Monday
September 26, 2016

Posts by DrBob222

Total # Posts: 53,142

Chemistry
You have made a typo (maybe two typos). You mean either FeSO4 or Fe2(SO4)3 and also, the equation is not balanced. I will assume FeSO4 but if my assumption is wrong, you will need adjust the molar mass of the product accordingly. First and second, correct the products, then ...
April 20, 2016

Chemistry
(V1/T1) = (V2/T2) Don't forget T must be in kelvin.
April 20, 2016

Chemistry
p1v1 = p2v2
April 20, 2016

chemestry
You may want to spell chemistry right. E = hc/wavelength for one atom. That x 6.02E22 atoms for 0.1 mol.
April 20, 2016

Chemistry-Dr.Bob222
Treat this as just another ammonia, NH3, problem. Remember, NH3 + HOH ==> NH4^+ + OH^- and you know how to solve those problems. This is the same thing. See here for the structure. https://en.wikipedia.org/wiki/Pyridine Let's call pyridine a simple PN. Then ......PN + ...
April 19, 2016

Chem
q = mass H2O x specific heatH2O x delta T. Solve for q. Since the temperature rose you know the heat was generated by the combustion of the butane so it was an exothermic reaction. That q is in J/3.00 g. Change to kJ/3.00 g, then kJ/3.00 g x (molar mass butane) = kJ/mol.
April 19, 2016

Chemistry
I don't see a question here. I assume you want directions for preparing the buffer. Let's say you want 1 L of the buffer. pH = pKa + log (base)/(acid) 7.40 = pK2 + log (base)/(0.0100) You will need to look up pK2 for H3PO4. solve the equation for (base). Knowing you ...
April 19, 2016

Chemistry
Ba(OH)2 + 2HCl ==> BaCl2 _ 2H2O mols Ba(OH)2 = grams/molar mass = ? Using the coefficient sin the balanced equation, convert mols Ba(OH)2 to mols HCl. Now convert mols HCl to grams. grams = mols HCl x molar mass HCl.
April 19, 2016

Chemistry
It really would have been nice if you told us how much ethanol (I presume that is number of mL) but you didn't type that in. Can't work the problem without proper information.
April 19, 2016

Chemistry
Not much to go on here. If you have delta H, I assume the next step is to calculate delta S and delta G. Then dGrxn = -RTlnK.
April 19, 2016

pre-ap chemistry
How many mols do you need? That's mols = M x L = ? Then mols = grams/molar mass. You know molar mas and mols, solve fo grams. Place that many grams in a 100 mL volumetric flask, add some water and swirl until all of the CuSO4 is dissolved, add DI water to the mark of the ...
April 19, 2016

Chemistry
I don't understand why it couldn't hold 19L or 30 L or for that matter 100 L if it were strong enough to resist bursting. 15.7 L is the answer for the problem that says v1 is 19L under certain conditions and you want to know v2 at different conditions but this problem ...
April 19, 2016

Chemistry
Cr2O3 Here is how you do it in a very simple way. Write CrO Over the Cr place a 3 Over the O place a 2 Place a . beside Cr at the bottom. Place a . beside O at the bottom. The bottom will look like this. Cr.O. and along the top (I can't do it because of spacing issues) ...
April 19, 2016

Chemistry
Kelly, I don't get it. How does Na2SO4 fit in. How does NaCl fit in. Where do they go? And where does the H2O go? When you write Pair of compounds, I see benzene and hexane but that leaves out Na2SO4.
April 19, 2016

Chemistry
Yes, or a net ionic equation. NaCl and Pb(NO3)2 will do it.
April 19, 2016

Chemistry
Your question is not clear. What solid?
April 19, 2016

chemistry
Write and balance the equation. Then dSo rxn = (n*dSo products) - (dSo reactants) Substitute and solve for dSo rxn.
April 19, 2016

Chemistry
Have you made a typo? Is that supposed to be AsO4^3-
April 19, 2016

Chemistry
Here is the NO3^- half. 1. Write it down. NO3^- ==> NO 2. Oxidation state of N on left is +5; on the right is +2. Change in oxidation state is gain of 3e. Do that as step 3.[5+ +(-3) = 2+] 3. NO3^- +3e ==> NO 4. Count up the charge on both sides. I see -4 on the left and...
April 19, 2016

