Sunday
December 21, 2014

Posts by DrBob222


Total # Posts: 46,146

to mohit---chemistry
The mass of the solution is 500. How much is urea and how much is water? Let X = g urea and 500-x = grams H2O Then mols urea = X/60 mol H2O = (500-X/18) Then nurea/(nurea + nH2O) = 0.2 (X/60)/{[(X/60)] + [(500-X)/18]} = 0.2 I solved for X and obtained about 227 g for urea and ...
October 29, 2014

to lol--chemistry
Your question is answered above.
October 29, 2014

chemistry
Calculate dH for the reaction and dS for the reaction. Then dGrxn = dHrxn - TdSrxn Set dGrxn = 0, substitute the values you have for dHrxn and dSrxn and solve for T.
October 29, 2014

chem
1. How many grams KHP do you have? 2. What is the molarity of the NaOH? 3. Find the caps key on your computer and learn to use it.
October 29, 2014

Analytical Chemistry
a. 2HClO4 + Na2CO3 ==> 2NaCl + 2H2O mols HClO4 = M x L = 0.035 x 0.175 = approx 0.006125 mols Na2CO3 = 1/2 that from 2 mol HClO4 = 1 mol Na2CO3 mol Na2CO3 = grams/molar mass or grams = mols x molar mass = 0.00306 x 106 = approx 0.320 g. Now do the same thing with 45 mL ...
October 29, 2014

Chemistry
32.3/3.80 = ?
October 29, 2014

Chemistry 400/ Chem 1A
wavelength = h/mv Substitute for h and m and v. h is 6.626E034 J.s, m is 9.11E-31 kg, v is given in the problem. Solve for wavelength in meters. Then convert to nm.
October 29, 2014

Chemistry
457.6 A^3 = V 457.6 A^3 x (1 x 10^-8 cm)^3 = volume in cubic centimeters. mass = volume x density = calculate mass = approx 3E-21 grams. mols Ag2CO3 = grams/molar mass = ? There is 1 mol C for 1 mol Ag2CO3 so mols C = mols Ag2CO3 Then g C atoms = mols C atoms x atomic mass C ...
October 28, 2014

AP Chem
I assume those concns listed are at equilibrium. Take 1 L solution so you have the mols present in the 1L XNO = mols NO/total mols b. Substitute the equilibrium conditions into the Kc expression and solve. c. Kp = Kc(RT)^dN d. I would simply take 0.35x0.70 for the products and...
October 28, 2014

AP Chem
You need to clean up you post. "The initial partial pressure of WHAT at .....0.5 atm?
October 28, 2014

AP Chem
I believe this problem is solved this way. ........(NH4)2CO3 ==> 2NH3 + CO2 + H2O If H2O is p, then CO2 is p and NH3 is 4p. Substitute into Kp expression and solve for p and 4p.
October 28, 2014

AP Chem
..........(NH4)2CO3 ==> 2NH3 + CO2 + H2O I..........solid.........0......0.....0 C..........solid........2p......p.....p E..........solid........2p......p.....p Kp = p^2NH3 * pCO2 * pH2O Ptotal = pNH3 + pCO2 + pH2O 0.473 = 2p + p + p = 4p Solve for p and substitute into Kp ...
October 28, 2014

Hon. Chemestry
The following equation is not a possible reaction; I wrote it only to show there is 1 mol Pb in 1 mol PbS. PbS ==> Pb + S We want 1000 g Pb. Convert to mols Pb. mols Pb = grams/atomic mass = approx 4.8 Since the ratio of Pb to PbS is 1:1, then 4.8 = mols PbS we must start ...
October 28, 2014

Chemistry
We have (NH4)2SO4 contg 1.75 g N atoms. 1.75 g N atoms = ? mols N atoms That's mol = g/molar mass = 1.75/14 = approx 0.125. There are 2 mol N atoms in 1 mo (NH4)2SO4; therefore, we must have 0.1235/2 = mols (NH4)2SO4 = approx 0.0625. Since there is 1 mol S in 1 mol (NH4)...
October 28, 2014

Chemistry
This is a limiting reagent (LR) problem and we know that because amounts are given for BOTH reactants. H2SO4 + 2NaHCO3 ==> Na2SO4 + 2H2O + 2CO2 mols H2SO4 = M x L = 0.002 mols NaHCO3 = g/molar mass = approx 0.036 but that's only an estimate and you should do all of ...
October 28, 2014

