Sunday
May 1, 2016

Posts by drbob222

Total # Posts: 52,198

Chemistry
See your other post above.
April 5, 2016

Chemistry
What reaction?
April 5, 2016

CHEM
What's wrong with what I gave you last night? The directions are there; I made 1 L of solution so adjust to 100 mL for this and you have it. I'll be glad to help you through it but I don't want to do the work for you.
April 5, 2016

Chemistry
2HCl + Ca(OH)2 ==> 2H2O + CaCl2 mols HCl = M x L = ? mols Ca(ON)2 = 2 x mols HCl (look at the coefficients in the balanced equation). Then M Ca(OH)2 = mols Ca(OH)2/L Ca(OH)2. You know M and mols, solve for L.Convert to mL if needed.
April 5, 2016

CHEM
Usually you know the pH but you don't show that. You know pKa for NH3 to be about 9.26 but use the number in your text/notes. If you want the buffer to be between 0.01 and 0.5, why not choose say 0.3. If base + acid = 0.3, then base = 0.1 and acid must be 0.2 so pH = pKa...
April 5, 2016

Chem
(p1v1/t1) = (p2v2/t2) Remember t must be in kelvin.
April 5, 2016

chemistry
Calculate X for A(which I'm calling a) and X for B (which I'm calling b). Poa and Pob are Poa and Pob respectively. pa + pb = 40 mm pa = Xa*Poa Knowing pa you calculate pb Then pb = Xb*Pob You know pb and Xb, solve for pob. Post your work if you get stuck and I can ...
April 5, 2016

Chemistry
This is a little hard to show in writing but here goes. ......M^2+ + 4CN^- ==> [M(CN)4]^2- I..0.150....0.870.......0 C.-0.150...-0.600....+0.150 E.....0.....0.270.....0.150 The first equilibrium shows the formation of the complex on the right. With such a large Kf of over ...
April 5, 2016

Chemistry
Pb(OH)2 ==> Pb^2+ + 2OH^- Al(OH)3 ==> Al^3+ + 3OH^- Calculate OH^- needed for a 0.21M Pb^2+ solution to ppt Pb(OH)2, Calculate OH^- needed for a 0.41M Al^3+ solution to ppt Al(OH)3. You will want the (OH^-) to be less than you calculate to prevent pptn of Pb(OH)2. ...
April 5, 2016

Chemistry
........PbSO4 ==> Pb^2+ + SO4^2- ........SrSO4 ==> Sr^2+ + SO4^2- You know Ksp for each and you know metal is 0.039. I like to solve for OH^- needed to ppt each. Using my values for Ksp (which won't be the same as yours probably since texts differ), SO4^2- for Pb = 4...
April 5, 2016

Chemistry
http://chemistry.elmhurst.edu/vchembook/568denaturation.html
April 5, 2016

Chem
100.0 g CO2 x (molar mass O2/molar mass CO2) = ? g O2 in 100.0 g CO2.
April 5, 2016

Chemistry
Add eqn 1 to eqn 3 to the reverse of eqn 2. Add the dH values; when you reverse the rxn change the sign of dH for that rxn. Post your work if you get stuck.
April 5, 2016

Chemistry
Probably several but you can't beat this one for simplicity. Any other method that will test the acidity/basicity will work.
April 5, 2016

Chemistry
Add water, test with litmus paper.
April 5, 2016

Chemistry
Kw = 1E-14 = (H^+)(OH^-) You know Kw and (H^+). Solve for (OH^-).
April 4, 2016

Chemistry
q = 1387.4 kJ x (12.5 g/26 g) = ? kJ liberated
April 4, 2016

Chemistry
I'm not sure this is the question you intended to ask but here is the answer. mols AgNO3 = grams AgNO3/molar mass AgNO3.
April 4, 2016

Chemistry-Dr.Bob222
When you post a problem like this please include your work and/or what you used for constants; otherwise we can't get the same answer you obtained. I obtained an answer of 0.005 M using k2 of 5.6E-11 so your answer probably is correct.
April 4, 2016

Chemistry
Your post makes no sense to me as written. I understand what is being asked but I don't understand how the solution was made.
April 4, 2016

Chemistry
Do you have an equation to use? I don't see how you can get HNO3 out of N2 and O2.
April 4, 2016

Chem
The question tells you how to do it. SnO(s) +2HF(aq) ==> SnF2 + H2O
April 4, 2016

Chemistry
mols Ag2SO4 = grams/molar mass - ? and that is the M since it is in 1 L. I estimate that to be 0.015 M ........Ag2SO4 <--> 2Ag^+ + SO4^2 I.......solid........0.......0 C.......solid........2x......x E.......solid........2x......x Substitute the E line into the Ksp ...
April 4, 2016

