Thursday
August 21, 2014

Posts by DrBob222


Total # Posts: 43,319

chemistry---كيمياء
mols K from KCl = M x L = ?. volume = 0.1L mols K from K2SO4 = M x L x 2 = ? volume = 0.2L M K after mixing is total mols K/total volume in L.
June 5, 2014

Chemistry
Look up the delta H formation for the materials in your text/notes. Then dH rxn = (n*dHo formation products) - (n*dHo formation reactants)
June 5, 2014

Chemistry
...........HA --> H^+ + A^- I.........0.01....0......0 C..........-x.....x......x E........0.01-x...x......x Ka = 1E-6 = (H^+)(A^-)/(HA) Substitute the E line into Ka expression and solve for x = (H^+).
June 5, 2014

chemistry
............2IBr ==> I2 + Br2 I........ 0.0124......0....0 C...........-2x.......x....x E........0.0124-2x....x....x Keq = 4.13E-5 = (I2)(Br)2/(IBr)^2 Substitute the E line into Keq expression and solve for x = (Br)2 = (I2)
June 5, 2014

Chemistry
The procedure is right and it appears you have substituted correctly but I didn't go through the math. It's a little easier if you use (P1V1/T1) = (P2V2/T2) and you get the answer in one math operation instead of two.
June 5, 2014

Chemistry
I have trouble following what you've done. The first part where you end up with 1081.67 mL is not right for two reasons. 1. The formula should be V1/T1 = V2/T2 2. You didn't convert T to kelvin. The second calculation you did is correct.
June 5, 2014

chemistry
Please don't post in all caps. It makes the question difficult to read. 0.1 mol NO2 and 0.2 mol N2O4. So you have 0.1 mol N from NO2 = 0.05 mol N2 from NO2. You have 2*0.2 = 0.4 mol N2 from N2O4. Total is 0.4 + 0.05 = ?
June 5, 2014

chemistry
See the S8 and NO2/N2O4 problems.
June 5, 2014

chemistry
I don't know what a wave point is. 1 mol C atoms is 12 grams and that contains 6.02E23 atoms C.
June 5, 2014

chemistry
1 mol NaOH = 40 grams and that contains 6.02E23 molecules NaOH.
June 5, 2014

chemistry
You need to find the caps key on your computer and use it. mols S in 9.8 kg H2SO4 = grams/molar mass = 9800/molar mass H2SO4 = estimated 100 8S ==> S8 100 mol S x (1 mol S8/8 mol S)
June 5, 2014

chemistry
See your other post above.
June 5, 2014

Chemistry
To do what? Is that a combustion reaction or something different. If combustion it will be (CH3)2CHCH2OH + 6O2 ==> 5H2O + 4CO2 Use the coefficients in the balanced equation to convert mols isopropyl alcohol to mols O2. That will be 3.5 mol isop x (6 mols O2/1 mol isop) = 3....
June 5, 2014

chemistry
XO2 = 0.68 pO2 = XO2 x Ptotal
June 5, 2014

Chemistry
Your set up is right. This is a common ion problem and the effect of the CoBr2 (Br is the common ion) DECREASES the solubility of CuBr as you would predict from LeChatelier's Principle. CoBr2 is a soluble salt and dissociates at 100% to CoBr2 --> Co^2+ + 2Br...
June 4, 2014

Science
Did you look at these? https://www.google.com/search?q=alpha-1+antitrypsin+deficiency%3F&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:en-US:official&client=firefox-a&channel=fflb
June 4, 2014

chem
mass = volume x density
June 4, 2014

Chemistry
right
June 4, 2014

Chemistry
Note the correct spelling of celsius. mols C10H8 = grams/molar mass = 7.58/molar mass C10H8 = ? Then molality = m = mols/kg solvent m = mols from above/0.120 = ? Then delta T = Kb*m. You know Kb and m, solve for delta T, then add that to the normal boiling point of benzene in ...
June 4, 2014

chemistry
You can't follow the instructions?
June 4, 2014

chemistry
Please don't write in all caps. It makes the question difficult to read. mols NaCl = grams/molar mass Change mL to L. Then M = mols/L solution.
June 4, 2014

science
First, I'm not a biologist and I suggest you confirm these. From what I can find on the web I think 1,2,3,5,and 6 are correct. I'm wondering if an alternate choice in 4 is leaves and an alternate choice in 7 is chloroplasts. If so I would consider reversing the answers...
June 4, 2014

not complete---science
no chart
June 4, 2014

chemistry
For H^+, e is in n = 8 so the follwing transitions can occur. n = 8 to n = 7 8 to 6 8 to 5 8 to 4 8 to 3 8 to 2 and 8 to 1; then n = 7 to n = 6 7 to 5 7 to 4 7 to 3 7 to 2 and 7 to 1; then n = 6 to n = 5 6 to 4 6 to 3 6 to 2 and 6 to 1 You get the idea here. Do the same for ...
June 4, 2014

