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June 27, 2016

Posts by DrBob222

Total # Posts: 52,582

Chemistry - radioactivity
According to this table it appears to me that 78Pt200 is subject to beta decay while 192 and 196 are stable and 188 is electron capture. https://en.wikipedia.org/wiki/Isotopes_of_platinum
November 17, 2015

Chemistry (Help)
I don't get 35,120. I get 75,520 for the balanced equation. If you take the question literally you divide by 2 but that gives my number still higher. I normally don't divide by 2 UNLESS the problem states that they want kJ/mol but I don't know the context of your ...
November 17, 2015

Chemistry (Help)
I am really embarrassed. I completely ignored that coefficient of 2 for the first material. Ok so the equation is ok. Let me recalculate the dH.
November 17, 2015

Chemistry (Help)
Yes it is. 2C57H110O6 (s) + 163O2(g) --> 114CO2(g) + 55H2O(l) You have 110 H on the left and 110 on the right.
November 17, 2015

Chemistry (Help)
The equation isn't balanced. You have (163*2)+(2*6) = 338 O on the left and (114*2) + 110*2) = 448 on the right. You can make it balance with 55 H2O and not 110 H2O.
November 17, 2015

Chemistry (Help)
That's what I obtained.
November 17, 2015

Chemistry (Help)
If you show each step perhaps I can figures out what you're doing wrong. For example: 6*-393.5 = ? 6*-285.84 = ? Total = ? etc.
November 17, 2015

Chemistry (Help)
I think it is set up right but I don't get that answer. It is exothermic and the equation is balanced.
November 17, 2015

Chemistry
Note here that you obtained 75520 for dHrxn but on page 1 you are not using half of that if you are doing for 1 mole. And the 75520 agrees with the number I had (before dividing by 2) for 1 mole. Here, I obtained 890 for the molar mass but I used 12 for C, 16 for O and 1 for H...
November 17, 2015

Chemistry
I don't get that. The best way you can do this is to show the balanced equation, then show step by step what your math is like and I can find the error if you've made one. I think we're wasting time with your multiple answers and my no that isn't right.
November 17, 2015

Chemistry
Balance the equation. dHrxn = (n*dHf products) - (n*dHf reactants) in units of kJ/mol q = dHrxn x (578/2*molar mass tristearin) = ?
November 17, 2015

general chemistry
mols Na2CO3 = grams/molar mass = ? Then M Na2CO3 = mols/L (but the problem SHOULD SAY in 1.50 L of SOLUTION). (Na^+) = 2 x (Na2CO3) (CO3^2-) = (Na2CO3) For ppm, convert 2.57E-4 g Na2CO3 in 1.50 L to mg/L and that will be the ppm.
November 17, 2015

Chemistry
m^-1 means per meter and since R is measured in per meter the wavelength comes out in meters. So solve as you have suggested and convert the answer for wavelength in meters to nanometers. By the way, you want to substitute 1 for n1 and solve for n2.
November 17, 2015

Chemistry
I think I can answer your question but your phrasing is bad. You don't ask a question, really, and that word "is" is out of place. Delta G is zero but not because it is standard but because it is in equilibrium at the boiling point (I assume that is the b.p. for ...
November 17, 2015

chem
millimols AgNO3 = mL x M = 25*0.1 = 2.5 millimols Na3PO4 = 50 x 1.5 = 75 ......3AgNO3 + Na3PO4 ==> Ag3PO4 + 3NaNO3 I......2.5......75..........0........0 C.....-2.5.....-2.5/3......2.5/3....2.5 E.......0.......74.17.......0.8333..2.5 For solubility product with the PO4^3- ...
November 17, 2015

chem
Refer to your other problem with Ag3PO4.
November 17, 2015

Chemsitry
And you can't do this for what reason(s)?
November 17, 2015

chem
I have seen you write tsp twice. What in the world is tsp? Do you mean Ksp. ...........SrCrO4 --> Sr^2+ + CrO4^2- I..........solid.......0........0 C..........solid.......x........x E..........solid.......x........x Ksp = (Sr^2+)(CrO4^2-) You must determine the ...
November 17, 2015

