Tuesday
July 29, 2014

Posts by DrBob222


Total # Posts: 43,218

CHEM
Your post isn't very clear. Do you mean this is a concentration cell with one half cell of 1E-2M and the other 3.2E-2. If so then Ecell = -(0.05916/1)log (dilute/concd)

chemistry
mols sample = 0.05/114 = approx (but you do it for the real number) = 0.00044 q = mass H2O x specific heat H2O x delta T. q = 200g x 1 cal/g*C x 5.7 q = approx 1100 calories for 0.05g or 1100/0.05 = approx 23000 calories 23,000 calories x (1 kcal/1000 cal) = 23 kcal = 23 nutri...

chemistry
3,5,5 look just like 1 and 2. 6 and 7 are done by working backward. delta T = i*Kf or Kb *m You're given delta T, solve for m. Then m = mols/kg solvent. Solve for mols Then mols = grams/molar mass. You're given mols and grams; solve for molar mass. i = 1 for both 6 and 7

chemistry
2. Find the freezing point of a solution composed of 50g IBr in 120 g of water. Assume 100% ionization. KBr = k1+Br1-. I assume you made a typo and IBr really is KBr. mols KBr = grams/molar mass. Solve for mols. molality = m = mols/kg solvent Solve for m delta T = i*Kf*m i fo...

chemistry
1. Find the boiling point of a solution composed of 110g of HgCl2 (a non-ionizing solute) in 175g of water. mols HgCl2 = grams/molar mass Substitute and solve for mols. molality = m = mols/Kg solvent Substitute and solve for m delta T = i*Kb*m Your post says i = 1 Kb = 1.51 S...

chemistry
dGo = -nFEo Solve for n. That will give you the change in electrons.

Chemistry
I differ slightly (84.82) probably because you rounded to 1.62 while I kept everything in the calculator until the final answer. But to three significant figures I would round the answer to 83.8 (probably krypton).

Chemistry
(rate1/rate2) = sqrt(M2/M1) Substitute and solve for molar mass.

science
Oh my! Twisted minds. I'm still smarting over carbon dioxide and water having the same physical properties.

science
Generally days are shorter in the winter than in the winter.

Science
A is the correct answer. Water is H2O and carbon dioxide is CO2. They have different physical properties (water is a liquid while CO2 is a gas at room temperature.) Both have a set ratio of atoms as shown by the formulas I've written. Water and CO2 have different chemical ...

Science
And a c'mon to Kalie, too. What are physical properties? What are chemical properties.

Science
I don't agree with that answer. Carbon dioxide is a gas; water is a liquid. And you think they have the same physical properties? C'mon.

chem
You're right about Pgas = X*Ptotal but I don't think you understand the equation I wrote. Dalton's Law of partial pressures tells us that the total pressure inside a container is the sum of the individual gas pressures. So I wrote the equation Ptotal = pO2 + pH2O. ...

chem
The temperature is used to look in a table of T vs vapor pressure. It tells you the vapor pressure of the water (in this case 25.81 mm Hg) at 26.4 C. I don't agree with your answer. And why in the world would you change mm and torr to atm if the problem didn't ask for ...

chem
Ptotal = pO2 + pH2O

chemistry
You can calculate delta S for the system and delta H for the system at 25 degrees C by using dHo formation and dSo formation and dHo rxn = (n*dH products) - (n*dH reactants) dSo rxn = (n*dH products) - (n*dH reactants). What's the temperature. dS surrounds = -dH/T dS syste...

CHEMISTRY HELP !!!!
dGsystem < 0 for any spontaneous process.