Chemistry- Dr.Bob222
I'm not sure how to answer this question. Technically there is no such compound as NH4OH and I hope your prof is teaching you that. Based on that being zero, then NH3 > NH4^+ = OH^- > NH4OH = 0 What this should tell you is that the the NH3 gas dissolves in the ...
April 3, 2016

Chemistry
See your previous post. However, aren't these definitions in your text/notes?
April 3, 2016

Chemistry
BF3. Can you draw the lewis dot structure for this. Look on the web and google Lewis dot structure BF3.It's close to this. F:B:F :F: wotj extra dots around the F atoms. Note the BF3 does not obey the rule of eight; i.e., it only six electrons around B in BF3. Therefore, ...
April 3, 2016

Chemistry
I think you have made a typo. That surely is a Ka of 3.5E-8. ........HClO ==> H^+ + ClO^- I......0.45M.....0......0 C......-x........x......x E.....0.45-x.....x......x Substitute the E line into the Ka expression and solve for x = (H^+) = (ClO^-) Convert H^+ to pH
April 3, 2016

chemistry
What's 1 com? What were your observations? All you gotta do is look, unless, of course, you're doing a dry lab.
April 3, 2016

Chemistry - Dr.Bob 222
Can't you calculate that> pH = -log(H^+) 0 = -log(H^+) (H^+)= 10^-pH = 1.0M Now you do 14.
April 3, 2016

chem
(COOH)2.2H2O + 2NaOH ==> (COONa)2 + 4H2O mols NaOH = M x L = ? mols (COOH)2 = 2 x mols NaOH from the coefficients in the balanced equation. grams (COOH)2.2H2O = mols x molar mass. This is the theoretical yield (TY) %(COOH)2.2H2O in the sample is (TY/mass sample)*100 = ?
April 3, 2016

Chemistry
1. Balance the equation. That's done. 2. Separate into ions with the following rules. a. If weak acid or weak base or weak electrolyte (such as H2O), keep as molecule. b. If solid, keep as molecule. c. If gas, keep as molecule d. All others show as ions. This step gives ...
April 3, 2016

Chemistry
Yes, d is the correct answer.
April 3, 2016

Chemistry
C'mon, delta T = i*Kb*M i - 2 ]Kb = 1.52 M = 1 M Then delta T = 2*1.52*1 = ? dT = 3.04 for a. The others are done the same way. Go back and look at my response to your question on the 0.08M monoprotic acid. If you will explain what you don't understand perhaps I can ...
April 3, 2016

Chemistry
You can calculate each if your wish or take a short cut. To calculate, delta T = i*Kb*m i is the van't Hoff factor and is 2 for all cases in this question. You know Kb is 1.52. The shortcut is just i*M since Kb is the same for all of them. The higher i*m the higher delta T...
April 3, 2016

Chemistry
Since solubility is proportional to the pressure, wouldn't that be just half the initial P.
April 3, 2016

chemistry
2C8H18 + 25O2 ==> 16CO2 + 18H2O mols C8H18 = grams/molar mass = ? Using the coefficients in the balanced equation, convert mols C8H18 to mols CO2. Now convert mols CO2 to g. grams CO2 = mols CO2 x molar mass CO2.
April 3, 2016

Chemistry
1000 mL x 1.02 g/mL x 0.0013 = approx 1.4 grams Ca(OH)2 but that's just a close estimate. Then mols = grams/molar mass Ca(OH)2 and since that is mols/L that is the M and = approx 0.02. Again, that's an estimate. .......Ca(OH)2 ==> Ca^2+ + 2OH^- I......0.02.........0...
April 3, 2016

Chemistry
Look it up in the tables, dHo formation C2H2.
April 3, 2016

Chemistry
That doesn't help me. What are you confused about. In detail. Show your work as far as you can get and explain what you don't understand about the next step.
April 3, 2016

Chemistry
Weak monoprotic acid is HA ..........HA --> H^+ + A^- I.......0.08.....0.....0 C........-x......x.....x E......0.08-x....x.....x Substitute the E line into the Ka expression. The problem tells you that x = 1E-4. You may need to solve the quadratic; i.e., you may not be able...
April 3, 2016

Chemistry
Yes grams are and no grams are not. You calculated grams in part 1 by using PV = nRT, then since n = grams/molar mass, you substituted molar mass of 4 for He and calculated grams. For part 2, you used PV = nRT again and if you wanted to use grams, then mols = n = grams/molar ...
April 3, 2016