Chemistry
grams O2 = density x volume = 1.118 g/cc x 1 cc = ? mols O2 = n = grams/molar mass = ? Then use PV = nRT and solve for P. Remember to use K for temperature and L for volume.
November 17, 2015

Chemistry
NH4Cl is a salt that ionizes completely; therefore, (NH4^+) = 1.50 M. NH3 is a weak base that has a Kb. ...........NH3 + H2O ==> NH4^+ + OH^- I.........0.50............0.......0 C..........-x.............x.......x E.......0.50-x............x.......x Kb = look it up = (NH4...
November 17, 2015

Chem
M CaSO4 = mols/L. You have 1 L and mols = grams/molar mass. Solve for M. Ksp = (Ca^2+)(SO4^2-). Plug in M Ca^2+ and SO4^2- and solve for Ksp.
November 17, 2015

Chemistry
heat lost by Cu + heat gained by H2O = 0 [mass Cu x specific heat Cu x (Tfinal-Tinitial)] + [mass H2O x specific heat H2O x (Tfinal-Tinitial)] = 0
November 17, 2015

Chemistry
40 mL of 0.1 M HCl obviously will take exactly 40 mL of 0.1 M NaOH to arrive at the equivalence point. So a and b are before the eq pt and c is after the eq pt. For a. HCl + NaOH ==> NaCl + H2O. millimols HCl = 40 x 0.1 = 4 mmols NaOH = 28 x 0.1 = 2.8 Difference [which is ...
November 17, 2015

Chemistry
C6H12O6 + 6O2 ==> 6CO2 + 6H2O dHrxn = (n*dHf products) - (n*dHf reactants) and dHrxn will be in kJ/mol. Divide by 1 and divide by molar mass C6H12O6 to get kJ/gram. To convert to fuel value change the negative sign to a + sign. Do the same for tristearin. The equation is ...
November 17, 2015

chemistry
1. It appears the problem states the single dose is 1g per 10 mL. mols of the stuff = grams/molar mass = ? Then M = mols/0.010 L = ? 2. Sure is a funny way of stating the problem but it is mL1 x M1 = mL2 x M2 mL1 x 6 = 75 mL x 0.5 Solve for mL 1. 3. mL1 x M1 = mL2 x M2
November 17, 2015

chem
1. 148 ng/L = 148E-9 g/L. Then g/L is 1.48E-9 g/L x #L = ? 2. mols NaF = grams/molar mass M = mols/L 3. You have 0.030 g in 48,000 g and you want to convert that to g in 1000. So 0.030 g x 1000/48000 = ? 4. mols = grams/molar mass Then M = mols/L 5. 5 ug x (1 mg/1000 ug) = ? ...
November 17, 2015

Chemistry (Help)
No. mols CO2 = 114 mol H2O = 110 so dHrxn = [(114*-393.5) + (110*-285.84)] - [ etc.
November 17, 2015

Chemistry (Check)
Go back to the C57 compound and see how I did that. You are using TOTAL mols and that isn't the right way to do it.
November 17, 2015

chem
I suggest you repost this at the top of the page but add what you don't understand about the question or what numbers you have to show in your work.
November 17, 2015

chemistry
You want how many mols? That's mols = M x L = ? with M = 0.01 and L = 0.015 Then grams = mols x molar mass. You know molar mass and mols, solve for grams.
November 17, 2015

chemistry
Use the Henderson-Hasselbalch equation. ou will need pKa for acetic acid. The base in the HH equation is 0.250 and the acid is 0.350 M. Plug in and turn the crank.
November 17, 2015

Moorpark
I answered this question for you below. If you don't understand something tells us what it is instead of just posting the same thing.
November 16, 2015

chemistry
This is pretty basic stuff. Li(g) ==> Li^+(g) + e The equation in the problem doesn't have the electrons in it but that basic ionization equation is as I wrote it. Your answer key MAY omit the e that I have.
November 16, 2015

