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Posts by DrBob222

Total # Posts: 54,989

Chemistry
I don't believe the Eo values you have but we'll go with what you posted. Zn ==> Zn^+ 2e Eo = +0.96 Cu^2+ + 2e ==> Cu Eo = +-.3 ----------------------------- Zn + Cu^2+ ==> Zn^2+ + Cu Ecell = 0.96+0.3 = ? Then dG = -nEF Calculate dG. n is 2; F is 96,485 ...

chemistry(a mystery)
chlorine. Cl2 is a single bond; N2 is a triple bond. Cl has just 1 electron to add to make an octet and it forms an ionic bond. N needs 3e to make an octet and few N compounds are ionic; i.e., most are covalent.

Chemistry
let x = mL of 0.4 and 50-x = mL of 0.025 --------------------- 0.025(50-x) + 0.4x = 50(.04) solve for x and 50-x

chemistrey
(p1v1/t1) = (p2v2/t2)

chemistry
mols NaH2PO4 = M x L = ? mols Bi^3+ = mols NaH2PO4 from the coefficients in the balanced titration equation (1:1). Convert mols Bi^3+ to mols eulytite by mols Bi^3+ x (molar mass eulytite/2*atomic mass Bi) = ? Then g eulytite = mols eulytite x molar mass eulytite. Then % ...

chemistry
mols I2 initially = M x L = ? Excess I2 titrated with S2O3^2- is I2 + 2S2O3^2- ==> 2I^- + S4O6^2- mols S2O3^2- = M x L = ? Convert mols S2O3^2- to mols I2(that will be mols S2O3^2- x 1/2 = ? and this is the excess I2). I2 used in the Pb(C2H5)4 = mols I2 initially - mols I2 ...

oops---Chemistry-ksp and kb
I see I wrote y = (M^+) and that isn't right. y = (MOH) = (X^-). You know Kb for MOH and you know OH so you can calculate (M^+).

Chemistry-ksp and kb
y gives the concn of X^- and therefore of KX. And X^- is not hydrolyzed for the reason you state. This question is so far down the list that I almost assumed you had not responded to my first response. If you have further comments please copy and post a new at the top of the ...

Chemistry-ksp and kb
I had trouble following your thoughts after the first few lines but the first part is OK. You started out right. You need Ksp/Kb = 0.15 ......MX ==> M^+ + X^- Ksp = .... ......OH^- + M^+ ==> MOH 1/Kb =... ------------------------------- Add to get MX(s) + OH^- =>MOH...

Chemistry
https://www.google.com/search?q=crysrallization&ie=utf-8&oe=utf-8

Chemistry
See your other post. Read the section in Wikipedia.

Chemistry
Sublimation first and seeding second. If you had ever done a crystallization you would know the answers to all of these.

Chemistry
B

chemistry
http://www.jiskha.com/display.cgi?id=1480355412

math
YOU CANNOT COPY AND PASTE TO THIS SITE!

math
You can't copy and paste to this site.

science
What is the investigation?

i need help with mah
I see no data.

Chemistry
mL1 x M2 = mL2 x M2 12 x 0.790 = 50 x M2 OR, since it's dilution, you start with 0.790M and multiply by a factor less than 1 like this 0.790 x 12/50 = ? Technically, M2 is the concentration of Cu(NO3)2 but since 1 mol Cu = 1 mol Cu(NO3)2 it's all the same.

math
A has a horse worth $900 initially. When A goes through the various transactions he ends up with the same horse now worth 891. $900-891 = 9.00 I see how you came up with $171. You're confusing loss and gain with the worth of the horse. You're mixing apples and oranges...

oops--typo--math
I hit the - key instead of the = key. That line should be The loss to A is 900-891 = 9.00.

math
A has the horse at $900. A sells the horse to B at 10% loss so 900 x 0.1 = 90 and 900-90 = $810. Now B sells the horse with a 10% profit or 810 x 0.1 = 81 and 81 + 810 = $891. The loss to A is 900-891 - 9.00. I don't know how you come up with $171. Are you converting the ...

Math
I don't think so. Put this is numbers as in the problem with x and y dollars.

Math
He makes $50 and saves $40 so he spends $10. Right? Convert that to x and y and you have it. Don't get confused with x and y. Sometimes it helps to put it in numbers.

