Thursday
May 5, 2016

Posts by DrBob222

Total # Posts: 52,253

chemistry
grams acetone = volume x density = approx 115 grams but you need a more accurate number than that. So you get 1790 kJ for 58 g C3H6O; how much will you get from 115 g. 1790 x (115/58) = ? kJ released.
November 3, 2015

AP Chemistry
(rate 1/rate 2) = (mm 2/mm 2) where mm is molar mass. (0.05/0.025) = (mm 2/17) solve for mm and compare with the answers. The answer is approximate; pick the closest gas.
November 3, 2015

chem
2CH2 + 3O2 ==> 2CO2 + 2H2O mols CO2 = 44/44 = 1 mols O2 = 1 mol CO2 x (3 mols O2/2 mols CO2) = 1*3/2 = ? You can check this to see you get the same number using water.' mols H2O = 18/18 = 1 mols O2 = 1 mol H2O x (3 mols O2/2 mols H2O) = 1*3/2 = ? Convert mols O2 to ...
November 3, 2015

chem
I don't think so. How do you add 8 and -8 and get -11.
November 3, 2015

chem
I would draw a 2D square. Each side is 1E8 atoms. If each atom is 2E-8 cm (that's 2 Angstroms each), then 1E8 atom x (2E-8 cm/atom) = ?
November 3, 2015

chem
Sorry. I'm letting this one go.
November 3, 2015

chem
I don't understand this question and i skipped it last night since I didn't understand it then either.
November 3, 2015

chem
Carbon is being oxidized and Fe3O4 is being reduced. Reducing agents are the same as what is oxidized. What do you not understand about determining oxidation states? http://www.chemteam.info/Redox/Redox-Rules.html
November 3, 2015

Chem
You're doing a little better with caps but note that Co, CO, and co all mean something different; therefore, use caps for formulas. Ca(OH)2 + H2SO4 ==> 2H2O + CaSO4. mols Ca(OH)2 = grams/molar mass = ? mols H2SO4 = M x L = ? The difference in mols is the excess reagent ...
November 3, 2015

cjemistry
http://chemistry.about.com/od/acidsbases/a/phosphatebutter.htm
November 3, 2015

Chemistry (Check)
I think you need some help on limiting reagents and finding mols and stoichiometry. Here is step by step but no numbers. 1. You have the balanced equation. 2a. Convert grams PF3 to mols. mols = grams/molar mass = ? 2b. Do the same to convert mols XeF4 to mols PF5. 3a. Using ...
November 3, 2015

Chemistry
I don't know what you've done. What's the 18.998? Where did you come up with 85.9995? The molar mass of Fe2O3 is 159.7. The atomic mass Fe is 55.85. How do you know Al is the limiting reagent. I think it is Fe2O3. If you know Al is the limiting reagent, go from ...
November 3, 2015

Chemistry - Acid and Bases
If you look these up in Ka or Kb tables, you can do this yourself. If a Ka or Kb is listed it is weak; if not it is strong. NaCl, of course, is neither so would be other.
November 2, 2015

CHEMISTRY!!
Look at k1 vs k2. k2 is about 1000 times weaker than k1 so the pH is essentially determined by k1. .........H2A ==> H^+ + HA^- I........0.08....0......0 C........-x......x......x E......0.08-x....x......x Substitute the E line into Ka1 expression and solve for x = H^+ and ...
November 2, 2015

Chemisrty
Ca + 2HCl ==> H2 + CaCl2 mols Ca = grams/molar mass = ? mols H2 = mols Ca from the equation. Then use PV = nRT and V = nRT/P. You know n, R, T. P is 753- vapor pressure H2O at 30 C. You look up v.p. H2O at 30 C in tables in your test. It will be approximately 30 torr.
November 2, 2015

chem
Fe3O4(s) + 2C(s) > 2CO2 + 3Fe mols CO2 = grams/molar mass = ? Using the coefficients in the balanced equation, convert mols CO2 to mols Fe3O4.
November 2, 2015

