 3, 2014

big time oops----chemistry
The first part of my response is ok. It's the work that isn't. As you've probably already noticed I used mols for volume and that's a no, no. Work = is pdV with the proper sign. pdV = dn RT. Substitute R, T and delta n (delta n is 34 mols) and solve for pdV ...
November 3, 2014

chemistry
I would do this. dE = q+w dE = -2252 kJ + w. Modifying PV = nRT and remembering that pdV = work, then pdV = dnRT and dn is 11 + 23 = 34 mols. pdV = 34*0.08205*298 = ? L*atm. Convert to J by multiplying by 101.325 and convert that to kJ. What't the sign of work in this case...
November 3, 2014

Chemistry
I worked this below. I'll try to find it and give you a link. http://www.jiskha.com/display.cgi?id=1415056292 Any questions?
November 3, 2014

Chemistry
I worked this below. I'll try to find it and give you a link.
November 3, 2014

chemsitry
delta g lost = 0.1 %error = (0.1/1.3)*100 = ?
November 3, 2014

chemistry
This is black magic, not chemistry. Stick to the subject.
November 3, 2014

Organic Chemistry
Frankly, I don't know why it redissolves upon adding too much HCl but why not recalculate the c1v1 = c2v2 and see how much NaOH to add to neutralize that extra HCl you added. That should get you back to the starting point or at least where you had the ppt form.
November 3, 2014

Organic Chemistry
I wish I could help but there is nothing in your post to tell us what experiment you were doing. Sorry. My tea leaves aren't working tonight.
November 3, 2014

chemistry
q = Ccal*dT = 4.84 kJ*(27.1-23.7) = ? kJ heat combustion is -?kJ/0.009298 = -?kJ/mol
November 3, 2014

Chemistry
mL1 x M1 = mL2 x M2 Substitute. mL1 x 0.355M = 19.9 mL x 15.0M Solve for mL1
November 3, 2014

Chemistry
% w/w = mass solute/mass solution. (X/369)*100 = 3.04 Solve for X = grams NaCl.
November 3, 2014

Chemistry
Take 100 g sample which gives you 7.252 g Na 75.084 g U 17.664 g O ------------ convert to mols by mols = grams/atomic mass. 7.252/23 = approx 0.315 75.084/238 = approx 0.315 17.664/16 = approx 1.10 For the empirical formula you want to find the ratio of these elements to each...
November 3, 2014

chemsitry
I don't know but if all of the Ag in AgNO3 is converted to Ag2CrO4, then 1 mol 2AgNO3 = 1 mol Ag2CrO4; therefore, 1 mol AgNO3 will produce 1/2 mol Ag2CrO4. You have mols AgNO3 = 146/molar mass AgNO3 = approx 0.86 but that's an estimate. Then 0.86 mols AgNO3 = 0.43 mols...
November 3, 2014

To Maria---chemistry
It is better to post your own question instead of riding piggy back on another post. I've already answered your question above.
November 3, 2014

chemistry
heat lost by water + heat gained by calorimeter = 0 [(mass H2O x specific heat H2O x (Tfinal-Tinitial)] + [(Ccal*(Tfinal-Tinitial)] = 0
November 3, 2014

chemistry
I work these buffer problems with millimols instead of M. You want 250 mL x 0.450M = 112.5 millimols of the buffer. so equation 1 is base + acid = 112.5 Equation 2 comes from the HH equation. pH = pKa + log (base)/(acid) 4.00 = 4.74 + log b/a Solve for b/a and rearrange to ...
November 3, 2014

chemistry
And I think you are correct.
November 3, 2014

chemistry
If your question says Li is a solid and the ferric nitrate is a solid (which isn't in the initial post) then I would write no reaction because the two solids will not react. It was I that wrote in the (s) and (aq). However, in the case that it is in your problem as Li(s...
November 3, 2014

chemistry
Frankly, I don't think it will go but I think the spirit of the question is 3Li + Fe(NO3)3 ==> 3LiNO3 + Fe The reason I don't think this will happen is that if we do it as solids, like this 3Li(s) + Fe(NO3)3(s) ==> no reaction because the solids will not react. ...
November 3, 2014

Organic chemisty
That's a relative difference; i.e., say the products are 85%A and 15%B then A is the major product and B is the minor product. However, I don't think these numbers are carved in stone. I think if it were 75/25 it is major vs minor or even 60/40 but I think 55/45 would ...
November 3, 2014

chemistry
I would like to know why you're having trouble with these? If would could find the root cause we might be able to remedy the situation. I think all of these are activity series questions. The halogens replace "down the series"; i.e., F2 will oxidize Cl^- to Cl2; ...
November 3, 2014

Math Help!
I would choose A.
November 3, 2014

Math Help!
That line is the hypotenuse of the triangle for slope of 3/4. Right? Would that make the sides 3,4 and the hypotenuse 5.
November 3, 2014

