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December 20, 2014

Posts by DrBob222


Total # Posts: 46,145

Chemistry
Lattice energy generally decreases as we go down the periodic table and with charge. So mark off all of the group I oxides since they have +1 charge and that leaves just two from which to choose; i.e., SrO and BeO. BeO is more covalent bond whereas SrO is ionic. I think I ...
November 10, 2014

Physical Science
It takes 80 calories to melt 1 g of ice. So you have 400,000 calories. 400,000/80 = 5,000. So 5,000 grams of ice will melt and you should end up with 5000 g liquid water and 9,000 g un-melted ice all at zero C.
November 10, 2014

Physical Science
See your other post. Same process.
November 10, 2014

pharmacy math
Let x = amount of the 0.025% (and it's easier if we just leave it in percent). Then 180-x = amount of the 0.1%. 0.025x + (180-x)*0.1 = 180*0.05 Solve for x and 180-x I've estimated this will be 120 of the 0.025% and 60 of the 0.1% to give 180 of 0.05% but you should ...
November 10, 2014

chemistry
Fe2O3 + 3CO ==> 3CO2 + 2Fe mols Fe2O3 = grams/molar mass = ? Using the coefficients in the balanced equation, convert mols Fe2O3 to mols CO Now convert mols CO to grams CO. gCO = mols CO x molar mass CO
November 9, 2014

Chemistry 2
You made a typo in your post. Aniline is C6H5NH2 Let's call aniline a simple ANH2. ........ANH2 + HOH ==> ANH3^+ + OH^- I.......0.13............0........0 C........-x.............x........x E.......0.13-x..........x........x Substitute the E line into the Kb expression ...
November 9, 2014

Chem
.........2SO2(g) + O2(g)=> 2SO3(g) I.........0.51.....0.51......0 C..........-2x......-x......2x E.......0.51-2x...0.51-x....2x Substitute the E line into Kp expression and solve for x, then evaluate the other numbers.
November 9, 2014

chemistry
This is a limiting reagent (LR) problem; you know that because amounts are given for BOTH reactants. C2H5OH + 3O2 ==> 2CO2 + 3H2O grams ethanol = volume x density = approx 40 but that's an estimate as are all of the other calculations here. mols ethanol = grams/molar ...
November 9, 2014

Chemisty
2CH3OH + 3O2 ==> 2CO2 + 4H2O mols methanol = grams/molar mass = ? Using the coefficients in the balanced equation, convert mols methanol to mols CO2. The convert mols CO2 to grams. g = mols x molar mass.
November 9, 2014

chemistry
I wonder if you really meant CuNO3. I'll assume you did. mols CuNO3 = grams/molar mass = ? The M = mols/L solution. You know M and you know mols, solve for L solution.
November 9, 2014

Chemistry
I'm sure someone could help if we just knew what you wanted? "What happens" paints with such a broad brush. It could be color, volume, temperature, delta S, delta H, delta G, and so on into the night. Give us a hint what you are looking for.
November 9, 2014

chemistry
C6H6Br + Mg ==> C6H6MgBr which is the phenylmagnesium bromide. C6H6MgBr + C10H13O ==> C16H19OMgBr C16H19OMgBr + H2O(H^+) ==> C16H19OH + MgOHBr. I can't draw the structures. I think I've counted the C, H, O etc but you should check it out. The follows this ...
November 9, 2014

Chemistry
Cu3+------Cu2+-----Cu+-----Cuo ...........|...0.15.|..0.52..| |......1.28.........| I hope the spacing comes out well enough that you can make it out. The idea here is that you have the total of voltage from 3+ to 1+ and you have the single leg of Cu2+ to Cu+. What you need to...
November 9, 2014

chemistry
Note the correct spelling of celsius. n x = 0.5 mol TaCl5 = grams/molar mass Xx = nx/total mols XTaCl5 = nTaCl5/total mols. pTaCl5 = Xx*PoTaCl5
November 9, 2014

chemistry
Use PV = nRT and solve for n = number of mols. Then n = grams/molar mass. You have mols and grams, solve for molar mass.
November 9, 2014

