Tuesday
June 30, 2015

Posts by DrBob222


Total # Posts: 49,357

chemistry
See your other post.
May 12, 2015

chemistry
You CANNOT continue in chemistry and not use the caps key. I will get you started. Cr goes from +6 for each on the left to +3 on the right for each. I on the let is -1 and on the right is zero. Make things easy by making that 2KI on the left. You may need to change it later ...
May 12, 2015

Chemistry
H2CO3 has two ionization constants; i.e., ka1 and ka2. Generally the Ka values for diprotic acids is far apart and you simply treat these as two separate ionizations; the second one contributes little so you ignore it. ..........H2CO3 ==> H^+ + HCO3^- I........0.23.......0...
May 12, 2015

science(check answers)
I don't see anything to check. (No answer)
May 12, 2015

Chemistry
7.2 is right for pK2. And I obtained 6.0g NaH2PO4 which is quite close to your number. The difference is that I used 43.15 mL of 1M NaOH to do that and that's the difference. Do you want to work on that a little or want me to show you what I did.
May 12, 2015

Chemistry
I don't think so. pH = 7.21 + log (0.007/0.007) pH = 7.21 which isn't 8.00 7 mL x 1 M = 7 millmols NaOH = 0.007 mols.
May 12, 2015

Chemistry
If we are to try for the same number I need to know what you used for pK2.
May 12, 2015

Chemistry
I obtained 0.038 for x. So Y is 2x isn't it? ...........XY2 ==> X^2+ + 2Y^- I........solid.....0.......0 C........solid.....z......2z E........solid.....z......2z Note that Y is just twice X. I tried, with different manipulations, to obtain 0.0318 but couldn't do it...
May 12, 2015

Chemistry
No, the answer is 2.0E-5. I've looked at the problem again and it appears not to have any "tricks of the trade" attached to it so I believe if you have a database version or an answer sheet that those are incorrect.
May 12, 2015

Chemistry
.......X2Y(s)<-->2X^+(aq)+Y^(2-)(aq). Ksp = (X^2+)^2(Y^2-) X = 0.02 Y = 0.05 Ksp = (0.02)^2(0.05) = ?
May 12, 2015

chem
N2 + O2 --> 2NO mols N2 = grams/molar mass = 10/28 = approx 0.3 but you need a more accurate answer than that estimate. Use the balanced equation to convert mols N2 to mols NO. That's 0.3 x (2 mols NO/1 mol N2) = approx 0.3 x 2/1 = approx 0.6 mol NO. Then grams NO = ...
May 12, 2015

Chemistry
See your post above.
May 12, 2015

Electronics, Physics
The parallel group has an equivalent resistance of 1/R = 1/R1 + 1/R2 1/R = 1/60 + 1/5 R = ? which I will call Rp Then the total for the circuit is Rtotal = 10 + Rp = ?
May 12, 2015

Math to hard please help
The 4x^2 and 3x^2 are like terms. You can add or subtract like terms but not unlike terms. The 15x is a different terms than x^2 and has no other like term. So 4x^2 - 3x^2 = x^2 +15x has nothing to add or subtract so it remains 15x. -3 and -5 = -8
May 11, 2015

Chemistry
I don't intend to work this problem for you under any name. You take those numbers I gave you earlier and substitute them. Telling me you don't know how to solve for t doesn't help. Substitute the numbers, show me your work, go as far as you can, then tell me what ...
May 11, 2015

Science
http://www.enviropedia.org.uk/Weather/Movement_of_Air.php
May 11, 2015

chemistry B-11
P1V1 = P2V2
May 11, 2015

Chemistry
mols H2 gas = mL/22,400 = ? Using the coefficients in the balanced equation, convert mols H2 gas to mols K. Now convert mols K to grams. g = mols K x atomic mass K = ?
May 11, 2015

