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September 18, 2014

Posts by DrBob222


Total # Posts: 43,860

chemistry
If the volume decreases (by say a factor of 2) that will double the (PH3) and double (BCl3). For a factor of 1.774 concn will be increased for EACH by 1.774. Remember the solid doesn't appear in Kc. Kc = 1/(PH3)(BCl3) So Kc > Q = 534.8/(1.774)(1.774)
May 6, 2014

chemistry
Do you mean for this reaction be be written as N2 + O2 ==> 2NO with Kc = 2400. That's the way you have your arrows.
May 6, 2014

chemistry
Substitute the equilibrium concentrations given in the problem into the Kc expression and solve for K.
May 6, 2014

chemistry
q = mols H2O x molar heat capacity x (Tfinal-Tinitial)
May 6, 2014

Chem 130
You need to find the arrow key and use it. mols CaCO3 = grams/molar mass Using the coefficients in the balanced equation, convert mols CaCO3 to mols CO2. Now convert mols CO2 to grams CO2. g = mols x molar mass
May 5, 2014

Chem 130
You have a 100 L tank and you want to fill it with He to a pressure of 155 atm at 22 C. This problem is two problems in one. One for He and the other for H2. Here is the He one done for you. It's just a matter of substituting into PV = nRT and using n for solve for grams. ...
May 5, 2014

Chem 130
Use PV = nRT and solve for n in each tank. Then n = grams/molar mass. You know molar mass and n, solve for grams in each tank.
May 5, 2014

chemistry
Ptotal = pO2 + pH2O You know Ptotal and pH2O, solve for pO2. Note Ptotal and pH2O are not in the same units.
May 5, 2014

Chem 130
Ptotal = pO2 + pH2O You know Ptotal and pH2O, solve for pO2.
May 5, 2014

Chemistry
%Z(w/w) = (g Z/total grams)*100 = ? where total grams = gX + gY + gZ
May 5, 2014

Chemistry
dHsurr = -dH/T
May 5, 2014

Chemistry
Is that 2.6M HCl? I will assume so. Zn + 2HCl ==> ZnCl2 + H2 How many mols H2 is that? Ptotal = 845 torr pH2O at 65C = approx 190 torr. You need to look up this value in your text/notes because I've estimated it from some tables I have. pH2 = 845-190 = about 655 mm or ...
May 5, 2014

Chemistry
See your other post.
May 5, 2014

Chem 130
mols He = 2.03/molar mass He = n1 mols He = 6.19/molar mass He = n2 (n1/12L) = (n2/xL) Solve for x L.
May 5, 2014

Chemistry
............MgF2 ==> Mg^2+ + 2F^- I...........solid.....0.......0 C...........solid.....x.......2x E...........solid.....x.......2x Ksp = (x)(2x)^2 You know x = 2.3E-3M.Substitute and solve for Ksp.
May 5, 2014

Chemistry
Let's call aniline BNH2 ...........BNH2 + HOH ==> BNH3^+ + OH^- I..........0.201...........0........0 C...........-x.............x........x E.........0.201-x..........x........x Kb = (BNH3^+)(OH^-)/(BNH2) You know x. Substitute into Kb expression and solve for Kb.
May 5, 2014

Chemistry - Science (Dr. Bob222)
I worked through it and came up with 1.09v also. 1.13 seems to be the closest ad I would go with that. Sometimes answer sheets give approximate answers and this could be one of them. If I'm missing something I don't see it.
May 5, 2014

chemistry
Use PV = nRT and solve for P (in atmospheres) and convert to mm Hg. 1 atm = 760 mm Hg. Don't forget T must be in kelvin.
May 5, 2014

Organic CHM II
http://lipidlibrary.aocs.org/Lipids/tag2/index.htm
May 5, 2014

chemistry: please check work
I agree with the procedure as well as the value and the number of significant figures.
May 5, 2014

Chemistry
http://en.wikipedia.org/wiki/Delocalized_electron
May 5, 2014

chemistry
What do you need help with? The lower concn will be the increasing and the higher concn will be decreasing until both have the same concn. So you know the lower concn will be oxidized and the higher concn will be reduced.
May 5, 2014