Chemistry
pH = -log(H^+) Substitute and solve for pH.

chemistry
M of the diluted stuff is 1.14 g/mL x 1000 mL x 0.20 x 1/98 = 2.33M M of the strong stuff is 1.84 x 1000 x 0.98 x 1/98 = 18.4M Then use the dilution formula. mLA x MA = mLB x MB 100 x 2.33 = mLB x 18.4M Solve for mL B. I obtained approx 13 mL

chemistry
mols glyc = grams/molar mass mols H2O = grams/molar mass Xgly = mols gly/total mols XH2O = mols H2O/total mols.

chemistry
PV = nRT

Chemistry
I'm not sure what you want for #1. We can't draw structures on this forum. For #2, the Cl outside the coordination sphere is the ionic Cl, therefore Cl- + Ag^+ ==> AgNO3. The two coordinated Cl atoms within the sphere are not ionic and do not react with AgNO3.

chem
1. mols NH3 = M x L = ? Using the coefficients in the balanced eqauation, convert mols NH3 to mols H2SO4. Now M H2SO4 = mols/L, You know mols and M, solve for L and convert to mL if needed. 2. You have mols NH3. Using the coefficients convert mols NH3 to mols (NH4)2SO4. Now co...

Chemistry
Write and balance the equation. Convert 400.0g C3H8 to mols. mol = grams/molar mass Using the coefficients in the balanced equation, convert mols C3H8 to mols or the product. Now convert mols of the product to volume. mols x 22.4 L/mol = Liters.

chemistry
How many mols NaCl do you want? That's M x L = ? Then mols = grams/molar mass. You know molar mass and mols, solve for grams.

chem
Density = 1.025 g/mL; therefore, 100 mL has a mass of 1.025g/mL x 100 mL = 102.5g. 100 mL H2O should weigh 100 g; therefore, there are 2.5 g vinegar in the sample and that is 2.5%. This assumes that the volumes of vinegar and H2O are additive.

Chem
q = mass Al x heat fusion Note that mass is in grams and heat fusion is in kJ/mol; therefore, you must convert g Al to mol or heat fusion from kJ/mol to kJ/g

chemistry
What is the "mass you calculated" refer to?

chemistry
What reaction? What change in % did you calculate? I don't get the question?

chemistry
mols F^- = 0.0025g/atomic mass F and since that is is 1 L, that is the concn in mols/L. Evaluate Qsp and compare with Ksp.

chemistry
(P1V1/T1) = (P2V2/T2) P1 = 1 V1 = 0.550 T1 = 273 P2 = ? V2 = 7.50E-2L T2 = 273 + 20

Chemistry
No and partly because I may have led you astray. The numbers I gave you are for 1L of the solution at that concn. You only want 500 mL of that (which I missed on first reading) so you need only 1/2 of your final figure or 5.346/2 = ?.

Chemistry
Li3PO4. You want (Li^+) = 0.1385M You want to make this out of Li3PO4. But since Li3PO4 furnishes 3 Li ions for every molecule of Li3PO4, you only need 1/3 that number or 0.1385/3 = ? mols Li3PO4. Then g Li3PO4 = mols x molar mass.

Chemistry
CH3COOH + NaOH ==> CH3COONa + H2O mols NaOH = M x L = ? mols CH3COOH = mols NaOH (because of the 1:1 coefficients in the balanced equation.) g CH3COOH = mols CH3COOH x molar mass CH3COOH. Then % CH3COOH = (g CH3COOH/mass sample)*100 = ?

Chemistry
This is a limiting reagent (LR) problem. You know that when an amount for BOTH reactants is given. Zn + 2HCl ==> H2 + ZnCl2 mols Zn = grams/molar mass. mols HCl = M x L = ? Using the coefficients in the balanced equation, convert mols Zn to mols H2. Do the same for mols HCl...

Chemistry
The Eo voltage in tables may changes as a result of acid or basic conditions; however, there are no H or OH ions in the half reactions you've written so you need not worry about that.

Chemistry
If that is the smallest Ecell, then turn those half cells into a reaction. Arrange the half cells so they produce a positive voltage. 2Eu^2+ + Sn^2+ ==> 2Eu^3+ + Sn

Chemistry
2Fe3+(aq)+H2(g)→2Fe2+(aq)+2H+(aq). Ecell = Eocell - (0.5916/2*log Q and I know that confuses you but don't be. Plug in the numbers Eo and n and for Q plug in concns/pressures(in atm) as follows: Q = [(H^)^2*(Fe^2+)^2]/[(Fe^3+)^2*pH2] I write it this way because I'...

Chemistry
See your other post. delta e wrong at 6.

General Chemistry
3e not 6.