Chemistry
mL1 x M1 = mL2 x M2 50 mL x 0.25M = mL2 x 0.1.
October 28, 2014

Chemistry
I can classify matter many different ways so this is like looking for a needle in a hay stack. One way follows but I don't know if the author of your problem was thinking of this classification. Perhaps you mean states of matter; solids, liquid, gases which is the old ...
October 28, 2014

Chemistry
2C8H18 + 25 O2 ==> 16CO2 + 18H2O 10 mols Octane x (18 mols H2O/2 mol octane) = 10 x 18/2 = 90 mols H2O g H2O = mols x molar mass = ? if 100% yield
October 28, 2014

chemistry
P1V1 = P2V2
October 28, 2014

chemistry
For what? Are you doing an experiment? Baking a cake? Buying a car?
October 28, 2014

Chemistry
Sr(MnO4)2 is strontium permanganate Ammonium chromate is (NH4)2CrO4. Personally I see no reason for the di but I can't keep up with the IUPAC rules.
October 28, 2014

Chemistry
mass Al2(CO3)3 = 3.45E6 amu x (1.66E-24 g/amu) = ? grams. mols Al2(SO4)3 = grams/molar mass = ? mols Al = mols Al2(CO3)3 x 2 since there are two mols Al in 1 mol Al2(SO4)3. #atoms = mols Al x (6.022E23 atoms/mol) =?
October 28, 2014

chemistry
Use the dilution formula mL1 x M1 = mL2 x M2 The biggest problem here is that you don't have the M of the NaOH. So change grams NaOH to mols (mols = g/molar mass) and M = mol/L solution then plug into the dilution formula.
October 28, 2014

chemistry
Another acid/base titration problem. The only difference is that KHP is a solid and not a liquid. (The liquids are mlols = grams/molar mass.). Solids are mols = g/molar mass.
October 28, 2014

chemistry
Isn't this just like the NaOH/HCl titration problem I did earlier? If you have something you don't understand post it here; otherwise, I shouldn't need to do but one of a kind for you.
October 28, 2014

Chemistry
Note the correct spelling of celsius. mols Al2(SO4)3 = grams/molar mass = ? Then M Al2(SO4)3 = mols/L solution = mols/0.1L = ?
October 28, 2014

chemistry
HCl + NaOH ==> NaCl + H2O mols NaOH = M x L = ? Using the coefficients in the balanced equation, convert mols NaOH to mols HCl. You can see the ratio is 1 mol HCl to 1 mol NaOH; therefore, mols HCl = mols NaOH. Then M HCl = mols HCl/L HCl.
October 28, 2014

chemistry
No, it will not. The whole concept of a titration is that the indicator will turn when mols base = mols acid. Add water does not change the number of mols acid or base. Remember mols acid or base = M x L = mols. When I demonstrated a titration to my students I always used ...
October 28, 2014

Chemistry
Yes, you are right but you need to tweek your thinking a little. 1. You have 4 significant figures in 25.00 and 3 in 1.00g; therefore, you are allowed only 3 s.f. in the answer. Thus, your answer of 0.7128 should be rounded to three s.f. of 0.713M. Some profs will count 0.7128...
October 28, 2014

Chemistry
Fe^2+ goes to Fe^3+ MnO4^- goes to MnO2 in basic solution (which this is with NaOH)
October 28, 2014

Chemistry
Mass = volume x density You know density and mass, substitute and solve for volume
October 28, 2014

chemistry
http://www.chem.hope.edu/~polik/Chem345-2000/bombcalorimetry.htm Read the above and see if you would do dE = -CvdT dE = -(6.30)(26.8) = kJ for (3.10/molar mass C8H18). Convert that to kJ/mol.
October 28, 2014

chemistry
mols CO2 = grams/molar mass = ? Then mols CO2 x (22.4L/mol) = ? L
October 28, 2014

science
I think A is your best choice.
October 28, 2014

Chemistry
#1. I work these as two equations and solve them simultaneously. Let X = mass CuO and Y = mass Cu2O -------------------- equation 1 is X + Y = 0.5 Equation 2 comes from this. The grams copper from CuO + copper from Cu2O = 0.425g. With MM standing for molar mass and AM for ...
October 28, 2014