Chemistry
No, of course you don't know the final T. That's what you're trying to find. It ways that in the problem, "What is the final T if ..." heat lost by Ni + heat gained by H2O = 0 [mass Ni x specific heat Ni x (Tfinal-Tinitial)] + [mass H2O x specific heat ...
May 5, 2014

Chemistry
You can but that's the hard way to do it. It is much easier to substitute the individual numbers and work it out by pieces.
May 5, 2014

Chemistry
heat lost by Ni + heat gained by H2O = 0 [mass Ni x specific heat Ni x (Tfinal-Tinitial)] + [mass H2O x specific heat H2O x (Tfinal-Tinitial)] = 0
May 5, 2014

Chemistry
You want 1 mol SO3 and not 2 so divide by 2. You want the reverse so change the sign.
May 5, 2014

Chem Check Please!!!
I disagree with 1. I agree with 2,3,4. I con't see all of the name typed on 5 but e is right if that is chromium IV.
May 5, 2014

Chemistry
It's twice dHof
May 5, 2014

Chemistry
zero or very low
May 5, 2014

Chemistry
Take equation 1 and add it to the reverse of equation 2 and add that to the reverse of 1/2 equation 3. When reversing dH, change the sign. When taking 1/2 equation, also take 1/2 dH.
May 5, 2014

chemistry
Q = coulombs = amperes x seconds Q = 0.680A x 20m x (60s/m) = ? = about 816 96,485 coulombs will deposit (63.54/2)g Cu. You have 816 coulombs; therefore, 63.54/2 x (816/96,485) = about 0.3g if I punched the right buttons.
May 5, 2014

Underwater explosion
Other tutors may wish to weigh in on this question but I think the answer is yes IF the timing is just right and the compressed air force can be sustained long enough.
May 5, 2014

Chem
This is an example of a back titration; i.e., the KI/KIO3 produces I2, the I2 reacts with some of the vit C, the excess I2 is titrated with thiosulfate. 6H^+ + I^- + IO3^- ==> 3I2 + 3H2O Then vitC + I2 ==> 2I^- + vitCx mols IO3 added initially = M x L = 0.025 x 0.01988...
May 5, 2014

chemistry
The question isn't exactly clear; it isn't clear that it is the greatest amount of acid per grams antacid or per mol antacid. H^+ + OH^- ==> H2O So the one with the largest OH per mol will neutralize the most acid. That is Al(OH)3. And you don't capitalize ...
May 5, 2014

chemistry
Wouldn't that be 100g/5 dm^3 = 20g/dm^3
May 5, 2014

Chemistry
No, the problem says to write the equilibrium constant expression. Nothing about finding the value of K.
May 5, 2014

Chemistry
What is your problem with these. Keq expressions are the same. K = (products)^x/(reactants)^y and raise each substance to the power indicated by the coefficient.
May 5, 2014

chemistry
How many mols do you want? That's M x L = ? Then mols = grams/molar mass. You know molar mass and mols, solve for grams.
May 5, 2014

chemistry
mols acetic acid = grams/molar mass, then M acetic acid = mols/L
May 5, 2014

chemistry
M = mols/L
May 5, 2014

chemistry
See your post above.
May 5, 2014

Chemistry
Yes you do exactly what you have outlined. I would look at change in C and change in O for n. If we see ethanol as C2H6O and assign oxiatioin states of -2 for O and +6 for 6H, that makes 2 C in ethanol as -4. On the right the 2C are +8 so the change in e is 12. We can check ...
May 5, 2014

chemestry
I suggest you google these terms.
May 5, 2014

Chemistry
Same process. Write the balanced equation. Convert g CO2 to mols with mols = grams/molar mass. Use the coefficients to convert mols CO2 to mols HCl. Then M HCl = mols HCl/L HCl.
May 5, 2014

