Tuesday
July 26, 2016

Posts by DrBob222

Total # Posts: 52,750

Chemistry
No. Show your work and I'll find the error.
May 16, 2016

Chemistry
Here are the formulas you need for this problem. There are three. When you are in the same phase (everything is liquid, or gases, or solids, you use q = mass x specific heat x (Tfinal-Tinitiail). That's equation 1. When you are at the phase change from solid to liquid use ...
May 16, 2016

Chemistry
I don't see a question here.
May 15, 2016

Chemistry
q1 = heat to melt ice at zero C to liquid water at zero C. q1 = mass ice x heat fusion = ? q2 = heat to change T liquid H2O at zero C to liquid H2O @ 100 C. q2 = mass water x specific heat H2O x (Tfinal-Tinitial) = ? q3 = heat to change liquid H2O at 100 C to steam at 100 C. ...
May 15, 2016

chemistry
You've just asked for someone to write 1/2 of a chemistry textbook. Few of us here will take the time for that.
May 15, 2016

chemistry
https://www.google.com/search?q=29.5+inches+Hg+to+atm&ie=utf-8&oe=utf-8
May 15, 2016

chemistry
If I understand the question correctly, H2SO4 is about 98% which makes SO3 about 11%. So (x+y) = about 109 (x-y) = about 87 (x+y)/(x-y) = about 109/87 = ?
May 14, 2016

chem
q1 = heat to raise T of ice at -2 to zero C. q1 = mass ice x specific heat ice x (Tfinal-Tinitial) q2 = heat to change ice at zero C to liquid water at zero C. q2 = mass ice x heat fusion water. q3 = heat to raise T of water at zero C to water at 75 C. Then q total = q1 + q2 + q3
May 14, 2016

Chemestry
Use PV = nRT to solve for n = mols CO2. mols CO2 = mols K2CO3 Then grams K2CO3 = mols K2CO3 x molar mass K2CO3. %K2CO3 = (grams K2CO3/mass sample)*100 = ?
May 13, 2016

chemistry
mols Na from Na2CrO4 = 0.095 x 2.50 = ? mols Na from AgNO3 = 0 total volume = (95 mL + 125 mL)/1000) = ?L (Na) = mols Na/total volume in L.
May 13, 2016

chemistry
Do the steps outlined before; i.e., write and balance the equation, convert mols O2 to mols H2O, then use PV = nRT to solve for volume.
May 12, 2016

Chemistry
See your other post on concen, density, molarity. The general formula is density x 1000 x (%/100) x (1/molar mass material) = Molarity mataerial
May 12, 2016

Chemistry
% w/w = grams solute/100 g solution. 16.5M = 16.4 mols/L solution. grams = mols x molar mass so 16.4 x 40 = ? grams NaOH/L solution and that divided by 10 = grams NaOH/100 mL of solution. Then mass = volume x density. You know density and volume, that will give you the mass of...
May 12, 2016

Chemistry
We can help you better if you don't change screen names. Work this problem just backwards from the NaOH problem above.
May 12, 2016

Chemistry
I assume you meant "passed". Assuming both Na and Cu will deposit, then Q = 2 x 30 x 60 23 g Na will deposit for every 96,485 coulombs. Convert coulombs from above to grams Na. Then 63.54/2 g Cu will deposit for every 96,485 coulombs. Convert above coulombs to grams ...
May 12, 2016

chemistry
mass in grams salt crystal = volume x density. Then g/0.375 = ? g/L.
May 12, 2016

Chemistry
Don't you have a table or graph that you can find the solubility?
May 12, 2016

science-chemistry
0.75 x 0.04 = 0.03 0.75-0.03 = 0.72 ........HA ==> H^+ + A^- I.....0.75.....0.....0 C....-0.03....0.03...0.03 E....0.72......0.03...0.03 Substitute the E line into the Ka expression and solve for Ka. I assume that is 0.04 ad not 0.04%.
May 12, 2016

Chemistry
Would you believe Na(SO4)2 doesn't exist. If it did, this would be how do it. 9.2 mols Na(SO4)2. mols S is 2x that.
May 12, 2016