Chemistry
.......N2 + 3H2 ==> 2NH3 I.....1.15..1.36......0 C......-x....-3x.....2x E....1.15-x..1.36-3x..2x So if 2x = 0.78 then x = 0.39 The way they get 86.02% is this. (3x)/1.36]*100 = 86.029 but that makes no sense to me. I Googled "extent of reaction" and came up with ...
May 11, 2015

Chemistry
I don't know what you mean by extent of reaction.
May 11, 2015

Math
Yes, D is correct.
May 11, 2015

oops--four typos--Math
If n is supposed to be that series, then you do 5*3^n 5*3^1 = ? 5*3^2 = ? 5*3^3 = ? 5*3^4 = ? etc. What you must do is evaluate the 3^n part and multiply by 5. 5*3^1 = 5*3 = 15. etc.
May 11, 2015

Math
If n is supposed to be that series, then you do 5*3^n 5*3^1 = ? 5*3^2 = ? 5^3^3 = ? 5^3^4 = ? etc. What you must do is evaluate the 3^n part and multiply by 5. 5^3^1 = 5^3 = 15. etc.
May 11, 2015

Math
If you don't know what n is, how did you arrive at A as being the best answer? Guessed, I suppose. I think n is supposed to 1, then 2, then 3, then 4, etc. so that you have a series of answers.
May 11, 2015

Math
If n is supposed to be 1,2,3,4 sequentially, your answer of A is not right.
May 11, 2015

Math
Your question isn't very clear. What's n?
May 11, 2015

Chemistry
Here is the process that will work EVERY ONE of the titration problems. In fact it will work ALL of the stoichiometry problems, bar none. By the way, most of us here use carets to denote an exponent. No caret means it is a coefficient OR a subscript. Placed BEFORE the equation...
May 11, 2015

Math
try 87.532 That's 80 +07 +0.5 +0.03 +0.002 Total is 87.532
May 11, 2015

Science
The amplitude of the two waves add (algebraically) and the new is zero amplitude.
May 11, 2015

Science
The formula for visible light is a new one on me. The speed of light is dictated by the formula C = frequency*wavelength but that works no matter visible or not visible light. When light passes through a medium it bends slightly(is refracted) because it slows down slightly. ...
May 11, 2015

Science
For 1, P = E*I
May 11, 2015

Science
very poor; however, it will burn.
May 11, 2015

oops--typo--chemistry
0.01kg = 10.0 grams water.
May 11, 2015

Chemistry 20
When one has gases one may treat L as if they were moles and not go through the conversion to mols step. 17 L CH4 x (3 mols O2/2 mols CH4) = 17 x 3/2 = ? L O2.
May 11, 2015

Science
7 is correct. 8 is incorrect. Look back at my comments to #1. Henceforth, please make your answers at the point of entry. A letter will do, asterisks will do, almost any notation will do but it takes at least three or four scroll downs and scroll ups to check one question (for...
May 11, 2015

Science
6 is incorrect if you mean 2 N. If you mean answer b (of 3N) 6 is correct.
May 11, 2015

Science
C is not correct for 5. 52 x 10 = 520 for the cheetah. 5000 x 1 = 5000 for the elephant which is not less than 520
May 11, 2015

Science
4 is correct.
May 11, 2015

Science
3 is correct.
May 11, 2015

Science
2 is correct.
May 11, 2015

Science
1 is correct. Total momentum before = total momentum after. You could have made this a lot easier to check if you had put your answera AT THE QUESTION.
May 11, 2015

chemistry
Go the top of your class.
May 11, 2015

Science
f = ma; therefore, a = f/m. f is equal on both. Which has the larger/smaller mass. What does that do to a?
May 11, 2015

chemistry
R = resistivity*L/A Calculate R and substitute L for length and A for cross section area and solve for resistivity. I believe L is in meters and A in square meters for resistivity to be reported in ohm-m.
May 10, 2015

Chemistry
See this link. I would read that as 105 g NaNO3/100 g H2O http://staff.concord.org/~ddamelin/chemsite/h_solutions/handouts/SolubilityCurves.pdf So mols NaNO3 = 105 g/85 = about 1.2 and 1.2 mol/0.1 kg solvent = about 12 m. So 3 m should be .......?
May 10, 2015