Chemistry
Na2CO3 + 2HCl ==> 2NaCl + H2O + CO2 mols Na2CO3 = M x L = ? Using the coefficients in the balanced equation, convert mols Na2CO3 to mols HCl. Then the defintion of M HCl = mols HCl/L HCl. You know M and mols, solve for L.
May 5, 2014

science
L1 x %1 = L2 x %2 ?L x 0.8% = 0.5L x 9% ?L = ?
May 5, 2014

what is the answer
Set up a ratio and proportion. (feet/shadow) = (feet/shadow) (8.1/24.3) = 20.1/x) Solve for x.
May 4, 2014

chemistry
The temperature at which water boils at high altitudes is lower than the temperature it boils at lower altitudes. Therefore, when cooking on a high mountain the water may boil 98 instead of 100 C so you should boil it (less, more). 2. Water boils when water boils. Turning up ...
May 4, 2014

Chemistry
NOPE. You changed SO4^2- on the right to S2O4^2- and you can't do that. Also you have the e on the wrong side. Other than that it is ok. 2OH^- + SO3^2- ==> SO4^2- + 2e + H2O
May 4, 2014

Chemistry
I shall be glad to help you through this but you need to learn to do these yourself. I do these the looong way. The first step is to determine the oxidation step of each element. I will help you here. S on the left is +4 and on the right is +6. Add electrons to the appropriate...
May 4, 2014

chemistry
It will take mass H2O x heat vaporization to turn the 30g into steam at 100 C.
May 4, 2014

Chemistry
This one is right. If you haven't already do so go back and look at the sulfite ==> sulfate because the one is not right.
May 4, 2014

Chemistry
I think the trouble you are having is caused by not putting the charges in. That H on the right should be 4H^+. The MnO4 on the right should be MnO4^-. When you do that the e need on the right is not 8 but 3 so the charge on the left is zero and on the right is (-1+4-3) = zero...
May 4, 2014

Chemistry
Again you need to learn to do these. Mn on the left is +4 and on the right is +7. Cu on the left is 2+ and on the right is zero. Balance the electron change first. Mn on the left goes to Mn on the right with ? change of e. Cu on the left goes to Cu on the right with ? change ...
May 4, 2014

CHEMISTRY
I worked this for you yesterday.
May 4, 2014

Chemistry
mols malic acid = grams/molar mass M = mols/L solution.
May 4, 2014

Chemistry
I worked it using the numbers you provided and came up with the same answer you did of 0.963 so there is nothing wrong with your math. The problem is that the reduction potential of Ni is not 0.26. It is -0.26.
May 4, 2014

chemistry
I don't believe you didn't know how to do any of this. 1. delta Tb = impure b.p.- pure b.p. 2. delta T = Kb*m Substitute and solve for m. 3. Isn't the mass given in the problem. Convert to kg. 4. m = mols/kg solvent. You know m and kg solvent, solve for mols
May 4, 2014

chemistry
See your post above.
May 4, 2014

chemistry
I suggest you read these things before you post them. You provided absolutely no information other than it is in the introductory information. But I don't see any introductory information.
May 4, 2014

Chemistry
You say you've looked up these values. My values won't be the same as yours because I'm using an old book but they will be close. Here is how you do the first one. Cr==> Cr^3+ + 3e You look in your table and find this potential. It will be listed "backwards...
May 4, 2014

chemistry
(H3O^+) = (A^-)
May 4, 2014

chemistry
pH = -log(H3O^+) 4.95 = -log(H3O^+) -4.95 = log(H3O^+) Another way of writing this is (H3O^+) = 10^-4.95 Solve for (H3O^+)
May 4, 2014

chemistry
An interesting problem. Three equation and three unknowns but we can work it around with just two since these are related. Let X = mass BaO and Y = mass CaO and mm stand for molar mass. ---------------- eqn 1 is X + Y = mass whatever that may be. Convert to sulfates and you ...
May 4, 2014

chemistry
Mg + 2HCl ==> MgCl2 + H2 mols Mg = X mols H2 produced = X (look at the coefficients; 1 mol H2 produced for 1 mol Mg used) Volume = mols*22.4L/mol volume 22.4X liters.
May 4, 2014

to Bob P--Chemistry
I've gone cross eyed with these large numbers but I don't believe H and O balance in your equation.
May 4, 2014