Chemistry
2KOH + H2SO4 --> K2SO4 + 2H2O mols KOH = M x L = estimated 0.01964 and it will react with 1/2*(0.01964) = estd 0.00982 mols H2SO4. How much H2SO4 do you have? That's M x L = estd 0.0139 so you have more than enough H2SO4 to exactly neutralize it. That means an excess of...
June 3, 2014

chemistry
mols CaCl2 = grams/molar mass M = mols CaCl2/L soln
June 3, 2014

Chemistry
I think you're right about A. Wouldn't you need to work to make KE into PE? C. To evaporate H2O you must add heat so that must be endo. D. If you burn a piece of wood that is combustion. It gets hot, right? So that must be? E. When water freezes it is exothermic. No, I...
June 3, 2014

Chemistry
And you think what? and why?
June 3, 2014

Chemistry
Under some circumstances the last one COULD be right but I agree with your answer. I obtained 32.5 L of the gas at STP and most reactions will occur if there is an excess of reagent and the conditions are right.
June 3, 2014

Chemistry
I think the problem is this. I believe you have calculated N for N2O5 correctly. That's N2O5 LEFT. Then 1-N = mols N2O5 that decomposed to form O2, take 1/2 that and convert to V using PV = nRT If I do that I obtain 6.76 which rounds to 6.8L. I don't remember but I may...
June 3, 2014

Chemistry
I agree with all of the answers given by Bob Pursley. The correct choice from your list is #8. You haven't entered the correct choice; i.e., 8.
June 3, 2014

Chemistry
(HCHO) = (H2) = (CO) = 1 mol/2L = 0.5 M add (HCHO) = 2/2 = 1.0M add (CO) = 1/2 = 0.5M ..........HCHO(g) --> H2(g) + CO(g) E........0.5M........0.5M.....0.5M add.......1.0M..........0......0.5M Substitute the E line into Kc expression and calculate Kc. #2. a. Since the ...
June 3, 2014

chemistry
Take enough solution to have 1 mol total. That means you have 0.15mol H2SO4 and 0.85 mol H2O. Convert H2O to grams which is 0.85 x (18 g H2O/mol H2O) = approx 15 Then m = mol/kg solvent m = 0.15/0.015 = ? estimated.
June 3, 2014

Chemistry
I don't see any products. Heat formation of what? Just type normally, we know what should be a subscript.
June 3, 2014

Chemistry
All of these are acid/base reactions. B. CH3CH2NH2 + HBr ==> CH3CH2NH3^+ + Br^- or as a compound CH3CH2NH3Br
June 3, 2014

Chemistry
Wouldn't this be ln(No/N) = kt You know No and k, t is given but change so k and t are in the same units. Solve for N = mols N2O5 at end of 20 hours, then take 1/2 that for mols O2 and use PV = nRT to calculate volume O2.
June 3, 2014

Chemistry
Yes, A is correct. C is worded funny and I don't know what it means but it could be true depending upon how it is interpreted.
June 3, 2014

Chemistry
Right. C is correct. NH3 is the base.
June 3, 2014

Chemisty
MgSO4 + BaCl2 ==> BaSO4 + MgCl2 BaSO4 ppts. Net ionic is SO4^2-(aq) + Ba^2+(aq) --> BaSO4(s)
June 3, 2014

Chemistry
You had a problem almost like this that Bob Pursley helped you with. You ant 11.5 g pot benzoate so the reaction must produce a theoretical yield of 11.5g/0.71 = ? Then mols K benzoate = ?/molar mass K benzoate Convert to mols tolune, then g tolune = mols x molar mass toluene.
June 3, 2014

Chemistry
ln(No/N) = kt No = 4.73E-4 N = ? k = in the problem t = 24 hours changed to min since k in in min.
June 3, 2014

Chemistry
See your post below.
June 2, 2014

Chemistry
phosphate tetrahedral in shape; therefore is non-polar. SO3 is trigonal planar which makes it non-polar.(see http://www.tutor-homework.com/Chemistry_Help/Molecular_Geometry/049_Sulfur_Trioxide_SO3.html) NO2- is trigonal planar electronic geometry but molecular geometry is bent...
June 2, 2014

Chemistry
I posted an answer under the other screen name of Gloria then erased it after reading your responses to this question because I misinterpreted the question as wanting an answer of ionic or covalent. I think all of your answers are correct. I assume you can answer the other ...
June 2, 2014

Chemistry
See other post under Dory
June 2, 2014

Chemistry
That's density 32 g what. mass = volume x density If that density is right, substitute that and volume and solve for rmass.
June 2, 2014