Chemistry
Do you have a table or a graph in your text/notes that gives the solubility of NaNO3 at 40 C?
May 10, 2015

Chemistry
What's 6000m? Did you mean 6000 mL? No, not quite. That's what the total volume must be; assuming volumes are additive you would add 6000-500 = ? mL.
May 10, 2015

Chemistry
m = mols/kg solvent = 0.66/kg solvent.
May 10, 2015

science
Technically it is a polyol which makes it a sugar alcohol. But here is the straight scoop from the FDA how it is labeled if in food. http://www.pgchemicals.com/wp-content/uploads/2012/05/Nutritional-Information-2012-Website.pdf
May 10, 2015

chemistry
There are three equations. KOH may react with 1,2,or 3 of the H ions in H3PO4. if all of them are neutralized it will be 3NaOH + H3PO4 ==> Na3PO4 + 3H2O
May 10, 2015

chemistry
For whatever it's worth, there is no salt with the formula KCl3. I expect you mean KClO3. Another for whatever it's worth, is that the solubility varies with temperature. What temperature do you have in mind. You might Google KClO3 and see if Wikipedia list it. If it ...
May 10, 2015

chemistry
I don't have all of the solubilities of the thousands of salts memorized; surely yu must have a graph or a table in your text/notes that gives you this information.
May 10, 2015

Chemistry
The 0.017 mol L^-1 is 0.017 mols/L which is 0.017 M. You multiply that by 0.094 L to get mols. Now I see your latest post. I obtained 0.996% which to two significant figures will round to 1.0%
May 10, 2015

Chemistry
No, You left out the first step. You never calculated mols. mols vanillin extracted = M x L = ?
May 10, 2015

Chemistry
mols vanillin extracted = M x L = ? g vanillin extrated = mols vanillin x molar mass vanillin. Then % vanillin = (g extracted/g pods)*100 - ?
May 10, 2015

Chemistry (Acids and Bases)
Because you calculate the pOH, not the pH. Since NaOH ==> Na^+ + OH^- then the OH is 0.3 M. To convert from pOH to pH it is pH + pOH = pKw = 14. Knowing pKw and either of the others, you can interchange pH ad pOH quickly and easily.
May 10, 2015

Chemistry (Acids and Bases)
You can't? 0.400 molar is 0.400 M. The pH looks ok to me. 1 M HCl has pH of 0 so 0.400 M should be just a bit higher and it is.
May 10, 2015

chemistry
http://www.jiskha.com/display.cgi?id=1431110694
May 10, 2015

chemistry
Didn't I do this a couple days ago for you. Instead of reposting, tell me what you didn't understand about the answer and we can get through it. t is the only unknown in the equation.
May 10, 2015

Chemistry
Do this. dHrxn = (n*dHformation products) - (n*dHformation reactants) You can look up the dH formation, usually labeled as delta Hfo in your text/notes/on the web. Post your work if you get stuck.
May 10, 2015

chemistry
You can read this site. http://chemistry.oregonstate.edu/courses/ch361-464/ch362/irinstrs.htm Part way down the first page you see the following: All of the source energy gets to the sample, improving the inherent signal-to-noise ratio. The digitization and computer interface ...
May 10, 2015

analytical chemistry
I don't know the answer to your first question since I don't know what your prof had in mind. The information and questions after that is out of my league. I've never done any work with synchronous spectra; in fact, I don't know what it is. Sorry about that.
May 10, 2015

Chemistry
There may be shorter ways to do this but here is what I would do. PbxOy + C ==> yCO2 + xPb Use PV = nRT and solve for mols CO2 at rtp. Convert mols CO2 to g oxygen. g Pb = 13.70-g O = g Pb Then mols Pb = grams pb/atomic mass Pb = ? mols O atoms = grams O/atomc mass O = ? ...
May 10, 2015