Chemistry
2C60H87O23N12P +173O2 ==>120CO2 + 72H2O + 24HNO3 + 2H3PO4 Check this carefully. mols biomass = grams/molar mass Using the coefficients in the balanced equation, convert mols biomass to mols CO2. Now convert mols CO2 to grams. g = mols CO2 x molar mass CO2
May 4, 2014

chemistry
pH = -log(H^+)
May 4, 2014

Chemistry
The easiest way to do these problems is in parts and you need three formulas to do it. q at a phase change; i.e., solid to liquid or liquid to gas. For solid to liquid (melting point) it is q = mass solid x heat fusion. For liquid to gas (boiling point) it is q = mass liquid x...
May 4, 2014

CHEMISTRY
I worked this for you last night. Did you look at that?
May 4, 2014

chemistry
I believe you forgot the coefficients (e.g. 8). 8CH4 ==> C8H8+ 12H2 dGfrxn = (n*dGfC8H8 + n*dGfH2)-(n*dGfCH4) 620.735 = [(1*214.417) + (12*0)] - (8*dGfCH4) 620.735 = 214.417 + 0 - 8x Solve for x.
May 3, 2014

Chemistry
dH = mass H2O x specific heat H2O x (Tfinal-Tinitial) This will give you the enthalpy change for the reaction as stated in the problem and that is for 0.05g P. Generally these problems don't want that; they want the enthalpy change per mol but this problem doesn't ask ...
May 3, 2014

chemistry
I suppose you are to use M and m as the same. 0.121g/100 gH2O = solubility. mol N2O = 0.121/60 = approx o.002 and 0.002/0.1kg solvent = 0.02m p = KcC 1 atm = Kc*0.02 Kc = 1 atm/0.02 = 50 atm/m p = KcC 1.600 = Kc from above *C Solve for C in molality and convert to g/100 if ...
May 3, 2014

Science
In warmer climates the winters are warmer. The moisture from a hot shower is in the form of vapor (gas); however, it could be a liquid if it hasn't had time to completely vaporize and the water droplets are still visible (and you can feel those droplets on the skin).
May 3, 2014

Chemistry
mols H2SO4 = M x L = approx 0.1 mols NaHCO3 = M x L = approx 0.05 2NaHCO3(aq) + H2SO4(aq) ==>Na2SO4(aq) + 2H2O(l) + 2CO2(g) This should get you started. Post your work if you get stuck and clearly explain what you don't understand.
May 3, 2014

Chemistry
m = mols/kg solvent 2.0 = mols/3.5 Solve for mols, then mol = grams/molar mass. You know m and molar mass, solve for grams.
May 3, 2014

Chem Check Please!!!
I don't agree with 4. I agree with 5 and 6.
May 3, 2014

Chem Check Please!!!
I don't agree with 2. I agree with 3.
May 3, 2014

Chem Check Please!!!
I don't agree with #1.
May 3, 2014

Chemistry
I think Ni is initial N. and Nf is final N so the electron is making the transition from N = 1 to N = 2 so this is an absorption but the formula I list is for emission. That won't change frequency or wavelength but it will change the sign of E. delta E = R(1/1 - 1/4) where...
May 3, 2014

Chemistry
Take 100 g sample for 58.5g C 4.1g H 11.4 g N 26.0 g O Convert to mols. I'll use approximations. 58.5/12 = 4.875 4.1/1 = 4.1 11.4/14 = 0.814 26/16 = 1.625 Now find the ratio in small whole numbers with the smallest number being 1.00. The easy way to do that is to divide ...
May 3, 2014

