Friday
July 29, 2016

Posts by DrBob222

Total # Posts: 52,771

help !! chemistry
I suggest you submit a question along with the appropriate information in standard form. I don't see a question here.
April 27, 2016

CHM130
With all gases one can use volume in L directly as mols as a short cut. 5.66 L CO2 x (9 O2/6 CO2) = ?
April 27, 2016

Chemistry
I would do this. Zn(OH)2 ==> Zn^2+ 2OH Ksp = ? Zn^2+ + 4OH^- ==> [Zn(OH)4]^2- Kf=? Add these two equations. Zn(OH)2 + 2OH^- ==> [Zn(OH)4]^2- .solid....+2x.........-x Krxn = Ksp*Kf = approx 6 Then [(x)/(2x)^2] = 6 Solve for x and convert to pH.
April 27, 2016

Chemistry
MgCl2 ==> Mg^2+ + 2Cl^- .........0.23....0.46 Substitute those number into the Ksp expression and solve for Ksp. part 2. Then Ksp = (Mg^2)(Cl^-)^2 Plug in 0.00537 for Mg^2+ and solve for Cl^-.
April 27, 2016

Chemistry
millimols F^- initially = mL x M = 50 x 0.5 = 25 At zero mL HCl added, the pH is determined by the hydrolysis of F^- ......F^- + HOH ==> HF + OH^- I....0.5M...........0.....0 C.....-x............x.....x E.....0.5-x.........x.....x Kb = approx E-11 = (x)(x)/(0.5-x) Solvr for...
April 27, 2016

Chemistry
CHNH2 + HCl ==> CH3NH3Cl b. Look up the delta Go values in your text/notes and solve for dGo for the rxn, then dGo = -RTlnK. Substitute and solve for K. c. ..CH3NH2 + HOH ==> CH3NH3^+ + OH^- I..0.030............0..........0 C.....-x............x..........x E..0.030-x...
April 27, 2016

Chemistry
Use (p1v1)=(p2v2)
April 27, 2016

Chemistry
We could help you better (and faster) if you didn't change screen names. Use (v1/t1) = (v2/t2) Remember to change the T to kelvin.
April 27, 2016

Chemistry
What is the mass of the 250 cc solution. That's 1.10 g/cc x 250 cc = 275 grams. 10% NaCl means 10g NaCl/100 g solution. So how much NaCl is in 250 cc? That's 10 g x 250/100 = 25 g. So 275 g total - 25 g salt = 250 g H2O. Check my work carefully.
April 27, 2016

Chemistry-Dr.Bob222
.......Ca(OH)2 ==> Ca^2+ + 2OH^- I.......solid.......0.......0 C.......solid.......x.......2x E.......solid......x.......2x (H^+) for pH 4 is 1E-4 Ksp = (Ca^2+)(OH^-) From the above, (Ca^2+) = x (OH^-) = x + 1E-4. Substitute and solve for x = solubility. Note: for the total...
April 27, 2016

Chemistry-Dr.Bob222
Why not simply calculate the solubililty of each.
April 27, 2016

Chem
2N2H4(g)+N2O4(g)→3N2(g)+4H2O(g) ...2......1.......3.......4 ...x......9.......y.......z (2)18.....9.......27......36 (3)....... (4)....... (5) x....3.6......y.......z ..2*3.6..3.6....3*3.6...4*3.6 I agree with 1 I did 2. Disagree with 3. I think that 14 should be 13.5 ...
April 27, 2016

Chemisty
NaOH + HCl ==> NaCl + H2O mols NaOH = M x L = ? mols HCL = mols NaOH since 1 mol NaOH reacts with 1 mols NaOH. Then M HCl = mols HCl/L HCl = ?
April 27, 2016

Chemistry
delta T = i*Kf*m i = van't Hoff factor = 1 for glucose i = 2 for NaCl. m is the same, Kf is the same;the only difference is i so ......is the lowest.
April 27, 2016

Chemistry
First calculate the molality. m = mols NaCl/kg solvent. 1.1% NaCl = 1.1 g NaCl/100 g solution. That is 1.1 g NaCl/98.9 g H2O) = 1.1 g NaCl/0.0989 kg H2O. mols NaCl in 1.1 g = 1.1/58.45 = 0.0188 mols NaCl = g NaCl/molar mass NaCl = about 1.1/58.45 = about 0.0188. Then m = mols ...
April 27, 2016