Chem
I have consulted with a friend who is an organic chemist and he tells me all of these are acid/base reactions. Hence for part B CH3CH2NH2 + HBr ==> CH3CH2NH3^+ + Br^- or you may want to write that as CH3CH2NH3Br. That is the salt but is ionic and ionizes as I have it above.
June 2, 2014

Trigonometry, can someone check this please
I agree with Steve. I think you have mis-labeled the diagram. The distance AB is 120m and that is the hypotenuse of the triangle and not the base.
June 2, 2014

Chemistry
The systematic name is butan-1-ol
June 2, 2014

Chemistry
Just the name butanol USUALLY means n-butanol or 1-butanol (that is, with the OH on the terminal C)
June 2, 2014

Chemistry. HELP.
I do these the long way. mols O2 = 25/22.4 = estimated 1+. g ethanol = m = vd = 50.0 x 0.789 = estimated 40 g, then mol = g/molar mass = estd 40/46 = estd 0.9 C2H5OH + 3O2 ==> 2CO2 + 3H2O Convert mols O2 to mols CO2 using the coefficients in the balanced equation. 1+mol O2 ...
June 2, 2014

chemistry
You know ALL compounds are zero. Ca is +2 each. 3*2 = 6+ You know O is -2 each. 8*-2 = -16 Since everything must add to zero, then +6 +(-16) + 2P = 0 -10 + 2P = 0 2P = 10 P = +5 each
June 2, 2014

chemistry
This is akin to asking us to write a term paper for you. I'll get you started. Air conditioning. Compressor compresses gas in outside unit, liquid flows to cooler, liquid evaporates and cools in the process, a fan blows across the coils that are now quite cold and the cool...
June 2, 2014

Math
The slope is y/x y = 23-8 = 15 x = 15-4 = 11
June 2, 2014

check my arctan please
right. 4.8 degrees.
June 2, 2014

Chemistry
The long way of doing this is to look up the reduction potentials of each. Zn^2+ + 2e ==> Zn has a reduction potential of -0.763 and you want the reverse of that which is Zn ==> Zn^2+ + 2e E = +0.763 and do likewise for Ag ==> Ag^+ + e E = -0.8 Now look up, in ...
June 2, 2014

chemistry
mL acid x M acid = mL base x M base
June 1, 2014

check my set up please
yes
June 1, 2014

check my set up please
I believe your set up finds the height of the tower. The line of sight to the BASE of the tower is 34 meters by measurement. The line of sight to the TOP of the tower is cos 72 = 34/x
June 1, 2014

chemistry
Well, to be a smart aleck, I would say it's 5.6g/950 mL since you didn' specify %, M, m, or what. If you want molarity, M, then mols KOH = grams/molar mass and M = mols/L solution.
June 1, 2014

physical chemistry
Decomposition how? If you want 2H2O2 ==> O2 + 2H2O, then dHrxn = (n*dHo products) - (n*dHo reactants)
June 1, 2014

Chemistry
You need a mass of NaCl. Then mols NaCl = grams/molar mass = ? Finally, mols Na^+ = mols NaCl x 6.02E23 mols Cl^- = mols NaCl x 6.02E23 # particles will be the sum of #Na^+ + #Cl^-
June 1, 2014

Chemestry
Redox equations are balanced by a procedure. Others are balanced by inspection which is just another word for trial and error. If you will post an equation you want balanced (not a made up one but a real one) I can show you how to do it.
June 1, 2014

Analytical Chemistry
You don't have a clear question. How many mL is a question, of course, but to do what? And is that m or M. I assume you know there is a difference.
June 1, 2014

chemistry
CH3OH ==> 2H2O mols CH3OH = grams/molar mass = approx 0.2 but that's only an estimate. mols H2O = 2x that from the coefficients. molecules H2O = mols H2O x 6.02E23 = ?
June 1, 2014

Chemistry
Coordination number has slightly different meanings depending upon how it is used. One is in crystallography and the other is in complex formation. Here is a site that you can read about both. http://en.wikipedia.org/wiki/Coordination_number Basically, coordination number in ...
June 1, 2014

chemistry
I can help with specific questions about this process, chemically, but you must write your paper. This is a discussions question that basically has little to do with chemistry but a lot to do with politics and society and the human side of radioactive decay, including its use ...
May 31, 2014

Chemistry
mL1 x M1 = mL2 x M2 56mL*1.93M = mL2 x 0.9M mL2 = approx 120 mL (which is the total volume). So you must have added 120-56 = ? and that is assuming that the volumes are additive.
May 31, 2014

Chemistry
c = p*K For O2, c = 1.3E-3 mol/L*atm x (0.2) and for N2, c = 6.8E-4 mol/L*atm x (0.8). Add to find total mols, then XO2 = nO2/total mols XN2 = nN2/total mols.
May 31, 2014

