Wednesday
September 2, 2015

Posts by DrBob222


Total # Posts: 49,874

science
mols toluene = 0.700 Using the coefficients in the balanced equation, convert mols toluene to mols CO2. Now convert mols CO2 to grams. g = mols CO2 x molar mass CO2
April 8, 2015

chemistry
I worked this problem below.
April 8, 2015

chemistry
CaCO3 + 2HCl --> CaCl2 + H2O + CO2 mols CaCO3 = grams/molar mass = ? mols HCl = 2 x mols CaCO3 from the coefficient in the balanced equation. M HCl = mols HCl/L HCl. You know M HCl and mols HCl, solve for L HCl and convert to mL.
April 8, 2015

chemistry
XF2 = pF2/Ptotal mole % = X*100 = ?
April 8, 2015

Chemistry
1. You need a balanced equation. 2. Are these concentrations at equilibrium?
April 8, 2015

Physical Science heat & temp. Chapter
Convert -200 F to C Convert 40 F to C. Convert 2.7 lb ice to grams ice. q1 = heat needed to raise T from -200 F (in C of course) to zero C q1 = mass ice x specific heat ice x (Tfinal-Tinitial) q2 = heat needed to change phase of ice from solid at zero C to liquid at zero C; i....
April 8, 2015

science (chemistry)
It would have helped if you had told us about the experiment; I assume you were adding powdered metal to an acid solution. I think the answer is that at first you have MANY H^+ to react with the metal to produce the chloride + H2 gas. As the HCl is used up, the concn of the ...
April 8, 2015

Chemistry
g = mols x molar mass Use the coefficients in the balanced equation to convert mols ethane to mols H2O 16 mol ethane x (6 mols H2O/2 mols ethane) = ?
April 8, 2015

chemistry
You turned the factor upside down. Note that psi x psi/atm = (psi)^2/atm and that isn't the unit you want. You want the factor to cancel the unit you don't want to keep and keep the unit you want. So you want the psi of 75 to cancel the psi of the factor and that ...
April 8, 2015

science
Your question has a type somewhere. If you mean 17 mL of 2 molar then it has mols = M x L = ? and grams = mols x molar mass = ?
April 8, 2015

chemistry
ml can be +l to -l in increments of 1 including zero. So -1, 0, +1 and each ml can have two electrons in with ms being +1/2 or -1/2. That looks like 6 to me. There's an easier way to do it. if l = 1 that is a p electron and we all know we can have 6 p electrons.
April 8, 2015

chemistry
That equation I gave you for the Fe and H2O works all of the heat problems involving two substance at different temperatures. Plug in the numbers and solve for the only unknown in the equation.
April 7, 2015

Chemistry
You are adding a common ion and that shifts the equilibrium to the left making it less soluble. See the link below. http://www.digipac.ca/chemical/mtom/contents/chapter4/commonionlab.htm
April 7, 2015

Chemistry
What is the concn of the KCl and NaCl in the mixture?
April 7, 2015

Chemistry
I assume the answser is yes; NaCl increases the ionic strength and substances are more soluble as ionic strength increases.
April 7, 2015

Chemistry
Were you performing an experiment involving ionic strength?
April 7, 2015

Chemistry
heat lost by Fe + heat gained by H2O = 0 [mass Fe x specific heat Fe x (Tfinal-Tinitial)] + [mass H2O x specific heat H2O x (Tfinal-Tinitial)] = 0 Substitute and solve for Tfinal.
April 7, 2015

Chemistry
Note the correct spelling of celsius. Equimolar means Xtol = Xben = 0.5 ptol = Xtol*Po toluene. pben = Xben*P. benzene. Ptotal = ptol + pben Xtol vapor = ptol vapor/Ptotal Xben vapor = pben vapor/Ptotal
April 7, 2015

oops--chemistry
q1 = mass H2O x specific heat H2O x (Tfinal-Tintial)
April 7, 2015

chemistry
q1 = heat needed to raise T from 47 C to 100 C. q1 = mass H2O x (Tfinal-Tinitial) q2 = heat need to vaporize H2O at 100. q2 = mass H2O x heat vaporization. Total = q1 + q2
April 7, 2015

