Sunday
April 20, 2014

Posts by DrBob222


Total # Posts: 41,834

chem
M = mols/L mol = 36.0/58.5 volume = mass/density = 136/(1.13*1000) So M = (36.0/58.5)/[136/(1.13*1000] Check me out on this. This would make it (36.0/58.5) x (1.13*1000/136) = (36.0 x 1.13 x 1000/136 x 58.5 = ?

chemistry
millimols C2H5NH2 = mL x M = 25 x 0.5 = 12.5 mmols HCl = 5 mL x 0.5M = 2.5 HCl. .......C2H5NH2 + HCl --> C2H5NH3^+ + Cl^- I.......12.5.......0.........0......0 added............2.5................ C.......-2.5....-2.5........+2.5....2.5 E.......10.0......0..........2.5....2...

chemistry
Three equations and three unknowns but the way they are set up makes it as if it were two equations and two unknowns. Let X = mass NaX and Y = mass NaI and Z = mass NaNO3 (mm stands for molar mass) --------------------------- eqn 1 is Z + Y + Z = 0.8612g eqn 2 is mass AgBr fro...

Chemistry
Here is a copy of the activity series of metals. Any metal ion below Ag should oxidized Ag metal to Ag +1 ion. So Pt and Au ions should do it https://www.google.com/search?q=activity+series+metals&client=firefox-a&hs=dwv&rls=org.mozilla:en-US:official&channel=sb&tbm=isch&imgil...

Chemistry
Ag(s) ==> Ag^+ + e Eo = -0.799 Hg^2+ + 2e ==> Hg..Eo = +0.789 ------------------------ 2Ag(s) + Hg2^2+ => 2Ag^+ + Hg E = -0.01 If it would oxidize it yes, that would be the reaction; however, you can see that the Eo value is -0.01 so it isn't spontaneous. K for th...

Chemistry
Use the Clausius-Clapeyron equation. Don't forget to substitute dHvap in J/mol.

Chemistry
(mass ice x heat fusion) + [mass ice x specific heat water x (Tfinal-Tinitial)] [mass H2O x specific heat H2O x (Tfinal-Tionitial)] = 0 Substitute and solve for mass ice. Tfinal is 4, Tinitial is 26, mass H2O (that's the 26 C H2O) is 355. Massice is the only unknown.

Chemistry
Now you need dHof fpr H2O gas. dHrxn = (n*dH products) - (n*dH reactants)

chemistry
It's in the last sentence.

chemistry
q(v) = Ccal in kJ/C x delta T That gives you q = dE in kJ for 0.451g That x molar mass gives dE in kJ/mol.

Chemistry
Insects and animals use the odor as sex attractants, as ways to find food, and nature to do its thing. For example, bees are attracted to flowers and in that process they pollinate grasses, flowers, fruits, etc.

Chemistry
Use PV = nRT and solve for n = number of mols of gas. Then n = grams/molar mass. YOu know n and grams, solve for molar mass.

Chemistry
Cl2(gas) ==> 2NaCl which isn't balanced but the Cl is balanced and that's what the question is about. mols NaCl = grams/molar mass NaCl Using the coefficients in the balanced equation above to convert mols NaCl to mols Cl2. Then use PV = nRT and solve for V Cl2 in L.

Chemistry
dGo = -RTlnK Solve it. See if dGo is + or -

College Chemistry (DrBob222)
Yes, if you follow my directions above that will calculate Fe^2+. You have Eocell and Ecell which allows you to calculate Q. Then Q has the definition I gave and that has the concentrations in it. Q = (Fe^2+)/(Cu^2+). You know Q and Cu^2+, solve for Fe^2+. If you need help in ...

College Chemistry (DrBob222)
I presume you meant 25C and not 35. If you meant 35 then replace the 0.0592 below by (RT/2*F) Ecell = Eocell -(0.0592/2)log Q You have Ecell. Eocell = Eo for Cu^2+ + 2e --> Cu and add to Eo for Fe(s) ==> Fe^2+ + 2e That leaves Q. Q in this case is Q = (Fe^2+)/(Cu^2+) Sub...