Chemistry
What are the other reactions?
April 19, 2016

Chemistry
572 kJ x (54.0/2.00) = ? kJ
April 18, 2016

Chemistry
(32.6 bil bar/yr) x ?yrs = 1526 bil Solve for ? yrs in billions of barrels.
April 18, 2016

Chemistry
2H2(g) + O2(g) --> 2H2O(g) + 483.6 kJ. You want to go backwards with 5.00 mols H2O vapor instead of 2.00 mols. 483.6 kJ x (5.00/2.00) = ?
April 18, 2016

chemistry
dGo = =nFE
April 18, 2016

chem
In my 75 yrs if working with chemistry I've never run across Hal.
April 18, 2016

Chemistry
......Mg(OH)2 ==> Mg^2+ + 2OH^- I......solid.......0.......0 C......solid.......x.......2x E......solid.......x.......2x Then NH3 + HOH ==> NH4^+ + OH^- I....0.1...........0........0 C....-x............x........x E....0.1-x.........x........x First, determine the OH^- ...
April 18, 2016

Chemistry
See other post.
April 18, 2016

Chemistry
You're a genius if you can do this. You don't have enough information. You've omitted the joules necessary to raise the temperature by 5 C.
April 18, 2016

Chemistry
Use 1.047 g to calculate mols He. mols = grams/atomic mass. Then use PV = nRT and solve for P. This will be in atm; I would conert that to mm Hg. atm x 760 = pHe in mmHg. Then Ptotal = pHe + phexane You know Ptotal = 739.6 mm You know PHe from PV = nRT; solve for phexane.
April 18, 2016

Chemistry
I'm assume the solution is one of sucrose and water. delta T = Kb*m Solve for delta T, then add to the normal boiling point to find the new boiling point.
April 18, 2016

Chemistry
Mg + 2HCl ==> MgCl2 + H2
April 18, 2016

AP Chemistry
Ditto Bob Pursley and his comments.
April 18, 2016

chem
mols Al2(SO4)3 = grams/molar mass = ? There are 12 O atoms per 1 mol Al2(SO4)3 so there are 12 x mols Al2(SO4)3 there. Convert mols O to grams O. g = mols x 16 = ? I assume the question means grams O (atoms) and not O2 (molecules).
April 18, 2016

chem
"full mineralization of toluene???"
April 18, 2016

chemistry
0.717 g KH2PO4 in 500 mL to ppm. You want to convert to mg/L. 717 mg/500 mL = 1434 mg/L = 1434 ppm.
April 18, 2016

chemistry
1000 mL x 1.18 g/mL x 0.37 x (1/36.5) = ? mols/L = ? M concd HCl. b. M = mol/L. You know mols and M, solve for L and convert to mL. mass = volume x density. You know density and volume, solve for mass.
April 18, 2016

Chemistry
120 W = 120 J/s. For 1 hour that is 120 J/s x 60 s/hr = 7200 J. 7200 = mass H2O x delta H vaporization. Substitute and solve for mass H2O (sweat)
April 18, 2016

Chemistry
Your problem isn't chemistry at this point; it's math. You haven't used the first equation of X+Y = 0.4276. Solve that for Y as Y = 0.4276-X and substitute that into the equation you have for Y. That will give you just one unknown of X and you solve for that.
April 17, 2016

Chemistry
This is not an easy problem. You set up two equations and solve them simultaneously. I will give you the two equations and tell you what to do after that. Let X = grams LiOH and Y = grams KOH equation 1 is X+Y=0.4276 Equation 2 is obtained by an equation that adds mols LiOH (...
April 17, 2016

Chemistry
I don't understand the question. Perhaps if you post it in regular English we can read it.
April 17, 2016

Chemistry 101
You add the aq and l and s. Molecular equation: Na2CO3 + NiCl2 ==> 2NaCl + NiCO3(s) Total ionic equation: 2Na^+ + CO3^2- + Ni^2+ + 2Cl^- ==> 2Na^+ + 2Cl^- + NiCO3(s) Net ionic equation: Just cancel the ions that are common to both sides. What left is the net ionic ...
April 17, 2016

