Thursday
August 28, 2014

Posts by DrBob222


Total # Posts: 43,387

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

chemistry
Follow the instructions I gave. Actually there are two final temperatures and that's why I said to work the problem in steps. The FIRST final T which I've listed as Tfinal is the final T of the ice water + 100 C water. The ice melts and lowers the temperature of the ...
May 30, 2014

chemistry
I would do this is steps. First, determine the mass of the ice. mass ice = volume ice x density ice at 0C. You will need to look up the density at 0C. Then [mass H2O x heat fusion] + [mass melted ice x specific heat H2O x (Tfinal-0)] + [mass H2O @100 x specific heat H2O x (...
May 30, 2014

Chemistry
Ptotal = pH2 + pH2O Ptotal = 99.8 kpa pH2O = 2.33 kPa. PH2 = ?
May 30, 2014

Chemistry
PV = nRT. You don't have n but n = grams/molar mass.
May 30, 2014

chemistry
I would like to know how much ice and how much liquid water @ 100 C you have? I haven't thought through the problem and that info may or may no be needed; however, it would make me feel better to have that info.
May 29, 2014

chem
1 mole of anything contains 6.02E23 molecules. Convert 19.0 g MgCl2 to mols. mol = grams/molar mass. Then convert that many mols to molecules MgCl2 (use #1 as a template if needed). Then you notice there are 3 atoms for each molecule so 3x molecules gives you atoms.
May 29, 2014

chem 2
Were are parts B, C, and D. Rxn is (add the two half cells below) Cr(s) ==> Cr^3+ + 3e Ag^+ + e ==> Ag(s) -------------------- Cr(s) + 3Ag^+ ==> 3Ag(s) + Cr^3+
May 29, 2014

chemistry
I'm guessing the reaction is something like this and I'm assuming there is enough Ag to complete the reaction although I don't know what "amount AgNO3 used was unchanged" means. Cu(s) + 2Ag^+ ==> 2Ag(s) + Cu^2+ mols Cu = grams/atomic mass mols Ag = 2 x...
May 29, 2014

Science
That isn't a good answer.
May 29, 2014

Chemistry
I agree
May 29, 2014

Chemistry
k = 0.693/t1/2 Solve for k and substitute into the below equation. ln(No/N) = kt No = 12.0 mg N = ? mg k = from above t = 13.5 hrs
May 29, 2014

Science (Please check!)
If it is a stove top burner and you set the pan on it, the heat is transferred by conduction.
May 29, 2014

Chemistry II
There is no way to answer this question without some kind of rate equation.
May 29, 2014

ALGERBRA
-7*5 = 5*91X -35 = 455X X = ?
May 28, 2014

College Algebra
That's what I would do first.
May 28, 2014

Chemistry
P1V1 = P2V2
May 28, 2014

Chemistry
http://www.jiskha.com/display.cgi?id=1401311215
May 28, 2014

Science
http://www.jiskha.com/display.cgi?id=1401311215
May 28, 2014

chemistry
Do you mean 2.10 M? If so then pOH = -log(2.10) and pH + pOH = pKw = 14 With pOH and pKw you can solve for pH.
May 28, 2014

chemistry
It COULD be right but as far as I know that is no such compound as NaHClO3. NaClO3 is sodium chlorate. HClO3 is chloric acid. I don't know of anything with the formula NaHClO3.
May 28, 2014

chemistry
I don't see a question here.
May 28, 2014

chemistry
If you say so. I don't see a question.
May 28, 2014

science
Is this a question? If so it isn't clear; please rephrase it.
May 27, 2014

Chemistry
PV = nRT n = grams/molar mass = 23.0/207 = ? Remember T must be in kelvin.
May 27, 2014

Chemistry
I know it is exothermic because I've been there and done that and I know it gets hot. You can look up delta G of products and reactants in tables and calculate delta Grxn BUT those values are based on knowing both delta H and delta S so I don't think that is a ...
May 27, 2014

Chemistry
It IS an exothermic reaction but I don't know that the release of CO2 is the reason. The entropy is +.
May 27, 2014

chemistry
Of course. van't Hoff factors are at best just good guesses; you might be closer to reality by picking something with i = 1; i.e., a complete non-electrolyte like ethyl alcohol or something like that.
May 27, 2014

chemistry
I think you must assume some things. 1. Since you know the solvent is water you can look up the Kf value of 1.86/mol. 2. You have your choice of solute so you can pick one that has an i = 1 or an i of some other value. 3. So 3.7 = iKm if you chose i = 2 you could pick a solute...
May 27, 2014

Chemistry
And in the "older" olden days it was amyl-propyl-ether
May 27, 2014

Chemistry
1) pH + pOH = pKw = 14. You know pH and pKw, solve for pOH. Not that hard if you can subtract. 2) I don't know where you're headed but M = mols/L or M strong acid is M of H^+ or pH = -log M.
May 27, 2014

oops --Damon--Science
I think Damon made a typo. That is kJ and not J.
May 27, 2014

Pages: <<Prev | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | Next>>

Search
Members