Math
let x = number of seats. Then (2/3)x = 300 Solve for x.

Math
let x = total students then (1/12)x = those absent and (11/12)x = those in school But (1/5) of the (11/12)x went on field trip = (11/60)x. So x - (11/60)x - (1/12)x = 704 Solve for x.

Chemistry
I'm not sure EXACTLY what you did. 1 is OK 2 is OK 3 is not right. The mass H2O is 139.0 g and q = mc(dT). You didn't use specific hrat H2O as far as I can see. 4. Apparently you are to calculate the initial T of the metal. [mass Cu x specific heat Cu x (Tf-Ti)] + [...

Chemistry
Plug and chug.delta T is 2.8

Chemistry
You don't ask the question but I assume you will be calculate delta H or something like that. Yes, use q = mcdT. That's right, you don't have Tfinal and Tinitial BUT the problem tells you T increased by 28 C so Tfinal-Tinitial = 28

chemistry
http://www.jiskha.com/display.cgi?id=1495566182

chemistry
You have typed your entire lab experiment here. I'm not inclined to answer each line by line question but I'll be glad to help if you tell me what I can help you with. Note that you have initial volumes and final reading the buret. Subtract the two to find the volume ...

Chemistry
1. Use the solid. How many moles do you want? That's M x L = 0.5 x 0.100 = 0.05 How many grams is that? mols = grams/molar mass or grams = mols x molar mass = 0.05 x 40 g/mol = ? Weigh ? grams NaOH, place in a 100 mL volumetric flask, add some water, swirl to dissolve, add...

chemistry
mols Mg = grams Mg/atomic mass Mg = ? Using the coefficients in the balanced equation, convert mols Mg to mols H2. Now convert mols H2 to volume (in L) knowing that 1 mol will occupy 22.4 L.

Science/chemistry
You transposed some letters; I assume you meant CO2 and not OC2. mols CH4 = grams/molar mass = ? Using the coefficients in the balanced equation, convert mols CH4 to mols H2O. Then convert mols H2O to grams. grams H2O - mols H2O x molar mass H2O Post your work if you get stuck.

Chemistry
Use PV = nRT You have P, R, T. n = grams/molar mass. Don't forget to convert 35C to kelvin.

Math
Let x = speed of the boat. Then x+7 is total speed with the current. Against the current it is x-7 x+7 = 3(x-7) Solve for x.

Chemistry
KHP + KOH ==> K2P + H2O mols KHP = grams/molar mass = ? mols KOH = mols KHP (look at the coefficients and see they are 1:1). Then M KOH = mols KOH/L KOH.

chem
......PbI2 ==> Pb^2+ + 2I^= I....solid......0.......0 C....solid......x......2x E....solid......x......2x The other ionization is NaI and that is ionized 100% (completely that is). ........NaI ==> Na^+ + I^- I.....0.05M......0.....0 C....-0.05.....0.05...0.05 E......0...

chemistry
The KMnO4 oxidizes the Fe(NH4)2(SO4)2 from iron(II) to iron(III) and is reduced from Mn(VII) to Mn(II) in acid solution

chemistry- morality
I don't know about the morality of these answers but I'll try. First, I assume your 8.00 m actually is 8.00 M. m means molality. M means molarity. Use the dilution formula of mL1 x M1 = mL2 x M2 1.19 x 8.00 = mL2 x 1.50 Solve for mL2. Post your work if you get stuck.

chemistry
I'm at a loss since I don't know what experiment, the details, etc. If the "final" solution is the KHX, adding NaOH will titrate the H and leave K2X as if more NaOH were added in the first place as in H2X + 2KOH ==> K2X + 2H2O

chemistry
Follow along and confirm my conclusions. My rationale is as follows: millimols KOH = 50 x 0.2 = 10; therefore, any H2X < 10 mmols will leave excess (xs) KOH in the solution and that will be more basic. So we must have at least 10 mmols H2X. Using exactly 10 mmols H2X will ...

Chemistry
7.5 mg MeOH/mL x 1000 mL = 7500 mg/L or 7.5 g/L. mols MeOH = grams/molar mass and M = mols/L. Then use the dilution formula of mL1 x M1 = mL2 x M2

Chemistry
I have copied this question and moved it to the top where I hope it will be easier to find. Please make any comments to that location and not to this one.