Chem Help!
a) Because the Ksp for AgCl is exceeded. b) Ba^2+ + SO4^2- ==> BaSO4(s) c) See answers to a and b above. Put that into words. d) Yes, if dilute HCl were used. e) identity of the material, its solubility and ease of making solutions, its stability, etc. f) AgCl + 2NH3 ==>...

Chem Help
a. Ksp PbCl2 = (Pb^2+)(Cl^-)^2 Qrxn = (0.2)(5E-3)^2 = 5E-6 and this is smaller than Ksp; therefore, no PbCl2 ppts. Ksp AgCl = (Ag^+)(Cl^-) Qrxn = (0.2)(5E-3) = 1E-3 which is larger than Ksp; therefore, AgCl ppts. b. The total chloride is now 3M + 5E-3M. I will ignore the small...

Chem Help
What values do you have for Ksp PbCl2 and AgCl. I can look them up in my text but the numbers probably will not the same as in your text. I would rather use your numbers.

Chemistry
molsKClO3 = 9.50E25/6.02E23 = ? Convert mol KClO3 to mols mols KCl and mols O2 using the coefficients in the balanced equation. Then convert mols KCl to g. g = mols x molar mass Similarly, g O2 = mols x molar mass.

CHEM.
Yes if you have Kb. The problem says "qualitatively" which means make the best educated guess. Qualitative in that sense always means to make the best estimate. If you know Kb (which is 1.8E-5) you can calculate it as follows: ..........NH3 + HOH ==> NH4^+ + OH^- ...

CHEM.
a). NH3, NH4^+, OH^-, H3O^+ b) NH3 is a weak base so you know it will be basic and you might guess pH 10 or so. c) Mn^2+ + 2OH^- ==> Mn(OH)2(s) d) Adding HNO3 would react with the OH^- of Mn(OH)2 to product H2O and the ppt would dissolve because the OH^- has been decreased.

Chemistry URGENT
Li is right as is O. As is not right. As is +5 Here is a good site that explains how to do oxidation numbers. http://www.chemteam.info/Redox/Redox-Rules.html

chemistry
Use PV = nRT and solve for n = number of mols. Then n = grams/molar mass. You know molar mass (or can find it) and n, solve for grams.

chemistry
Use PV = nRT and solve for n = number of mols of the gas. Then n = grams/molar mass. You know grams and n, solve for molar mass.

Chemistry
a. X^- + HOH ==> HX + OH^- The anion hydrolyzes with water producing OH^- ions which is why they are basic. b. .....X^- + HOH ==> HX + OH^-. For 0.3M I...0.3.............0.....0 C....-y.............y.....y E...0.3-y...........y.....y Kb for X,Y, or Z = (Kw/Ka for HX, k2 ...

chemistry
mols = grams/molar mass Then M = mols/L solution

Chemistry
#1. Br2 + 2e ==> 2Br^- written as a reduction. (Reduction is the gain of electrons and this gained e). Look in the table of standard reduction potentials (tabulated I suspect in your text). If Br2 + 2e ==> 2Br^- is more less positive than 1.23 (volts for electrolysis of ...

Chemistry
For #1, I suspect they expect you to calculate dGo which you get from dGo = dHo - TdSo from tables. However, most tables have dGo already tabulated and you need not go through the dH-TdS part. Then dGo = -RTlnK should get it. #2. I'll look at 2 later.

chemistry
Use (P1V1/T1) = (P2V2/T2) P1 = 84.6 kPa for wet gas pH2O = 12.3 kPa P1 = 84.6 kPa - 12.3 kPa = ? kPa for dry gas. P2 = 120 kPa

Chemistry
A cell can deposit atomic mass Al/3 (about 27/3 = approx 9g) Al when 96,485 coulombs is passed through a solution. How many coulombs do you have? That's coulombs = amperes (that's amps) x seconds. So you have C = 5.00 x 5.00 hrs x (60 min/1 hr) x (60 sec/1 min) = about...

