Thursday
April 24, 2014

Posts by DrBob222


Total # Posts: 41,920

chemistry
Convert Kb to Ka by KaKb = Kw and change that to pKa; then Use the Henderson-Hasselbalch equation.

Chemistry
Two equations in two unknowns; solve simultaneously. Let X = mass NaCl and Y = mass K2SO4 ------------------- eqn 1 is X + Y = 10.0 eqn 2 is mass PbCl2 (from NaCl) + mass PbSO4(from K2SO4) = 21.75g. eqn 2 in terms of X and Y is this (X*MMPbCl2/2*MMNaCl) + (Y*MMPbSO4/MMK2SO4) =...

Chemistry
mols Cl2 = grams/molar mass Use density to convert mL acetone to grams then to kg. Then m = mols Cl2/kg solvent

Chemistry
What's with the "same air bag"?

chemistry
This is a bear of a problem but I will get you started.First you must determine the limiting reagent(LR). Start by using PV = nRT and calculating mols of each material. Find the LR from that and determine how much of each product is formed. Then multiply by 0.9 to correct for ...

Chem Check Please!!!
I think your work is sloppy. It's delta G and not G (yes I know what you mean) and you've omitted all of the negative signs (yes I could see what you did). I think you put the 103 in the wrong place but calculated as if you had it in the right place. At any rate I obta...

Chemistry Check Please!!!
I think Eox = -0.771 and Ered = +1.36 Then 1.36 + (-0.771) = ? Your answer is right; I don't agree with what you called Eox. The anode is oxidized, yes, and that is an oxidation, yes. But the potential for that electrode is -0.771. The reduction potential is 0.771; the oxi...

chemistry
33.01 g CO2 27.04 g H2O mols CO2 = 33.01/44 = ? = mols C. mols H2O = 27.04/18 = ? and that x 2 = mols H. Now find the ratio of C to H with C being no larger than 1.0

Chem
c) work = -p*delta v d) q = mass x specific heat x (Tfinal-Tinitial) e) qp = delta H

Chemistry
mols = grams/molar mass. Substitute and solve for mols. m = molality = mol/kg solvent Substitute and solve for m. delta T = Kf*m Substitute and solve for delta T. Then subtract delta T from the normal freezing point of camphor.

chem
ammonium phosphate is (NH4)3PO4 I see 20 atoms per molecule. aluminum carbonate is Al2(CO3)3 I see 14 atoms per molecule. iron cyanide is Fe3CN. I see 5 atoms per molecule

Chemistry
(0.75g/20) = (x g/105.4) Solve for x.

Chemistry
Is that a typo first line. Perhaps should be CaCl2.6H2O. If so just add the two equations to obtain CaCl2(s) ==> CaCl2(aq) about -82 kJ/mol but that isn't exact.

Chemistry
See your other post.

Chemistry
3m = 3 mols KCl/1 kg solvent 1 mol KCl = estimated 74.5 but you should be more accurate than that. 3*74.5 = about 223g. So that is about 223g/223+1000 = 223g/1223 g solution % KCl w/w = (223/1223)*100 = >

chemistry
See your post below.

chemistry
C = p*k C = 2.5*0.037 Solve for C in M. M = mol/L. You know L and M, solve for mol. mol = grams/molar mass. You know molar mass and mol, solve for grams.

Chemistry HELP URGENT PLEASE!!!
yes

Chem.
mols KHP = grams/molar mass = ? mols NaOH = mols KHP M NaOH = mols NaOH/L NaOH

chemistry
q = mass x specific heat x (Tfinal-Tinitial)

chemistry
Ag^+ + Cl^- ==> AgCl(s) Ba^2+ + SO4^2- ==> BaSO4(s) Cu^2+ + 2OH^- ==> Cu(OH)2(s) Add Cl^-, filter AgCl. Treat with Na2SO4 and filter BaSO4. Add NaOH. Filter Cu(OH)2.

chemistry
See your post below.

chemistry
3Cl2 => 2CHCl3 mols CHCl3 = 7.20 Convert to mols Cl2. 7.20 mols CHCl3 x (3 mols Cl2/2 mols CHCl3) = ? Then ? mols Cl2 x molar mass Cl2 = grams.

chmistry
density = 1.19 g/mL. mass of 1000 mL is 1.19 g/mL x 1000 = 1190g How much of that is HCl. 37% so 1190 g x 0.37 = about 440g but that is an estimate. How many mols is that? 440/36.46 = about 12 mols. 12 mols/1000 mL = about 12 M.

chemistry
Is there a question here?