Chemistry
Is that water at -10. Does it go through freezing or not.
May 12, 2016

Chemistry
Why don't you look up the definition of activation energy. Your guess isn't right.
May 12, 2016

chemistry
And?
May 12, 2016

chemistry
4.6E-3 g/100 cc = 4.6E-2/1000 cc. mols = 4.6E-2/molar mass Mg(OH)2. Then M = mols/L. I will call that S whatever it is. ........Mg(OH)2 ==> Mg^2+ + 2OH^- I.......solid.......0........0 C.......solid.......s........2s E.......solid.......s........2s Substitute the E line ...
May 12, 2016

Chemistry
(0.692*mass) + (0.308*mass) = ?
May 12, 2016

chemistry
Is this a gas sample? Use PV = nRT P = 8.3 atm V = 45 L n = 2.5 mols R = 0.08206 T = ?
May 12, 2016

Chemistry (Stoich)
You made two error in naming but they cancel. 27.8 x 0.115 is 0.003197 MILLImoles (not mols) BUT at the end you divide millimoles/mL and that is M. Your answer of 39.1 mL is right.
May 12, 2016

Chemistry
I think you need only one ICE table. ........HF + OH^- ==> F^- + H2O I.....0.75...0.......0.25...... add.........0.05............. C....-0.05.-0.05......+0.05 E.....0.70....0........0.30 Substitute the E line into the HH equation and solve for pH.
May 12, 2016

Chemistry
Use a universal indicator. Look that up on Google.
May 11, 2016

Chemistry
mols H2SO4 = grams/molar mas = ? Then M = mols/L
May 11, 2016

Chem
I think you didn't use the M of the H2SO4.
May 11, 2016

Chem
mols H2SO4 = M x L =? mols NaHCO3 = 2x that grams NaHCO3 = mols NaHCO3 x molar mass NaHCO3. I think the answer is closer to 1.5 grams.
May 11, 2016

chemistry
2C2H6 + 7O2 => 4CO2 + 6H2O This is a limiting reagent problem; you know that because amounts are given for BOTH reactants. Therefore, you must identify the limiting reagent. How much H2O can be produced by 0.1 mol C2H6. That is 0.1 mols C2H6 x (6 mols H2O/2 mols C2H6) = ? ...
May 11, 2016

chemistry
Do you mean 1m or 1 M. Do you know the difference? I will assume you mean 1 M. Or is that 1 mol? psolution = XH2O*PoH2O If this is 1 m we can do it as is. If it 1M, we will the need the density of the solution.
May 11, 2016

@athenalChemistry
Using mols will not work. The Keq involves concentrations; mols are not concentrations.
May 11, 2016

Chemistry
You don't have information listed. Concentration is what goes into the Keq calculation. You have no volume.
May 11, 2016

Chemistry
See your other post.
May 11, 2016

Chemistry
Chris/Elsie/et al pi = MRT
May 11, 2016

Chemistry
I don't know why students want to change screen names (as you have done). We can help better if you keep the same name. Which Cr isotope do you want this information for? See https://www.webelements.com/
May 10, 2016

Chemistry
How many mols do you want? That's mols = M x L = ? Then mols = grams/molar mass. You know molar mass and mols, solve for grams.
May 10, 2016

Chemistry
We worked the problem last night but they wanted to know grams PbI2 pptd. In this problem, the only difference is that they want to know how much 1.50M KI must be added. 1. mols Pb(NO3)2 = M x L = ? 2. Convert mols Pb(NO3)2 to mols KI using the coefficients in the balanced ...
May 10, 2016

Chemisty
4Al + 3O2 ==> 2Al2O3 mols Al you want = grams/atomic mass Al. Using the coefficients in the balanced equation, convert mols Al to mols Al2O3. Then grams Al2O3 = mols Al2O3 x molar mass Al2O3. This assume bauxite is pure Al2O3 and it isn't. Actually this is not a good ...
May 10, 2016

CHEM 2
23% w/w LiCl means 23 g LiCl in (23g LiCl + 77 g H2O). mols LiCl = 23/molar mass LiCl mols H2O = 77/molar mass H2O XH2O = mols H2O/total mols.
May 10, 2016

