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March 30, 2017

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Posts by drbob222

Total # Posts: 54,305

chemistry
I believe that's 3,3- dimethylheptane
March 28, 2017

Chemistry
I believe you have a typo Both are H2SO4. Did you mean one to be HNO3?
March 28, 2017

Chemistry
Use the Henderson-Hasselbalch equation, use pKa for acetic acid of 4.76 (I think but you should confirm that), then solve for (base)/(acid)
March 27, 2017

Chemistry
Follow the size of the anion.
March 27, 2017

chemistry
The short way is this. 3.238 x (molar mass what of you want/molar mass of what you have) = ?
March 27, 2017

Chemistry
I agree
March 26, 2017

AP Chem
No. K is K. It changes ONLY with temperature. Ksp is given Kf is given. If you wonder how I know Keq is Kf*Ksp, here is what you do. Write the Ksp expression and multiply that by the Kf
March 26, 2017

AP Chem
Fe(OH)2 ==> Fe^2+ + 2OH^- Ksp = ? Fe^2+ + 6CN^- ==> [Fe(CN6]^4 Kf = ? -------------------------- Fe(OH)2+ 6CN^- => Fe^2+ +2OH^- +[Fe(CN)6]^4- CN^- is the ligand Keq for the rxn as shown is Kf*Ksp = ?
March 26, 2017

Chemistry
Right b will increase it for the reason you cite. Adding HCl certainly will increase the solubility. CuCO3 ==> Cu^2+ + CO3^2- You will not that adding HCl reacts with the CO3^2- to form H2CO3 which then decomposes to H2O and CO2. So decreasing the (CO3^2-) forces the ...
March 26, 2017

Chemistry
This is Le Chatelier's Principle. What do you not understand about. D it? Do you have any ideas what to do?
March 26, 2017

Chemistry
No and no. First, the volume will be 200 mL ONLY IF the volumes are additive and they are not(but they will be so close you will call that being picky). If you assume they are additive then the final concn will be 2.00 M x (100 mL/200 mL) = ? Just a note: If you add 50 mL ...
March 26, 2017

Chemistry
You want twice the reverse reaction given in the problem. So that's -(-286)*2 = ?
March 26, 2017

Chemistry
No but I'm having a little trouble understanding the problem. Look up the dHo formation for NH3. I'll call that x. IF THE problem is asking for dH rxn it is N2(g) + 3H2(g) ==> 2NH3(g) + 2x kJ BUT IF THE problem wants dHo formation for NH3/mol it is 1/2 N2(g) + 3/2 ...
March 26, 2017

Chemistry
The problem says so much heat is EVOLVED. That means that much heat is released so the sign is negative. However, I would redo the numbers. My calculator reads slightly over 560 ane 570. Also, note that you made a typo on the last line but you plugged in the right number.
March 26, 2017

Chemistry
Looks ok to me.
March 26, 2017

Chemistry
The problem is poorly worded. If you answered correctly you would answer, carbonate, sulfite, nitrate, bromate, chlorate, iodate, and phosphite. By merging those into answers both B and D are correct. Check to make sure there isn't a typo. That might be bromite or ...
March 26, 2017

Chemistry
That's right. Nitrite(NO2-) and hypochlorite(ClO-) and sulfate [SO4]^2- don't have 3. B is OK. Isn't D OK too?
March 26, 2017

Chem
Add equation 1 to the reverse of equation 2. I did this in my head so write it down and confirm it before proceeding.
March 26, 2017

Chemistry
Looks ok but I didn't check the calculation.
March 26, 2017

Chemistry
The equation is correct. Br2 in the elemental state is a liquid. It vaporizes easily and boils about 60C.
March 26, 2017

Chemistry
Add 0.02 mol HCl to 1L means (H^+) = 0.02M .......CN^- + H^+ ==> HCN I....0.150....0.......0.2 add.........0.02......... C...-0.02..-0.02......+0.02 E....0.130...0.......+0.22 (HCN) = 0.22M assuming the HCl was added as a gas
March 26, 2017

AP chem
Here are tutorials on each phase of the redox process you may need. If you had shown your work I could hav found your problem easily. As it is I have no idea what you're doing wrong. The equation you posted isn't balanced, though, so you know it can't be right. ...
March 26, 2017