chem
2E-13/0.01 = 2E-13/1E-2 = 2E-11
November 2, 2015

Chemistry
1. Write and balance the equation. C3H8 + 5O2 ==> 3CO2 + 4H2O 2. grams C3H8 = volume x density = ? 3. mols C3H8 = grams/molar mass = ? 4. Using the coefficients in the balanced equation, convert mols C3H8 to mols CO2. 5. Convert mols CO2 to grams CO2. g = mols x molar mass = ?
November 2, 2015

chemistry
You need to know the delta H solution.
November 2, 2015

Chemistry
H3PO4(aq) + 3 KOH(aq) → K3PO4(aq) + 3 H2O(l) mols H3PO4 = grams/molar mass = ? Using the coefficients in the balanced equation, convert mols H3PO4 to mols KOH. Now convert mols KOH to grams. g = mols x molar mass = ?
November 2, 2015

Chem
You need to find the caps key on the keyboard and use it. Did you know there is a difference between 0.55 m and 0.55 M? Which do you want. By the way, caoh doesn't exist.
November 2, 2015

chem
Ksp = 1.8E-10 = (Ag^+)(I^-) ............AgI(s) ==> (Ag^+)(I^-) I...........solid........0.....0 C...........solid........x.....x E...........solid........x.....x Substitute the E line into the Ksp expression and solve for x. .......Ca3(PO4)2 ==> 3Ca^2+ + 2PO4^3- Qsp = (...
November 2, 2015

Chemistry
You don't have a balanced equation. mols Sn = grams/atomic mass = ? mols H2 = mols Sn Use PV = nRT and solve for volume.
November 2, 2015

Chemistry
Reaction with what.
November 1, 2015

Chemistry
I am sure that is not right.
November 1, 2015

Chemistry
Give me some indication of what you know about this. This is a "keep you busy for the next hour" problem.
November 1, 2015

Chemistry
mols Ca(OH)2 = grams/molar mass = approx 0.2 but you need a better number than that. How much heat was released for the 15 g Ca(OH)2? That is 16.2 kJ/mol x approx 0.2 mol = approx 3 kJ. So you need approx 3 kJ from the LiOH. How many mols do you need? 23.6 x # mols LiOH = ...
November 1, 2015

Chemistry
1. Write and balance the equation for oxalate and permananate, then calculate the M of the permanganate. 2. Write and balance the equation for the Sn and permanganate. 3. mols MnO4^- = M x L = ? Convert mols MnO4^- to mols Sn using the coefficients in the balanced equation. ...
October 31, 2015

Chemistry
You want 1 ppm and that is 1 mg/L. Convert 1 mg Fe^2+ to ferrous ammonium sulfate. 1 mg Fe^2+ x [molar mass Fe(NH4)2(SO4)2] = ?
October 31, 2015

chemistry
Ca(OH)2 = 74.09 65.3 kJ x (318/74.09) = ?
October 31, 2015

chemistry
Reacts with what? What are the delta Hf values?
October 31, 2015

Chemistry
I don't think that equation is correct. For AlO^2- to be correct means Al must be zero and there is no redox when Al(s) goes to AlO^2- since Al is zero in that anion. Same for NO^2-. I might believe [AlO2]^- and [NO2]^- 1. Al ==> [AlO2]^- 2. Assign oxidation states and ...
October 30, 2015

Cheistry
Your second equation is not right. It should be I2 + 2[S2O3]^2- ==> [S4O6]^2- + 2I^- 1 mol ClO^- = 1 mol I2 = 2 mols [S2O3]^2-; therefore, 1 mol ClO^- = 2 mols [S2O3]^2-. mols S2O3]^2- = M x L = ? mols ClO^- = 1/2 mols [S2O3]^2-
October 30, 2015

Chemistry
1 mol occupies 22.4 L so how much will 22.4 L weigh if 1 L weighs 1.428 g?
October 30, 2015

Chemistry
1 mol of any compound (NH3, N2H4, etc) has 6.02E23 molecules. Then NH3 has 3x that many H atoms, N2H4 has 4 x that many H atoms, etc.
October 29, 2015

Chemistry
1 mol Si has 6.02E23 atoms and 2 mols will have twice that. 0.5 mols will have 0.5 that and 0.1 will have o.1 that.
October 29, 2015