CHEMISTRY
I just posted a response at the original site below.

CHEMISTRY
Put that endothermic part into the equation so you can see how it affects the reaction. SO2Cl2 + heat ==> SO2 + Cl2 Le Chatelier's Principle says that when we do something to a reaction that is in equilibrium that the reaction will shift so as to undo what we've don...

CHEMISTRY
You can work this out with numbers or with reasoning. Numbers take longer but may lead to some more confidence. Kc = (B)^5/(A)^6 So if pressure decreases you know the reaction will shift to the left. That means Qc will be too large meaning B is too large and A is too small. Th...

Chemistry
You don't get pH from Ka UNLESS you have the concentration of the acid. In this case you don't have that so you can't get a straight pH. If you are referring to the first question, which is The following questions refer to the following acids and bases. A) Hydrazoi...

Chemistry
Zach, this is about a 20 question post which I've done several times in the last day or so. All of these questions are similar. Can you summarize what it is you don't understand about these. We need to get at the root so you can do these yourself.

CHEMISTRY
Kp = Kc(RT)delta n where delta n = n products - n reactants

CHEMISTRY
P = products R = reactants c = coefficients Kc = (p)^c/(R)^c) I've seen some text where the products are called RHS (right hand side) and the reactants called LHS (left hand side) then Kc is defined as (RHS)/(LHS) with coefficients becoming exponents.

CHEMISTRY
Kp = Kc(RT)delta n

CHEMISTRY
.........A ==> 2B I....0.154.....0 C........-x....2x E...0.154-x....2x Substitute the E line into Kc expression and solve for x and 0.154-x. I don't know if the prof expects you to answer this with math (working out the above equation) or by reason but the math should d...

CHEMISTRY
........H2 + Cl2 ==> 2HCl I...0.1877.0.1432......0 C.......-x....-x.......2x E...0.1877-x.0.1432-x..2x Substitute the E line into Kc expression and solve for x, then evaluate each individual term.

CHEMISTRY
Reactants ==> products K = (products)/(reactants) So a large K means more products and fewer reactants. That's the only way to get a large number for K. A small K means fewer products and more reactants. That's the only way to get a small number for K. So large K me...

CHEMISTRY
.......PCl5 --> PCl3 + Cl2 I...0.1983.......0......0 C.......-x.......x......x E....0.1983-x....x......x Substitute the E line into the Kc expression for PCl5 and solve for x.

CHEMISTRY
Use the Arrhenius equation. Don't forget to convert kJ/mol to J/mol. And K must go into the equation as kelvin.

CHEMISTRY
I hate to be picky but why do I want to answer 10 questions so you can compare answers. It is much more efficient for you to post your answers and let me find any errors. While you're doing all that typing (which I would have had to do) I can be working your other posts.

no one's here to help us!!! -.-
I like Writeacher's comments! I'll second that! I'll add a third. 3. A student who post his/her work and asks us to check it for errors is more likely to get a quick response than one that posts a LOOONG question consisting of many parts and asks us to work the pro...

Chem
I strongly suspect you know how to do some of these and for those it's redundant for me to help. Post your work on what you know and clearly explain what you don't understand about the others and I'll help you through them.

chemistry
delta T = Kb*m delta T = 101.86 - normal boiling point. Substitute and solve for m = molality. m = mols/Kg solvent. You know kg solvent and m, solve for mols.

Chem
5. Which solution will have the highest concentration of Na+ ions? A) Na2CO3 B) NaHCO3 C) NaCl D) NaHSO4 E) All are equal There is no answer for this one BECAUSE there is no concn listed for any of them. For equal concentrations, which probably is what the asker meant, is A be...

Chem
4. Based on my responses above what do you think. A is not right.

Chem
3) Which aqueous solutions are acidic? A) Na2CO3 and NaHCO3 B) NaCl and NH4Cl C) NaHSO4 and NH4Cl D) NaHSO4 and NaHCO3 E) NaHSO4, NaHCO3, and NH4Cl A. If Na2CO3 is very basic and NaHCO3 is slightly basic, then a mixture should be acid or basic....? B. NaCl is neutral; NH4Cl is...