Chemistry
(P1V1/T1) = (P2V2/T2) Remember T must be in kelvin.
March 25, 2017

Chemistry
mols benzoic acid = grams/molar mass = ? Then q = mols benz acid x Ccal(delta T) q is +3238 kJ. Substitute and solve for Ccal.
March 25, 2017

chem
That won't get it. We HELP you do your homework; we don't do it for you. I told you how to work the problem. If you don't understand, show what you've done or explain what it is you don't understand. I'll be glad to help you through it but I won't ...
March 25, 2017

Chemistry
Yes and no. Yes, the correct number is 572 kJ/reaction (not /mol since it's for two mols) AND I don't think you should call it dHo. dHo is -285 kJ/mol is for the H2 + 1/2 O2 ==> H2O. When you turn it around it becomes for the reaction and multiplying by 2 makes is ...
March 25, 2017

Chemistry
Right except for the typo. It's Al and not A in one of the equations.
March 25, 2017

chem
No that isn't right and I don't know how you obtained that. For converting to kelvin, it is 61+273 (61+273.15 if you want to be exact about it). Now you plug those values in to the formula I gave you and solve for T2. The answer will be in kelvin.
March 25, 2017

chem
V1/T1 = V2/T2 Remember T must be in kelvin.
March 25, 2017

Chemistry
See your other post.
March 25, 2017

Chemistry
Please don't change you screen name. It makes is difficult to know how to answer your question the best way. Use p1v1 = p2v2 v1 is 0.5L v2 is 2.0 L
March 25, 2017

Chemistry
Your first calculation of P = 740.2 mm pressure for the pure (dry) gas is correct. The last part involving P1V1 = P2V2 isn't and I don't think you can calculate a volume of the H2 gas because you list no volumes in the problem. The numbers you have substituted are ...
March 25, 2017

Chemistry
I agree EXCEPT that isn't B.
March 24, 2017

chemistry
Use V = nRT. Substitute and solve for n.
March 24, 2017

chemistry
I will assume the Keq given is for the reaction Fe^3+ + SCN^- ==> [FeSCN]^2+ K = [FeSCN]^2+/[Fe^3+][SCN^-] Substitute the numbers in the problem and calculate the only unknown there.
March 24, 2017

Chemistry
See your other post under Coolest.
March 24, 2017

Chemistry
See your other post.
March 24, 2017

chemistry
Qp = (SO3)^2/(SO2)^2(O2) = 3.70E7 so reverse is correct.
March 24, 2017

Chemistry
q = mcdT 1.4E3J = mass sand*specific heat sand*(Tfinal-Tinitial). You need to know the specific heat of the sand. Then plug in the numbers and solve for mass sand.
March 24, 2017

chemistry
q = mols ether x Hvap. mols = grams/molar mass = ? You know Hvap and can solve for mols. Substitute and solve for q.
March 24, 2017

chem
(P1V1/T1) = (P2V2/T2) Remember T must be in Kelvin.
March 23, 2017

chemistry
P1V1 = P2V2 V1 = 0.5 V2 - 2.0
March 23, 2017

chem
You can do also by using P1V1 = P2V2 P1 = 1.08 atm and P2 = 1.08+0.25*1.08 = ? V1 is given. Solve for V2
March 23, 2017

Chemistry
I didn't check the math but the method looks ok to me.
March 23, 2017

Chemistry
I don't believe you can do that. C(s) + H2O(g) ==> CO2(g) a. The equation is not balanced. b. In those equations to be used you don't have H2O(g) anywhere but only H2O(l) c. The equation you have posted isn't balanced. You're OK with C but O doesn't ...
March 23, 2017

Chemistry
I disagree with both of you. A) 2CH3OH(l) + 3O2(g) --> 4H2O(l) + 2CO2(g) 3 mols gas goes to 2 mols. Not expanding so it isn't A. B) S(s, rhombic) + O2(g) --> SO2(g) Can't be B. 1 mols gas on left goes to 1 mol gas on the right. Volume stays the same. Not ...
March 23, 2017

Chemistry
Step 1. Write and balance the equation. The one you have is incorrect. I have corrected it. 2Pb(NO3)2 ==> 2PbO + 4NO2 + O2 Step 2. Convert what you have to mols. mols Pb(NO)2 = grams/molar mass = ? Step 3. Convert mols of what you have to mols of what you want. Use the ...
March 23, 2017