Chemistry
#2. Determine the molarity (M) of the concentrated acid. 1000 mL x 1.18 g/mL x 0.3 x (1/36.5) = ?M My estimated value for this is 12M but you need to refine the answer. Then use the dilution formula of mL1 x M1 = mL2 x M2 mL1 x 12 = 1,500 x 0.5 Solve for mL of the 12 M HCl to ...
October 28, 2014

Chemistry
mols H2O = grams/molar mass H2O = approx 1.6 but this is an estimate and you need a more accurate answer. I've estimated all of the others, too, so be sure to redo each step for better accuracy. M H2O = mols/L = approx 0.16 M. .....3Fes) + 4H2Og) ==> Fe3O4s) + 4H2g) I...
October 28, 2014

AP Chemistry
No. If it takes more energy to break a bond than form a bond, the energy must come from somewhere and that somewhere is the surroundings so it must be endothermic.
October 28, 2014

Chemistry
2NH3 + H3PO4 ==> (NH4)2HPO4 mols H3PO4 ==> grams/molar mass = ? Using the coefficients in the balanced equation, convert mols H3PO4 to mols NH3. Now convert mols NH3 to grams. g = mols x molar mass
October 27, 2014

chemistry
mols = grams/molar mass. a. 0.025/32 = ?
October 27, 2014

Science 10
decomposition: 2NaHCO3 + heat ==> Na2CO3 + H2O + CO2 (baking soda decomposition: C12H22O11 ==> C6H12O6 + C6H12O6 sucrose.......glucose....fructose (table sugar) The sucrose decomposition requires a catalyst; usually a little acid. double replacement: NaHCO3 + HAc(acetic ...
October 27, 2014

Science 10
I disagree. The conditions are there. The results are (and I missed them) in the preamble saying they are listed from fastest to slowest. Therefore, the first one listed dissolved the quickest and the last one listed took the longest. Go through this logically. I would do this...
October 27, 2014

Science 10
I see the trials but no results. Look at your results and arrange them in the order requested. Or are you doing a dry lab of the experiment.
October 27, 2014

science
Some of the answers by anonymous are not correct.
October 27, 2014

science
4. https://www.google.com/search?q=metric+system&client=firefox-a&hs=btG&rls=org.mozilla:en-US:official&channel=sb&tbm=isch&tbo=u&source=univ&sa=X&ei=KN9OVPDzGeTbsAScoYG4Aw&ved=0CDQQsAQ&biw=995&bih=601 5. http://www.answers.com/Q/...
October 27, 2014

science
I gave you the answer to 1 earlier. Look in your text/notes for the others. Google the topics. You can find the answers to most of these with Google.
October 27, 2014

coustmary units
or if you like to use the factor label method (dimensional analysis) this would be 198 inches x (1 foot/12 inches) = ?
October 27, 2014

chemistry
You can't plug and chug? PV = nRT The problem says you have 1.2 dm^23 (which is 1L) CO2 at the conditions listed. P = 1 atm V = 1.2 L n = ? R = 0.08206 L*atm/mol*K T = 273 + 250 = 523 K (1)(1.2) = n*0.08206*523 n = (1*1.2)/(0.08206*523) n = 0.02796 mols which I would round...
October 27, 2014

chemistry
If you only want the mols, that's PV = nRT and solve for n. P = 1 atm V = 1.2 L R = 0.0206 T = 273 + 250 = ?K
October 27, 2014

chemistry
No. 3.84 mols K x (2 mols H2O/2 mols K) = 3.84 x 2/2 = 3.84 x 1/1 = 3.84 mols H2O.
October 27, 2014

Chemistry
It does now.
October 27, 2014

Chemistry
Rachael. See your post. I've looked at it.
October 27, 2014

Chemistry
See my earlier post. Repost if you have other questions about it.
October 27, 2014

chemistry
All you needed to do is/was follow my instructions. You found mols K. See the second step in my earlier post. http://www.jiskha.com/display.cgi?id=1414442701 Second step. Using the coefficients in the balanced equation, convert mols K to mols H2O. That's ? mols K x (2 mol ...
October 27, 2014

science
All of us are volunteers so we show up when we can or when we have time. One thing you can do is to post a single problem per post. That way we can help with whatever question(s) we feel comfortable with and we can grab a single question at a time instead of needing a large ...
October 27, 2014

science
Rachael, I looked at your post earlier. I would answer #1 as C and not D since most labs have various ways of coping with trash. In the early day of chemistry we would have flushed it down the sink but rules of today are different. Many of the rest of these are just not in my ...
October 27, 2014