Riddle
Ms. Sue is on the ball.
May 10, 2016

Chemistry
For questions like this you should tell us what you think or at least something about what you don't understand about the question. Alkanes are CnH(2n+2) alkenes are CnH2n alkynes are CnHn In a reaction, for example, A + B --> C + D If more A is added or if more B is ...
May 10, 2016

typo--Chemistry
Please forgive the typos. That should be PV = nRT. I got a - sign in there and it should be an = sign.
May 10, 2016

Chemistry
Thank you. Here are the steps together with the problem. I suggest you print this and keep it. Most stoichiometry problems are worked this way. Limiting reagent problems are slightly (but not much) different. This problem is in molarity and liters so I will stick to that and ...
May 10, 2016

Chemistry
You posted a question earlier that is just another stoichiometry problem. Here it is.http://www.jiskha.com/display.cgi?id=1462776118 What about these problems do you not understand?
May 10, 2016

chemistry
mols DNA = grams/molar mass Then M - mols/4.7L = ?
May 10, 2016

Chemistry
You would do better to post a single question with your proposed answer and why.
May 10, 2016

Chemistry
You aren't pushing hard enough.
May 10, 2016

Chemistry
If you want pH = pKa then you want (NH3) = (NH4^+). You get that from pH = pKa + log (NH3)/(NH4^+) 9.25 = 9.25 + (NH3)/(NH4^+) and that means (NH3) = (NH4^+) ......NH4^+ + OH^- ==> NH3 + H2O I.....0.3..............0.15 add............x............. C......-x.....-x.......+x...
May 10, 2016

chemistry
Zn(s) + CuSO4(aq) ==> ZnSO4(aq) + Cu(s)
May 10, 2016

Chemistry
What is the molarity of the initial HNO3? That's 1000 cc x 1.42 g/cc x 0.70 x (1/63) = approx 16 M but you need to do that more accurately. Then mL1 x M1 = mL2 x M2 mL1 x 16 = mL2 x 3.0 mL1 = ? = mL of the initial 70% solution.
May 10, 2016

chemistry 12u
Sure it will. 2.73 = -log(H3O^+) -2.73 = log*H3O^+) Hit the 10^x button and punch in -2.73.
May 10, 2016

chemistry 12u
pH = -log(H3O^+) The nitrous acid bit has nothing to do with the problem. ANY acid or base with a pH of 2.73 will have this H3O^+.
May 10, 2016

chemistry
Another one is LEO the lion goes Grr. LEO is loss electrons oxidation
May 9, 2016

chemistry
backwards. The first one is ADDING electrons. The second one is LOSING electrons.
May 9, 2016

Chemistry
5% what. weight/volume? weight/weight? volume/volume? I assume you mean w/v since you want 300 mL of solution. 5% means 5 g sucrose/100 mL solution. You want 300 so 5g x (300/100) = 15g So you need 15 g sucrose/300 mL solution.
May 9, 2016

Check my answers? Science
I'm serious. You must be kidding.
May 9, 2016

Electroplating in Chem
The Cu strip is going into solution. That one is Cu ==> Cu^2+ + 2e Then the Cu^2+ ions in solution are plated onto the penny as pure copper. That one is Cu^2+ + 2e ==> Cu If you remember the definitions you can't go wrong with which is which. Oxidation is the loss of...
May 9, 2016

Chemistry
mols Al = grams/atomic mass Al Using the coefficients in the balanced equation, convert mols Al to mols AlCl3. Now convert mols AlCl3 to grams. g AlCl3 = mols AlCl3 x molar mass AlCl3.
May 9, 2016

Chemistry
I answered this question earlier. http://www.jiskha.com/display.cgi?id=1462663618
May 9, 2016

Chem
PbCl2 ==> Pb^++ + 2Cl^- AgCl --> Ag^+ + Cl^- Using Ksp for PbCl2, calculate what the (Cl^-) must be to ppt PbCl2. You know (Pb^++) and Ksp, solve for (Cl^-). Do the same for AgCl. You know Ag^+ and Ksp, solve for (Cl^-). The one with the lower Cl^- will appear first so ...
May 9, 2016