Chemistry
358 x (2200/1000) = ?
November 9, 2014

chemistry
I don't get the question. Keq = Kc isn't it?
November 9, 2014

chemistry
1. You're allowed 2 significant figures and you've used only one. So you've rounded too much. 2. exponent is not right. 3. exponnt wrong 4. same as 1? duplicate? 5. no answer. should be 1.7E-2
November 9, 2014

Clinical chemistry
mL1 x %1 = mL2 x %2
November 9, 2014

Clinical chemistry
80% what. I presume you mean 80% w/v . 80% w/v solution NaOH means 80 g NaOH/100 mL solution. mols NaOH in 80g is mols = grams/molar mass = 80/40 = 2 mols. 2 mols/100 mL solution = 2mol/0.1L = 20 M mL1 x M1 = mL2 x M2 500mL x 0.25M = mL2 x 20 Solve for mL2, place that amount ...
November 9, 2014

Chemistry
P = ? V = 5.00 L n = 500 R = 0.08205 T = 25+273 = 298 Substitute and solve. I'm not sure I understand what your problem is.
November 9, 2014

chemistry
Probably so except for those drinks with solids floating around in them. I suppose this isn't a trick question since the drinks have a bit of CO2 dissolved in them but in my opinion they still are aqueous solutions.
November 8, 2014

Chemistry
Ptotal = pC3H8 + pH2O You know Ptotal is 680. Look up the vapor pressure of H2O in tables (from your text or otherwise), substitute and solve for pC3H8. That will be dry C3H8 at the conditions listed. Then use (P1V1/T1) = (P2V2/T2) to convert to standard conditions.
November 8, 2014

Chemistry
P*Molar masss = density*R*T. The answer will be in g/L. Convert to mg/mL.
November 8, 2014

Chemistry
PV = nRT and solve for n = number of mols. Then n = grams/molar mass. You know n and grams, solve for molar mass.
November 8, 2014

chemistry
part right; part wrong; overall is wrong. Yes, mols = grams/molar mass = 0.1426 Then M = mols/L = 0.1426/3.00 L = ? Then round to 3 significant figures.
November 8, 2014

Chemistry
M = mol solute/L solution mols = grams K3PO4/molar mass K3PO4 and L solution = 1.5L
November 8, 2014

Science: Chemistry
You don't look for answers? I responded to your first post below. If you have questions about it follow up with them but just posting again is no help to either of us. Show your work if you have questions.
November 8, 2014

chemistry
No. My calculator gives 5.22 which would round to 1 s.f. to 5.
November 8, 2014

chemistry
I posted after your correction. For c, 1.86E6 is right but you're allowed only two significant figures. You should round the 1.86E6 to 1.9E6 For d, the digits are right but s.f. not. You're allowed 1 so the answer is 1.53E7 which to 1 s.f. I would round to 2E7.
November 8, 2014

chemistry
I don't see a question. a and b you multiplied instead of dividing. c and d the digits are right, the exponents are wrong and number of significant figures is wrong.
November 8, 2014

Chemistry
a. 4 b. There are 6.022E23 unit cells in 1 mol units cells. c. volume = mass/density = 4*196.67/19.3 = ? d. c/6.022E23 = ? e. volume = a^3. Solve for a. f. 4*radius = a*(2)^1/2. You want the diameter so that will be 2*r. My answer is about 1.44E-8 cm for r or about 2.88E-8 cm ...
November 8, 2014

Chemistry
mols solution 1 = M x L = ? mols solution 2 = M x L = ? M of mixed solution = total mols/total L
November 8, 2014

Chemistry
According to Wikipedia the water molecule in liquid water is (H2O)4(actually a little less than 4 on average about 3.6 or so) for liquid at zero C and (H2O)3 at 100 C. You can read the details here. http://en.wikipedia.org/wiki/Hydrogen_bond Here is another site that agrees ...
November 8, 2014