Chemisty
This post makes no sense.
October 27, 2014

Chemistry
I came up with 3.11 g CH4 and 6.89 g C2H4. I checked those answers this way. The dHrxn for CH4 I found as -890.3 kJ/mol. and dHrxn for C2H4 as -1410.09 kJ/mol. Heat produced by 3.11g CH4 is 890.3 kJ/mol x (3.11/16) = 173 kJ. Heat produced by C2H4 is 1410.09 x (6.89/28) = 347 ...
October 27, 2014

Chemistry
I never worked it through the other day but in setting it up today I think I may have erred in that first post. Give me some time and I'll try to come up with an answer. You can help if you will post what you calculated for dH1, dH2 and the equations.
October 27, 2014

Chemistry
I thought I worked this for you a couple of days ago.
October 27, 2014

chemistry
See your other posts.
October 27, 2014

chemistry
2K + 2H2O ==> 2KOH + 2H2 mols K = grams/molar mass = ? Using the coefficients in the balanced equation, convert mols K to mols H2O. That's ? mols K x (2 mols H2O/2 mol K) = ? mols K x 2/2 = ? mols H2O Now convert mols H2O to grams. g = mols x molar mass.
October 27, 2014

Physical Science
What's the problem? You go from -25 C to zero C(the melting point) with equation 1 (single phase, ice to start and ice to end) You melt the ice at 0C using equation 2 (heat fusion one) (this is a phase change from solid to liquid) You go from liquid water at zero C to 100 ...
October 27, 2014

Physical Science
This isn't complicated but it's a 4 or 5 step process. Here is how you do any problem like this. There are really only two formulas you need (3 actually but two are almost the same). q = heat required to move T from any T to any other T IN THE SAME PHASE is q = mass x ...
October 27, 2014

science
:-)
October 27, 2014

science
Sorry but we (and you) can't draw diagrams on this forum.
October 27, 2014

Physical Science
q1 = heat required to raise T from 20 C to melting point. q1 = (mass Pb(in g) x specific heat x (T m.p. - Tinitial) q2 = heat required to melt the Pb at 328 but keep T at 328. q2 = mass Pb x heat fusion. Add q1 + q2 for q total.
October 27, 2014

Chemistry
How to write the equation? It's given to you but it would help if you wrote the product as Fe3O4 (which I suspect is a typo). Also, Fe and H2O don't react with Fe3O4 + H2. Fe and H2O yields Fe3O4 and H2. 3Fe(s) + 4H2O(g)==> Fe3O4(s) + 4H2(g) Step 1. Write and ...
October 27, 2014

chemistry
1/1E-8 = 1E8
October 27, 2014

chemistry
1/0.000015 = 1/1.5E-5 Divide the two parts; i.e., 1/1.5 and 1/1E-5 Divide 1/1.5 = 0.667 Divide 1/1E-5 = 1E5. Answer is 0.667E5 or 6.67E4 in scientific notation.
October 27, 2014

Chemistry
1/10e-8 = 1/1.0E-7 = 1E7
October 27, 2014

Chemistry
q = mass Fe x specific heat Fe x (Tfinal-Tinitial) Note the correct spelling of celsisus.
October 27, 2014

Chemistry
mols N2O5 = grams/molar mass mols N atoms = 2x that since there are two N atoms/molecule N2O5. Then 1 mol N atoms contain 6.02E23 atoms so ? mols N atoms will contain ......
October 27, 2014

chemistry phyics HELP PLEASE STUCK
Use PV = nRT and solve for n = number of mols He. Then n = grams/molar mass. You have n and molar mass, solve for grams. same process for part B.
October 27, 2014

Chemistry
You don't know how to use the calculator to do this? or some other problem?
October 26, 2014

Chemistry
Explain your trouble with this. If you know the factors it should be easier than falling off a log. I don't know all of these conversion factors; I've memorized a few so I don't always get there the short way. For example, I don't know kPa to mm Hg but I know ...
October 26, 2014