Chem
.......Ag2SO4 ==> 2Ag^+ + SO4^= I......solid.......0........0 C......solid.......2x.......x E......solid.......2x.......x Substitute the E line into the Ksp expression and solve for x = solubility.
May 9, 2016

chemistry
I have no idea what tetraoxosulphate(6) is. Perhaps you are referring to sulfuric acid, H2SO4.
May 9, 2016

Chemistry
Google as I did for this one. https://www.google.com/search?q=3-methylpentanoic+acid&ie=utf-8&oe=utf-8
May 8, 2016

chemistry
P*molar mass = density*R*T Substitute P, d, R and T and solve for molar mass.
May 8, 2016

chemistry
How many mols do you need? That's mols = grams/molar mass. You know molar mass and grams, solve for mols. Then M HCl = mols HCl/L HCl. You know mols and M, solve for L and convert to mL.
May 8, 2016

Chemistry
I don't see a question here.
May 8, 2016

Chemistry
g BaSO4 x (molar mass sulfa stuff/3*molar mass BaSO4)*100 = ?
May 8, 2016

Chemistry- Dr.Bob222
The first thing wrong is you are using Ksp. You still haven't answered my question about the Kf. Kf is the formation constant for the complex. Ag^+ + 2NH3 ==> [Ag(NH3)2]^+ The literature shows that as about 1.7E7 and your question gives it as 0.0031. I think that 0.0031...
May 8, 2016

Chemistry- Dr.Bob222
Basically I said the definition for Kf is for Ag^+ + 2NH3 ==> [Ag(NH3)2]^+ and that is something like 1.7E7. I don't think your Kf you quoted of 0.0031 is Kf; I think it is for AgCl + 2NH3 ==> [Ag(NH3)2]^+ + Cl^- and that makes it Keq for that reaction and that is ...
May 7, 2016

chem
Technically I would think M+ ion is the Cu^2+ ion that comes from the bpy complex; i.e., if the ionization is Cu(bpy)2^2+ ==> Cu^2+ + 2bpy So you might expect three separate peaks but then you haven't told us that this is; i.e., infrared, mass spec, magnetic resonance, ...
May 7, 2016

Chemistry- Dr.Bob222
I don't get that answer. Are you sure you have typed in the correct values? I think that 0.0031 is closer to the Knet for the reaction and not Kf for the formation of the complex. I think that number is very much higher; i.e., something like 10^7 or so. If I use 0.0031 for...
May 7, 2016

Chemistry
You did the most important first two. The next one is the easy one. So you want to neutralize 6 mols H2SO4, that will take 12 mols NaOH as you correctly stated. Then M NaOH = mols NaOH/L NaOH. You know mols NaOH and M NaOH, solve for L NaOH. Convert to mL if needed.
May 7, 2016

chemistry
AgNO3 + KCl ==> AgCl + KNO3. NaNO3 + KCl ==> no reaction. So you obtained 3.97 g AgCl. Convert that to g AgNO3 this way. 3.97 x (molar mass AgNO3/molar mass AgCl) = ? g AgNO3. %AgNO3 = (g AgNO3/mass sample)*100 = ?
May 7, 2016

Chemistry
Use PV = nRT with n = grams/molar mass
May 7, 2016

Chemistry
2C2H6 + 7O2 ==> 4CO2 + 6H2O When gases are involved one can take a shortcut and use liters and mols interchangeably. So 4.00 L C2H6 x (7 mols O2/2 mols C2H6) = 4.00 x 7/2 = ? L O2
May 7, 2016

Chemistry
This sounds like a take off on soda lime glass. You can read more about that here. https://en.wikipedia.org/wiki/Soda-lime_glass
May 7, 2016

AlphaPlus
Alpha Plus is the name of the subject? L1 x M1 = L2 x M2 L1 x 4.85 = 7 x 1.25 Solve for L1
May 7, 2016