Organic Chemistry
C7H8 + 2KMnO4 ---> C7H6O2 + 2MnO2 + 2KOH will balance that one. I would balance the second one this way. 2KMnO4 + NaOH + 3NaHSO3 ==> 2MnO2 + 2Na2SO4 + K2SO4 + 2H2O Your equation balances in every respect but it doesn't use the OH^-. If the OH is omitted, as you did, ...
November 7, 2014

Chemistry
And the set up is exactly what I gave you. Step 1 Calculate the mols you have. That is done by mols = M x L. You have M of 1.39 in the problem and you have L of 0.1424 (in the problem it is 142.4 mL and I've converted that to L). Step 2. You know mols = grams/molar mass. ...
November 7, 2014

Chemistry
How many mols do you have? That's M x L = ? Then mol = grams/molar mass. You have molar mass (or can calculate it) and mols, solve for grams.
November 7, 2014

Chemistry
I think you mis-read the problem. mass of the solution is 422g and not 442; otherwise, your procedure is ok.
November 7, 2014

Chemistry
[(x grams solute/(grams solution)]*100 = % Solve for grams solute.
November 7, 2014

Chemistry
Here is a set of rules that may be a little easier to see. http://www.csudh.edu/oliver/chemdata/solrules.htm The revised post looks a lot better. D is not the last one but it is the right answer. BaS is not soluble. All of the products from the other reactions are soluble. ...
November 7, 2014

Chemistry
I suggest two things here. 1. You need to re-read your post. The last two or three reactions appear to have been combined and as such they don't make sense. #2. You need to know the solubility rules to know which salts are soluble. Here is a simplified set of solubility ...
November 7, 2014

chemistry
mols NaOH = grams/molar mass = ? M NaOH = mols NaOH/L solution (OH^-) = (NaOH) Then (H3O^+)(OH^-) = Kw = 1E-14 Solve for (H3O^+).
November 7, 2014

Chemistry
At STP is is 32/22.4 = ? At 1 atm and 20C use PMolar mass = density*RT and solve for density. Remember T must be in kelvin. Use P*molar mass = gRT/V Solve for molar mass and since it is X2 divide by 2 to find atomic mass. Look it up on the periodic table.
November 7, 2014

Chemisty
No. mass H2O = 5E6/2260 =?g just as I said above. Then mass = volume x density. Substitute ?g for mass and the density and solve for volume.
November 7, 2014

Chemisty
I don't know what you're asking? 5E6 J = grams H2O x 2260 J/g grams H2O = 5E6J/2260 J/g = ? grams H2O Then use density H2O at 100 C to convert to L H2O.
November 7, 2014

Chemisty
5 MJ = 5E6 J q = mass H2O in grams x delta H vap in J/g. 5E6J = mass H2O x delta H vap. Look up delta H vaporization/condensation, substitute and solve for mass H2O, then look up the density of H2O at 100 C and convert grams H2O to mL H2O, then convert to L.
November 7, 2014

Chemistry Physics
I agree
November 7, 2014

Chemistry Physics
q = mass H2O x delta Hvap. You don't need the specific heat H2O. You need the delta H vaporization/condensation.
November 7, 2014

Physics Science
right
November 7, 2014

chemistry
(CH3)2CHCH2OH
November 7, 2014

chemistry
We can't draw structures on this forum but this may help. http://en.wikipedia.org/wiki/2-Pentanol
November 7, 2014

chemistry
What's your problem with this? Esters are RCOOCR' Acids are RCOOH
November 7, 2014

chemistry
Isn't this listed in your text? I would choose a and b
November 7, 2014

chemistry
You get better service if you use the same screen name. Look up teflon on google.
November 7, 2014

chemistry
I would choose c.
November 7, 2014

Chem please help
right
November 7, 2014

Chem please help
I just answered your earlier post.
November 7, 2014

chemistry
M1V1 = M2V2 15.0*17.6 = 0.495*mL
November 7, 2014

Science
mols = M x L = ?
November 7, 2014

Chemistry due soon
Nope. If the reaction as written is -56 kJ/mol then it would be -112 kJ for 2 mols and rhe REVERSE of that is +112 kJ/2 mol.
November 7, 2014

