Friday
April 18, 2014

Posts by DrBob222


Total # Posts: 41,790

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.

Science (Chemistry)
Pb(NO3)2 + Na2X2O4 ==>Pb(C2O4 + 2NaNO3 millimols Pb(NO3)2 = 35 x 2.82 = approx 98.7 mmols Na2C2O4 = 20 x 0.00221 = approx 0.0442 So 0.0442 mmols PbC2O4 will be formed. (concn) = millimols/mL solution. (Pb^2+) = essentially 98.6/55 = approx 1.8M (NO3^-) = (2*98.7/55) = ? (Na...

Chemistry
0.50M KOH = mols KOH/L solution 0.50 M KOH x 0.050 L = ? mols. Then mols = grams/molar mass. You know mols and molar mass, solve for grams.

Chemistry
millimols = mL x M = ? NOTE: I think 20.0M acetic acid is hard to come by. 18 perhaps but not 20.

Math
Do you have a question?

Science
I agree.

Chemistry
Stoichiometry by any other name is stoichiometry. Since all are gases and the conditions apply to everything you can use the shortcut. 750 cc N2O5 x (5 mol O2/2 mols N2O5) = 750 cc (5/2) = ?

Ap Chemistry
Two equations and two unknowns. Solve simultaneously. eqn 1. g NaCl + g KCl = 0.1586g eqn 2. mol AgCl from NaCl + mol AgCl from KCl = mol AgCl total Now put those into math form. Let X = g NaCl and Y = g KCl MM stands for molar mass. --------------------- eqn 1. X + Y = 0.1586...

Chemistry
See your SO2/SO3 question below. Same process.

Chemistry
Balance the equation. 2SO2 + O2 ==> 2SO3 A short cut to stoichiometry problems occurs when all are gases and at the same P and T. The shortcut is that you may use volume and mols interchangeably. 15.0 L O2 x (2 mol SO2/1 mol O2) = ? L SO2.

incomplete question --sc

Math Ratio or Proportion
1 mile x (100/150) = 2/3 mile; i.e., the jogger uses the same calories in 2/3 mile that the walker uses in 1 mile.

Chemistry
yes. The problem in words works out this way. You have so many mols NH3 at the beginning. You had an excess of HCl which reacts with all of the NH3 and leaves extra HCl in the solution. The first thing you want to do is to find the how much excess HCl is there. You do that by ...

Chemistry
NH3 + HCl ==>NH4Cl Excess HCl + NaOH ==> NaCl + H2O Mols HCl added initially = M x L = 0.1M x 0.050L = ? mols NaOH to neutralize excess HCl = M x L = 0.025M x 0.02150 = ? mols HCl used by ammonia = mols initially - mols excess = ? = mols NH3 initially. M NH3 = mols NH3/L...

chemistry
1.10 g/mL x 18.4 mL x (34 g Na2CO3/100 g) = ?g Na2CO3

chemistry
I assume a jugful means an excess of N2. mol H2 = grams/molar mass Using the coefficients in the balanced equation, convert mols H2 to mols NH3. Now convert mols NH3 to grams. g = mols NH3 x molar mass NH3.

Chemistry
0.5 m solution = 0.5 mol solute/kg solvent. mol = g/molar mass and molar mass = about 82 g/mol. 0.5 mol = 1/2*82 = about 41 So 41g CH3COONa in 1 kg H2O = total mass of 1041g. You want 0.2 mol CH3COONa so 1041g x (0.2/0.5) = ? mass solution

Chemistry
Do this in steps and add each step to find total q. 1. Within a phase the formula is q = mass x specfic heat x (Tfinal-Tinitial). For example to heat 20g liquid water at zero C to 100 C (all in the same phase) q = 20 x specific heat x (100-0) = ? 2. At the phase change (solid ...

CHemistry
See your other post.

chemistry
Again, I don't know how you're determining the NaHCO3. If you're titrating it with HCl I don't think there would be a difference. Although you the use of H2SO4 as a titrant would cause pptn of BaSO4 I think it could be done with H2SO4 also.

chemistry
Heated to what temperature? How big was the piece of Kimwipe? Is the NaHCO3 going to Na2CO3 or Na2O?

Chemistry
You didn't furnish enough information to answer; i.e., I don't know what you're determining. If NaHCO3, then be aware that HCl and NaHCO3 react as follows: NaHCO3 + HCl ==> H2O + CO2 + NaCl./ Therefore, some of the NaHCO3 added in the NaHCO3/KCl mixture will not...

Course Help meeee
All or just one what? If you enroll in pre-med, curricula differ somewhat on where you enroll and where you hope to get into med school. You will take courses (note plural) in biology, chemistry, math, the usual social science, history, English, etc. At many schools that takes...

chemistry
I assume you have a sequence of measurements of mols/grams/amount vs time in seconds. amount at start - amount at 1 sec = amount consumed. This answer is general I know but so is your question with no data.

CHEMISTRY
Assuming Cal = 4 for protein, 4 for carbohydrates and 9 for fat, then 110 Cal-(7*9)-(9*4)-(4x) And your question would make more sense without the {\rm g} mishmash.

chemistry
What's that 0.100? 0.100 L? millimols HF = mL x M = 100 x 0.25 = 25.0 millimols NaF = 100 x 0.500 = 50,0 Add 0.002 = 2 millomils HNO3 .........F^- + H^+ ==> HF I.......50.0...0......25.0 add.............2.......... C........-2....-2......+2 E........48.....0.....27 Then...