Chemistry
48.5% x (0.75L/5.60L) = ?%
May 7, 2016

Chemistry
How many mols Ba(NO3)2 do you have? That's mols = grams/molar mass = ? approx 0.02 but that's just an estimate. Then M = mols/L You know M(1.25) and mols (estimated 0.02), solve for L.
May 7, 2016

oops---Chemistry
I don't believe the above answer is right. It should be A2B ==> 2A^+ + B^2- Ksp = (A^+)^2(B^2-) = (0.00147)^2(0.000735) = ?
May 6, 2016

chemistry
Mg + 2HCl ==> MgCl2 + H2 mols Mg = grams/atomic mass = ? Using the coefficients in the balanced equation convert mols Mg to mols HCl. In this case mols HCl = 2 x mols Mg. Now that you know mols HCl, M HCl = mols HCl/L HCl. You know M and mols, solve for L and convert to mL...
May 6, 2016

Chemistry
C7H8 is toluene. 92.14 is molar mass.
May 6, 2016

Chemistry
delta T = kf*m Substitute and solve for m = molality. You know delta T and Kf. m = mols/kg solvent You know kg solvent and m. mols = grams/molar mass. Substitute and solve for molar mass. Yo know grams and mols.
May 6, 2016

chem 161
This is a limiting reagent problem. You know that because amounts are given for BOTH reactants. AgNO3 + NaCl ==> AgCl + NaNO3 mols AgNO3 = M x L = approx 0.013 but need that more accurately. mols NaCl = M x L = ? approx 0.0083 So the amount of AgCl that can be formed from ...
May 6, 2016

chem 161
H3PO4 + 3NaOH ==> Na3PO4 + 3H2O mols H3PO4 = M x L = ? Using the coefficients in the balanced equation, convert mols H3PO4 to mols NaOH. That will be mols NaOH = 3 * mols H3PO4. Then M NaOH = mols NaOH/L NaOH. YOu know mols NaOH and M NaOH, solve for L NaOH and convert to ...
May 6, 2016

Chemistry
This is a two part question. First you set up to see how much of the complex is formed, then you run the problem backwards to see how much of the Cd and others components are formed/or remain. Here is the first part and you assume, with such a huge K value that ALL of the Cd^2...
May 5, 2016

Chemistry
right. See above for my response.
May 5, 2016

Chemistry
If you answered the question I asked I might be able to help.
May 5, 2016

Chemistry
I must be missing something. With no CN^- there how does any [Cd(CN)4]^2- get formed?
May 5, 2016

chemistry
You are both right and wrong. The second equation is wrong. The first one is right. Pb^2+ ==> Pb02 + 2e. The lead ion from lead lactate is +2 and it is going to PbO2 where Pb is +4. That is a loss of electrons which is oxidiation. And the PbO2 will deposit at the anode ...
May 5, 2016

Chemistry
2AgNO3 + CaCl2 ==> 2AgCl + 2NaNO3 mols CaCl2 = M x L = ? Using the coefficients in the balanced equation, convert mols CaCl2 to mols AgNO3. mols AgNO3 - 2x mols CaCl2. Then M AgNO = mols AgNO3/L AgNO3. Ou know mols and M, solve for L and convert to mL.
May 5, 2016

chemistry
I don't see a question here.
May 5, 2016

chemistry
mols NaOH = grams/molar mass ? M = mols NaOH/dm^3 solution
May 5, 2016

Chemistry
I think you are trying to make this too hard. To start the 0.01 PbCl2 is in solution. ......PbCl2 ==> Pb^2+ + 2Cl^- I.....0.01......0.01....0.02 You can show this is in solution. Qsp = (0.01)(0.02)^2 = 4E-6 which is < Ksp so it hasn't pptd and all is in solution. ...
May 5, 2016

Chemistry
Poor question for it has 3 answers and another type is not listed.. Usually c (for acid/base titrations) but sometimes a or b. And the Mohr titration depends upon the Ksp of Ag2CrO4 which is none of the aboe.
May 4, 2016

Chemistry
Stop playing screen names games. This is a limiting reagent problem. Do you know how to do them?
May 4, 2016

Chemistry
Stop playing games with screen names. 1 mol contains 6.022E23 molecules. So if 38 g contain 3E23 molecules what would be the weight of 6.022E23 molecules?
May 4, 2016

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