Chemistry
Actually, I don't know and perhaps another tutor can add to this but I think the H bonding in solids is quasi-permanent and there is not the transitions one sees in liquids. I say this because H bonds adds to the rigidity of polymers such as nylons and polyamides and if ...
November 7, 2014

chemistry due soon
Why not add arrows for clarity? That's what they're for. Have I put them in at the right place? Only the author knows. A. C(s) + 2S(s)==> CS2(l) + 89.4 kJ B. C(s) + 2S(s) + 89.4 kJ ==>CS2(l) C. C(s) + 2S(s) + 89.4 kJ ==> CS2(l) + 89.4 kJ D. C(s) + 2S(s) ==>...
November 7, 2014

Chem
K = (NH3)(HCl). Substitute and calculate K.
November 7, 2014

chemistry
b,c
November 7, 2014

Chemistry
1s2 2s2 2p3
November 7, 2014

chemistry
It has a double bond so is an alkene.
November 7, 2014

science help!!!!!!!!!
I would choose D also.
November 6, 2014

Chemistry due soon
You're right. It's a or b but it is not kinetic energy. http://chemwiki.ucdavis.edu/Physical_Chemistry/Thermodynamics/State_Functions/Enthalpy
November 6, 2014

physical science
6,500 J x 0.12 = ? B. 1 J/s = 1 watt.
November 6, 2014

chemistry
I believe David used the wrong symbol (among other issues); i.e., He is zero electron affinity (but isn't in the list but Ne is zero also) and I is the largest. So from lowest to highest it is Ne<Na<Bi<Te<I The problem ask to rank from most positive to most ...
November 6, 2014

Chemistry
I believe you have them grouped right except for N^3- but you don't delineate between the groups very well. I think you should put them in "boxes" so to speak, something like this just to separate them. Ne Mg2+ S2- Ti4+ K+ He Li+ Be2+ I think N3- should go with ...
November 6, 2014

Chemistry
You got it. Great! Good work.
November 6, 2014

CHEMISTRY
You need to post ALL of the problem.
November 6, 2014

Chemistry
What's the density of the solution? mols C6H12O6 = grams/molar mass = ? volume solution = mass/density Then M = mols/L solution. Or did you mean molality =m If so then m = mols solute/kg solution = mols from above/0.560 = ?
November 6, 2014

chemistry
http://www.thegeoexchange.org/chemistry/bonding/Lewis-Structures/N2O5-lewis-structure.html
November 6, 2014

chemistry
Ptotal = pO2 + pH2 + pN2
November 6, 2014

chemistry
Something is wrong with the post. You're titrating NH3 with HNO3 but you want the pH before any KOH is added. Where did the KOH come from? I assume you want the pH of a solution of 0.1M NH3. At the beginning, before any HNO3 has been added ...........NH3 + HOH ==> NH4...
November 6, 2014

Chemistry
Try this. n initial = PV/RT Solve for n initial. Then redo at the lower pressure and solve for n final. The delta n = n final- n initial = mols O2 used. Then grams = mols x molar mass.
November 6, 2014

Chemistry
http://pubs.acs.org/doi/abs/10.1021/je60034a008
November 6, 2014

Organice Chem
Why not try it and see. I've not done it but I think the it may be too soluble in acetone.
November 6, 2014

Chemistry
I think the answer is A. I would choose heat, also, but T measures heat. And choosing heat means ONLY heat would be evidence but CHANGE in T is what counts; i.e., it could get colder or hotter and be evidence that a change in energy had occurred. So temperature I think is the ...
November 6, 2014

chemistry
It's a math symbol for divide. 4/2 = 2 15/5 = 3
November 6, 2014

chemistry
Yes as long as the copper you left wet doesn't oxidize or otherwise react with something OR if the wet stuff left is not pure H2O. Water from the faucet usually contains Ca and Mg salts and when the liquid evaporates it leaves a very small residue in a beaker. It isn't...
November 5, 2014