Chemistry
-600 has 1 significant figure(s.f.); i.e., the 6. The first multiplication has 2 s.f. for the answer since 2.0 has only 2. The second has 2 s.f. since 1.0 has only 2. So the answer must have 2 s.f.. I would make that -622.43 kJ round to -6.2E2 kJ.
April 17, 2016

Chemistry
Why didn't you show what you had tried? Then we could find the error in your work/thinking. a = mass x specific heat x delta T. 686 = 110 x sp.h. x (172-38) Solve for sp.h. = ? The answer is not 0.385
April 17, 2016

chemistry
No. K = (C)^4/(A)^2(B^)^3
April 17, 2016

chemistry
I think you have made one or more typos in your equation. I will assume the equation should be 2Cl + 7 O + 100 kcal => Cl2O7 If it takes 100 kcal for 1 mol then it will take 100 x 10/1 = ? kcal. What would it take for 7. Can you handle that?
April 16, 2016

chemistry
Technically the question should say 244 mL SOLUTION and not water. mols Ca(NO3)2 = grams/molar mass = ? Then M = mols/L = ?mols/0.244L = ?
April 16, 2016

Chemistry
I like to work in millimols. Let's just take 100 mL of each solution. To save space and typing let's call C2H5NH2 just RNH2. millimols RNH2 = mL x M = 100 x 1.68 = 168 mmols HClO4 = 100 x 0.966 = 96.6 ...RNH2 + HClO4 => RNH3^+ + ClO4^- I..168.....0.........0.......0...
April 16, 2016

Chemistry
Did you make a typo. Is that I2 and not Is. I don't see a question here.
April 16, 2016

Dr.Bob
I didn't go through your work step by step but I worked the problem from scratch. Using 1.8E-5 for Kb, I obtained the same answer you did. Good work.
April 16, 2016

Chemistry- Dr.Bob
My response below at the original post.
April 16, 2016

Chemistry
Yes, 8. something is right (I think I obtained 8.11 and I used 4E-4 for Ka for HNO2.
April 16, 2016

Chemistry
I estimated the pH and didn't come close to 11 or 12 but I may not have used the same Ka value you did. Most tables in text books don't agree. Post your work and I'll look at it.
April 16, 2016

Chem
Please don't post just parts of a problem.
April 16, 2016

Chemistry: Buffer Intensity problem
I assume 1 M/pH means 1 mol in a liter for a pH of 1.0 First, determine the ratio of base(b) to acid(a). 4.76 = 4.76 + log (b/a) b/a = 1 or b=a initially. You should confirm that. Than make an ICE table. We will work this backwards since we want to know how much to start with...
April 16, 2016

chemestry
By the way, you need to spell chemistry right also. Further, I don't think this is the first time I've reminded you of that.
April 16, 2016

chemestry
You need to find the caps key on your keyboard AND USE IT. I don't get the s42 stuff. And when you say lead salt in the above you COULD mean Pb(NO3)2 or PbSO4. I will assume you mean PbSO4. Pb^2+ + SO4^2- --> PbSO4. mols Pb^2+ = grams/molar mass = ? Since the ratio is 1...
April 16, 2016

chemistry
Refer to your post just below. Same process. Post your work if you get stuck and tell us what you don't understand. We can help you through it..
April 15, 2016

chemistry
2Na + Cl2 ==> 2NaCl mols Na = grams/atomic mass = ? Using the coefficients in the balanced equation, convert mols Na to mols Cl2. Then use PV = nRT to convert mols Cl2 to volume at the conditions listed.
April 15, 2016

Chemistry
I looked them up on Google. Cl2 is more soluble. At 20 C Cl2 is about 7 g/kg water. For I2 about 1 g/3.5 kg water.
April 15, 2016

chemistry
I have a problem with the problem and I also have a problem with the answer. The answer first. You aren't doubling the volume. Assuming the volumes are additive, and with this concn NaCl they probably are not, the volume is increased from 1.5L to 4.5 L so the new concn is ...
April 15, 2016