Chemistry
mols MgCl2 = grams/molar mass = ? M MgCl2 = mols/L solution = ? Since there are two mols Cl in 1 mol MgCl2, then M Cl = twice that of MgCl2.

Chemistry
An equation like this is confusing because I^-(on the left) is going to I2 (on the right) but it then dissolves in KI to make KI3 so let's simplify it by taking the KI out of it, balance it, then put the KI back in. 2I^- --> I2 I is -2 on left and 0 on right. Balance wi...

chemistry help~~~~ Please!!!
k = 0.693/t1/2 Then ln(No/N) = kt. No = 25 N = 1 k from above. t = solve for this.

Chemistry-need help ASAP
I'll get you started but I don't believe you can't do any of it. I don't know what the problem is asking for when it says "difference in pH". Difference in pH from WHAT? 15 mL of 3M NaOH added to 500 mL. (NaOH) = 3M x (15/515) = ? (Note: This assumes ...

Chemistry-need help ASAP
How much of this do you know how to do?

Chemistry
HAc + NaOH ==> NaAc + H2O First determine the M of the HAc. mL x M = mL x M 22.5 x .21 = 50x (I worked this part for you at your original post yesterday. Apparently you never went back to look at it.) M HAc = approx 0.9 but you need to do it more accurately. Now divide the ...

Chemistry
I responded earlier with this. How much do you know how to do?

Chemistry
Here us a site that tells you the details. http://www.chemteam.info/Redox/Redox.html I don't do them that way. Here is how I do the CrO4^-. You can add the states. CrO4^2- ==> Cr^3+ Cr is +6 on left and +3 on right. Add 3e to left. CrO4^2- +3e ==> Cr^3+ Count the cha...

chemistry
Did you square 1.75 or multiply it by 2. I think you did the latter; you should have squared it.

Chemistry
Mn is +7 in MnO4^-. It is +2 in Mn^2+. To balance the change in electrons we have MnO4^- + 5e ==> Mn^2+. I do it that way and make this the first step of the process of balancing. Some say there is a shorter way and you do this the LAST step and not the first. To do it that...

Chemistry
MnO4^- + 8H^+ + 5e ==> Mn^2+ + 4H2O

chemistry 2
HAc + NaOH ==> NaAc + H2O First, determine the molarity of the HAc. mL x M = mL x M 22.5 x 0.21 = 50*x x = 0.0945M Now divide the titration curve into four sections. a. at the beginning. b. between initial and eq point c. eq pt d. after eq pt Which of these do you have trou...

chem090
I work these limiting reagent (LR) problems the long way. 2K3PO4 + 3BaCl2 ==> Ba3(PO4)2 + 6KCl mols K3PO4 = grams/molar mass = 100/212.26 = about 0.47 mols BaCl2 = 100/208.23 = about 0.48 Now convert mols K3PO4 to mols Ba3(PO4)2 using the coefficients in the balanced equati...

Chemistry
Here is the way I write these. The atomic number goes on the left, the mass number on the right. So the Po would be 84Po212 ==> 82Pb208 + AXZ where A is atomic number, Z is mass number, X is the element. The left side must add up and the right side add up; i.e., atomic numb...

Chemistry
Following my post above. atomic number on left, element in middle, mass number on right. Left numbers must add up on both side; right numbers must add up on both sides. So for Th we write 90Th234 ==> beta + ? beta is an electron which is -1e0. 90Th234 ==> -1e0 + AXZ So 9...

chem 101
q = mass x heat vaporization Change 42.8g to mols. mols = grams/molar mass

Chemistry
assume the question is to determine M I2. ascorbic acid + I2 ==> 2I^= + ..... mols ascorbic acid = grams/molar mass mols I2 = mols ascorbic acid (1:1 ratio from the equation) M I2 = mols I2/L I2.

chemistry
You don't ask a question. I assume the problem is to determine the heat of neutralization in kJ/mol. Also, I assume there is no calorimeter constant so we ignore that. Please check the post to make sure you have all of it correctly. The answer should be about 55 kJ/mol and...

Chemistry - Science (Dr. Bob222)
Cr on the left is +6 each so 6*14 = 84+ and on the right is 14*3 = 42+. 84-42 = 42 e xfrd. I on the left is zero. On the right each I is 7+ and 6*7 = 42+. 42-0 = 42e xfd.