Chemistry
You want how many mols. That is M x L = 7.1 x 1.5 = ? mols = grams/molar mass. You know molar mass ethanol and mols, solve for grams.
April 27, 2016

Chemistry
But do you know why a,d,e are more soluble?
April 27, 2016

Chemistry
ade
April 27, 2016

chemistry
I can only guess as to the meaning of some of the symbols. Assuming my guesses are right, and I don't guarantee they are, I would go with B followed by A.
April 26, 2016

chemistry
See your post above.
April 26, 2016

Chemistry
........HCOOH ==> H^+ + HCOO^- I.........M.......0......0 C........-x.......x......x E........M-x......x......x The problem tells you the pH is 1.98. Use pH = -log(H^+) to find x. Then substitute into Ka expression for HCOOH (you will need to look up Ka for HCOOH) and solve...
April 26, 2016

chemistry
mols NaCl = M x L = ? grams NaCl = mols NaCl x molar mass NaaCl.
April 26, 2016

Chemistry
440 g Mg x (molar mass MgCl2/atomic mass Mg) = ? Another way to look at this is %Mg in MgCl2 is (atomic mass Mg/molar mass MgCl2) = approx 25.5% Then 0.255 x g MgCl2 = 440. Solve for g MgCl2.
April 26, 2016

Chemistry
See your other post above.
April 26, 2016

chemistry
avg speed = v = sqrt(8RT/pi*M) rrms = sqrt (3RT/M) Solve v equation for T Solve rms sped for T Set v = vrms = to each other. Substitute values and solve for T Post your work if you gets stuck.
April 26, 2016

chemistry
You need to re-read my explanation. If you want to convert 1.210 g to mols that's ok but more work than you need to do. I presume m1 is the mass of CH4 (that's my X) and m2 is the mass of C2H6(that's my Y). Your equation of m1/M1 + m2/M2 = 0.766 is right but ...
April 26, 2016

chemistry
I don't get a negative number. Post your work and I'll find the error.
April 26, 2016

chemistry
This is a problem with two unknowns; therefore, you need two equations and solve them simultaneously. Write and balance the combustion equations. CH4 + 2O2 ==> CO2 + 2H2O 2C2H6 + 7O2 ==> 4CO2 + 6H2O Let X = grams CH4 and Y = grams C2H6 ---------------------- eqn 1 is X...
April 26, 2016

Chemistry
HNO3 + KOH ==> KNO3 + H2O millimols HNO3 = M x mL = approx 200 but this is just an estimate. mmols KOH - 0.57 x 400 = approx 228. So HNO3 is the limiting reagent; all of the HNO3 will be used and 28 mmols KOH will be left over. So the pH will be determined by the excess KOH...
April 26, 2016

Chemistry
You don't? 1.20-2x = 1.02 -2x = 1.02-1.20 = -0.18 2x = 0.18 x = 0.18/2 = 0.09 So N2 = x = 0.09 H2O is 2x = 2*0.09 = 0.18 N2 left is 0.95-2x = ?
April 26, 2016

Chemistry
.......2H2 + 2NO->N2 + 2H2O. I.....1.20..0.95..0.....0 +5sec.-2x....-2x..x....2x final.1.20-2x.0.95-2x..x...2x The problem tells you that 1.20-2x = 1.02. Solve for x and evaluate the other values. Post your work if you get stuck.
April 26, 2016

Chemistry
dE = dH + w dH = +100 J w = -50 J
April 26, 2016

Chemistry
I never worked a problem like this before. mass 100 mL of 1M H2SO4 = 1.5 g/mL x 100 mL = 150 grams. mass H2SO4 in that 100 mL is 98 g/mol x 100/1000 = 9.8 g H2SO4 g H2O in that 100 solution is 150g - 9.8 g H2SO4 = 140.2 g H2O in the final solution is 400 + 140.2 = 540.2 and ...
April 26, 2016

Chemistry
You didn't include the volume of water that dissolved the benzoic acid.
April 26, 2016