BioChem
It appears to have posted correctly this time.
October 29, 2015

BioChem
I have posted this twice and it doesn't want to post correctly. Here is another try. On the second HH equation it takes the I (initial) line and what follows onto the equation line of base + H^+ ==> acid and it may do that again. Use the HH equation with 3.5 for pH and ...
October 29, 2015

Chemistry
This is a new one on me. I don't know that there is a name for the mass of an atom's nucleus. Mass of nucleons would be appropriate but I've not heard that applied. The name for the NUMBER of protons and neutrons (nucleons) is the mass number and almost all of the ...
October 29, 2015

Chemistry
Yes, Isn't the atomic number that is on the periodic table the number of protons i the nucleus? Yes it is. So 3 protons makes it Li and 4 protons makes it Be since Be is atomic number 4. Adding a bunch more would make 92U. Look at the numbers. The subscripts add up and the...
October 29, 2015

Chemistry
Is this just an academic question or does more follow? I don't like to buy a "pig in a poke". Add a proton to Li-7, if that's all you do, will make a + ion, yes, but it is an ion of Be. 3Li7 + 1P1 ==> 4Be8. Unless this picks up an electron (and stray ...
October 29, 2015

Chemistry
Ca(OH)2(aq) + SO2(g) ==> CaSO3(s) + H2O(l) You will need So for each component, then dSo rxn = (n*dSo products) - (n*dSo reactants)
October 29, 2015

Chemistry
mols = M x L = ?
October 29, 2015

Chemistry
I don't know what values you are using. Tables vary so I can't get the same answer unless you give me the numbers you used.
October 29, 2015

Chemistry
I didn't do the math but I don't think your set up is quite right but almost right. K = 846.4 = (4.6-2x)^2/(0.5-2x)^2*(0.1+x) For cubic equations you can find a calculator on the web that will solve them. Let me point out a couple of things that I'm picky about. 1...
October 29, 2015

stoichiometry
Pick a number and you'll be right. My crystal ball is not working very well today and I have no idea what you are talking about. What's the problem?
October 29, 2015

chemistry
For a the question asks for dG for the rxn so that would be 2.6 kJ and not 2.6 kJ/mol. (It's 1.3 kJ/mol and you have 2 mols of it).
October 28, 2015

chemistry
q = 27,000 = mass H2O x specific heat H2O x (Tfinal-Tintial)
October 28, 2015

Chemistry
q = mass H2O x specific heat H2O x (Tfinal- Tinitial) = ? That gives you q = delta H for 0.0144 mols PbS formed.
October 28, 2015

Chemistry
glad to help
October 28, 2015

Chemistry
I don't understand much of what you have written. For the mols oxalic acid, it is grams = mols x molar mass. If you know molar mass and grams and you want mols, that is g = mols x molar mass g/molar mass = mols x molar mass/molar mass Now on the right side, molar mass in ...
October 28, 2015

Chemistry
Yes, for step 2.
October 28, 2015

Chemistry
This four step process will just about work them all. Print this and save it. 1. Write and balance the equation. You've done that. 2. mols H2C2O4 = grams/molar mass = ? 3. Using the coefficients in the balanced equation, convert mols H2C2O4 5o mols KMnO4. That will be mols...
October 28, 2015

Chemistry! HELP
Isn't an s orbital circular? If so, then how could it lie along the x-axis? https://www.google.com/search?q=s+orbital&ie=utf-8&oe=utf-8
October 28, 2015

Chemistry! HELP
I think your answer misses the mark. A 2px means it is a 2p electron along the x axis (as opposed to a 2py or a 2pz) and it has a spin of +1/2.
October 28, 2015

Chemistry
hos many mols do you have? That's mols = grams/molar mass = ? Convert kJ/mol to J/mol Then mols H2O x heat vap(in J/m) = q
October 28, 2015

Chemistry
mols NaOH = grams/molar mass = 0.03875 mols HCl = M x L = 0.0375 The difference will tell you that NaOH is in excess and by how many mols. Then M NaOH = mols/L.
October 28, 2015