Chemistry
q = mass ice x heat fusion. heat fusion for ice is 80 calories/gram. To convert, 1 Cal = 1000 cal 1 cal = 4.184 J 1000 J = 1 kJ.
November 16, 2015

chem
You can look these up on www.webelements.com
November 16, 2015

chem
See your other post.
November 16, 2015

Chemistry (Check)
Again, here, I don't think the equation is balanced.
November 16, 2015

Chemistry (Check)
You don't show the balanced equation but I think that is the problem. My balanced equation is 6CO2 and not 14 C6H12O6 + 6O2 ==> 6CO2 + 6H2O
November 16, 2015

Chemistry
https://www.google.com/search?q=solubility+KNO3+vs+temperature&tbm=isch&imgil=9QJGKEHcM1fAoM%253A%253BU4q0MForzpxyDM%253Bhttp%25253A%25252F%25252Fwww.nakka-rocketry.net%25252Fknsyn1.html&source=iu&pf=m&fir=9QJGKEHcM1fAoM%253A%252CU4q0MForzpxyDM%252C_&biw=1024&bih=632&usg=...
November 16, 2015

Chemistry (Check)
I think EN does have an influence, the other one is the size of the anion. The greater the distance (HI for example) the weaker the bond.
November 16, 2015

Chemistry
At the point of pptn, (I^-) = 0.35M x (29.6/65.9) = ? (Pb^2+) = Ksp/(I^-) = ?
November 16, 2015

chemistry
15.46 mg Au = 0.01546 g Au. mols Au = grams/molar mass = ? = mols Cu Then g Cu = mols Cu x atomic mass Cu.
November 16, 2015

why does photosynthesis require energy
6CO2 + 6H2O ==> C6H12O6 + 6O2 Because it takes more energy to break 6CO2 bonds and 6 H2O bonds than is formed by the formation of the product bonds.
November 16, 2015

chemistry
7.5 g CaCl2*9H2O x (molar mass CaCl2/molar mass CaCl2*9H2O)_
November 16, 2015

Chemistry
Surely you have made a typo (or two). There is no way the pH can be 4.90. The equivalence point for the titration of a weak acid and strong base is approximately 8.3 or so. Adding BASE to that will make it higher, not lower.
November 16, 2015

chemistry
H2O ==> H^+ + OH^- Kw = (H^+)(OH^-) pH = 4.73 = -log(H^+) and I get approx 2E-5 but that's just a close estimate for (H^+). That makes (OH^-) = estimated 5E-10M # mols OH^- = M x L = ? and each mols has 6.02E23 ions.
November 16, 2015

Chemistry
It depends upon exactly what you mean by saturated. If it is just saturated and there is no solid in the solution, nothing will happen. If, however, there is a relatively small amount of KNO3 solid, the solid will dissolve as the solution is heated and the solution will be ...
November 16, 2015

chem
to do what? make 0.148 M NaI in 500 mL? How many mols do you need? That's M x L = mols. Then mols = grams/molar mass. You have mols and molar mass, solve for grams.
November 16, 2015

chemistry
You need to find the arrow key(s) and use it(them). --> or ==> Keq = (NH3)^2/(N2)(H2)^3 It's always (product)/(reactants) and each coefficient becomes an exponent.
November 16, 2015

Chemistry
We can't draw diagrams on this forum. You can look on Google for that.
November 16, 2015

Chemistry
I would look at a, c(slight with anything almost), and d.
November 16, 2015

Analytical Chemistry
I gave you detailed instructions for this problem yesterday (late yesterday).
November 16, 2015

Chemistry
Which constant and for what?
November 16, 2015

Science: Chemistry
dHrxn = (n*dHf products) - (n*dHf reactants) = ?
November 15, 2015

Science: Chemistry
mols pentane = grams/molar mass = ? Using the coefficients in the balanced equation, convert mols pentane to mols CO2. Then g CO2 = mols CO2 x molar mass CO2 and this is the mass at 100% yield. Mass CO2 at 58.0% yield is mass at 100% yield x 0.580 = ?
November 15, 2015

chem
You gave the electron configuration for Al, not Al^3+. You should remove the last three electrons for the Al^3+ ion. Same thing for P^3-. You should add 3e to what you have.
November 15, 2015