Chemistry
n = 1.25 and 5.025 g He is correct for #1. #2. PV = nRT P is 0.565 atm T is 6.0. Convert to kelvin first. n from above is 1.25 R you know Solve for V and compare it with the manufaturer's value of not bursting up to 47.0 L
April 3, 2016

chemistry
If you have copied the problem right the answer is 78.9 g. You have three significant figures i 3.75 and 350. mL has 3. 2.75 x 0.350 x 82.0 = 78.92 which rounds to 78.9 g to 3 s.f.
April 3, 2016

Chemistry
How many mols do you want? That's mols = M x L = approx 0.003 but that's just an estimate. Then grams = mols x molar mass = approx 0.9 g So you weigh out the amount of K2Cr2O7 you want, add to a 250 mL volumetric flask, add some water, swirl to dissolve, then add to ...
April 3, 2016

Chemistry
Yes, but why don't don't you know? It's just substitute and solve for the answer.
April 3, 2016

Chemistry
volume percent = [(volume solute/total volume solution)]*100 = ? % v/v = (210/300)*100 = ?
April 3, 2016

Chemistry
q = mass steam x specific heat steam x (Tfinal-Tinitial)
April 3, 2016

college general chemistry 2
No. Show your work and I'll find the error. The pH should be somewhere in the pH range of 8 or 9.
April 3, 2016

Chem
The pH is determined by the hydrolysis of the CH3COONa, which I will call NaAc. .........Ac^- + HOH --> HAc + OH^- I.......0.115............0.....0 C.......-x...............x.....x E.....0.115-x............x.....x Kb for Ac^- = (Kw/Ka for HAc) = (x)(x)/(0.115-x) Substitute ...
April 3, 2016

Chemistry
Convert pH 4.60 to (H^+) = M2 gallons1 x M1 = gallons2 x M2 320 x 15 = gallons2 x 2.51E-5 Solve for gallons2 gallons 2 includes the 320 gallons that were added.
April 3, 2016

chem
Damon's equation is correct but the state symbols are not included in his answer. Mg is(s) HNO3 is (aq) H2 is (g) Mg(NO3)2 (aq)
April 3, 2016

Kris
Use PV = nRT P = ? V = 3 L n = sum of mols. R is gas constant T must be in kelvin.
April 3, 2016

Chemistry
polarity. I wouldn't call water an electronegative compound. The elements H and O have electronegativities but water doesn't.
April 2, 2016

chemistry
See your post above.
April 2, 2016

Chemistry
a. I have no idea what you're talking about. b. AgBr is compound formed. mass Br (not Br2) in the AgBr is 0.6964 x (atomic mass Br/molar mass AgBr) = ? c. %Br (not Br2) in compound is %Br = [(answer b)/mass sample)]*100 = ?
April 2, 2016

chemistry stoichiometry
Ca^2+ + 2Hresin ==> 2H^+ + Ca(resin)2 Then H^+ + NaOH ==> H2O + Na^+ mols H^+ = M x L = (35/1000) x 0.1 mols Ca^2+ = 1/2 mols H^+ or (35/1000)x 1/2 mols Ca^2+ per gram = (35/1000) x 1/2 x 1/0.2 = ?
April 2, 2016

Chemistry
Yes, solve for the final volume and explain what to do. Remember to add the ACID to the water, let cool (if needed) and make to final volume. For the CoCl2.6H2O, how many mols do you need. That's mols = M x L = ? Then mols = grams/molar mass. YOu know molar mass and mols, ...
April 2, 2016

analytical chemistry
millimols CH3COOH = 25.0 x 0.12 = 3.0 millimols NaOH = 10 x 0.1 = 1 ..CH3COOH + NaOH ==> CH3COONa + H2O I...3.0......0........0..........0 add..........1.0................. C...-1.0....-1.0......+1.0....... E....2.0......0.......1.0 Substitute the E line into the Henderson-...
April 2, 2016

Chemistry
Answered above.
April 2, 2016

chemistry
Ca3(PO4)2 + what?
April 1, 2016

Chemistry
RbOH + HBr ==> RbBr + H2O mols HBr = M x L = ? mols RbOH = mols HBr M RbOH = mols HBr/L HBr = ?
April 1, 2016

Chemistry
ZnCO3 ==> ZnO + CO2 ZnO + 2HCl ==> ZnCl2 + H2O mols ZnCO3 = grams/molar mass = ? 1 mol ZnCO3 gives 1 mol ZnO 1 mol ZnO produces 1 mol ZnCl2. grams ZnCl2 = mols ZnCl2 x molar mass ZnCl3.
April 1, 2016

