Wednesday
April 16, 2014

Posts by DrBob222


Total # Posts: 41,745

Chemistry
0.038 mol FeCl2 x (1 mol K2Cr2O7/6 mol FeCl2) = mols K2Cr2O7. Then M = mols/L so L = mols/M = Then multiply by 1000 to convert to mL.

chemistry
I didn't get 177 mL. mols KMnO4 = grams/molar mass mols Na2C2O4 = mols KMnO4 x (5 mols ox/2 mol MnO4) = ? Them M Na2C2O4 = mols/L Solve for L and convert to mL.

Chem 2
delta T = i*Kf*m for freezing point, subtract 0 C - delta T. i for Na2SO4 = 3 delta T = i*Kb*m for boiling point add delta T + 100 = ?

chemistry
Us the dilution formula of L1 x M1 = L2 x M2 1.64L x 4.95M = ?L x 2.58M ?L = ?

AP chem
Five separate problems can take a long time. Exactly what do you understand (and not understand)?

Chemistry
3.566 XeF4 x (atomic mass Xe/molar mass XeF4) = g Xe

Chem
The only way this can be done that I know of is to have at hand a calibration curve for sugar solutions. If you have such a curve (% sugar on one axis and density on the other) you can read % sugar from the graph. I'm a little surprised that the density is < 1.00g/cc al...

Chemistry
You can't do this? Look up the atomic masses to five or more places for each element (a periodic table or the web) and find the sum.

Chemistry
See your post above.

General Chemistry
If the intermolecular force is greater the vapor pressure will be less because the molecules must have more kinetic energy to escape as a vapor.

Chemistry
I would look in a text for periodic trends and find my answer there.

Chemistry
See your other post.

Ap Chemistry
does not or will not goes in the blank.

chemistry
(18.9 kJ/0.5g) x (1 cal/4.184 J) = ?

AP Chemistry
I don't get it. If it has pH of 7.4 at neutralization why would anything need to be added to neutralize it? BTW, 25 mL of what M of what?

Science
d

Chemistry AP
Several steps to this problem. Here is an outline. 1. Use the HH equation and solve for the ratio of base/acid; i.e., sodium benzoate to benzoic acid. Then convert that to percent of each. 2. Use the percents to calculate a van't Hoff factor. That is 2*%base + 1*%acid = to...

Chemistry
Piece a cake. Check out the site for balancing equations. 4HCl + 3As2O3 + 4NaNO3 + 7H2O --> 4NO + 6H3AsO4 + 4NaCl http://www.chemteam.info/Redox/Redox.html

Chemistry
q = mass H2O x specific heat H2O x (Tfinal-Tinitial)

chemistry
(0.325/0.482)*100 = ?

Chemistry
3Mg + 2H3PO4 ==> 3H2 + Mg3(PO4)2 mols H3PO4 = grams/molar mass. Using the coefficients in the balanced equation, convert mols H3PO4 to mols Mg. Then convert mols Mg to grams. g = mols Mg x atomic mass Mg.

Chemistry
Note that 1 mol SA = 1 mol aspirin and 1 mol SA = 1 mol acetic anhydride. Therefore, 75 mol SA will produce 75 mols aspirin. Then g aspirin = mols x molar mass. 75 mol SA will use 75 mol acetic anhydride; g = mols x molar mass.

chemistry
Please explain what your problem is here. It seems to me that if you've seen a bunsen burner operate you should know the answer to 1 & 2. If you haven't seen one in operation you should. For 3,5,5,6. Aren't these described in some detail in your lab manual or you c...

chemistry
Yes, R is 8.314 Then P1 goes with T1 and P2 goes with T2. Delta H is 557.0 kJ/mol but you should use 557,000 in the formula;i.e., convert to J/mol.

chemistry
Use the Clausius-Clapeyron equation

gwagwa
KE = 1/2*m*v^2

sciene(HELP)
I answered this below. Go back and read your posts to see if there is a response before posting again.

chemistry
and 5.

chemistry
and 4.

chemistry
triplicate

chemistry
duplicate

chemistry
See this. http://www.jiskha.com/display.cgi?id=1391564392

science(CHECK ANSWERS)
I don't think A is the right answer. A is absorbing sunlight for photosynthesis but that is being trqansformed into chemical energy in which CO2 and H2O form glucose. B is absorbing EM to form heat and that is thermal energy, C. The solar panel is absorbing EM and making e...

Chemistry
pi = nRT pi = 821/760 Substitute R and T (remember T must be in kelvin) and solve for n. Then n = grams/molar mass. You know n and grams, solve for molar mass. M = mols/L solution.

Chemistry
But this is what you started with, not what the prof gave you as an unknown. The most likely reason for >100% recovery, as I've already said, is not drying the samples sufficiently so you weigh all of the sample plus some extra water. And you had to dry three samples; i...

Chemistry
I'm glad to know you omitted those last steps. Do you know what the actual percentages are. If we knew that we could make some educated guesses about why may have gone wrong although that won't answer either of the two question posed.