Chemistry
Convert 5 g CuO to grams CuSO4.5H2O. That s 5 g CuO x (molar mass CuSO4.5H2O/molar mass CuO) = ?g CuSO4.5H2O equivalent. This is the theoretical yield (TY). The actual yield (AY) from the problemn is 10g. %yield = (AY/TY)*100 = ?
May 10, 2015

chemistry
I don't know that this will answer the question but it's interesting, anyway. https://www.google.com/search?q=can+FT+be+used+for+UV-vis+spectra&ie=utf-8&oe=utf-8
May 10, 2015

Chemistry
CH3CH2CH2CH2CH2-OH + CH3-COOH ==> CH3CH2CH2CH2CH2OOCCH3 + H2O
May 10, 2015

wave optics
sound waves
May 10, 2015

ap chemistry
negative S means -entropy and negative means minus. So the sign is the opposite of +.
May 9, 2015

ap chemistry
What does negative S mean to you?
May 9, 2015

ap chemistry
I believe all three are negative S.
May 9, 2015

Science
Scroll down to Basic Concepts. http://en.wikipedia.org/wiki/Global_Positioning_System
May 9, 2015

Science
From what I have been able to read, four are required unless the receiver clock is synchronized with the satellite clocks in which case only three are required. I think the key part of this question is "pinpoint.......on EARTH'S SURFACE". Knowing on earth's ...
May 9, 2015

chemistry
2HCl + Ba(OH)2 ==> 2H2O + BaCl2 mols HCl = M x L = ? mols Ba(OH)2 = M x L = ? Determine the limiting reagent and go from there. Post your work if you get stuck and I can help you through.
May 9, 2015

chemistry
I would use dG = 0 = dGo + RTlnQ but that doesn't give me 775 atm.
May 9, 2015

Chemistry - Acids/Bases
I think it is time that someone clarified the definition of strong/weak acids/bases and/or examples of those that are insoluble. Of course I could be mixed up; in that case, perhaps I could be clarified. :-)
May 9, 2015

Chemistry - Acids/Bases
Most of us have classified strong and weak acids/bases as all or nothing; i.e., strong has to do with does it ionize 100%(or close to 100%) or not. If yes we say it is strong, if not we say it is weak. If you read much on the internet, especially about strong/weak bases you ...
May 9, 2015

ELECTROCHEMISTRY
What Eo values are you using for Cd and H.
May 9, 2015

chem 100 electrochemisty
If you had shown your work I could find the error. You're right, the Cl doesn't change oxidation state; however, it enters the reaction (formation PbCl2) so it should be included in the equation.And I assume you meant to say USE Eo to calculate Ereaction.
May 9, 2015

chemistry
q1 = heat needed to raise T of ice from -18 C to zero C. q1 = mass ice x specific heat ice x (Tfinal-Tinitial) q2 = heat needed to melt ice at zero C to liquid H2O at zero C. q2 = mass ice x heat fusion q3 = heat needed to raise T liquid H2O from zero C to 25 C. q3 = mass ...
May 9, 2015

chem 100 electrochemisty
Add -nFEo for Cu^3+ + 2e ==> Cu^+ to -nFEo for Cu^+ ==> Cu^2+ + e Then total = -nFEo. Solve for Eo I ran through it quickly and if I didn't punch in the wrong numbers it's about +2.5 v for Cu^3+ + e ==> Cu^2+
May 9, 2015