General Chem 2
2Al^3+ + 6I^- ==> 2Al(s) + 3I2(s) dGo = -nFEo n = 6
May 3, 2014

Chemistry - Science (Dr. Bob222)
x = 2 y = 1 How did I do that? V on the left has a oxidation state of +5 and on the right it is +4. S on the left is +4 and on the right is +6. V has changed by 1e S has changed by 2e So V couple must be multiplied by 2 and S couple by 1 to make each lose/gain 2 electrons.
May 3, 2014

Chemistry
mols = grams/molar mass
May 3, 2014

Chemistry - Science (Dr. Bob222)
Thanks. I just didn't think the 50% could be right. The concept behind disproportionation is that an element in an "intermediate" oxidation state (in this case Cu^+ is halfway between Cu below it and Cu^2+ above it) can "react with itself" if the ...
May 3, 2014

chemistry - Science
I would do this. Calculate g Zn that goes into solution and g Cu that are deposited from solution. Coulombs = amperes x seconds = ?. 95,485 coulombs will use (65.4/2)g Zn and deposit (63.5/2)g Cu. Calculate g Zn used, convert to mols, and add to the 0.1 mol already there. ...
May 3, 2014

chemistry - Science
See your other post.
May 3, 2014

Chem Check Please!!!
2 is ok 3 is ok I don't agree with 4.
May 2, 2014

Chem Check Please!!!
1. Cris, I don't agree with C as an answer. Here is the way you keep these straight. Just remember the definition of oxidation and reduction. Oxidation is the loss of electrons. Reduction is the gain of electrons. The substance oxidized is the reducing agent. The substance...
May 2, 2014

chemistry
By the way, it's past my bed time but I'll be around tomorrow.
May 2, 2014

chemistry
87 is right. 37 and 50 are right Check your numbers for PEN. You can't possibly get 74 something. 50 x 1+ is about 50. 37 x 1+ = about 37 and add in a pinch for electron mass and you have AT LEAST 50+37+pinch = 87. And it can't be less than 86.909187 because it LOSES ...
May 2, 2014

chemistry
I can't follow what you've done. I have mass p + mass N + mass e = 87.723173 and that - 86.909187 = 0.813986 amu and that converted to kg = 1.3516563E-27 kg. Let me know if we are on the same page to this point and please show your work for as far as you are and we can...
May 2, 2014

chemistry
How would you answer these and why?
May 2, 2014

Chemistry
d2sp3 but obviously those atoms without d orbitals are not eligible for this.
May 2, 2014

chemistry
You can deposit 196.97/3 = approx 66 g Au with 96,485 coulombs of electricity. So how much will be required to deposit 19.7g 96,485 x (19.7/66) = approx 29,000 coulombs. coulombs = amperes x seconds. Substitute coulombs and seconds and solve for amperes. Note those numbers I ...
May 2, 2014

Chemistry
TiO2 + 2C ==> 2CO + Ti We don't need to make any corrections for molar mass and kg if we keep everything in kg. kg mols C = 14.0/12 = approx 1.17 kg mols TiO2 = 44.0/79.88 = approx 0.5 Using the coefficients in the balanced equation, convert kg mols of each to kg mols ...
May 2, 2014

Science
I'm not positive how to answer this. Certainly b and d are not driven by humans and can be eliminated. Global warming, c, is attributed to human impact so that's a definite yes. A is the one I'm unsure about. The greenhouse effect is the name we have given to gases...
May 2, 2014

CHEM 101
We can't draw pictures, structures, diagrams, etc on this forum.
May 2, 2014

chemistry
CaCO3 ==> CaO + CO2 mols CaCO3 = grams/molar mass. Using the coefficients in the balanced equation, convert mols CaCO3 to mols CO2. Now convert mols CO2 to grams. g = molls x molar mass.
May 2, 2014

chemistry chem science
time in seconds is 35 min x (60 seconds/min) = ? amperes = 160 mA = 0.160 A. Calculate Q = # coulombs = amperes x seconds. Then you know that 96,485 coulombs will deposit 112.4/2 grams Cd (that's molar mass Cd/valence). (112.4/2)g Cd x ?coulombs from above/96,485 = ?
May 2, 2014

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