Chemistry
I don't think your professor will buy either argument you gave above. The mass of NaCl will not change and SiO2 won't absorb into the atmosphere. Frankly, I don't understand how this separates the CaCO3. Did you omit a step? In the process you give the CaCO3 and Si...

Chemistry
First, I don't know what process you used for separating the components. One common error is this type lab procedure is not drying each and that always contributes to greater than 100% recovery. If you care to type in the procedure you used perhaps I can help with the othe...

ap chemistry
a. Use the Henderson-Hasselbalch equation.

ap chemistry
Approach this problem as in the NH3/HCl problem below and see where you are on the titration curve. Post your work if you need addition assistance.

ap chemistry
millimols HCl = 34 x 0.2 = 6.8 mmols NH3 = 29 x 0.05 = 1.45 ..........HCl + NH3 ==> NH4Cl I.........6.8...1.45......0 C........-1.45.-1.45.....+1.45 E.........5.35...0........1.45 If you look at the numbers you will notice that the titration with HCl has neutralized all of ...

Chemistry
I don't know that you can except in some circumstances. First, most gases are not very soluble (some exceptions are NH3, SO2, SO3 etc) so unless it reacts with water and is quite soluble, you don't expect it to be a gas. Most liquids are not soluble in H2O unless they ...

ap chemistry
Substitute into the HH equation.

ap chemistry
Use the HH equation and solve for Ac. pH = pKa + log (Ac/HAc) 5.027 = 4.744 + log Ac/0.5 Now convert M Ac to grams.

ap chemistry
Use the HH equation.

chemistry
17(0.25) + 21.3(0.75) = ?

ap chemistry
Use the HH equation.

ap chemistry
The HH equation again.

ap chemistry
HH equation

ap chemistr
Use the HH equation

ap chemistry
.......KOH + HA ==> KA + H2O I.....0.23..0.45....0....0 C....-0.23.-0.23...0.23..0.23 E......0....0.22...0.23 (KA) = 0.23 mols/0.680 L = ?M (HA) = 0.22 mols/0.680 L = ?M pH = pKa + log (base)/(acid) pH = ?

Chemistry
3 M means 3 mols/L of solution which is 3*molar ,mass NaCl = approx 175 g NaCl/L solution mass of the 1L = 1000 mL x 1.05 g/mL = 1050g solution - 175 = appox 875 g H2O or 0.875 kg. m = mols/kg solvent = about 175/0.875 = ? You need to work the problem with more accuracy than I...

science
Why don't you Google electron microscopes and scanning probe microscopes.

Chemistry
You must describe what you are doing before we know how to answer. Probably this is a limiting reagent problem.

heat energy
It get cooler, of course.

Math
(2/5)lb per person x 15 people = 6 lbs total.

college chemistry
Linda, I answered this problem for you earlier. Don't you check your questions for responses.?

Biochemistry
acetate = Ac acetic acid = HAc ------------------------- millimols Ac = mL x M = 5.00 mmols HCl = 3.30 x 0.5 = about 1.6 ..........Ac + H^+ ==> HAc I........5.00..1.6.....0 C........-1.6.-1.6.....+1.6 E........3.4....0.....1.6 pH = pKa + log(3.4/1.6) final (Ac) = millimols/...

college chemistry
Yes, on the right track. The 16 x 4 will give kcal for carbs. The 17 x 9 will give kcal for fat. The 5 x 4 will give kcal for proteins. Then add all of them together for total kcal. You don't need to factor in the 1/2 cup because the problem tells you the grams of protein,...

college chemistry
q = mass H2O x specific heat H2O x (Tfinal-Tintial) You choose the mass H2O specific heat = 1 Kcal/g Tfinal = 37 Tinitial = you choose. Of course it can't be 100 C (or even 90C) without causing severe burns.

science
f = ma

chemistry
a. The law of impenetrability says that two objects can't occupy the same space at the same time. So the object displaces its own volume. b. "instruments that must be followed" Are you talking about protocol or objects? c. Safety precautions for what. It sure wou...

chemistry
a. I don't understand the question. Also, I think it matters how and where the temperature is being measured. b. clean it up. c. volumetric pipettes. volumetric flasks.

chemistry
You may but that isn't required. About 3 g means you could weigh 2.995, 2.900, 3.001, 3.050, 3.100, 3.200, etc. You want somewhere close to 3g and I would think anywhere between 2.500 and 3.500 would be ok. Others may think a better range is 2.750 to 3.250. It really depen...

definitions
consortium

Chemistry
mL x N x mew = grams. 20 x 0.1 x mew = 0.25 Solve for milliequivalent weight. Then equivalent weight = 1000 x mew. (molar mass/3) = equivalent weight. Solve for molar mass

Chemistry
If I can sort through this maze of hieroglyphics mols aspirin = grams/molar mass Substitute and solve for mols. m = mol/kg solvent Substitute and solve for m delta T = Kf*m Substitute and solve for delta T. Then add delta T to normal boiling point to find the new boiling point.

chemistry
What is the question?

chemistry
This is a limiting reagent (LR) problem. You know that because amounts are given for BOTH reactants. 6Na + Fe2O3 ==> 3Na2O + 2Fe 1. mols Na = grams/molar mass 2. mols Fe2O3 = grams/molar mass 3a. Using the coefficients in the balanced equation, convert mols Na to mols of th...