Chemistry
You need to proof and include that has been added to what. I suggest you repost at the top of the page.
April 26, 2016

Chemistry please help
rate exp 2 = k1*(A)^x(B)^y -------------------------- rate exp 1 = k1*(A)^x(B)^y Now plug in values for exp 1 and exp 2. That will give you 1.60E-2 = k1*(0.300)^x*(0.0.150)^y --------=-------------------------8.00E-3 = k1*(0.15o)^x(0.150)^y k1 cancels. 0.150)^y cancels and you...
April 25, 2016

Chemistry
Kb for HCOO^- = Kw/Ka for HCOOH but I don't know what Ka for C7H5O2 has to do with the problem.
April 25, 2016

oops--Chemistry
Note that 10/200 is not 0.1 but is ? Then pOH = -log(OH^-). Calculate pOH. Then pH + pOH = pKw = 14. You know pKw and you know pOH, solve for pH.
April 25, 2016

Chemistry
millimols acid = mL x M = 100 x 0.1 = 10 millimols NaOH = 20 x 1 = 20 So all of the acid is neutralized and y ou have 10 mmols NaOH in excess. So (OH^-) = mmols/total mL = 10/200 = 0.1 pOH must be 1 so pH must be 13.
April 25, 2016

Chemistry
I didn't work through it but your logic is not right. When we talk about doubling the temperature, we usually think in terms of C. Remember you must convert that to kelvin and that isn't doubled.
April 25, 2016

Chemistry
You can't do this without knowing that the sample was monobasic or not. I will assume it is. mols HCl = M x L = ? mols base = same. mols = grams/molar mass. You know mols and grams, solve for molar mass.
April 24, 2016

Chemistry
I think you made a typo on the first time; i.e., I assume that is to be CH3COCH3. The spacing can't be done very well on this forum. Here is a link that will tell you how to do it. https://www.youtube.com/watch?v=ghHjnXgm4v0
April 24, 2016

Chemistry
Unless you know of a way to make N2 and H2 in solution react there is no Ksp.
April 24, 2016

Chemistry
The question is worded funny. You don't need energy "required" since moving T from 22 C to ice at minus whatever removes heat, not adds heat. Anyway, q1 = heat removed to change T of liquid water @ 22 C to liquid water at zero C. q1 = mass H2O x specific heat ...
April 24, 2016

Chemistry
No. Density is water generally is 1.0 g/mL for most of these problems. Therefore, volume in mL = mass in grams.
April 24, 2016

Chemistry
Don't we assume that if it is a 30 gallon water heater that it will be full of H2O so it will hold 30 gallons. 1 gallon = 3.785 L.
April 24, 2016

Chemistry- Dr.Bob222
Yes there is but it depends somewhat upon the pH of the buffer. Let's say the pH of your buffer is 5.0. The buffer capacity is the number of mols that may added to 1 L of a buffer solution that will not change the pH more than +/- 1. So for a buffer with a pH of 5.0 you ...
April 24, 2016

Chemistry
Didn't Mr. P:ursley answer this for you yesterday?
April 24, 2016

organic chemistry
The COOH peak will be shorter, broadened, and shifted to a shorter wavelength.
April 24, 2016

chemistry
The second one is easier than the first. wt/vol% = (grams solute/100 ml solution) = 0.3885 g/100 mL = 0.3885 % w/v For #1, you have a molarity of 0.0303. That means you have 0.0303 mols/L solution. 0.0303 x 41.99 = about 1.3 g/L Approx (1.3/1000)&100 = ?% w/v
April 24, 2016

Chemistry
Wouldn't that be (0.012-0.0017)/28 = ?
April 24, 2016

chemistry
I have responded several times that I don't think it can be done without know the volume. I've changed my mind. I believe I know that they are asking for now. Here is what you do. The problem you have for 2 gives you a 7.35 value. You know the base and acid for 7.40. ...
April 24, 2016

chemistry
You might help yourself if you used a name that isn't used often. Anonymous is used by several people so you can't tell which is your post. I responded last night that I didn't think there was enough information to answer part 2 and part 3. You MUST hav a volume in...
April 24, 2016

Chemistry
E = hc/wavelength You know E from the problem, h is Planck's constant, c is speed of light (3E8 m/s) and you solve for wavelength.
April 24, 2016