Chemistry
It would much easier and certainly simpler for you to show how you solve them. That way we can find the error and understand where you're going wrong instead of us working all of them and you comparing your answers with ours.
April 15, 2016

Chemistry
See my response bedow.
April 15, 2016

Chemistry
I would do this. AgCl(s) ==> Ag^+ + Cl^- Ksp = 1E-10 Ag^+ + 2Cl^---> [AgCl2]^- Kf = 3E5 ---------------------- AgCl(s) + Cl^- --> [AgCl2]^- Keq = Ksp*Kf = approx 3E-5 which is not a large number which means the amount of NaCl will be relatively large. I..0.1....0...
April 15, 2016

chemistry
You want 1.2L or 1200 mL. mass = volume x density = 1200 x 1.15 = approx 1400 grams. Remember to redo these calculations with more accuracy than my estimates. To make 15% solution you need 15 g Pb(NO3)2 in 100 g solution. So for 1400 g solution you will need 15 g x 1400/100 = ...
April 15, 2016

Chemistry
which what? You may be referring to temperature. When comparing what characteristic of CO2 to CO? volume, pressure, size of molecules,mass molecule. I don't have a clue.
April 14, 2016

Chem 1410
Use PV = nRT
April 14, 2016

chemistry
In some cases these are complete questions. But this is a laundry list. We don't do complete assignments. If you will tell us what you don't understand about one or more of these perhaps we can help you through them.
April 14, 2016

Chemistry
Didn't we go over this yesterday? You need to learn to do this. I gave you a link. If you will identify your hang up I can help you through it.
April 14, 2016

Chem LAB
What you have written is already in the form of the net ionic equation.
April 14, 2016

CHEM
This is a limiting reagent problem Do it just as the other LR problem except this is with heat involved. O2 is the limiting reagent. Since the sign of dH is - that means heat is released.
April 13, 2016

Chemisty
mols Cd(NO3)2 = grams/molar mass = ? and M Cd(NO3)2 = mols/L = ? Next,you will need to calculate (OH^-) from 0.800 M NH3. Then Qsp = (Cd^2+)(OH^-)^2 Substitute M Cd^2+ and M for OH^- into Qsp. If Qsp>Ksp, there will ppt. If Qsp<Ksp, no ppt. The idea with Qsp is to see if...
April 13, 2016

chemistry
That's ok but you have too many significant figures in the answer.
April 13, 2016

chemistry
5890 J x (2*23/0.567) = ?
April 13, 2016

chemistry
AgBr in HNO3 is no effect (or the same solubility). You're right, there is no common ion and the only rxn that you need to consider is combination of H with Br. IF (and it isn't) HBr were a weak acid it would be more soluble but since HBr is a strong acid there is no ...
April 13, 2016

chemistry
Le Chatlier's Principle says that when a system at equilibrium is disturbed it will shift so as to undo what we've done it it. AgBr in 0.1 M HBr. ......AgBr ==> Ag^|Using the balanced chemical equation, calculate the equilibrium constant for this system. AgBr(s) ==&...
April 13, 2016

chemestry
This is a limiting reagent (LR) problem and you know that because amounts are given for BOTH reactants. First, make sure the equation is balanced. mols H2O2 = grams/molar mass = ? mols N2H4 = grams/molar mass = ? Next, using the coefficients in the balanced equation, convert ...
April 13, 2016

chemestry
Where is the equation? And please spell chemistry right next time.
April 13, 2016

@ color wheel--Chemistry
How many mols do you want? That's M x L = ? Then mols = grams/molar mass. You know mols and molar mass; solve for grams. What you want to do is weigh out that amount of Cu(NO3)2.3H2O, place it in a 100 mL volumetric flask, add some water, swirl to dissolve all of the salt...
April 13, 2016

Chemistry
No. The reaction takes place at 25 C so the Keq will Keq at 25C. The problem doesn't make that clear. If the problem were stated correctly it would say, "Using the balanced chemical equation, calculate the equilibrium constant for this system at 25 C."
April 13, 2016