Chemistry
10.5 g Zn heated to constant mass may form ZnO but not ZnCO3.
April 1, 2016

Chemistry
M.O. changes color approx 4 (a little < 4.0) and H2C2O4 and NaoH don't change at that point.
April 1, 2016

Chemistry
Fe2O3 ==> 2Fe so you see there are 2 mols Fe in 2 mol Fe2O3. To get 1100 kg Fe will require 1100 kg Fe x (1 mol Fe2O3/2 mols Fe) = about 550 kg Fe2O3. That is only 84% Fe2O3 in the ore itself; therefore, 550/0.84 = ? kg of the ore.
March 31, 2016

Chemistry
Ksp = (Ba^2+)(F^-)^2 You know (F^-) = 1.5E-2 M You know (Ba^2+) = 1/2 the F^- Plug those into Ksp expression and solve for Ksp.
March 31, 2016

Chemistry
I assume you must have some connection to the two equations.
March 31, 2016

chemistry
(p1v1/t1) = (p2v2/t2) Remember T must be in kelvin
March 30, 2016

Chemistry
2 electrons for the two H atoms, +8 electrons for the O atom = 10 for one H2O molecules. That x 4 = 40 for the 4 H2O molecules. That means M^2+ must be 50-40= 10. If M^2+ is 10, the neutral metal M must be 12. What has an atomic number of 12?
March 30, 2016

Chemistry
mols Mg = grams/atomic mass = ? Using the coefficients in the balanced equation, convert mols Mg to mols H2. You can see it's a 1:1 ratio; therefore, mols Mg = mols H2 produced. Then convert mols H2 to grams. g H2 = mols H2 x molar mass H2 = ? This is the theoretical yield...
March 30, 2016

Chemistry
A slight twist on limiting reagent (LR). CaCl2 _+ Na2SO4 ==> CaSO4 + 2NaCl mols CaCl2 = grams/molar mass = ? mols Na2SO4 = grams/molar mass = ? Using the coefficients in the balanced equationk convert mols Cacl2 to mols CaSO4. Do the same and convert mols Na2SO4 to mols ...
March 30, 2016

Chemistry
Use PV = nRT and the conditions listed to determine the volume of F2. Then specific mass = density = molar mass/volume in L = ?
March 30, 2016

chemistry concentrations
0.171 ppm in initial 64 oz bottle. Of course the concn is the same no matter what kind of bottle you put it in. Remove 10.0 mL and dilute to 40 mL in another bottle. The concn in the other bottle is 0.171 x (10/40) = ? ppm.
March 30, 2016

Chemistry
HCl(aq) + MnO2(s) → 2 H2O(l) + MnCl2(s) + Cl2(g). mols MnO2 = grams/molar mass = ? mols Cl2 produced = mols Cl2 produced since the reaction of 1 mol MnO2 produces 1 mol Cl2. Then grams Cl2 = mols Cl2 x molar mass Cl2 = ?
March 30, 2016

Chemistry
You have 0.07 mols (NH4)2SO4. There are 6.02E23 molecules in 1 mol (NH4)2SO4 so there are 6.02E23 x 0.07 = ? molecules (NH4)2SO4 in that 0.07 mols. Since there are two NH4^+ in 1 molecule of (NH4)2SO4, there must be twice the number of NH4^+ ions as there are (NH4)2SO4 molecules.
March 30, 2016

chemistry
..........PbI2 ==> Pb^2+ + 2I^- I.........solid....0........0 C.........solid....x........2x E.........solid....x........2x ......CaI2 ==> Ca^2+ + 2I^- I...0.0123.....0........0 C..-0.0123....0.0123..2*0.0123 E.......0.....0.0123...0.0246 Ksp - (Pb^2+)(I^-)^2 (Pb^2+) = x...
March 30, 2016

Chemistry
mols = grams/molar mass = ?
March 30, 2016

chemistry
For many solids the polar nature of the solid with that of water makes them more or less soluble. Remember like dissolves like and even organic compounds with not much polarity contain OH groups and that is similar to H2O. For gases dissolved in water, there is no such ...
March 30, 2016

chemistry
CuSO4 is a polar molecule as is water. Many organic solvents are non-polar.
March 30, 2016