Applied Chemistry - HELP!
OK but how do I do that without naming them for you or is that what you want? Here is a link. You can see as well as I and these don't look all that hard to understand. https://www.google.com/search?q=warning+labels&ie=utf-8&oe=utf-8
April 7, 2015

Chemistry
#1. dGo rxn = (n*dGo products) - (n*dGo reactants) #2. Are you sure you don't mean dG rxn at 125 C. I was always under the impression that dGo is the standard at 25C. This T is not 25 C and I would call it dG rxn and not dGo rxn For that calculate dHo rxn = (n*dHo products...
April 7, 2015

chemistry
What is your problem with this? mols Na in Na2SO4 = 2 x (M x L) = ? mols Na in NaNO3 = M x L = ? mols Na in Na2SO4 + mols Na in NaNO3 = total mols Na. Total volume = sum of the volumes. Then M Na = mols Na/L
April 7, 2015

Science
https://www.google.com/search?q=energy+pyramid&ie=utf-8&oe=utf-8
April 7, 2015

Chemistry
I would try this. dGo = dHo - TdSo Then dGo = -RTlnK and solve for Kp Then Kp = pHg(g)
April 7, 2015

chemistry
reverse equation 1 and add to equation 2 and add to the reverse of equation 3. When you reverse and equation change the sign of dH.
April 7, 2015

Chemistry
See your other posts below. This is the same kind of problem.
April 7, 2015

Chemistry
Use mL1 x M1 = mL2 x M2
April 7, 2015

Chemistry
M = mols/L solution For those with grams, use mols = grams/molar mass to find mols.
April 7, 2015

Chem II
way to go.
April 7, 2015

science.......,,....
I'm having trouble visualizing a train with a mass of 120 mg. Even toy trains are heavier than that.
April 7, 2015

Chemistry
I think the formula is dG = -RTlnK but that won't get -12.2. It changes the sign of the number you obtained from - to +.
April 7, 2015

chemistry
I agree and for that reason. D is the reverse for a true statement, the negative is true for c. A is true but doesn't go far enough but could be negative and dissolution could still take place.
April 7, 2015

chemistry
What do you think and why?
April 7, 2015

Chemistry
First, I made a typo and didn't see it (on both 0.25 numbers) and I'm glad you picked that up. Here is the problem. You included (Ag)solid as part of the Kc expression which I warned you not to do. That should be 3E-3 = (x)/(0.25-x)^2 and solve. You get a quadratic and...
April 7, 2015

Chemistry
The problem isn't clear but I will assume that is 0.25M AgNO3 and 0.25M Fe(NO3)2 AFTER they are mixed; otherwise each will be diluted by the other. 
......Ag+aq + Fe2+aq => Fe3+aq + Ag(s) I...0.25M...0.25M........0........0 C...-x........-x.........x........x E..0...
April 7, 2015

Chemistry
Emily, what do you not understand about limiting reagent problems. Actually they are just two stoichometry problems put together.
April 7, 2015

Chemistry
Can't you use PV = nRT and solve for P(in atm) and convert to mm Hg. n = grams O2/molar mass O2
April 7, 2015

chem
PV = nRT P in kPa. V in L T in kelvin R = 8.314 Solve for n, then n = grams/atomic mass. You have n and atomic mass, solve for grams.
April 7, 2015

Chemistry
See your H2SO4 + KOH problem below. It's the same process.
April 7, 2015