Chemistry
2C4H10 + 13O2 ==> 8CO2 + 10H2O mols C4H10 = grams/molar mass Using the coefficients in the balanced equation, convert mols C4H10 to mols O2. Then use PV = nRT to solve for V. Note 93.5 kPa = 93.5/101.325 atm. Don't forget to change T to kelvin.

chemistry
good

College science
Do you have answers. If you checked my last answer and it was right you can look at this one. X = distance = Vo*t + 1/2*g*t^2 Vo is 0 and the mass of the pick (piton) doesn't matter. X = 295 m, solve for t = time to strike the ground. Then use V = Vo + g*t. Again, Vo is 0.

chemistry
For the cola drink: If you're using 4 Cal/g carb, then 140/4 = 35 g carb which I would round to 40 and to 1 s.f. that is 4 x 10^1 or 4E1. I don't know what 40 once means.

chemistry
Are you using the same values I am for grams fat, grams protein, grams carbs? Total Cal = g fat + g carb + g protein. 110 Cal = (7*9) + (9*4) + (4*g carb) g carb = (110-63-36)/4 = 2.75 which is rounded to 3.00 and to 1 s.f. is 3 grams. Of course you know that 110 Calories = 11...

Physics
I obtained 38.8889 so I would round that to 38.9 but I believe you're allowed only 2 s.f.

Physics
eff = [(126-77)/126]*100 = ?

Chemistry
My physics is quite rusty but I believe that would be V^2 = Vo^2 + 2ax V^2 will be zero at the top since eventually the pull of gravity will stop the balls upward flight. 0 = (40 m/s)^2 + 2*(-9.8)*x Solve for x = distance in meters.

physics?

Chemistry
(6.00 oz/serving) x 3 servings/mo = 18.00 oz blue fish per month. (0.341 oz Hg/10^6 oz fish( x 18.00 oz fish = ? oz Hg in 18.00 oz bluefish.

Chemistry
2070 BTU/hr x 24 hr/day x (365 days/yr) x 1.055 kJ/BTU x (1 megajoule/1000 kJ) = ?

SICK
I suggest you do it. Don't make us hunt for them. Be specific or post again.

science - gas chromatography
Since the chromatogram reads in amout on the vertical axis and time on the horizontal axis, how else would you measure it?

College Chemistry
NaHCO3 + HCl ==> NaCl + H2O + CO2 mols NaHCO3 = grams/molar mass mols NaHCO3 = mols HCl (from the coefficients in the balanced equation.) mols HCl = M x L. You know M and mols, solve for L.

Chemistry
C14H30 ==> C2H4 + H2 + C12H24 C16H34 ==> 2C2H4 + C3H6 + C9H20

Chemistry
192 in one s.f. is: round to 200, then 2 x 10^2 or 2E2. I obtained 196 and not 192 BUT I may be using different numbers for kcal vs grams. I used 4 kcal/g carb 4 kcal/g protein 9 kcal/g fat.

college chemistry
1. Write and balance the equation. 2. Use density gasoline to convert 9.0 gallons to grams. 3. Look up the heat of combustion or calculate it from the delta H formation values. 4. heat combustion x (grams gasoline/molar mass gasoline). Post your work or supply details (numbers...

Chemistry
N2 + 3H2 ==> 2NH3 At equilibrium, (N2) = 3.0/5.00 = ? (H2) = 2.40/5.00 = ? (NH3) = 0.565/5.00 = ? Substitute these equilibrium values into the Kc expression and evaluate Kc.

Chemistry
See your other post.

Correction
How would you like us to help with this question. I think the easiest way to start is to tackle each question one at a time.

Acne
I had severe acne from the time I was 14 (maybe 15) or so and I suffered the same way you do/have. My wife had it but it had cleared up by the time we were married. Mine diminished as I grew older but I had pockets of it until I was 50. Our son got a double dose from his paren...

Chemsitry
..........A ==> 2B + 3C I.........10.....0.....0 C.........-x.....2x...3x E........10-x....2x...3x Ptotal = 12.13 = 10-x+3x+2x Solve for x and find pressures of A, B, C; substitute into Kp expression below and solve for Kp. Kp = p^3C*p^2B/pA Then dG = -RT*ln*Kp T is 25C (fr...

chemistry
mLHCl x MHCl = mLNaOH x MNaOH Substitute and solve for MHCl and compare with 0.400. Of course you need not do a calculation. If the NaOH is 0.400 and it takes more HCl to neutralize the NaOH you know HCl is weaker than NaOH or HCl < 0.400M

Chemistry
-91.8 kJ x (500/28) = -?

Chemistry
See your other post.

Chemistry
12*(x) + 13(1-x) = 12.35 Solve for x

Chemistry
I worked this last night. If you have questions about that show your work and explain what you don't understand.

AP Chem
I shifts to the left; II to the right.

chemistry
How many WHAT? are in 7.40 cc? By the way, cc is a much simpler way to write that than 7.40 \{rm cm}^{3}\

Chemistry
q is computed in steps. Within a phase q = mass x specific heat x (Tfinal-Tinitial). For example, to heat 20 g H2O from zero to 100 C (within the liquid phase) it requires q = 20g x 4.184 J/g*C x (100C-0C) = ? At a phase change (solid to liquid or liquid to vapor) it is q = ma...

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