Chem
2) Which solution will be the strongest base? A) Na2CO3 B) NaHCO3 C) NaCl D) NaHSO4 E) NH4Cl My response to #1 should give youthe answers to #2.

Chem
1) Which solution will have the lowest OH- A) Na2CO3 B) NaHCO3 C) NaCl D) NaHSO4 E) NH4Cl The lowest OH will be the highest H^+ so which is the strongest acid? You can go through and eliminate most of these. You know CO3^2- hydrolyzes extensively so you know they are basic due...

CHEMISTRY
I presume this forms CuOH and KNO3 but I can't confirm that CuOH or CuNO3 exists. KOH + CuNO3 --> CuOH + KNO3 OH^- + Cu^+ ==> CuOH.

Chemistry
dGo rxn = -nFEo dGrxn = -nFE

Chemistry
Na2SO3 ==> 2Na^+ + SO3^2^- 0.390....2*0.390...0.390 Na+ ....see above SO3 2-.....see above Then hydrolysis of the sulfite ion .....SO3^2- HOH ==> HSO3^- + OH^- I...0.390.............0.......0 C....-x...............x.......x E..0.390-x............x.......x Kb for sulfite ...

To TOM
I accidentally erased your post on the hydrolysis of various anions. The answer is Kb(for the anion) = (Kw/Ka for the Ka for the acid) where Ka will be Ka for monoprotic acids, k2 for diprotic acids, or k3 for triprotic acids So to make OH^- the smallest you want Ka to be the ...

college chem
That's what I would do.

chemistry
I think you must have made at least one typo (for E1 I suspect that is -20 x 10^-19 J). a. delta E = E3 - E1 = hc/wavelength Substitute and solve for wavelength, convert to frequency by c = freq x wavelength. b. (0-E1) = ? c. delta E = E6-E4 = hc/wavelength and convert to nm.

college chem
millimols NaOH = mL x m = 17.47 x 0.1 = 1.747 millimols HA = 25 x 0.1 = 2.5 .........HA + NaOH ==> NaA + H2O I........2.5....0.......0......0 added.........1.747............ C......-1.747.-1.747...1.747.....1.747 E......0.753....0......1.747 Substitute into the Henderson-Ha...

Chemistry
mols HCl = grams/molar mass Then M HCl =mols HCl/L HCl M HCl = M (H^+) Then pH = -log(H^+) and pH + pOH = pKw = 14. You know pH and pKw, convert to pOH.

college chemistry
Convert each of the Kb values to pKb = -log Kb and convert those to pKa by pKa + pKb = 14 The closest pKa values to the desired pH is the one you want.

Chemistry
See your other post.

Chemistry
mols CaCl2 = grams/molar mass Then M = mols/L solution

science
You might hypothesize that pyrite (FeS2) burns with coal to produce SO2 as one of the products. SO2 then might dissolve n lakes and streams to produce H2SO3 and that would increase the acidity of the H2O. I would add the equations and balance them.

chemistry
I didn't check any of your calculations. There is no indication of what concentration they want the buffer; therefore, I would assume some convenient (and reasonable) amount of one of the salts, say Na2CO3 = 0.05 mols (which would make the Na2CO3 about 0.5M). That will be ...

chemistry/science
a is ok. b. You have how much in solution. 100 millimols Na2CO3 x (25 mL/250 mL) = 10 200 millimols NaHCO3 x (25/250) = 20 You are adding 20 mL x 0.050M = 1 millimol HCl. .........CO3^2- + H^+ ==> HCO3^- I........10........0.......20 added.............1.............. C........

Chemistry
Yes, fractional orders are allowed.

chemistry
See your other post above.