Chemistry
2KOH(aq) + H2SO4(aq) -> K2SO4(aq) + H2O(l) Can you take it from here. Convert the balanced molecular equation above to an ionic equation; e.g. KOH would be 2K^+*(aq) + OH^-(aq) H2SO4 would be 2H^+(aq) + SO4^2-(aq) For the net ionic equation, just cancel ions common to both ...
April 7, 2015

chemistry cp
I don't think so; in fact, answer a is the reason some profs like to use formula mass instead of molar mass. That is, ionic compounds do NOT exist as individual molecules.
April 7, 2015

Chemistry
No, neither is right.
April 7, 2015

Chemistry
Is WHAT oxidized or reduced. One of the reactants is oxidized; the other is reduced.
April 7, 2015

chemistry
See this site for #2, http://chemwiki.ucdavis.edu/Analytical_Chemistry/Electrochemistry/Electrochemistry_7%3A_Electrochemical_Corrosion #1 example. Fe rusts.
April 7, 2015

Chemistry
yes
April 6, 2015

Chemistry
Refer to your other problem just below. The HH equation will do this one too.
April 6, 2015

Chemistry
Can't you answer this with the Henderson-Hasselbalch equation? Plug in pH and pKa and solve for (base)/(acid). That should answer if A is right, if B is right, or D is right. C can be answered from the problem.
April 6, 2015

chem
a. Ptotal = pHg + pAr b. mols Ar gas = grams/molar mass = ? mols Hg gas = grams/molar mass = ? Total mols gas = nHg + nAr Then use PV = nRT and solve for P at the conditions listed. Remember V is in L.
April 6, 2015

chem
NaHCO3 + HCl ==> NaCl + H2O + CO2 mols HCl = M x L = ? Use the coefficients in the balanced equation to convert mols HCl to mols CO2. Then use PV = nRT to convert mols CO2 to L at the conditions listed.
April 6, 2015

Chemistry
I don't have any idea. If you know the density of the solution we might make some headway. But grams solvent usually is reserved for m solutions. So we could work the problem for 1.48 m. For M we can't even calculate mL H2O.
April 6, 2015

helpppppp??? please
Herry, let's not mess up this other post. Please post your reply to the other site.
April 6, 2015

helpppppp??? please
Herry, I looked at your posts and I don' know what the pharmaceutical terms mean. What does q.s. mean? What does Ad mean?
April 6, 2015

helpppppp??? please
I don't know enough about poetry to help but other tutors do. Other tutors will want to know how we can help you with this assignment.
April 6, 2015

Chemistry
I don't think it makes any difference in real life; however, most of the time we follow some generalizations. USUALLY we call the material present in the larger quantity the solvent and the one in lesser quantity the solute. So H2O is the solvent in a. I would classify ...
April 6, 2015

chemistry
(P1V1/T1) = (P2V2/T2) Don't forget to convert celsius to kelvin.
April 6, 2015

chemistry
That's 17/22.4 = ? g/L Gases are almost always quoted as g/L for density. For liquids & solids it is usually g/mL.
April 6, 2015

Chem
You want the acid with pKa closest to 4.00. Convert those Ka values to pKa and compare.
April 6, 2015

Chemistry
2C2H2 + 5O2 ==> 4CO2 + 2H2O Using the coefficients in the balanced equation, convert mols C2H2 to mols CO2. Then convert mols CO2 t5o grams; g CO2 = mols CO2 x molar mass CO2.
April 6, 2015

Chemistry
What you have done is almost correct but you've made two mistakes to get there for both parts. The first big problem is Ksp. Let me do it correctly, then point out the error. ..........Ag2CrO4 --> 2Ag^+ + CrO4^2- I........solid.........0.......0 C........solid........2x...
April 6, 2015

science
5C2O4^2- + 2MnO4^- ==> 2Mn^2+ + 10CO2 I know that doesn't balanced the equation and if you wish to add the H^+ on the left and H2O on the right I recommend it; however, the redox part is balanced and that is all that is needed to work the problem. Your prof may want you...
April 6, 2015