Chemistry
I suppose you want to know the mass of H2O but you don't ask it directly. Heat lost by Fe + heat gained by H2O = 0 Note: sph = specific heat [mass Fe x sph Fe x (Tfinal-Tinitial)] + [mass H2O x sph H2O x (Tfinal-Tinitial)] = 0
March 22, 2017

Chemistry (Ochem)
I don't think so. Sterocenter refers to the "atom" that causes the molecule to be a stereoisomer while stereochemistry refers to the SUBJECT.
March 22, 2017

Chemistry
I think both of you are right.
March 22, 2017

Chem
The shape of the water molecule is what makes it polar.
March 22, 2017

Chemistry
Good for you. Keep up the good work.
March 22, 2017

Chemistry
Won't work. Check your post. c is not balanced; i.e., no H on the left. Check the others, too. I didn't check them.
March 22, 2017

chemistry
Write and balance the equations for H2 + O2 ==> C + O2 --> CH4 + O2 ==> Reverse 3 and add to 1 and 2. See if you don't get C + 2H2 ==> CH4.
March 22, 2017

Chemistry
a. mols PbO2 = grams/molar mass = ? b. 1 mol PbO2 produces 1 mol Pb; therefore, mols Pb = mols PbO2. c. grams Pb = mols Pb x atomic mass Pb. Remember this. This will work all of your stoichiometry problems. Step #1 is to write the balanced equation but you already had that.
March 22, 2017

Chemistry
Helium is the lighter gas (density less and atomic mass/molar mass less) so it will pass through the whole faster. You don't need a pinhole, either. Helium is small enough that it will pass through the pores of the balloon over a day or so.
March 22, 2017

Chemistry
mols N = 0.606/14 = about 0.043 mols O = 1.39/16 = about 0.087 Now find the ratio. The easy way to do that is to divide each number by the smaller number. N - 0.043/0.043 = 1.00 O = 0.087/0,043 = 2.02 and rounds to 2. It may come out a little closer if you do the calculations ...
March 21, 2017

chmistry
What about it.
March 21, 2017

chemistry
PV = nRT and solve for n = mols. Then mols = grams/molar mass. You have mols and grams, solve for molar mass. Remember K must be in kelvin and P must be in atm if you use R as 0.08206
March 21, 2017

Chemistry
Dream on. What is your main issue with these. I can give you a web site or you can tell me what your main problem is. I will glad to help you through these but I won't balance them for you.
March 21, 2017

chemistry
sph = specific heat heat lost by Fe + heat gained by Au = 0 [mass Fe x sph Fe x (Tfinal-Tinitial)] + [mass Au x sph Au x (Tfinal-Tinitial)] = 0 Solve for Tfinal
March 21, 2017

Chemistry
You do this the same way as the Tom post. We prefer you don't change screen names.
March 21, 2017

chemistry
Mg + 2HCl ==> H2 + MgCl2 mols Mg = grams/atomic mass = ? Using the coefficients in the balanced equation, convert mols Mg to mols HCl.That's 1 mol Mg = 2 mol HCl Now M HCl = mols HCl/L HCl. You know mols HCl and M HCl, solve for L HCl and convert to cc3 (mL).
March 21, 2017

chemistry
I responded to your question about how to solve the two equations simultaneously at the initial post. The answer is there.
March 21, 2017

Chemistry
(S2) = mols/L = 8.9/5.00 = approx 1.8 but you need a better number than that. Recalculate all that follows. ......S2 + C(s) ==> CS2 I....1.8............0 C.....-x............x E....1.8-x..........x Note that C does not appear in the Kc expression because it is a solid. Kc...
March 20, 2017

Chemistry
Where did you come up with the Kc expression? It should be Kc = [FeSCN]^2+/(Fe^3+{)(SCN^-). Kc = [3.49E-5]/[4.39E-4][1.93E-5]\ 411.9 which rounds to 412. :-)
March 20, 2017

chemistry
See your previous post. Make sure P1 and P2 are in the same units. 1 atm = 760 mm. Post your work if you get stuck.
March 20, 2017

Chemistry
(P1V1/T1) = (P2V2/T2) Make sure V1 and V2 are in the same units. I would change 2 atm and use P1 as 760 x 2 = ? torr. That way the asnwer will come out in torr.
March 20, 2017