Chemistry
mols ZnO = grams ZnO/molar mass ZnO Using the coefficients in the balanced equation, convert mols ZnO to mols Au. Now convert mols Au to grams. g = mols x atomic mass.

CHEMISTRY
See your other post. Same process but you must correct for concns that are not 1M. Use the Nernst equation for that. Post your work if you get stuck.

Chem HELP !!!
Look up Eo values for Fe^3+ + e ==> Fe^2+ and change the sign. Look up Cl2(g) ==> 2Cl^-(aq) Add the two for Eocell.

Chemistry Help Please
See your other post.

Chem Check Please!!!
Follow these directions. Look up the delta Go f (that's delta Gof of each of the products and each of the reactants. Pure elements like H2 are zero but the others are not. Then calculate dGo f for the reaction by dGofrxn = (n*dGf products) - (n*dGf reactants) Finally, dG =...

math help--Please help!

Chemistry
Reason your way through it. I assume A2B is a solid. .........A2B --> 2A^+ + B^2- .....4.35E-4M....x......x For every molecule of A2B that dissolves, you must have two (2) ions of A^+ and one (1) ion of B^2-; therefore, for every 4.35E-4 mols A2B that dissolve, you must hav...

chemistry
There must be a question in here somewhere.

chemstry
267.2 WHAT?

To Nina
I think you transposed the numbers for mass proton on your post yesterday which may be the reason you had trouble getting the answer in the book. I've posted a response at the original post which can be found here. http://www.jiskha.com/display.cgi?id=1394937578

Chemistry
Actually it makes little difference which we call the solute and which the solvent; however, usually we assign the solute to the smaller quantity and the solvent to the larger number. Or if solid/liquid, we usually call the solute the solid and the solvent the liquid. In the c...

Chemistry
6.44% by mass means 6.44 g glucose/100 g solution. What is the volume of the solution? That is mass = volume x density. You know d and you know mass; solve for volume in mL and convert to L. Then find mols solute. That is 6.44g/molar mass glucose. Finally, M = mols/L solution....

Chemistry 151
Use the dilution formula for these. c1v1 = c2v2 c = concn v = volume for a. 100 mL x 0.1M = ? mL x 1M Solve for ?mL of the 1M. b. 250 mL x 0.5M = ? mL x 1 M Solve for ?mL of 1 M.

Chemistry
These are limiting reagent problems. I solve these the long way. Starting with one of the reactants, calculate how much of one of the products will be formed. Do the same for the other reactant and the same product. If both answers are the same everything is in the right propo...

Chemistry
How many mols Cu(OH)2 do you need? That's mols = g/molar mass = 100/97.56 = approx 1 mol but you need to do it more accurately. Convert mols Cu(OH)2 to mols NaOH = twice that = about 2 mol (again, do it more accurately). M NaOH = mols/L. You know mols NaOH and M NaOH, solv...

Chemistry
I think it's your math. I obtained the same equation as you and it looks ok to me. I went through the math and obtained two values for x of 0.0631 (which can't be right since 0.110-2x gives a negative number) and 0.0471. That value plugged back into Kp expression gives...

chemistry
q = mass EtOH x specific heat EtOH x (Tfinal-Tinitial) Substitute and solve for Tf.

Chemistry
(1/A) - (1/Ao) = kt Substitute and solve for k. Second part. rate = delta A/delta T = -0.01/200

chemistry
mol NH4NO3 = grams/molar mass Then M = mols/L solution. You know mols and L soln, solve for M.

I don't get it--Chemistry

Chemistry (titrations)
Yes they are in the 1:1 ratio. 1.8E-4 mols EDTA = 1.8E-4 mols Fe 1.8E-4 mols Fe x atomic mass Fe = grams Fe. Thus you have that many grams Fe in 50 g (50 mL solution) = 2.01E-4 g/g or 201 g/1 million grams = 201 ppm.