Chem
Al + N2 ==> Al3N2 (not balanced) Al is zero on the left and +3 on the right. N is zero on the left and -3 on the left. Oxidation is the loss of electrons; reduction is the gain of electrons.
November 15, 2015

chemistry Dr BOB
The oxidation half equation is Fe^2+ ==> Fe^3+ + e The reduction half equation is MnO4^- + 8H^+ + 5e ==> Mn^2+ + 4H2O
November 15, 2015

Analytical Chemistry
You have 0.0398 g CuSO4.5H2O. Convert that to g Cu as follows: 0.0398 x (atomic mass Cu/molar mass CuSO4.5H2O) = ? That gives you g Cu/100 mL (technically, that should be 100 mL OF SOLUTION. Then convert 0.0398 g Cu to mg Cu which is in 100 mL of solution then multiply by 10 ...
November 15, 2015

Chemistry 102
What are you using for Kformation for Ni(CN)4?
November 15, 2015

Chemistry
You balance the equations. NaCl(aq) ==> H2(g) + Cl2(g) + NaOH(aq) NaCl(l) ==> Na(l) + Cl2(g) (Note: For NaCl to be liquid, the temperature must be hot enough that Na will be melted also. The same applies to K beldow.) KBr(l) ==> K(l) + Br2(g)
November 15, 2015

Chemistry
The easiest way to do this is to reverse equation 1 and add in equation 2 for PbO2 + 4H^+ + SO4^2- + Pb + SO4^2- --> PbSO4 + PbSO4 or PbO2 + 2H2SO4 --> 2PbSO4 + 2H2O Ecell = 2.041 Then Ecell = Eocell - (0.05916/n)*log(1/(H2SO4). Plug in the numbers and solve for Ecell.
November 15, 2015

Chemistry
I don't see anything wrong with what you have.
November 15, 2015

Chemistry
H2A + 2NaOH ==> Na2A + 2H2O mols NaOH = M x L = ? Using the coefficients in the balanced equation, convert mols NaOH to mols H2A (that is 1/2 mols NaOH) Then mols = grams/molar mass. You know grams and mols, solve for molar mass.
November 15, 2015

Chemistry
25.5(0.861) + 29.2(1-0.861) = ?
November 15, 2015

Chemistry
Technically, both C2H4 and NBr3 have polar covalent bonds but most organic chemists don't consider the C-H bond to be polar.
November 15, 2015

chemistry
2HNO3(aq) Na2CO3(aq)=>2NaNO3(aq) H20(l) CO2(g) mols HNO3 = M x L = ? Using the coefficients in the balanced equation, convert mols HNO3 to mols Na2CO3 (That will be 1/2 mols HNO3) Then grams Na2CO3 = mols Na2CO3 x molar mass Na2CO3. This will be the grams in the 25 cc of ...
November 15, 2015

Chemistry
The easy way to do this is Step 1. 2Fe2O3 + 3C ==> 3CO2 + 4Fe Step 2. Then don't worry about the tonnes. Step 3. mols Fe2O3 = 10,000/molar mass Fe2O3. Step 4. Using the coefficients in the balanced equation, convert mols Fe2O3 to mols Fe. Step 5. Then grams Fe = mols Fe...
November 15, 2015

chemisty
How many mols do you need? That's M x L = ? Then mols = g/molar mass. You know mols and molar mass, solve for grams needed.
November 15, 2015

Chemistry
mols = grams/molar mass. You know grams and mols, solve for molar mass.
November 15, 2015

Chem
a. P*molar mass = density*RT Substitute and solve for molar mass. b. Use the equation in a to solve for density c. XO2 = molar mass = ? 2*atomic mass O = 32 Subtract to find atomic mass X.
November 15, 2015

Chem
I made a stab at answering this once. You need to tell us what you did for us to know the system you're using.
November 15, 2015

Chemistry
See your other post.
November 15, 2015

chemistry
wavelength = h/mv You know wavelength (convert o m), you know h, you know v (0.01*3E8) so solve for m for mass of one atom. Convert to a mol of atoms.
November 14, 2015