Chemistry
If you want a formula for dilution it is mL1 x M1 = mL2 x M2 For example 15 x 2.4 = 100 x M2 and you solve for M2. Then you repeat that two more times to arrive at the final answer. For problems like this; however, I think it is easier to run each dilution like this. You know ...
April 24, 2016

Chemistry
mols = grams/molar mass and M = mols/L Convert 2.00 g each into mols with the above formula, then use the second one to find M. Plug these into the Henderson-Hasselbalch equation and solve for pH. Post your work if you get stuck.
April 24, 2016

chemistry
typo in equation. HCl + AgNO3 ==> AgCl + HNO3 mols HCl = M x L = 0.1 x 1 = 0.1 Convert mols HCl to mols AgNO3. 1 mol AgNO3 = 1 mol HCl; therefore, 0.1 mol HCl = 0.1 mol AgNO3. Then M AgNO3 = mols AgNO3/L AgNO3. You know mols and L, solve for M.
April 24, 2016

chemistry
See your other post.
April 24, 2016

chemistry
See your other posts.
April 24, 2016

chemistry
lamda = h/mv wavlength(lambda) will be in meters, convert to pm.
April 24, 2016

chemistry buffer
pH = pKa + log (base)/(acid) 450 = 4.76 + log (NaAc)/(0.1) Solve for (NaAc) in molarity. Then M NaAc = mols NaAc/L NaAc. You know L and M, solve for mols. Finally, mols = grams/molar mass. You know molar mass and mols, solve for grams.
April 24, 2016

chemistry
Even though it isn't quite correct since we don't write subscripts on this forum, you should use HPO4- and H2PO42- (I prefer HPO4^- and H2PO4^2-). Most will not know what HPO2-4 is. I responded to this problem a few days ago. Frankly, I don't think 2 and 3 can be ...
April 24, 2016

Chemistry
So you know 2.5 mols CH$ releases 2800 kJ of energy. (By the way that is calorimeter). Look up the energy values for paraffin and the glycol and compare them. That's all there is to it. You can find that information on Google.
April 23, 2016

chemistry
http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/vacfla.html#c2
April 23, 2016

Chemistry
Your post isn't clear to me. I'm confused by the "when THEY dissolve" What is meant by they?
April 23, 2016

Chemistry
CaCO3 ==> CaO + CO2 grams CaCO3 = 250 x 0.8 = 200g. mols CaCO3 = 200/molar mass CaCO3 Using the coefficients in the balanced equation, convert mols CaCO3 5o mols CaO. Now convert mols CaO to g. g CaO = mols CaO x molar mass CaO.
April 23, 2016

chemistry lab
I don't want to appear dumb but how am I supposed to know what you did?
April 23, 2016

chemistry
If you're sure of your numbers all you need is the final concentrations. pH = pKa + log (base)/(acid) pH = 4.76 + log (OAc^-)/(HOAc) but this can't be right. A buffer will have some acetate and some acetic acid. You can't have zero HOAc. If you truly have (HOAc) = ...
April 23, 2016

Chemistry
Your equation is not balanced and Q is not 27; therefore, those initial values you have are incorrect. Correct those and try the last part again. Also, is that -170 what? kJ? kJ/mol? kJ/rxn?
April 23, 2016

Chemistry
This is straightforward. What do you not understand about this? I'll be glad to help you through it but I need to know where the hang up is.
April 23, 2016

Chemistry
See your other posts with different screen names.
April 23, 2016

Chemistry
Too many screen names and you don't fool anyone.
April 23, 2016

Chemistry
See your other posts. Don't expect us to do all your work.
April 23, 2016

BIO chemistry
Use the Henderson-Hasselbalch equation. pH = pKa2 + log (base)/(acid) base is HPO4^-; acid is H2PO4^-
April 23, 2016

Chemistry
NiCl2.6H2O + 6NH3 ==> Ni(NH3)6Cl2 + 6H2O Ni(NH3)6Cl2 + 2NH4BF4 ==> [Ni(NH3)6][BF4]2 + 2NH4Cl Add the two equations to obtain an overall equation if that's what you want. By the way I think your spelling of tetrafluoroborate is incorrect.
April 23, 2016