Chemistry
CoCl2 is soluble; therefore, it has no Ksp. The easiest way to do these is to note that with a Kf so extremely high you know the solution at equilibrium will be far to the right; therefore, we set up an ICE chart and make the reaction go 100% to the right. That is an ok assump...

chemistry
Your equation is right. Your reasoning is wrong. Mg is more active because it replaces the Pb ions and forces the Pb out of solution. Here is how you tell which is more active. Here is the "activity series" of metals. https://www.google.com/search?q=activity+series+m...

chemistry
See your post above. Pb is above Ag in the table; therefore, Pb is the more active metal and it will displace Ag^+ from solution.

chemistry
You have written it correctly.

Radioactivity
When an element loses an electron (from the nucleus) it is because one of the neutrons becomes a proton and the electron is ejected as a beta particle. The mass number doesn't change because the number of protons + number of neutrons is the same but the number of protons h...

Science radioactivity
Alpha and beta particles really are particles in that sense of the word. The alpha particle is a helium nucleus and a beta particle is an electron. A gamma is a ray; i.e., an electromagnetic wave much like a radio or TV wave (but a much shorter wavelength and much higher energ...

chemistry
The general gas formula can be modified from PV = nRT to P*molar mass = density*RT Substitute and solve for density.

Chemistry
See your other post.

Science
How far can you get on this problem? What don't you understand about the next step>

Chemistry
Changing screen names won't help. Read over your post carefully and make sure you have included everything. With no data to calculate it and no calorimeter constant given, 4,5,6, et al are dead in the water..

chemistry
4. You don't have enough information to calculate the amount of heat absorbed/lost by the calorimeter. You need the calorimeter constant or data to calculate and you have neither. 5,6,7 depend upon 4.

chemistry
1. HCl + NaOH ==> NaCl + H2O 2. H^+ + OH^= ==> H2O 3. q = mass H2O x specific heat H2O x (Tfinal-Tinitial) assuming the calorimeter can be ignored. ' 4. I'm surprised there is no 4th question to calculate kJ/mol for the heat of neutralization.

Chemistry
mols Zn = grams/atomic mass = ? mols HCl = twice that (from the coefficients in the balanced equation). M HCl = mols HCl/L HCl. You know M and mols, solve for L HCl and convert to mL.

Chemistry
I looked on Google and under potassium hydroxide it lists as being soluble in alcohol. You can do the same for the others. Wikipedia is the best link and scroll down until the right hand boxes get to solubility.

Biology help please
Sorry, I can't help.

Chemistry - Science (Dr. Bob222)
Interesting because at 25C H3PO4 is not solid. It freezes about 17 C. mols H3PO4 = 0.4g/molar mass H3PO4 = estimated 0.004 mols NaOH added = M x L = estimated 0.02 You need to clean up the numbers before continuing. ......H3PO4 + 3NaOH ==> Na3PO4 + 3H2O Starting with 0.02 m...

Chemistry
Yes, unless you were told that the HCl you had was 1.000 M. Usually you are given instructions for preparing 1M HCl but those instructions only get a solution that is close to being 1.00M. You must standardize to find out EXACTLY what it is such as 0.1011M or 0.09876M

Chemistry
mols NaCl = grams/molar mass Then M = mols/L solution.

science
Frankly I don't think this is a very good question. Too many ifs in the answers. 1. I don't agree with a flying bird as an answer; however, it the bird were flying at the same speed (reference the ground) as the train and in the same direction, that could be the right ...

Chemistry
Do you have the heat of combustion? If not you can calculate it this way. 2C8H18 + 25O2 ==> 16CO2 + 18H2O dHrxn = dH combustion = (n*dHo formation products) - n*dHo reactants). So you will obtain that many kJ for 228 g octane. Convert that to grams needed for 5410 kJ. Post ...

science
Jaco, I worked this for you rour posts down under "chemistry".

Chemistry
Use PV = nRT and solve for n = number of mols. Then n = grams/molar mass. You know n and grams, solve for molar mass. You can do it another way knowing that an ideal gas at STP will occupy 22.4L. Therefore, n = 1.15L/22.4L = number of mols, then n = grams/molar mass.