Chemistry
Now I'm having doubts. As I think about it I'm suspicious that 0.002 just doesn't sound like a number that would be right. And if you look at 50 cc of 0.002 M H2X reacting with 50 cc of 0.2M KOH,it doesn't make sense that there is KOH left over sine an excess ...

Chemistry
I think you are VERY close but not quite there. For 1,I think you substituted into Ka1 to solve for C but in reality I think you should have used the Henderson-Hasselbalch equation because you have formed a buffer with KHX and H2X. pH = pKa1 + log (base)/(acid) 7 = 5 + log(0.1...

Chemistry
mols HCl = M x L = ? mols NaOH = mols HCl (look at tahe coefficients; the rxn is 1:1). Then M NaOH = mols NaOH/L NaOH.

chemistry
I don't believe there is a reaction between NH4Cl and KMnO4.

Chemistry
I like to work in millimols = mmols. M = mmols/mL. So you ask yourself how much NaOH it would take to neutralize ALL of the H2SO4, not just part of it. How much excess H2SO4 did we have? That's M H2SO4 = mmols/mL. M = 0.029297. mL in the final solution is 25.3 mL + 18.8 mL...

Chemistry
Yes, (l).

Chemistry
volume = (edge length)^3 = ? cm^3 mass = volume x density. You know volume and density. Solve for mass. Note that g/mL = g/cc = g/cm^3

@Connexus cheat - banned
Technically it is cheating; however, I'm not sure that's the way the students see it. I think in many cases it's a way to get someone to do their work for them. They are just too lazy to fill in the blanks/check the multiple guess/read the lesson/etc. and they see ...

Science
You can get better service if you don't change screen names.

Chemistry
delta T = Kf*m Kf = 1.86 m = mols/kg solvent and mols = grams/molar mass. Substitute and solve for m. Then substitute into dT = KfM and solve for dT. Post your work if you get stuck.

Science
Fe + S ==> FeS synthesis

Chemistry
The smallest set of whole numbers is C4H5N2O

Chemistry
See your other post.

Chemistry
2NaCl + 2H2O ==> Cl2 + H2 + 2NaOH coulombs = amperes x seconds = approx 2400 96,485 coulombs will form 40 g NaOH. g NaOH produced = 40 x 2400/96,485 = 0.995. How many mols is that? 0.995/40 = approx 0.25 Then you know the titration is NaOH + HCl ==> NaCl + H2O Approx (...

chemistry
I take it that 1.33E-10 is the average of Kb for acetic acid and you want to calculate Ka. Ka*Kb = Kw = 1E-14 You know Kw and Kb, solve for Ka.

Chemistry
Al is in group IIIA and is +3, I think, almost always. But you can tell by looking at the formula of Al2(SO4)3. The tells you oxidation number of Al is +3 and the 2 tell you the sulfate ion is -2. How to do S. Al is 2*+3 each = +6. O is 12*-2 = -24 Remember Al2(SO4)3 is zero ...

Chemistry - Significant Figures
rate = delta grams/delta time = 2.4/35 = ?

chemistry
http://www.jiskha.com/display.cgi?id=1495141830

chemistry
I don't know why it won't. You may have used the wrong color litmus paper to start.

chemistry under gas law
0.08206 x 101.25 kPa/atm = 8.314 J/mol

chemistry ( little urgent pls)
Yes, and that means dH must be large(negative) eough to off set dS. BTW, a little urgent is like being a little pregnant.

chemistry
PV = nRT. So if you know P, V, T and R, what's left?

Chemistry
Yes. Here are the definitions. Oxidation is the loss of electrons. Reduction is the gain of electrons. Oxidizing agent and reducing agents are the reverse. Oxidizing agent is reduced; therefore, it gains electrons. Reducing agent is oxidized; therefore, it loses electrons.

chemistry
Water is polar. Ethanol is polar. Hexane is non-polar. Like dissolves like.

chemistry
See your other post. Like dissolves like.

Chem
You need to find the arrow key and use it. CaC2(s) + 2H2O(l)=> Ca(OH)2(aq) + C2H2(g) Use the coefficients to convert anything to any other reactant or product. 4.7 mol CaC2 x (1 mol C2H2/1 mol CaC2) = 4.7 x 1/1 = 4.7 mol C2H2. Note that the units you don't want cancel (...