Chemistry
1 atm = 101.325 kPa so 1 kPa x (1 atm/101.325 kPa) = ? atm.
October 26, 2014

Chemistry
814.510 torr x (1 atm/760.00 torr) = ?
October 26, 2014

chemistry
Use PV = nRT. You know T, R, V and P. Solve for n = number of mols, then n = grams/molar mass. Plug in g and solve for molar mass. Divide that by 2 (because it's X2) and identify from the periodic table.
October 26, 2014

Clark Atlanta
This looks like a chemistry problem to me and Clark Atlanta surely didn't direct me to this question. You should show the subject in the subject area. Except for the decimal I agree with your answer. 10 x (1 mol CO2/44.01 g/mol) = 0.227 mols CO2 in 10 g. The number of C ...
October 26, 2014

chemistry
And what do you think and why?
October 26, 2014

chrmistry
I know what you're asking but I don't think the question is stated properly. Technically, an atom will not join with an "oxide" ion; i.e., the oxide ion is an atom of oxygen to which two electrons have been added. An oxide ion will add to 2 K ions or 1 Ca ion...
October 26, 2014

Chemistry
0.264 mol CH4 will produce 2x that of H2O and convert mols to g. g H2O = molls H2O x molar mass H2O
October 26, 2014

Chemistry
Pb(ClO3)2 + NaI ==> PbI2 + 2NaClO3 Concentrated is a relative term and doesn't mean anything to me.
October 26, 2014

Chemistry
58.8 atm x (101.325 kPa/atm) = ?
October 26, 2014

Chemistry
A. mols succinic acid in the initial 1.700 g is mols = grams/molar mass = ? Then you took 1/10 of that with ?mols x (25.00 mL/250.00 mL) = ? B. If we call succinic acid H2C, then H2C + 2NaOH ==> Na2C + 2H2O mols succinic acid from a = ? 2x that = mols NaOH M NaOH = mols ...
October 26, 2014

chemistry
I don't see a question here.
October 26, 2014

Chemistry
I would convert 875.1 kPa to atm first. 875.1 kPa x (1 atm/101.325 kPa) = ? Then convert atm to mm Hg. ? atm x (760 mm/1 atm) = ?
October 26, 2014

General Chemistry
I don't think your post is clear. I don't know what you're asking. It appears to me that if the pressure is 748 mm Hg then the pressure is 748/760 = ? atm and I know that isn't what you're asking.
October 26, 2014

Chemistry
0.35(85) + (0.65)(84) = ? Solve for ?
October 26, 2014

chemistry
pressure in atmospheres, pascals, kilopascals, mm Hg, inches H2O, etc
October 26, 2014

Chemistry
This is a long one and will take your complete concentration to follow but here is what you do. Here are the combustion equations. rxn 1. CH4 + 2O2 ==> CO2 + 2H2O rxn 2. C2H4 + 3O2 ==> 2CO2 + 2H2O Next you calculate the heat evolved with rxn 1 and rxn 2. These are done ...
October 26, 2014

Chemistry
You didn't provide any data.
October 26, 2014

CHEMISTRY
work function = hc/wavelength 3.340E-19 = hc/wavelength Solve for wavelength. I get approx 600 nm
October 26, 2014

General Chemistry
I think you have a typo in your post. T is 74+ 273 and you show it as 74/273; however, you must have used 347 because my answer comes out 104.83 atm also. I would round that to 105. You have 3 s.f. in the 112 and 118. Is that 74.0 C?
October 26, 2014

Chem
a. I don't see a question. b. I have no idea what you're doing.
October 26, 2014

chemistry
You lose me here. Which complex are you talking about? The one passed through the column I suppose? What is that complex. At any rate, g complex in this solution is grams = mols x molar mass
October 26, 2014

chemistry
If you had 6.67E-4 moles in 10 mL you should have 5x that in 50 mL.
October 26, 2014

chemistry
...........Co^3+ ==> Co^?+ + 3H^+ I...........x........0........0 C.......... E...........0.002/3..........0.002 Wouldn't that be 0.002/3 = 0.000667 in the 10.0 mL?
October 26, 2014

chemistry
I agree.
October 26, 2014

Pages: <<Prev | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | Next>>

Search
Members