Chemistry
I get close to that answer if we neglect the fact that an extra electron produced is ignored, AND I think you transposed numbers for the mass of the proton. I think (2.0141 - 2*1.00728) = ? amu Change to kg. ?amu x (1/6.022E23*1000) = kg E = kg*c^2 and that gives me 6.86E-14 p...

chemistry
This is just another stoichiometry problem but since everything is a gas and measured at the same conditions, it allows us to use a shortcut. C3H8 + 5O2 ==> 3CO2 + 4H2O We may use volume in liters as if L = mols. Simply convert L C3H8 to L CO2 using the coefficients in the ...

incomplete--chemistry

chemistry
Ba(OH)2 + 2HCl ==> BaCl2 + 2H2O Mols Ba(OH)2 = M x L = approx 0.012 mols HC = twice that (look at the coefficients in the balanced equation. HCl = appox 0.024 Then mol = M x L. You know M and mols, solve for L.

chemistry
Use the Henderson-Hasselbalch equation.

Chemistry
http://en.wikipedia.org/wiki/Silicon_carbide

Chemistry
See your post above.

chemistry
You want 23.1% w/w which means 23.1 g urea in 100 grams solution. (1.6/x)*100 = 23.1 Solve for x for TOTAL mass. I obtained about 7 g total (only approximate--you need to do it more accurately)--so you want about 7-1.6 = ? g H2O

chemistry
When reacted with H2O? 2Na + 2H2O ==> 2NaOH + H2 mols H2 you want = 781g/molar mass H2. Using the coefficients in the balanced erquation, convert mols H2 you want to mols Na to start. Then convert mols Na to g. grams = mols x atomic mass Na.

Chemistry
Based on these data I would go with AgCl(least soluble), NaCl, KCl(most soluble) with the idea being it takes less energy to break the crystal bonds for KCl and most to break the crystal bonds for AgCl. I think the actual solubilities are NaCl most and AgCl least.

Chemistry
This must be a multipart question sincer the Kc data for HCl is not relevant. You have 2ICl ==> I2 + Cl2 and you want the reverse of that. Just take the reciprocal of Kc for the forward rxn or Kc reverse = 1/Kc forward

Chemistry 32
mols = grams/molar mass M = mols/L solution pH = -log(Molarity HCl) I get pH = 1

Chem
Does it make sense to you that the bacteria started with 100, is doubling every 15 minutes and you HAVE LESS THAN YOU STARTED WITH after 120 minutes? Doesn't make sense to me. k is 0.693/t1/2 Look at this table from your post, then extend it to 120 minutes. min....count 0....

Chem
This is a first order process since rate = k(A)

Chem
The rate is doubling every 15.0 minutes so the half life is 15.0 min. k = 0.693/t1/2. Solve for k and substitute into the below equation. ln(No/N) = kt No = 100 N = ? k = from above t = 1.2E2 min Solve for N. I pulled the k = 0.693/t1/2 our of a hat but you can get it this way...

Science check my answers
1 is ok. I don't agree with 2.

CHEM
a is a whole number, usually 1 or 2; sometimes but rarely 3. For simple equations in which A ==> B, the formula is just .... = kt For 2A ==> B it is .....= 2kt For 3A ==> B is is ..... = 3kt etc.

CHEM
(1/A) - (1/Ao) = akt

TO DrBob222 or any science helper
yes, citric acid.

oops--TO DrBob222 or any science helper
I typed in C6H8O and not C6H8O7. So those three "possibilities" I gave you won't fit.

TO DrBob222 or any science helper
Doesn't it seem obvious it is an acid? Here is the formula. http://en.wikipedia.org/wiki/Citric_acid

TO DrBob222 or any science helper
Here are three it could be. http://en.wikipedia.org/wiki/C6H6O

TO DrBob222 or any science helper
I don't know what that is. It's just another empirical formula. CH3COOH I recognize as acetic acid but C2H4O2 (the empirical formula for aca\etic acid) is not recognizable. There are so many compounds it can be.