Chemistry Help Please!!!
#1 you have is close but not right. I would have written for the hydrolysis of NaC2H3O2 as a net ionic equation. CH3COO^- + H2O ==> CH3COOH + OH^- Kb for CH3COO^- = (Kw/Ka for CH3COOH) = about 1E-14/1.8E-5 = ? CO3^2- + HOH ==> HCO3^- + OH^- Kb for CO3^2- = (Kw/K2 for H2C...

science
http://en.wikipedia.org/wiki/Mid-ocean_ridge

science
This question asks for YOUR opinion and why, not my opinion and why.

science
I don't know that it is. Touching it right below is Li and diagonally below is Be.

science
By convection and radiation.

science
It changes speed (and is refracted).

science
Nothing is 100% efficient.

science
We protect outselves from ultraviolet rays from the sun by wearing sunscreen,proper clothing, and sun glasses.

science
Particles with a charge attract oppositely charged particles; magnets attract opposite magnetic fields.

science
I agree.

Science
I would go with d.

Chemistry
heat gained by ice moving from -17 to zero + heat gained by ice melting |+ heat lost by warm water + heat gained by cool water = 0 [mass ice x specific heat solid ice x (Tfinal-Tinitial) + (mass ice x heat fusion at zero C) + [masswarm H2O x specific heat H2O x (Tfinal-Tintial...

chemistry
Let acetic acid (CH3COOH) = HAc ......HAc + KOH ==> KAc + H2O pH = 2.14 so (H^+) = approx 7.2E-3, I think you need the (HAc)= ?

chemistry
See your other post.

chemistry
2 atoms/cell x 22.9898/6.02E23 = mass of unit cell = ? Then mass = volume x density and volume = mass/density = ? a = V^1/34.3E-8 cm but you should go through all of the calculations. This is an estimate as are all of the calculations that follow. For the body centered unit ce...

chemistry
Mg^2+ is twice the charge of Na^+ so the effect is 4x as much. (2^2 = 4) The Mg^2+ ion is smaller than the Na^+ and the closer the ions are togther the tougher it is to pull them apart.

chemistry
ionic charge ionic radius

chemistry
http://en.wikipedia.org/wiki/Effective_nuclear_charge#Calculating_the_effective_nuclear_charge

chemistry
You may be ok by now but all you need to do is to substitute HF and KF. There is no reaction. (KF) = 0.05 x (100/300) = ? (HF) = 0.05 x (200/300) = ? Then HF goes in for the acid concn and KF goes in for the base concn. Actually, there is an easier way to do it I think. Work w...

chemistry
Why not show your work with the HH equation and let me find the error.

college chemistry
millimols BOH = 25 mL x 0.1M = 2.5 millimols HCl = 5.25 mL x 0.1M = 0.515 ..........BOH + HCl ==> BCl + H2O I.........2.5....0.......0......0 added.........0.515............... C......-0.515..-0.515...+0.515 E...... 1.985....0.......0.515 I would substitute the E line into ...

chemistry
I would rank from low to high as N2, HCl, H2O, MgF2 but you should confirm that. Look on Google and check the boiling points.

Chemistry
(NH4)2S ==> 2NH4^+ + S^2- So (NH4)2S = 0.200 That means NH4^+ must be twice that and S^2- is the same as (NH4)2S

chemistry
C'mon. Find the caps key and use it. Oxidation is the loss of electrons. Hint: Fe is zero on the left and +3 on the right. Ag is +1 on the left and zero on the right. so which lost electrons?

physical science
Ozone absorbs most of the UV light from the sun; thus, ozone effectively blocks the UV-B rays from striking the earth.

physical science
To keep UV rays from damaging the skin and eyes.

Chemistry
See this table for ionization energy. http://www.lenntech.com/periodic-chart-elements/ionization-energy.htm

chemistry
Only one because all of the bond lengths are the same. We can't draw the actual structures so we draw several "resonance structures" and all of us understand that the "real" bond structure is an average of all those we have drawn but isn't any one o...

CAN ANYONE HELP?
I'm trying but I can help until I identify the problem. So stick with me and we'll get there. Don't blow by questions away.

Chem
You don't help yourself by changing screen names. I answered this question earlier.

Chemistry help
If dStotal is +, the reaction is spontaneous.

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