Chemistry DRBOB HELP ME PLEASE
Multiply equation 1 by 2 and add to the reverse of twice equation 2 and add 4 times the reverse of equation 3.
October 28, 2015

Chemistry DRBOB HELP ME PLEASE
See the post above.
October 28, 2015

Chemistry
I agree with 3.83 mmols ferric but the problem asks for mols and not mmols. I don't agree with 0.242 g Fe(OH)3 formed
October 28, 2015

chemistry conversion
I don't agree with either answer. https://www.google.com/search?q=0.04+micrograms%2Fmicroliter+to+nanograms%2FmL&ie=utf-8&oe=utf-8
October 28, 2015

Chemistry
Pick a number and you'll be right. You don't have any quantities listed; therefore, this is workable.
October 28, 2015

Chemistry
CH4 + 2O2 ==> CO2 + 2H2O dH= -213 kcal
October 28, 2015

Chemistry 218
I believe you are short some information. You can use the Henderson-Hasselbalch equation (you need pKa for aspirin) and with that (ionized)/(unionized) can be calculated. However, you need something additional to separate one from the other I think.
October 28, 2015

Chemistry
mols H2O = grams/molar mass Then there are 6.02E23 molecules in 1 mole.
October 28, 2015

Chemistry
Books are written on these. Exactly what do you want?
October 28, 2015

chem
Why don't you write out the experiment you did? We aren't mind readers (yet).
October 28, 2015

chemistry
You add the aq. 3Fe^2+ + 6Cl^- + 6NH4^+ + 2PO4^3- ==> Fe3(PO4)2(s) + 6NH4+ + 6Cl^- Now cancel the ions that are common to both sides; what is left is the net ionic equation.
October 28, 2015

chemistry
mols needed=- M x L = ? grams = mols x molar mass
October 27, 2015

National school
H2SO4 + Cu ==> no reaction in the cold. H2SO4 + Fe ==> FeSO4 + H2 4.48 L x (1 mol/24 L) = mols H2. Using the coefficients in the balanced equation to convert mols H2 to mols Fe. grams Fe = mols Fe x atomic mass Fe Subtract from initial sample to find mass Cu
October 27, 2015

Chemistry
I would look at that equation if I were you. Isn't that S2O3^2- and S4O6^2-?
October 27, 2015

chemistry
Work this problem the same as your Ca(OH)2 problem except that Al is the common ion here instead of OH as in the NaOH in that problem. Solve for OH and convert to pH. Post your work if you get stuck.
October 27, 2015

chemistry
Look up the Ksp for each salt and post again with this problem. Using the numbers in my book won't give the same answer as using numbers in your text.
October 27, 2015

chemistry
..........Ca(OH)2 ==> Ca^2+ + 2OH^- I..........solid.......0......0 C..........solid.......x......2x E..........solid.......x......2x ..........NaOH ==> Na^+ + OH^- I.........0.05.....0.......0 C........-0.05....0.05....0.05 E.........0.......0.05....0.05 Substitute the ...
October 27, 2015

chemistry
Just for the record what is a whoosh in a Kjeldahl determination. Calculate the M of the HCl.Information to do that is in the second paragraph. mols HCl initially = M x L = ? mols excess HCl = M x L = ? mols HCl used by the NH3 = difference grams NH3 = mols NH3 x molar mass ...
October 27, 2015

chemistry
Ag2CO3(aq) + 2HCl(aq) ¡÷ 2AgCl(s) + CO2(g) + H2O(l) ........Ag2CO3 ==> 2Ag^+ + CO3^2- I.......solid........0......0 C.......solid.......2x......x E.......solid.......2x......x Use PV = nRT and solve for mols CO2 = mols CO3^2-. Then (CO3^2-) = mols/L of the ...
October 27, 2015

chemistry
Two equations in two unknowns. Solve simultaneously for X and Y. Let X = mass NaBr and Y = mass NaI mm = molar mass am = atomic mass eqn 1: X(mm AgBr/mm NaBr) + Y(mm AgI/NaI) = 1.0186 eqn 2: X(2*mm AgCl/2*mm NaBr) + Y(2*mm AgCl/2* mm NaI) = 0.7125 Solve for X = NaBr and Y = ...
October 27, 2015