TO DrBob222 or any science helper
HCH3COO is acetic acid--acid NaCL is sodium chloride--salt H2CO3 is carbonic acid --acid C6H8)7 I can't interpret Mg(OH) is magnesium hydroxide--base NaOH is sodium hydroxide--base KBr is potassium bromide--salt Sr(OH)2 is strontium hydroxide--base HNO3 is nitric acid--acid

chemistry
The maximum number of electrons in ANY d orbital is 10. The maximum number of electrons in any shell is 2N^2. 72 is right but 22 is wrong.

chemistry
wavelength = h/mv Substitute and solve for v. Don't forget to change wavelength to m.

chemistry
Do you have a diagram from which to choose or are you to calculate the wavelength. Is that 8p1 a term symbol or something different?

chemistry
dE = 2.18E-18 J*(1/16 - 1/81) c = freq x wavelength = 3E8 m/s

chemistry
E = hc/wavelength E = must be in J/photon; therefore, 1350000/6.02E23 = E Then fill in h, c and solve for wavelength and convert to nm.

chem
Don't you need to know these? What do you not understand?

science, pls explain this!
A chemical change has occurred The products are not water anymore but two different entities. If it were a physical change (ice (solid H2O) to liquid water to steam(water vapor) you have H2O in all three phase so the water has not been broken down to different substances as in...

incomplete--chemistry

Chemistry
Frankly, I've never seen this before but if I had to name it I would write sulfur(II) chlorate Sulfur has common valencies of -2, 0, +4 and +6; the (II) is to denote a valence (oxidation state) of +2.

Chemistry
Cu + 2AgNO3 ==> 2Ag + Cu(NO3)2 mols Cu = grams/atomic mass Using the coefficients in the balanced equation, convert mols Cu to mols Ag. Now convert mols Ag to grams Ag. g = mols x atomic mass Ag This is the theoretical yield.

Chemistry
Look at your stoichiometry problem above. This is done the same way.

chemistry
per kg of solvent.

Chemistry
3.5M x (11.6 mL/214.8 mL) = ? or use the dilution formula of c1v1 = c2v2 3.5 x 11.6 = c2 x 214.8

Chemistry
Here is a site that lists ranges for hardness etc. Scroll down about half way on the page for the table. http://en.wikipedia.org/wiki/Hard_water

Chemistry
I don't believe the equilibrium is shifted by pressure in an all aqueous system although I have a little trouble visualizing varsol as an all aqueous phase.

Chemisty
A hydrocarbon is exactly what it says it is. Hydrogen and carbon. propane is C3H8 methane is CH4 butane is C4H10 octane is C8H18 ethane is C2H6

chem
Most are listed here. http://www.geo.arizona.edu/Antevs/nats104/00lect25atmcompo.html

Chemistry
I answered the first part for you but you may not have liked it. Most (and some prof too I think) believe dissolved CO2 affect the value for M NaOH no matter what. The anhydride (anhydride means without water) of an acid is a material which produces that acid when added to wat...

Chemistry
You must kidding? If you know how to do one of these you know how to do them all.

Chemistry
What's wrong with pH = -log(H3O^+)?

Chemistry Urgent
Read your post below.

Chemistry Urgent
Do you want enthalpy/grams or enthalpy/mol. Most prefer it to be kJ/mol. q = g H2O x specific heat H2O x (Tfinal-Tinitial) That gives you q/2.30g X = ? J/g If you want J/mol it is J/g x 82.0 = ? J/mol. You can change that to kJ/mol if you wish.

chemistry
heat gained by rod + heat lost by H2O = 0 [mass rod x specific heat rod x (Tfinal-Tinitial)] + [mass H2O x specific heat H2O x (Tfinal-Tinitial)] = 0 Substitute and solve for mass rod

Chemistry
yes

Chemistry
Since HCl is a strong acid (meaning it ionizes 100%), then (H^+) = (HCl). If you want to know OH and you have H^+, use (H^+)(OH^-) = Kw = 1E-14

chemestry
See your other post.

chemstry
mols = M x L = ? Then mols = grams/molar mass You know mols and grams, solve for grams.

Chemistry
That's a lot of significant figures you are quoting.

Chemistry
Actually, there isn't enough information to answer the question. The below will calculate the volume of NaOH required to reach the EQUIVALENCE POINT (which I assume is what the problem wants). The problem asks, however, mL required to read the END POINT. The end point depe...

Chemistry
Substitute the numbers into the Henderson-Hasselbalch equation and calculate the ratio of (base)/(acid). That will tell you whatever you need to know about the ratio.

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