Chemistry
plasma etching wet etching oxidation vapor deposition
May 31, 2014

Chemistry
What do you need help with?
May 31, 2014

Chemistry
I would do this. Convert 0.135m to ?M first. Take 1000 mL of 0.135m, it will contain 0.135 mols KF. How many grams is that? That's 0.135 x molar mass KF = about 7.8g(but that's an estimate and you should redo this and all of the other calculations that follow for they ...
May 31, 2014

Chemistry
Do you mean 0.135m or do you mean 0.135M?
May 31, 2014

Chemistry
18% w/w means 18g NH4Cl/100 g solution. mols NH4Cl = grams/molar mass = ? Convert 100 g solution to L using density; then M = mols/L.
May 31, 2014

Chemistry
7.9 x (5.9/100) = ?
May 31, 2014

Chemistry
1.55 g/mL x 1000 mL x 0.65 = 1007.5 g H2SO4. mols H2SO4 = grams/molar mass mass solution = 1.55 x 1000 = 1550. mass H2O = 1550-1007 = ? molality = mol H2SO4/kg H2O
May 31, 2014

oops--Chemistry
Do you have a 6.25m or a 6.25M solution? Mathmate's answer and definition is for 6.25M. The correct answer for 6.25m is below. m is molality and the problem states molality (not molarity). molality = mols solute/kg solvent. 6.25m means 6.25 mols NaOH/kg solvent. g = mols x...
May 31, 2014

Physics
I think you will get faster service if you don't switch change names.
May 30, 2014

chem
Ptotal = pO2 + pCO2 + pN2 Ptotal must be in torr if the others are in torr. 1 atm = 760 torr.
May 30, 2014

chem
(P1V1/T1) = (P2V2/T2) Remember T must be in kelvin.
May 30, 2014

rounding
No.If that is 146.627 FEET (you don't have the unit) then 147 is rounded to the nearest foot. To the nearest 0.1 foot it must be 146.6 feet. Why must it be a whole number?
May 30, 2014

chem
This is a "simple" stoichiometry problem. Here is the format for solving all of these. 1. Write and balance the equation. CS2 + 3O2 ==> CO2 + 2SO2 2. Convert what you have (in this case mL O2) to mols. The problem doesn't say it is a standard conditions but it...
May 30, 2014

chem
Use PV = nRT and solve for n = mols of gas, then n = grams/molar mass and solve for g.
May 30, 2014

chem
Use PV = nRT n isn't given but n = grams CO2/molar mass CO2
May 30, 2014

chem
All of these gas law problems stem from the same formula of (P1V1/T1) = (P2V2/T2) The four or five preceding this post are variations of this formula.
May 30, 2014

chem
See the next post up.
May 30, 2014

chem
See two posts up.
May 30, 2014

chem
See three posts up.
May 30, 2014

chem
See four posts up.
May 30, 2014

chem
(V1/T1) = (V2/T2)
May 30, 2014

chem
(V1/T1) = (V2/T2) Remember T must be in kelvin. Standard T is 273K
May 30, 2014

chem
P1V1 = P2V2. If you eneter P1 in atm then P2 will be in atm and you will need to convert to torr. Or you can convert 2.93 atm to torr (1 atm = 760 torr) initially and the final P will be in torr.
May 30, 2014

chem
I don't understand the question.
May 30, 2014

chemistry
See your earlier post.
May 30, 2014

chemistry
Use P1V1 = P2V2. Since no "real" value is given for P1 you can assign any convenient number for P1, then 16 times that will be P2 and work the problem OR you can simply subsitute 16*P1 for P2.
May 30, 2014

simplify the expression
What do you mean they don't match? 14^-4 = 1/(14^4) = 2.6E-5
May 30, 2014

how would i set this up?
Draw a figures, then side opposite angle is 1 ft and horizontal is 12 ft so tan angle = 1/12.
May 30, 2014

chemistry
Convert 50.0 mL ethanol to mass using mass = volume x density. I obtained approximately 50 x 0.789 = about 40g but that's an estimate only as are all of the other numbers. You need to go through the calculations yourself. mols ethanol = 40/molar mass = about 0.87 mols O2...
May 30, 2014

chemistry
22% by mass means 22 g solute/100 g solution. How many mols in 22g? That's 22/342 about 0.064 mols which is an estimate as are all of the other calculations that follow. You should recalculate each for yourself. So we have 0.064g solute/100 g solution. Use the density to ...
May 30, 2014

oops--chemistry
I posted the answer then re-read the problem and saw I had not included energy to remove that 50 mL H2O at the boiling point. Therefore, I deleted that post. Here is the complete answer. energy to melt ice + energy to raise melted ice to 100 from zero C + energy to raise 100 g...
May 30, 2014

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