Chem
The question asks how you did it and I don't know that. What does decorated mean? Ag HCl to ppt AgCl without the others. Add NaOH to ppt Al(OH)3 without the others. Adding NaOH will convert the NH4Cl to NH3 and that can be expelled. K^+ will be left.
November 14, 2015

Chemistry
I believe this is a screwed up question from the get go.
November 14, 2015

Chem
I guess slats is salts. But I don't know what the addition of his is.
November 14, 2015

Chemistry
The answer is c. a won't work. Why? Ni^2+ is -0.25 with H2 is 0 so Ecell is negative and that isn't spontaneous. But c will. Why? Ag^+ is 0.8 Ni to Ni^+ is +0.25 Add and Ecell is + so rxn is spontaneous. You can go through the others to convince yourself that all are ...
November 14, 2015

Chemistry
1/wavelength = R(1/(n1)^2 - 1/(n2)^2 The first term is 3^2 and the second is 4^2. R you can find in your book or on the web.
November 14, 2015

chemistry
We can't draw diagrams on this forum.
November 14, 2015

Chemistry
.......2HBr + 2K ==> 2KBr + H2 mols K = grams/molar mass Using the coefficients in the balanced equation, convert mols K to mols HBr. Now convert mols HBr to volume using M HBr = mols HBr/L HBr. You know M and mols, solve for L.
November 14, 2015

chemistry
I can't tell the difference between the question and what I assume is your answer.The skeleton equation is simply 5Fe^2+ + MnO4^- ==> 5Fe^3+ + Mn^2+ and you can add the states. Most of the rest of what you wrote is not right but the final equation you came up with is ...
November 14, 2015

chemistry
Use PV = nRT with n = g N2/molar mass N2. Remember T must be in kelvin.
November 14, 2015

Chemistry
a cd b However, I prefer to say the water molecules are attracted to the Na ions (of the crystal) and Cl ions (of the crystal).
November 14, 2015

Chemistry
The correct answer is b.
November 14, 2015

chemistry
........NH3 + H2O ==>NH4^+ + OH^- I........5............0.......0 C.......-x............x.......x E.......5-x...........x.......x Substitute the E line into Kb expression and solve for x = OH^-, then convert to pH.
November 14, 2015

Chemistry
q = [mass H2O x specific heat H2O x (Ttinal-Tinitial)] + Ccal x (Tfinal-Tinitial) and that gives you q for 2.1. Change to q for 1 g.
November 13, 2015

Chemistry
See your other post. Apparently you ignore the Ccal.
November 13, 2015

Chemistry
1000 kg coal = 1,000,000 g coal and if that contains 0.050% FeS2, then 1,000,000 x 0.0005 = ? g FeS2 to start. Go through the stoichiometry to find how much SO2 is produced, then do the stoichiometry to find NaOH required.
November 13, 2015

Chemistry (Check)
You did it right; I used 11/760 and left it in the calculator.
November 13, 2015

Chemistry (Check)
You have too many s.f. in that answer for A. Also, I don't get that exactly; the problem, I suspect, is that you rounded with intermediate numbers and I didn't. B is ok.
November 13, 2015

Chemistry
right
November 13, 2015

NOTE: Chemistry
I want to point out that you aren't allowed 4 significant figures.
November 13, 2015

Chemistry
Nope. Right digits but wrong decimal. By the way, the problem below with an answer of 0.530 is ok but the site wouldn't let me post an ok.
November 13, 2015

Chemistry (Check)
good. Come back anytime.
November 13, 2015

Chemistry (Check)
The difference: If I use 900/760 and round that number to 1.18 (which is correct), I get 12.22 which rounds to 12.2. However, if I set my calculator to read 6 places (which I do routinely for all of my work) then go through without taking anything out of the calculator; ie., ...
November 13, 2015

Chemistry (Check)
My calculator reads 12.267 so I would round that to 12.3 g.
November 13, 2015

Chemistry (Check)
500 mL x (742/795) = 467 mL
November 13, 2015

Chemistry
OK
November 13, 2015

Chemistry (Check)
ok
November 13, 2015

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