Chemistry
1 is a little tricky. They way you do it is to balance the redox part, then the tricky part. Cu is 0 on the left and +2 on the right. Draw a line from one to the other and show loss of 2e. Then you look at N. It is +5 on the left and it shows +5 on the right (with the NO3^-) ...

Science
Nothing is shown. I don't know where points A and B are.

chemistry
NH4OH + HClO4 ==> NH4ClO4 + H2O millimols NH4OH = M x L = 6 mmols HClO4 = M x L = 6 So the acid and base exactly neutralize each other and you have the NH4ClO4 in aqueous solution at the end of the reaction. The concentration of the salt is mmols/mL = 6/60 = 0.1 M. The pH ...

chemistry
We prefer you not change screen names. This is worked the same way as the NH4ClO4 problem BUT the LiOH and HNO2 don't neutralize each other completely so you have one of them left over and that determines the pH.

Chemistry
See my response above.

MJ Science 3
https://www.thoughtco.com/properties-basic-metals-element-group-606654

MJ Science 3
https://en.wikipedia.org/wiki/Chemical_bond#Strong_chemical_bonds

chemistry
http://www.jiskha.com/display.cgi?id=1401238255

MJ Science 3
D is not correct for 2.

Science
It would help if we knew what you were talking about. Outputs and side effects of WHAT?

Chemistry
You add the states. You don't say acid or base solution. Ag ==> Ag^+ + e 3e + CrO4^2 + 8H+- ==> Cr^3+ + 4H2O

chemistry
jello?

chemistry 20
I am willing to help but I am not willing to to this complete lab for you.

Chemistry
I have no idea what a BCA table is. BCA might be "beginning", "change", A? mols mols Na2CO3 = M x L = 0.075 ...CaCl2 + Na2CO3 ==> CaCO3 + 2NaCl Convert mols Na2CO3 to mols CaCl2 by 0.075 mols Na2CO3 x (1 mol CaCl2/1 mol CaCl2) = 0.075 x 1/1 - 0.075. So ...

Chemistry
mL1 x M1 = mL2 x M2 mL1 x 12 = 1000 x 1

chemistry
I'm blank on this.

however---CHECK my answers Physical science
Note that iron will NOT melt at 8- C. The melting point of Fe is a little more than 1500 C.

CHECK my answers Physical science
The freezing point and the melting point are the same so D is correct.It's called the melting point if it is solid going to liquid at that T; it's called the freezing point if it is going from the liquid to the solid at that T.

Chemistry
no

chemistry
dT = Kf*molality You know dT and Kf, solve for m m = mols/kg solvent. You know m and kg solvent, solve for mols. mols = grams/molar mass. You know mols and molar mass, solve for grams.

chemistry(buffer solutions)
Use the Henderson-Hasselbalch equation. NH3 is the base; NH4Cl is hte acid.

Chemistry
I gave you the wrong formula. Let me start over.

Chemistry
mols KCl = grams/molar mass = ? mols methanol = grams/molar mass = ? Xmethanol = mols methanol/total mols. p(methanol) = i*X.methanol i is 2 for KCl Post your work if you get stuck.

Chemistry
Use PV = nRT; substitute rtp conditions and solve for n. Then 2KNO3 ==> 2KNO2 + O2 You know mols O2 from above. Then mols KNO3 = mols O2 from above x (2 mol KNO3/2 mols O2). Finally, grams KNO3 = mols KNO3 x molar mass KNO3.

chemistry--------help please!!!!
Yes, Li is -3.04 but the question is for Li^+ and not Li.

Science
Proof your post. You're trying to convert Na2CO3 into NaHCO3 and you want to start with CaCO3? Wow. Good luck but don't hold your breath.

Science
I would go with #1 and the final T will be 10 C assuming the bucket doesn't "leak" heat.

Science
I found the site Ms. Sue found, also. Club soda and lemon juice are the only two choices that are acidic.

moves---science
Or you can use a sieve to separate the sand and beads sepending upon the size of the beads. .

science
A magnet removes the iron filings. Filter and the beads and sand stay in the filter paper. Salt and water go through. Dilstil and collect water; salt is left. Dry the bead and sand, shake and the beads will rise to the top and they can be removed phically.

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