Chemistry
Alex, you got me. I don't know. It looks ok to me. USUALLY it is a matter of an incorrect number of significant figures but this looks ok to me. The problem asks for pH and you didn't finish the calculation. Perhaps that is the problem.
March 30, 2016

chemistry
I assume you mean acetic acid solution. acetic acid = HAc HAc ==> H^+ + Ac^- H2O ==> H^+ + OH^- Charge balance: (H^+) = (Ac^-) + (OH^-)
March 30, 2016

chemistry
It makes it difficult with no arrow. I have rewritten the equation and moved the dH so you can see it is an endothermic reaction. 2NOBr(g)+ heat =>2NO(g) + Br2(g) Remember Le Chatelier's Principle says that when a system at equilibrium is disturbed, it will shift so as ...
March 30, 2016

Chemistry
I don't think so. Are you guessing? Post your work and I'll find the error.
March 29, 2016

Chemistry
Post your work and let me check it.
March 29, 2016

Chemistry
Mg(OH)2 + 2H^+ ==> 2H2O + Mg^2+ mmols Mg(OH)2 = mg/molar mass = approx 250/58.3 = about 4 but that's only an estimate. mmols H^+ = twice that approx. Again, an estimate. CaCO3 + 2H^+ ==> 2H2O + Ca^2+ mmols CaCO3 = 300/100 = about 3 mmols H^+ = twice that. Add mmols H...
March 29, 2016

Chemistry
Sarah, I showed you in detail how to do the last one. Just follow that procedure. The only difference in the two problems is that the other one was a strong acid and the salt of a weak acid. This one is a strong base (CsOH) and the salt of a weak acid (H2S or technically HS^-).
March 29, 2016

Chemistry
I don't think so. Where did you get 43.6 mL? That isn't anywhere in the problem. mols CuSO4.5H2O = 0.096/249.7 = approx 3.8E-4 M = mols/L = 3.8E-4 mols/0.5L = approx 7.7E-4 M for the solution in the first 500 mL flask. Then you dilute 10.8 mL to 500 so 7.7E-4M x (10.8/...
March 29, 2016

Chemistry
millimols HCl = 0.4 x 50 = 20 millimols NaF = 85 x 9.4 = 34 .......F^- + H^+ ==> HF I.....34.....0.......0 add.........20............ C....-20...-20.......+20 E.....14....0........20 Ka for the rxn = (HF)/(H^+)(F^-) Doesn't that look like 1/Ka of HF to you. You could ...
March 29, 2016

oops--Chemistry
I hit the wrong key. The answer should be a little less than 3.
March 29, 2016

Chemistry
pH + pOH = pKw = 14. You know pH, solve for pOH. Then pOH = -log(OH^-) Substitute and solve for OH. You should get a little less than 2 but that's just an estimate.
March 29, 2016

Chemistry
2H2 + O2 ==> 2H2O Use the coefficients to calculate this. 27.4 mols H2 x (1 mol O2/2 mols H2) = 27.4 x 1/2 = ?
March 29, 2016

Chemistry
Do you have choices? Ga^3+ would be smaller but so would many other ions.
March 29, 2016

chemistry
NaC2H3O2 = NaAc acetic acid = HC2H3O2 = HAc NaAc diluted = 0.293 x (190/750) = approx 0.074 but you need to confirm this and all other calculations that follow. I estimate and round. .......Ac^- + HOH ==> HAc + OH^- I....0.074............0......0 C.......-x............x...
March 29, 2016

AP Chemistry
I answered this at your other post above (with anonymous screen name).
March 29, 2016

chemistry
This is a limiting reagent (LR) problem; you know that because amounts are given for both reactants. 3Mg(s) + N2(g) --> Mg3N2(s) The long long way to do this. mols Mg = 8 from the problem. mols N2 = 2 from the problem. Using the coefficients in the balanced equation, ...
March 29, 2016

Chemistry- Dr.Bob222
No point in my weighing in!
March 28, 2016

Chemistry
CaCO3(s)-> CaO(s) + CO2(g) Convert 71.42 g CaCO3 to mols. mols = grams/molar mass = ? Using the coefficients in the balanced equation, convert mols CaCO3 to mols CaO. Now convert mols CaO to grams. g CaO = mols CaO x molar mass CaO. This is the theoretical yield (TY). The ...
March 28, 2016

Chemistry
No. Your error is you convert mols NaOH to grams NaOH then used GRAMS for mols in M = mols/L but you can't do that. You should convert 2 g to mols KHP, then to mols NaOH, then mols NaOH/M = L NaOH
March 28, 2016

chemistry
8.5E2 cal x (1 Cal/1000 cal) = ? 0.45 kJ = 450 J 450 J x (1 cal/4.184 J) = ?
March 28, 2016

Chemistry
Ben, I did this far below. http://www.jiskha.com/display.cgi?id=1459199032
March 28, 2016

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