Chemistry
I agree.
April 6, 2015

Chemistry
You have done very well. I carried the numbers out a little further and obtained 0.000377 mols Al(OH)3. You did the hard part. The rest is really simple. g Al(OH)3 = mols x molar mass Then % Al(OH)3 = [g Al(OH)3/g sample]*100 = ?
April 6, 2015

Chemistry
Caroline has a problem just above yours. Here is a link. http://www.jiskha.com/display.cgi?id=1428332431
April 6, 2015

chemistry
I gave you a hint on this when you first posted. It is not that difficult. Use the hint to work the problem. OR you can explain in detail what you don't understand about the problem.
April 6, 2015

chemistry
I answered this below almost as soon as you posted it. You should go back and look to see if your questions have been answered before posting again.
April 6, 2015

chemistry
For sugar: delta T = Kb*m Substitute and solve for m = molality. Then m = mols kg solvent. You know mols and m, solve for kg solvent Using that kg solvent, convert 2.5 mol Al(NO3)3 to m Then plug m and Kb into delta T = i*Kb*m You know Kb and m. The van't Hoff factor for ...
April 5, 2015

chemistry
q = mass ice x heat fusion. Plug in q (in cal) and heat fusion (in cal) and calculate mass ice that melts.
April 5, 2015

chemistry
How would you calculate pH when Kw is 1E-14 at 25C? This is done the same way; but don't expect the pH to be 7.00 which is the whole point of the problem.
April 5, 2015

science
Ptotal = pH2 + pH2O Ptotal is what you read as the room pressure. pH2O is the vapor pressure of H2O which you can obtain from tables in your book at the corresponding temperature.
April 5, 2015

Chemistry
Of course. It will change the calculated volume and since you are measuring the volume of the titrant + the volume of the bubble, it will be larger. Since this is a molarity of the base, you will calculate M = mols/L The indicator will change when mols acid you're ...
April 4, 2015

chemistry
work = -pdV = -p(Vfinal - Vinitial) Convert 100 w to watt*sec = joules and that will be q dE = q+w
April 4, 2015

chemistry
UF4 + 2Ca ==> 2CaF2 + U mols UF4 initially = grams/molar mass = 292,000/314 = approx 930 but you need to do this more accurately. All of the following calculations are estimates; recalculate those also. mols Ca = grams/atomic mass = 47,000/40.1 = estimated 1180 Using the ...
April 4, 2015

chemistry
This is a limiting reagent (LR) problem. You know that because amounts are given for BOTH reactants. This is a standard LR problem. What do you not understand?
April 4, 2015

chemistry
It's the Arrhenius equation. Substitute the numbers I gave in the earlier response and solve for k2.
April 4, 2015

chemistry
I don't understand. What does "but that get with this????" mean?
April 4, 2015

chemistry
Use the Arrhenius equation. Choose any concentration you wish but the easy number is 1. k1 is 1/4 k2 = ? T2 is 811 C converted to K. T1 is 748 C converted to K. Ea is 150,000 Post your work if you get stuck.
April 4, 2015

Chemistry
Double displacement is right. The equation is wrong. Your error in the equation is that you have tried to balance the equations by making the products fit the balanced numbers you need. It doesn't work that way. Here is what you do. The product will be K and NO3 for one ...
April 4, 2015

chemistry
C + O2 --> CO2 20g at 90% purity = 18 g pure C. Can you take it from there?
April 4, 2015

Chem 12
It would be much easier to help you if you didn't change screen names. See your post above on K (where you didn't post the equation). Mathmate answered that.
April 4, 2015

Chemistry
If you will post how you obtained the 152 mL I shall be happy to check it for you.
April 3, 2015