Chemistry
See your other post.
April 23, 2016

Chemistry
I looked, also, and didn't find an answer in print that answers the question in so many words ut I think you're right and for this reason. If we look at the hydrolysis of each we have CN^- + HOH ==> HCN + OH^- Kb for CN^- = Kw/Ka for HCN. Ka for HCN is approx 10^-10...
April 22, 2016

AP Chemistry
The vapor pressure of pure methanol is 760 mm at this temperature. psolution = Xmethanol*Po 642.3 = Xmethanol*760 Then Xmethanol + Xsolute = 1 Solve for Xsolute.
April 22, 2016

Chemistry
The question is written in such a manner that I can't make sense of it. Sorry.
April 22, 2016

Chemisty
I balanced it for you yesterday and said I didn't understand what you meant by break it down.
April 22, 2016

chemistry
What does all that funny business ater the 200 mean?
April 22, 2016

Chemistry
Your numbers look ok. I suspect the problem is that you are reporting too many significant figures. For example, that first one of 5144.6 is allowed only 3 places. Also, shouldn't you have a - sign for the total. Each of the three are exothermic; i.e.,, the first one is ...
April 22, 2016

Chemistry
Why didn't you show your work so we could figures out what you were doing wrong? You want to add the heat removed in changing T from 35 to zero, to the heat removed @ zero C to convert to ice, to the heat removed in changing T from zero C to -5.
April 22, 2016

Chemistry
......PbCl2 ==> Pb^2+ + 2Cl- I.....solid......0.......0 C.....solid......x.......x E.....solid......x.......x Substitute the E line into Ksp expression and solve for x = solubility PbCl2.
April 22, 2016

chemistry
http://www.jiskha.com/display.cgi?id=1461350333
April 22, 2016

Chemistry
You have looked up all of the boiling point and if you have copied them correctly, then CHI3 must be the right answer. It doesn't matter about intermol forces when you have the boiling points listed. 218 is 218.
April 22, 2016

Chemistry
On the left you have 3 mols of gas. ON the right you have only 2 mols gas. There is more randomness (more random possibilities) in 3 mols than 2 mols.
April 22, 2016

Chemistry
You're on a tight schedule. Most of the times we don't get the answers out that fast. 2Na + 2H2O ==> 2NaOH + H2 mols Na = grams/molar mass = ? M NaOH = mols NaOH/6.8 L = ?
April 22, 2016

Chemistry
Didn't I do parts of this a day or so ago for you. I know i did art 1. What is the trouble you're having.
April 22, 2016

Chemistry
See your other post.
April 22, 2016

Chemistry
Look up the appropriate potentials and post them. We can't get your answer without using your numbers.
April 22, 2016

chemistry
I don't see a question here.
April 22, 2016

chemistry
You don't provide enough information to answer this question. Look up the delta Ho formation and provide that data.
April 22, 2016

chemistry
pH = -log (H^+) (H^+) = ?. I estimate 5E-5 but you need a better answer than that. ...........HA ==> H^+ + A^- I........0.039....0......0 C.........-x......x......x E......0.039-x....x......x The pH tells you the value of x; i.e., approx 5E-5 so you can evaluate x and 0.039...
April 22, 2016

Chemistry
%yield = (4.13/7.10)*100 =
April 22, 2016

Chemisty
2H2S +3O2 = 2H2O + 2SO2 That's balanced. I don't know you mean by "breaking it down".
April 22, 2016

Chemistry
I'm not sure I understand the answers. However, I suspect the answer to this question is b. cold pack + heat = warm Warming the cold pack is endothermic; the cold pack is cooling something else and it absorbs heat to do that.
April 21, 2016

Chemit
34 g/hr x (24 hrs/day) x (30 days/month) = ? grams sucrose /month
April 21, 2016

Chemistry
KHP + NaOH ==> H2O + NaKP mols KHP = grams/molar mass = ? Look at the coefficients in the balanced equation; it is 1:1 so ? mols KPH = same mols NaOH. Then M NaOH = mols NaOH/
April 21, 2016

Chemistry
Yes, I would go with convection but in some cases it could be conduction. That isn't very efficient, though, for gases/liquids.
April 21, 2016

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