chemistry Dr BOB
According to the site I gave you, the reaction is for the fermentation. C6H12O6 ==> 2C2H5OH + 2CO2
October 27, 2015

analytical chemistry
See your post above.
October 27, 2015

analytical chemistry
See your post above.
October 27, 2015

analytical chemistry
See your other post above.
October 27, 2015

Chemistry Dr. BOB
See your other post above. I don't get it either although the equation from that site is the correct one for the fermentation.
October 27, 2015

Chemistry
mols CaCO3 = grams/molar mass = ? Using the coefficients in the balanced equation convert mols CaCO3 to mols CO2. Now convert mols CO2 to grams CO2. g = mols x molar mass = ? This is the theoretical yield (TY). The actual yield (AY) in the problem is 3.65 grams. %yield = (AY/...
October 26, 2015

chemistry
2Na3PO4 + 3CuCl2 ==> Cu3(PO4)2 + 6NaCl mols CuCl2 = M x L = ? Using the coefficients in the balanced equation, convert mols CuCl2 to mols Na3PO4. Then M Na3PO4 = mols/L. You know mols and M, solve for L Na3PO4.
October 26, 2015

CHEMISTRY
Spacing makes this a little hard to read but the first row is 2 mols N2H4 will use 1 mol N2O4 to produce 3 mols N2 and 4 mols H2O. You just follow the coefficients in the balanced equation.
October 26, 2015

Chemistry
hc/wavelength = 2.180E-18(1/1 - 1/x^2) Substitute for h, c, and wavelength (in meters for wavelength) and solve for x which will be the orbit to which the photon raised the electron in the ground hydrogen atom. Then count the lines it can emit from its excited state. Post your...
October 26, 2015

Chemistry
44 g CO2 x (485/393.5) = ?
October 26, 2015

Chemistry
See this site. Zymase is just a catalyst. https://en.wikipedia.org/wiki/Ethanol_fermentation
October 26, 2015

Chemistry
Depends upon the strength of the HCl doesn't it? NaHCO3 + HCl ==> H2O + CO2 + NaCl
October 26, 2015

AP Chemistry
What are your reduction potentials? My tables probably don't agree with your tables.
October 26, 2015

chem - help!
The equations are CaCO3 + 2HCl ==> CaCl2 + H2O + CO2 Mg(OH)2 + 2HCl ==> MgCl2 + 2H2O Can you go from there?
October 26, 2015

CHEMISTRY
CH3COOH and CH3COO^- Ka = (H^+)(ClO^-)/(HClO) pKa = -log Ka
October 26, 2015

Chemistry -Dr.Bob
I didn't obtain that answer. Convert mg to grams, then convert grams As/L to mols As/L and that is M. Does it sound reasonable to you that a small concentration (like 1 ppm) is more than 10,000 M. I don't think so.
October 25, 2015

Chemistry
grams = mols x atomic mass.
October 25, 2015

Chemistry
How many nL of a 1.00 molar solution OF WHAT?
October 24, 2015

Chemistry
Use the same formula anonymous used for the boiling water problem.
October 24, 2015

chemistry
mols CaCl2 = 0.2 mols Cl in CaCl2 = 2x that. mols MgCl2 = 0.15 mols Cl in MgCl2 = 2x that. mols NaCl = 0.75 mols Cl in NaCl = 1 x that. total mols Cl = sum of Cl. Then grams = mols x atomic mass.
October 24, 2015

chemistry
q = mass x specific heat x (Tfinal-Tinitial) Remember to convert 100 g to mols first.
October 24, 2015

chemistry
Is that question 1 which says 43.4 kcal or some other notation. If I have interpreted this correctly, then 1 mol HgO is (216.6) so 2 mols = 2*216.6. You have 10.8 g; therefore, 43.4 Kcal x [10.8/(2*216.6)] = ?
October 24, 2015

chemistry
How am I to understand the question if you don't type all of it?
October 24, 2015

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