Chemistry
I looked up the Ksp values. It would have helped if you had since my values in the book I used for Ksp values probably will not agreed with the values in your text. My book is old. Ag2SO4 ==> 2Ag^+ + SO4^2- Ksp = (Ag^+)^2(SO4^2-) Plug in Ag^+ and solve for SO4. I obtained a...

jacobs
Is Jacobs the name of the subject? Probably not. Looks like a math question to me. 29 booths x (3 people/booth) = ?

Chemistry
Use PV = nRT to solve for pH2 initial. Use PV = nRT to solve for p I obtained approx 100 for pBr2 and 128 for pH2 initially but you need to go through and do it more accurately. ...........H2 + B2 ==> 2HBr I..........128..100.....0 C...........-p..-p......+2p E.......128-p....

chemistry
All of them are solids for one. How many do you need? I suggest you google each, list the physical properties of each, then make a list of those in common.

Chem.
24.70-0.38 = ?

chemistry
q1 = heat needed to convert water at 25 to water at 100 q1 = mass x specific heat H2O x (Tfinal-Tinitial) (Note:) Tf is 100; Ti is 25 q2 = heat needed to convert H2O to steam. q2 = mass H2O x heat vaporization. qtotal = q1 + q2

Science
For a I would think it could be estimated to the nearest 0.5 mm which is 0.05 cm. For b, the problem doesn't say what the digits mean; i.e., four-digit display of what length? If it is 1234 then it can be read to 1 in the last place, whatever that last place is.

Chemistry
delta T = i*Kf*m 2.43 = 3*1.86*m solve for m.

Chemistry II
See your post above.

Science
Accoding to this article in Wikipedia foam insulation blocks all three. Conduction convection radiation You can read more about it here. http://en.wikipedia.org/wiki/Spray_foams_%28insulation%29

chemical calculations
Read your posts. This is double duty. I've answered this just below.

chem lab
You should rephrase the question. Of course nothing happened to the weight although it weighs less when suspended in the water than in air.

chemistry
For Au. I would change the dimensions to cm so the volume comes out in cc. volume square based pyramid is V = (1/3)*(b^2)*h = ?cc Look up the density of Au in g/cc and mass Au = density Au x volume from above. Using the conversion from grams to troy oz, convert to troy oz, the...

chemistry
Do you want gold or rhodium? I'm confused by the problem.

chemical calculations
I would change all of the dimensions to cm, then volume = length x width x thickness = volume in cc. Density = grams/cc

chemistry
mols Al = 9.1080E25 atoms/6.0221E23 = ? mols Al x atomic mass = grams Al Look up the density Al. volume = grams/density. Then volume = pi*(r^2)*h You know pi, r, and volume. Solve for h = length of the wire.Note that I would change r to meters so the answer will be in meters.

chemistry
In case the vacuum caused the flask to implode the shards of glass would be contained within the tape.

chemistry
I would filter it with a coffee filter. I might try setting the sample aside and see if the silt would settle to the bottom, then decant it.

chemistry
What experiment did you perform?

Chemistry
A very general question which requires a very general answer. The student made an error in weighing or some other part of the experiment. Another possibility is that the "chemistry" of the experiment did not go as expected.

chemistry
yes

chemistry
If you interpret the question to be to prepare 0.2% solution methanol and 0.2% solution of isopropanol, and you want to put them in the same container, you add the volume of each required as if the other component were not there. Remember that if you prepare them separately an...

Chemistry
We can't draw these things on this website. The best you can do is to google "lewis dot structure CH3CH3C3COH but don't know what this is. You have 5-valent carbons and 2 valent carbon. Can't be.

Science
I think the correct answer lies in how the question is interpreted. During the inhalation phase means what? At the beginning, in the middle, at the end, just where is during.

Science
CO2 is in the blood, not the body; therefore, I would go with B.

Analytical chemistry
You want 1000 ppm Cu. You have CuSO4.5H2O; how much of that do you need? That is 1000 x (molar mass CuSO4.5H2O/atomic mass Cu) = approx 3930 g CuSO4.5H2O. That is 3930 grams CuSO4.5H2O/10^6 g solution. You don't want 10^6 g solution, only want 500 g. 500 x (3930/1E6) = abo...

science(2 QUESTIONS)
#2. Don't the two ends repel each other since both are are the same? That means work must be performed in order to push them together. I don't understand 3.

Science
I agree with C and A

Chemistry
Use PV = nRT to convert 2 million liters H2S gas at the conditions listed to mols. Use the coefficients in the balanced equations to convert mols H2S to mols S. That will be mols H2S x (2 mols SO2/2 mols H2S) x (3 mols S/1 mol SO2) = mols S Convert mols S to grams. g = mols S ...

Chemistry
%KHCO3 = (0.95/1.50)*100 = ?

Chem AP
pi = inRT pi = 2.56 atm i = 2 R = 0.08206 T = 298K Solve for n, then n = grams/molar mass You know grams and n, solve for molar mass.

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