Chemistry
Ecell = Eocell = 0.0592/2*log (ratio) Eocell = 0 and Ecell = 0.12 Solve for ratio.
November 3, 2014

chemistry
Zn + 2HCl ==> ZnCl2 + H2 mols Zn = grams/molar mass = ? Using the coefficients in the balanced equation, convert mols Zn to mols HCl. Then M HCl = mols HCl/L HCl. You know M and mols, solve for L HCl and convert to mL.
November 3, 2014

chemistry
Ca(NO3)2 = calcium nitrate
November 3, 2014

chemistry
2AlCl3 → 2Al + 3Cl2 mass = volume x density mass = 78.3 x 2.70 = approx 211 g but you need a more accurate answer than my estimate. mols Al = grams/molar mass = ? Using the coefficients in the balanced equation, convert mols Al to mols AlCl3. Then g AlCl3 = mols AlCl3 x ...
November 3, 2014

physical science
If you posted these one at a time along with your answer to each (and include the work) you MIGHT get some of them checked. Posting 20 at a time with the answers AT THE END has minimal chance for success. You could increase the chances a little by re-posting and placing you ...
November 3, 2014

chemistry
How many mols do you want? That's M x L = mols Then mols = g/molar mass. You know molar mass and mols, solve for grams.
November 3, 2014

Chemistry
C12H22O11 + H2O ==> 4C2H5OH + 4CO2 100 lb x (453.6 g/lb) = ? g sugar mols = grams/molar mass 1 mol C12H22O11 produces 4 mols ethanol from the equation; convert ? mols sugar to ? mols ethanol. Convert ? mols ethanol to grams. grams = mols x molar mass = ? Using the density, ...
November 3, 2014

chemistry
Take the hint. Eugenol is a phenol and the other one is a hydrocarbon; add NaOH to make the Na salt and it will be soluble in water whereas the caryophyllene will more than likley be soluble in ether or some other non-polar solvent. Extract with the two liquids. The Na salt of...
November 3, 2014

chemistry
Limone = L water = W pL = partial pressure limone pW = partial pressure W ML = molar mass Limone MW = molar mass Water --------------------- (mass L/mass W) = (pL*ML/pW x MW) pTotal = pL + pW and pW = 690 from the problem and pTotal = 760. Solve for the mass ratio and convert ...
November 3, 2014

chemistry
Use V = nRT and solve for n. Then n = grams/molar mass.
November 3, 2014

CHEMISTRY
From what? Starting with your choice? Then take 0.1M HCl and dilute by a factor of 10,000 to give a pH of 5.0 and I'm ignoring the small amount of H^+ from the ionization of H2O.
November 2, 2014

Chemistry
Use density to convert volume to grams. Then q = mass ether x heat vaporization. If heat vap is in J then q will be in J and you will need to convert to kJ. You probably can find dHvap in tables in your text or on the web. I don't have these memorized.
November 2, 2014

Chemisrty
mL1 x M1 = mL2 x M2 mL1 x 6.00 = 50.0 mL x 0.195 So you want mL1 of the 6.00 M solution to be placed in a container and add water to a total of 50.0 mL.
November 2, 2014

chemistry
With A = mass of aniline and W = mass H2O, pA = partial pressure aniline and pW = partial pressure of H2O, then mass A/mass W = (pA*molar mass A)/pW x molar mass W) Plug in and solve for mass W. For pA you will want 760-43 since the pA + pW = 760 at the boiling point. mass A...
November 2, 2014

Chemistry
pKa = -log Ka. HA + H2O ==> H3o^+ + A^- Ka = (H3O^+)(A^-)/(HA) Then (A^-)/(HA) = Ka/(H3O^+). Therefore, if pH = 5, then (H3O^+) = 1E-5. Substitute into Ka expression and (A^-)/(HA) = 6.3E-3. When that ratio is = or > 10 you get the A^- color; when the ratio is = or < ...
November 2, 2014

Chemistry
q = mass H2O X specific heat H2O x (Tfinal-Tinitial) All the rest of that info is not needed UNLESS you want delta H/g and/or delta H/mol. dH/g = q/31.2 dH/mol = q/g x (77.7 g/mol) = ?
November 2, 2014

chemistry
6485.2 J is right and it is lost BUT by the reaction and not the calorimeter. Since the calorimeter changed T from 22.5 UP TO 34.9 that means the calorimeter gained heat and that means the reaction is exothermic (it released the heat which the calorimeter absorbed). b. How ...
November 2, 2014

chemistry
That's more to fewer mols = -dS Fewer to more mols = + dS
November 2, 2014

chemistry
I think that's dSrxn. Look at the mols gas on each side. Fewer mols = -dS. More mols = + dS
November 2, 2014