Chemistry Equilibrium
......NO2 + NO ==> N2O + O2 I......x.....x.....0......0 C.....-y.....-y....y......y E.....x-y...x-y....y......y So you want (N2O) = (O2) = 0.0446M mols = 0.0446*5L = 0.223 = y Kc = (N2O)(O2)/(NO2)(NO) Kc = (x-0.223)(x-0.223)/(0.223)(0.223) Solve for x = mols NO2 = mols NO T...

Chemistry Equilibrium
You need to find the arrow keys on your computer and use them. (N2O) = 0.174mol/4.00L = estimated 0.04 (NO2) = 0.337 mol/4.00L = estd 0.08 ...........N2O(g) + NO2(g)==> 3NO(g) I.........0.04.....0.08........0 C.........-x........-x.........3x E.........0.04-x...0.08-x.........

chemistry
A. I assume M^+ and A^- but it could be M^2+ and A^2- etc. (MA) = 0.0031 x (1000 mL/200 mL) = 0.0031*5 = ? Ksp = (M^+)(A^-) = (0.0031*5)^2 B. dG = -RT*lnK

Chemistry
I don't get anywhere near that figures but I may have made some wrong assumptions. If you wish to show your work I'll be happy to check it.

Energy question
q = mass ring x specific heat ring x (Tfinal-Tintial) You know q, mass ring, Tf and Ti. Solve for specific heat.

Chemistry
By definition, M Ca(OH)2 = mols/L solution. mols HClO4 = M x L = ? mols NaOH = 1/2 that (from the coefficients in the balanced equation). Then M Ca(OH)2 = mols Ca(OH)2/L Ca(OH)2.

Chemistry
You've worked more difficult problems than this. What's the trouble here?

word problem
q = mass metal x specific heat metal x (Tfinal-Tinitial) An easy way to do this is to assign some convenient number for q, give it some convenient starting T and solve for Tfinal. Or you can reason it out. If sp.h. Ag is 0.235 and that of Cu is 0.385 then it takes more heat to...

Chemistry
Your problem isn't chemistry. You just need a little help with algebra. 5.00-4.74 = 0.26 = log 15/x 15/x = antilog 0.26 = 1.82 So 1.82 = 15/x. Solve for x and convert to g/500 mL.

Chemistry
I worked this below. I can find it if you wish.

chemistry
avg rate = (12.5-10)/50 min = ? mM/min. rate = k(NPP). You know NPP initially and the rate, solve for k. Plug all of this into the Arrhenius equation an solve for activation energy.

CHEMISTRY
Convert g to mols. mols = g/atomic mass mols C = 97.30/12 = ? mols H = 16.22/1 = ? mols O = (200-16.22-97.3) = 86.48/16 = ? Now find the ratio of each element to the others(in small whole numbers) with the smallest number being 1.00. The easy way to do that is to divide the sm...

Energy question
Another thought. Incandescent bulbs don't pollute the environment with mercury. Most fluorescent bulbs(I don't know if all do or not) have mercury in them.

Energy question
This is my personal opinion but I don't think they are. My experience is that the new fluorescent bulbs don't live up to the hype on the box. Supposedly those incandescent bulbs burn out faster and it takes several to last as long as the newer fluorescent bulbs. In add...

Science help!!!!
These fill in the blanks are hard to do because more than one work/phrase often fits. A____solar panel__________________ is a tool used to capture the energy in sunlight. Recycling aluminum cans and taking shorter showers are two ways to practice the ___conservation___________...

Chemistry
q = -192 kJ since that is evolving heat. w = pdV = 125*(2) an that is - since it is expanding; i.e., it is doing work against the atmosphere while expanding. Note that w is in L*atm and need to be changed to J. Do that by x 101.325 then convert to kJ. Note: work is given in te...

chemistry
delta H at constant pressure is q. Or perhaps I should say it another way,k q at constant pressure is delta H. So delta H in this case is +252 kJ.

chemistry
q = 252 kJ and it's + so is endothermic w = 105 kJ and it's - since it is doing the work. delta E = q+w delta E = +252 kJ + (-105 kJ)

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