Chemistry
mols CaCl2 = M x L = ? mols X2CO3 = mols CaCl2 from the 1:1 ratio. mols (CO3)^2- = mols X2CO3 = mols CaCl2.
March 20, 2017

chemistry
Na2CO3 + 2HCl ==> 2NaCl + H2O + CO2 Going to the methyl orange end point titrates ALL of the Na2CO3. Titrating to the phenolphthalein end point titrates just 1/2 of it; i.e., to NaHCO3.
March 20, 2017

Chemistry
Pb(NO3)2(aq) + Na2SO4(aq) ==> PbSO4(s) + 2NaNO3(aq)
March 20, 2017

chemistry
Write some of the hydrocarbon rxns with oxygen. All give CO2 + H2O. The problem would be easier if you were given cc H2O (as a gas) but if you don't have that I would do this. CH4 + 2O2 ==> C2 + 2H2O C2H6 + 7O2 ==> 4CO2 + 6H2O C3H8 + 5O2 --> 3CO2 + 4H2O 2C4H10 + ...
March 20, 2017

chemistry
mols HCl - M x L = ? Equn is HCl + NaOH ==>NaOH + H2O so the ratio is 1 mol HCl to 1 mol NaOH. That means mols NaOH = mols HCl and you have that from above. Then M NaOH = mols NaOH/L NaOH. you have M and mols, solve for L and convert to mL.
March 20, 2017

chemistry
Wouldn't that be X2O3? X + O2 ==> X?O? 1.0L 1.5L Two ways: 1 short, 1 long. 1/22.4 = 0.446 mols X 1.5/22.4 = 0.067 mols O2 or 0.134 O Find the ratio. 0.0446/0.0446 = 1.00 0.134/0.0446 = 3.00 XO3. Short way: When dealing with gases we get mols by dividing by 22.4L (at ...
March 20, 2017

chemistry
I've gone through this time and time again and something isn't clicking. Here is the way to do it BUT the answers are not reasonable. %B = (6.1/29)*100 = 21.03 %Cl = (22.9/29)*100 = 78.97 Take 100 g sample which then gives you 21.03 g B and 78.97 g Cl. mols B = 21.03/...
March 20, 2017

Chemistry
Please use the same screen name. First we get confused. Second it takes us longer to sort things out. Third you're asking the same type question which is a waste of time. delta T = Kf* molality You know delta T. Look up Kf for benzene. Substitute and solve for molality. ...
March 20, 2017

Chemistry
Proof your question. You've made a typo. I think you must have meant -0.73 C.
March 20, 2017

chemistry
c. mols HCl = M x L = ? mols CaCO3 = 1/2 that grams CaCO3 = mols x molar mass = ? d. See my other response and plug in the numbers.
March 20, 2017

chemistry
The problem is a little more complicated because it wants mL (not mols or millimols). a. Excess acid = millimols NaOH = mL x M = 15.3 x 0.7034 M NaOH. I'll leave it to you to calculate how many mL HCl that is. b. mL HCl used in the neutralization was 30 mL - mL from part a...
March 20, 2017

Chemistry
How much Pb(NO3)2 is contained in the 4.5 dm^ at 70 C? That's 2.25 mols x 4.5/1.33 = approx 7.5 but you need a more accurate number. Now you have 4.5 dm^3 containing about 7.5 mols Pb(NO3)2 at 70 C. You cool it to 18 C where the solubility is lower. How much can that 4.5 ...
March 20, 2017

Chemistry
Yes. Isn't that what the equation says? Ca(OH)2 ==> Ca^2+ + 2OH^- So if you know the OH from Ca(OH)2 then 1/2 that is Ca^2+. By the way you should write Ca(OH)2 right; the way you write it is not right and I know what it is only because I've been working with the ...
March 20, 2017

Chemistry
I'll try to take care of both questions but it may be confusing to try t answer both with one post. For #3, yes, solubility Ca(OH)2 is (Ca^2+). You have total OH and you have OH from the NaOH. The difference is the OH from the Ca(OH)2 itself. 1/2 the OH from Ca(OH)2 gives ...
March 20, 2017

Chemistry
http://www.jiskha.com/display.cgi?id=1489957110
March 20, 2017

Chemistry
mL1 x M1 = mL2 x M2 40 x 0.045 = mL2 x 2.1 Solve for mL2 of the stock to take.
March 19, 2017

Chemistry
Use the Henderson-Hasselbalch equation. You SHOULD use M for acid and base BUT you can use a shortcut and save some time by using mols. However, make sure your prof will allow you to do take that shortcut. mols acid = M x L = 0.025 x 0.2 = ? mols base = 0.015 x 0.150 = ? ...
March 19, 2017