Chemistry
See your other post.
November 2, 2014

chemistry
See your other posts.
November 2, 2014

chemistry
2C6H6 + 15O2 ==> 12CO2 + 6H2O mols benzene = grams/molar mass Using the coefficients in the balanced equation, convert mols benzene to mols CO2. Convert mols H2O to grams H2O with g = mols x molar mass. This is the theoretical yield (TY). The actual yield (AY) in the ...
November 2, 2014

chemistry - DrBob?
See your other post below.
November 2, 2014

chem
Take 100 g sample which gives 40 g C 6.71 g H 53.29 g O Convert to mols by mols = grams/atomic mass 40/12 = approx 3.3 6.71/1 = 6.71 53.29/16 = approx 3.3 To determine the empirical formula, find the ratio of these elements to each other with the smallest number being 1.00. ...
November 2, 2014

chemistry
It looks ok to me.
November 2, 2014

chemistry - instrumentation
You can find a number of sites that discuss this. I typed in analytical method vs drug response factor method. Here is one site but many came up. https://www.inkling.com/read/ansel-pharmaceutical-dosage-form-drug-delivery-9th/chapter-4/physical-pharmacy-capsule-4-14
November 2, 2014

chemistry
What trouble are you having doing this? All look like single replacement reactions. Cl2 + NaF is NR. Au will not react with HNO3 either.
November 2, 2014

organic chemistry laboratory
For 1 I would have answered "test for ketones) since the Jones test is for aldehydes. 3c. Couldn't that also be alkyne? I didn't look at 4. 5 is right. The unknown can contain a halogen but not give a positive AgNO3 test.
November 2, 2014

oops--Chemistry
Also, while your at it, break the posts up. Bad English. Also, while you're at it, break the posts up into smaller bits, preferably no more than 2-3 per post. That way a person who has just a little time can answer a post that would not have time to answer one with 20 ...
November 2, 2014

Chemistry
I don't agree with 12,13,14,15
November 2, 2014

Chemistry
11 is ok.
November 2, 2014

Chemistry
The answers to 16 don't make sense. A and C appear to be the same but with a typo I disagree with answers to 17 and 18.
November 2, 2014

Chemistry
20 is ok. I don't agree with 19
November 2, 2014

Chemistry
I don't agree with 8 and 10. 6,7,9 are ok.
November 2, 2014

Chemistry
1,2,3,4,5 are correct.
November 2, 2014

Chemistry
Why don't you put your answer at the end of EACH question? That way we can look at the question and the answer. As you've done it we must read the question, scroll to the end to find the answer, scroll back to the top for the other choices, back to the bottom to ...
November 2, 2014

chemistry
2C2H2 + 3O2 ==> 2CO2 + 2H2O dH = 1300 kJ/mol C2H2 How many mols C2H2 do we have? That's mols g/molar mass = 1.0/26 = approx 0.038 but you should redo that since it is an estimate. The q = dH = mass H2O x specific heat H2O x delta T. Solved for dT.
November 2, 2014

chemistry
This is a limiting reagent (LR) problem and you know that because amounts are given for BOTH reactants. 4NO2 + 6H2O ==> 4NH3 + 7O2 mols NO2 = grams/molar mass = ? mols H2O = use PV = nRT and solve for n. Using the coefficients in the balanced equation, convert mols NO2 to ...
November 2, 2014

chemistry
fraction by volume = mols fraction. 2.6E-6 = fraction by volume. 2.6E-6 x 106 = ppm = 2.6 but wikipedia shows it as 18 ppm.
November 2, 2014

Chemistry
Use PV = nRT, solve for n. Then n = grams/molar mass. Yu know molar mass and n, solve for grams.
November 2, 2014

chemistry
Equivalent weight calculations depend upon the reaction. If you have a reaction it is molar mass/1 if one NaOH is used; it is molar mass/2 if 2 NaOH are used.
November 2, 2014

Chemistry
P1V1 = P2V2
November 2, 2014

Chemistry
The question is too general because the energy levels flip flop at certain points; however, here are some guidelines for a specific elements. For the second part first. For oxygen: Look at the atomic number. The AN is 8; therefore, it has 8 protons and that means 8 electrons ...
November 2, 2014

chemistry
q = mass Al x specific heat Al x (Tfinal-Tinitial)
November 2, 2014

Chem
That is partly right. For 2s: N = 2 l = 0 ml = 0 ms = +/- 1/2 for each electron For 2p: N = 2 l = 1 ml = -1,0,+1 ms = +/- 1/2 for each electron
November 2, 2014

Chem
In every orbital there CAN be two electrons (no more than two but they may have only one). How are they related: They are the negative of each other; i.e., one has a spin of +1/2 and the other (if there is another) has a spin of -1/2. Not to confuse you but most freshman texts...
November 2, 2014

chemistry
mols Li2O = 1000 g/molar mass Li2O mols CO2 = mols Li2O (from the coefficients in the balanced equation) Then use PV = nRT and convert mols CO2 to volume at the conditions listed..
November 2, 2014

chemistry
One thing you need to learn in chemistry: A MUST. Locate the caps key on your computer and USE it. m is not M. I assume you meant molarity (M) and not molality(m). If it is m you can't work the problem with the information provided. If it is M, then mL1 x M1 = mL2 x M2 mL1...
November 2, 2014

chemistry
6535 kJ/2 mol C6H6 = ? kJ/1 mol C2H6. mols C2H6 in 16.0g = grams/molar mass Then kJ heat released = kJ/mol x # mols in 16.0g = ?
November 2, 2014

chemistry
See my response above.
November 2, 2014

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