Chemistry
A ppm is 1g solute/10^6 g solution. You want 1.40 ppm and you want 5.40E6 g of that solution; therefore, (x g solute/5.40E6g soln)*10^6 = 1.40 x = 1.40*5.40 = 7.56 g Cl2. Then 7.56 g Cl2/5.40E6 g solution = 1.40 ppm
November 5, 2014

Chemistry
delta T = i*Kf*m So if Kf is he same and m is the same you can forget about K and m. Differences will be due only to i. i is the van't Hoff factor and i = # particles on dissociation; e.g., LiNO3 will be 2 and that will have the highest freezing point of the three listed. ...
November 5, 2014

Chemistry Physics
That's 1.3E-5 WHAT/C. meters, cm, ? Substitute into the following: delta L = alpha*delta T*L You can read more about it here. http://en.wikipedia.org/wiki/Thermal_expansion
November 5, 2014

chemistry
A single bond from overlapping s orbitals.
November 5, 2014

chemistry
By the way, you don't list the length of the cell.
November 5, 2014

chemistry
You need to proof what you post. How do you transfer a 1000 mL aliquot OUT of a 200.0 mL volumetric flask INTO a 100.00 mL volumetric flask containing......? I would like to see this done.
November 5, 2014

Chemistry
dO2/dT
November 5, 2014

Chemistry
mols Cr2O7^2- = M x L = ? Convert to mols C2H5OH by ?mols Cr2O7^2- x (1 mol C2H5OH/2 mol Cr2O6^2-) = ?mols Cr2O7^2- x 1/2 = ? Then grams ethanol = mols ethanol x molar mass ethanol %w/w = (mass ethanol/mass sample)*100 = ? mass ethanol from above. mass sample is 30.50 g from ...
November 5, 2014

Chemistry
2NO(g) + O2(g) --> 2NO2(g) When all gases are listed one can take a shortcut and use volume directly as mols. volume NO = 150 mL Convert NO to O2 150 mL NO x (1 mol O2/2 mols NO) = 150 x 1/2 = 75 mL O2 required.
November 5, 2014

Chemistry
I believe this is a first order with respect to H2O2. rate = k(H2O2)^1
November 5, 2014

chemistry
You have a typo. 3Cl2 +6KOH->KClO3 +5KCl + 3H2O z mols KOH x (1 mol KClO3/5 mols KOH) = ? mols KClO3
November 5, 2014

chemistry
You have a typo. 3Cl2 +6KOH->KClO3 +5KCl + 3H2O z mols KOH x (1 mol KClO3/5 mols KOH) = ? mols KClO3
November 5, 2014

chemistry
right!
November 5, 2014

chemistry
determine z as in the previous question for the reaction CH4 + O2 --> CO2 + H2O. z kJ/mol CH4 x # mols CH4 = 3287 kJ. Solve for # mols CH4. Then use PV = nRT and solve for V at the conditions listed. # mols CH4
November 5, 2014

chemistry
What's Table 9.4? 2CH3OH(g)+ 3O2(g) ==> 2CO2(g) + 4H2O(g) Look in you text/notes and find delta H formation. dHrxn = (n*dHformation products) - (m*dHformation reactants) = some number which I'll call z. Then z x (1.2/2*molar mass CH3OH)
November 5, 2014

Chemistry Physics
[mass cool H2O x specific heat H2O x (Tfinal-Tinitial)] + [mass cool H2O x specific heat H2O x (Tfinal-Tinitial)] = 0 Substitute all of the numbers; mass cool H2O @ 20C is the only unknonwn.
November 5, 2014

organic biochemistry
mols = M x L = ?
November 5, 2014

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