Chemistry
Kat, this is nothing more than plugging the numbers into the Keqp expression and evaluating it. What do you not understand about it. The Keq expression you wrote is correct.
April 13, 2016

Science
See your post below.
April 13, 2016

Chemisty
See your post above.
April 13, 2016

chemistry
mols H2 gas = grams/molar mass. Then each mols has 6.02E23 molecules. Each molecule has two H atoms. Each H atom has 1 electron, 1 proton and no neutrons.
April 13, 2016

Chemistry
I don't know enough of what you have to be absolutely sure. If that is 43.5 mL H2 gas collected OVER WATER the answer is different that if that's 43.5 mL dry H2 gas. I will assume it is 43.5 mL H2 gas collected over water so here is what you do. PV = nRT. Ptotal = pH2...
April 13, 2016

chem
millimoles Br2 used = mL x M = 4*0.23 = approx 0.9 1 mol Br2 adds to 1 mol alkene; therefore, mmols Br2 alkene = approx 0.9. mols in 50 cc at stp = 50/22,400 and millimols = 50*1000/22,400 = approx 2. % alkene = (mmols alk*100/mmols gas) = ? % alk = mols alkene/
April 13, 2016

Chemistry
What is that 4.2 H2C2O4?).
April 13, 2016

Chemistry
I don't have any idea of what your experiment was. My crystal ball is hazy. I think you should repost this as a physics question and please provide a little info so those physics guys/gals will know what you did.
April 13, 2016

Chemistry
Oxidation is the loss of electrons. Do you know know to determine the oxidation state? H on the left is zero and on the right is +1. N on the left is zero and on the right it is -3. Here is a link that will show you how to calculate the oxidation state. http://www.chemteam....
April 13, 2016

Chemisty
This looks so straight forward. What is your problem with this. Exactly what do you not understand.
April 13, 2016

chemisty
or grams?
April 13, 2016

Chemistry
First I would relabel the bottle as potassium nitrate. Then place some KNO3 in an open dish, place in an oven at 105 degrees C, leave for 2-3 hours (or constant weight if you prefer), place in a desiccator and allow to cool.
April 13, 2016

chemistry
Reverse equation 1 and add to equation 2. Divide the final equation by 2. Add the dH values; when an equation is reversed, change the sign of dH.
April 12, 2016

chemistry
I wonder why phosphoric acid is not as good as hydrophosphoric acid. Also, note that Zn is Zn(II) phosphate etc. 3Zn + 2H3PO4 ==> Zn3(PO4)2 + 3H2 mols Zn = grams/molar mass = ? Using the coefficients in the balanced equation, convert mols Zn to mols Zn3(PO4)2. Then g Zn3(...
April 12, 2016

Chemistry
6 L CO2. Knowing that 1 mol of any gas occupies 22.4 L at STP, then 6/22.4 = ? mols CO2. Then using the coefficients in the balanced equation, that many mols CO2 x 2 = mols HCl used Then M HCl = mols HCl/L HCl = ?
April 12, 2016

Chemistry
Is that an aqueous solution? 1337.6 kJ/0.0125 = ? kJ = heat released by 1 mol MgO I didn't check the mol calculation for MgO.
April 12, 2016

Chemistry
Do you mean 0.052 molar? pH = -log(HCl) = -log(0.052M) = ?
April 12, 2016

Chemistry
http://www.jiskha.com/display.cgi?id=1460431080
April 12, 2016

Chemistry
This is the H2A problem and I worked that for you re the link for the post just above.
April 12, 2016

Chemistry
You have no concns listed so you can't get Keq that way. Use dGo = -nEoF You will need to look up the value of Eo for the reaction. Obviously the one with Eo a positive number will give you a negative dGo and that is the one that is spontaneous. If you want Keq, you can ...
April 12, 2016

Chemistry
Is D density? Zn + 2HCl ==> ZnCl2 + H2 Calculate mols Zn and convert to mols H2. Then use PV = nRT P will be 1.234 atm - vp H2O (in atm)[or convert 1.234 atm to mm Hg and use 21.0 mm for vp H2O) Everything else is as usual and V will be ihn liters.
April 12, 2016

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