Chem 100
What about Cl2 + H2O2 ==> 2Cl^- + O2 + 2H^+ I don't know if this is the spontaneous direction or the reverse but you can look up the Eo potentials and decide which direction to write it.
May 9, 2015

college chemistry
dG = dH - TdS At the melting point of zero C the system is in equilibrium; therefore, dG = 0. Substitute and solve for dS.
May 9, 2015

college chemistry
Thomas, it wouldn't hurt to read over your posts before you push that submit button. No caps and no periods and typos to boot leave a post that's difficult to interpret. For this one I've guessed at half of the question; assuming I've guessed right you do the ...
May 9, 2015

college chemistry
I don't know what you're supposed to use (what are you studying in the chapter) but one way to do it is this. Look up dHvap and dSvap, then dG = dH - TdS Since dG = 0 at the boiling point, then T = dHvap/dSvap
May 9, 2015

chemistry
Any pH? Any concentration of sodium acetate? Any buffer strength? 25 drops acetic acid + 15 (split the difference) sodium acetate, add water, and viola! However, you don't have much of a buffer with all of that other information dangling.
May 9, 2015

Analytical Chemistry
ok. good. Now you understand that "standard 1" really isn't a standard. That's the unknown. If you were doing this on graph paper (I don't know how you do it on Excel), you would extrapolate that straight line starting at the 9.990 point and moving to the...
May 8, 2015

Analytical Chemistry
I commented in my first response that your concentrations were calculated correctly. However, I don't know what the 19.979; 29.986, etc are. These may be the intensity. Also, I note you have a b of 4.7499 which I didn't see in the first post. At least I don't ...
May 8, 2015

Pre-Ap Chemistry
2KClO3(s)->2KCl(s) + 3O2(g) mols KClO3 = grams molar mass = ? Using the coefficients in the balanced equation, convert mols KClO3 to mols O2 gas. Then substitute n into PV = nRT and solve for V in liters at the conditions listed. Use P = 0.683 atm, R is 0.08206 L*atm/mol*K...
May 8, 2015

Pre-Ap Chemistry
You need to rethink this. K = 273 + 34 which is NOT 315.4.
May 8, 2015

Pre-Ap Chemistry
mols Na = grams/molar mass = ? Using the coefficients in the balanced equation, convert mols Na to mols H2. Then convert mols H2 to L H2 by L H2 = mols H2 x 22.4 L/mol = ? Approx 2 L if I didn't punch in something wrong on the calculator.
May 8, 2015

chemistry
(1/[A]) - (1/[Ao]) = akt You know a, k, and can calculate (Ao). Solve for A.
May 8, 2015

chemistry
The dilution formula is mL1 x M1 = mL2 x M2 mL1 x 6 = ....
May 8, 2015

CHEMISTRY
OK but you are not allowed that many significant figures.
May 8, 2015

CHEMISTRY
When working with gases one may use volume as if L were mols. 794L NO2 x (1 mol NO/3 mol NO2) = ?
May 8, 2015

Chemistry
M HCl = mols/L solution = ? M H^+ = M HCl since HCl is a strong acid and ionizes 100%. pH = -log (H^+) pH + pOH = pKw = 14 allows you to calculate pOH after you know pH then pOH = -log(OH^-) gives you OH^- Alternatively, after you know (H^+), you can use (H^+)(OH^-) = Kw = 1E-...
May 8, 2015

Chemistry Help, Please!!!
(H^+)(OH^-) = Kw. You know Kw. You know from the ionization of H2O that (H^+) = (OH^-) from H2O ==> H^+ + OH^- Solve for (H^+) and convert to pH. I suspect you've already done this and didn't get pH = 7 so you think something is wrong. It isn't. The pH will not ...
May 8, 2015

THIS IS DUE BY 10PM
T is wrong. What's the 22.4? It doesn't belong there. Where is n? It belongs there. No surprise the data base gave you a thumbs down.
May 8, 2015

chemistry
I would do this. %C in H2C2O4 is approx 27% but you should get a more accurate answer. %C = (2*atomic mass C/molar mass)*1000. 1005g of 27% C gave a reading of 102540. So the % C in the soil is 27% times two correction factors. One factor converts for the difference in IR ...
May 8, 2015

chemistry
Another calculation site. http://www.piketech.com/skin/fashion_mosaic_blue/application-pdfs/CalculatingPathlength-LiquidCells.pdf
May 8, 2015

chemistry
http://www.smarteam.com.tw/calcell.pdf
May 8, 2015

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