Chemistry
mols NaCl = 50/molar mass = ?M which is approx 0.9 but you need a more accurate answer than that for this as well as the other calculations. M of the NaCl solution is about 0.9/0.5 = about 1.8 M. Then mL1 x M1 = mL2 x M2 mL1 x 1.8 = 1300 x 0.1M You're right. Remember the 1...
April 3, 2015

chemistry ap
I don't think so. mols Al = grams/atomic mass = ?
April 3, 2015

chemistry ap
After working those other problems, what about this do you not understand. Explain in detail. And while you're at it, balanced the equation.
April 3, 2015

chemistry
Start by balancing the equation. Convert 1.09L H2O vapor to mols. Convert mols H2O to iron(III) hydroxide using the coefficients in the balanced equation, the convert that to grams. I can help you through it if you get stuck but explain in detail what you don't understand.
April 3, 2015

chemistry ap
See the problem below.
April 3, 2015

chemistry ap
When using gases one can take a shortcut and use volume as if it were mols. 734 L NO2 x (1 mol NO/3 molls NO2) = 734 x 1/3 = ?
April 3, 2015

chemistry
PV = nRT and solve for n = mols gas. Then n = grams/molar mass. You know grams and n, solve for molar mass.
April 3, 2015

chemistry ap
See your problems above. Same procedure for all gas problems.
April 3, 2015

chemistry
Here is one just like it. http://www.jiskha.com/display.cgi?id=1428076442
April 3, 2015

chemistry
There are 6.02E23 molecules of NO2 in a mole of NO2. Since NO2 is a covalently bonded molecules that is the number of particles. For N. You have 1 atom N for each molecule NO2; therefore, you have that many atoms N. For O. You have 2 atoms O for each molecule NO2; theefore, ...
April 3, 2015

Chemistry
Try -nRTln(V2/V1)
April 3, 2015

chemistry
mols HBr = 0.025 from your work mols KOH = 0.015 from yur work. .......HBr + KOH ==> KBr + H2O I....0.025..0.015.....0.....0 C...-0.015.-0.015....0.015..0.015 E....0.010....0......0.015 HBr is in excess. (HBr)= mols/L = 0.010/(0.06+0.05) = approx 0.09 Then pH = -log(H...
April 3, 2015

chemistry
millimols HPO4^- = mL x M = approx 14 but you need to use a better number than that so recalculate all of these. mmols HCl added = 50 x 0.275 = approx 14. .......HPO4^2- + H^+ ==> H2PO4^- I......14........0........0 add .............14............ C.....-14.......-14......+...
April 3, 2015

chemistry
PV = nRT What's the trouble. Plug in P, V, R, T and solve for n. Remember to convert C to Kelvin
April 3, 2015

chemistry
AgCl ==> Ag^+ + Cl^- Ksp = (Ag^+)(Cl^-) Ag^+ + 2NH3 ==> [Ag(NH3)2]^+ Kf = --- Add the equations to get this: AgCl(s) + 2NH3 ==> Cl^- + [Ag(NH3)2]^+ So Keq = Ksp*Kf Set up an ICE chart and solve for (NH3). I think a quadratic will be necessary. Post your work if you ...
April 3, 2015

chemistry
Set up an ICE chart and use the Henderson-Hasselbalch equation.
April 3, 2015

chemistry
Use the Henderson-Hasselbalch equation to solve for pH of the solution. Use NH4Cl as the acid and NH3 as the base. Convert the pH to (OH^-) and set up Ksp with Mg(OH)2 and see if Qsp is greater than Ksp for Mg(OH)2. In the regular qual scheme of things, Mg ions are in group V ...
April 3, 2015

Chem pls!!!!!
To the first part, use #2 rxn as an example. #2 is a single replacement reaction. For #2, the field is wide open for an answer. I would try ppt but other answers will fit there too. And I might note that I don't like the wording. A solid would be formed from CuCl but not ...
April 2, 2015

chemistry
2HClO4 + Ca(OH)2 ==> 2H2O + Ca(ClO4)2 mols Ca(OH)2 = M x L = ? mols HClO4 = 2x that. M HClO4 = mols HClO4/L HClO4. You have mols and M, solve for L.
April 2, 2015

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