Chem
That's math, not chemistry. :). To make it easy typing let me call the acetic acid, a (for acid) and the sodium acetate, b (for base). So eqn 1 is pH = pKa + log b/a eqn 2 is a+b = 0.05 Substitute into eqn 1 as follows: 5.00 = 4.76 + log b/a 5.00-4.76 = log b/a 0.24 = log ...
March 19, 2017

Chem
pH = pKa + log (Ac^-)/(HAc) Plug in pH, pKa, and solve for (Ac^-)/(HAc). That is equation 1. Equation 2 is (HAc) + (Ac^-) = 0.05 Solve equations 1 and 2 simultaneously to find (Ac^-) and (HAc). Then mol HAc = M x 0.250 = ? and mols NaAc = M x 0.25 = ? The above gives you the ...
March 19, 2017

chemistry
Look up these values. Zn(s) ==> Zn^2 + 2e.....E = ? Ag^+ + e ==> Ag(s)......E = ? Add the two E values to find Ecell, then multiply by 4 since they are in series.
March 19, 2017

A.P Chemistry
dG = dH - TdS If dG = 0, then TdS = dH. Solve for T. Watch the units. dH is in kJ/mol and dS in J/mol
March 19, 2017

Chemistry
1. Cells in series adds the voltage. 2. You didn't provide enough information about the set up for me to answer.
March 19, 2017

chemistry
I would think the rxn is amost at 100% now; however, adding more OH^- (from NH3 + H2O ==> NH4^+ + OH^-) would add more OH to the left, the rxn would need to try to reduce the OH^- and it can do that by forming more Mg(OH)2(s). So to the right.
March 19, 2017

Reposting Chemistry Question -Emergency !!
I don't remember the former post but I think you said to #1, "do I just calculate this from the HCl" and the answer is yes. My assumption is that you used the saturated soln of Ca(OH)2 but it had no solid in it that was titrated. Total millimols OH^- = mL HCl x M...
March 19, 2017

Chemistry
3Mg + N2 ==> Mg3N2 Look at the coefficients. 3 mols Mg gives 1 mol Mg3N2; therefore, 1 mol Mg will give ..... mol Mg3N2.
March 19, 2017

Chemistry
First you must calculate the M of the salt, NaAc (sodium acetatate) at the equivalence point. That will be millimols/mL. mmols NaAc = 25 x 0.1056 = approx 2.6 but you should do it more accurately. Since the M NaOH is the same you know it will take 25 mL of the NaOH; therefore...
March 19, 2017

Chemistry Explanation??
Ca(OH)2 ==> Ca^2+ + 2OH^- and Ksp = (Ca^2+)(OH^-)^2 Ksp is a constant. NaOH is a strong base and ionizes 100%; therefore, NaOH ==> Na^+ + OH^-. Le Chatelier's Principle tells you that when the OH^- increases, due to the NaOH, the Ksp equilibrium of Ca(OH)2 is forced ...
March 19, 2017

Chemistry
Total of all atoms in C6H12 must be zero. H is +1 and that x 12 = +12. Then 6 C must be -2 each. C = 6*-2 = -12 H = 12*+1 = +12 total = 0 Remember oxidation number is a bookkeeping method.
March 19, 2017

Chemistry 2202
method 1: NaOH + HCl ==> NaCl + H2O mols NaOH = M x L = ? mols HCl = mols HCl (look at the equation; note 1 mol NaOH = 1 mol HCl) Then M HCl = mols HCl/L HCl = ? method 2: NaOH + HCl ==> NaCl + H2O Note 1 mol NaOH = 1 mol HCl mL NaOH x M NaOH = mL HCl x M HCl Substitute ...
March 19, 2017

Chemistry
(P1/T1) = (P2/T2) Substitute and solve for P2. Remember T MUST be in kelvin.
March 19, 2017

Chemistry
If this is REALLY 906 kJ/MOLE that is 906 kJ/17 g NH3. Then 17 x (500/906) = ? g NH3 required.
March 18, 2017

Chemistry
dHrxn = [(n*dHfo CO2 + (n*dHfo H2O]-[n*dHfo C4H10] You know all of the numbers except for dHo C4H10. Substitute and solve for that.
March 18, 2017

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