Thursday
April 17, 2014

Posts by DrBob222


Total # Posts: 41,772

Chem.
S2O82-(aq) + 2I-(aq)==> 2SO42-(aq) + I2(aq)

Chemistry
For each mL you used it is that, yes. I don't know the details of the experiment but if all of the 1 mL was consumed then the amount consumed is M x L = ?, yes.

Chemistry
mols = M x L

chemistry
63.38/2 = 31.69g = 1 eq. 1.25 eq would be 1.25*31.69 = about 49.86g. mols = grams/molar mass= about 0.625 mols.

chemistry
Technically, we don't know eqivalents without a reaction but there are three definitions that are usually used. The strict definition for chemistry is that amount of substance that will react with 1 g H2. For your question, the equivalent weight of Zn is the atomic mass of...

Chem
2650g H2O x (2 molar mass H2/molar mass H2O) = ?

chemistry
Strange wording. I assume you want to know % yield when 20g Znb produced 5.4L H2. Zn + H2O ==> ZnO + H2 mols Zn = grams/atomic mass Use the coefficients in the balanced equation to convert mols Zn to mols H2. Note that is a 1:1 conversion. Then convert mols Zn to L. 1 mol o...

Ap chem
I can't draw the Lewis structure on this board but here isw a link that will show you. https://www.google.com/search?q=lewis+structure+PF3&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:en-US:official&client=firefox-a&channel=sb The molecular structure is here. https://www.google....

Science
Here is a site that does a much better job than I can do on this site. An atom that has one or more electrons too many or too few for the neutral atom is an ion.

chem lab
I'm not sure what you mean by "diffference in H" but I'll assume you mean to find delta H rxn in kJ/mol. MgO + 2HCl ==> H2O + MgCl2 mols MgO = 0.8100/40.3 = about 0.02 but you may want more accuracy than that.(meaning you do it too) mols HCl = M x L = abou...

Chemistry
If the person bails at the same rate as the boat is taking on water, neither side wins and the boat contains the same amount of water as time marches on.

Chemistry
See your other post.

Aditya
It's easy to understand if you look at it this way. Le Chateier's Principle tells us that when a stress is added to a system in equilibrium, the system will shift so as to undo what we've done to it. The equation tells you that heat is given off when it reacts left...

Chemistry
It isn't a matter of strong base vs weak acid as much as it is the number of mols of each and how the salt reacts with H2O. HA + NaOH ==> H2O + NaA mols HA = 0.01 mols NaOH = 0.01 So the solution EXACTLY neutralizes and there is no excess NaOH or HA. You might think the...

Chemistry
I suggest you read in your text/notes or Google "intermolecular forces".

Science Mixture
No. Sugar dissolves in H2O and the sugar in solution goes through the filter paper with the H2O. However, if you had a saturated solution of sugar (it would take a lot of sugar because of the high solubility), you could separate by filtration that part that was not dissolved

Chemistry- acids/bases
M Ba(OH)2 solution = 0.0921 x (45.0/350.0) = ? M Ba(OH)2 is a strong base (ionizes 100%) to concn Ba(OH)2 is ?M from above. Then (OH^-) - twice that of the base since there are two OH ions per molecule of Ba(OH)2.

Chemistry- acids/bases
See your other post.

AP Chemistry- Acids
pH = -log(HNO3) -1.39 = log(HNO3) I found HNO3 approximately 0.05 but you need to do it more accurately. Then mol HNO3 = M x L = ? mols HCl = M x L total mols H^+ = mols HCl + mols HNO3. volume = 145 mL + 493 mL = ? M new solution = total mols/total liters. Then pH = -log(H^+)

Chemistry
2HNO3 + Na2CO3 ==> CO2 + H2O + 2NaNO3 mols HNO3 = grams/molar mass = ? Use the coefficients in the balanced equation to convert mols HNO3 to mols Na2CO3. Then convert mols Na2CO3 to grams. g = mols x molar mass = ?

sceince
What kind of a welding tool? I agree if it's the welding torch.

science
14 is ok but 15 still is wrong.

Chemistry
mol fraction = X XO2 = nO2/total mols XN2 = nN2/total mols Then pO2 = XO2*Ptotal and pN2 = XN2*Ptotal

chemistry
PV = nRT

Chemistry
p1v1 = p2v2

Chem; States of Matter
The book is doing Hvap/mol. My work was in Hvap/gram so I didn't need to go through the extra step.

Chem; States of Matter
This will get you started on a part. The problem tells you that all of the ice doesn't melt; therefore, you know the temperature must be zero (or all of the ice would have melted) to find how much has melted do this. steam condensed at 100C = 175g x heat vap = ? 175g H2O f...

Chemistry
That's what I obtained, too. I see you picked up on my typo, I wrote M2/M2 and it should have been sqrt(M2/M1)

Chemistry
I don't think so. If the unknown diffuses twice as fast it MUST be smaller (thqat is must have a molar mass less than that of CF4) If I call CF4 rate = 1L/min = r1 Then rate of unknown is 2L/min = r2 molar mass M1 = CF4 = 88 r1/r2 = (sqrt M2/M2) 1/2 = (sqrt M2/88) Solve t...

Chemistry
The easy way to do it is to make up a number (use any convenient number) for CH4, then make the rate twice as fast for the unknown gas.

Chemistry - DrBob222
Ava. I'm not an organic chemist and I don't know the answer. I googled "free radical halogenation of alkanes" and came up with this. It may or may not help. http://en.wikipedia.org/wiki/Free-radical_halogenation

Chemistry
This may help. http://www.wikihow.com/Build-a-Calorimeter

Chemistry
255g x (3*molar mass Na2C2O4/molar mass C6H6) = ? Check my work.

Neuroscience
http://en.wikipedia.org/wiki/Midbrain

Chemistry
mass unknown liquid = 110.810-82.450 = ?g volume = 50.0 density = mass/volume = ? 8 oz x (29.6 mL/1.00 oz) = ? mL 56.8g x (1 lb/453.59 g) x (16 oz/lb) = ? oz. Check my work.

chemistry
What's your problem with these problems? a. (9/5)*21]+32 = ?F b. (F-32)*5/9 = ?C c. There are 1E9 nm in a m and 1000 m in a km.

chemistry
You don't provide enough data to give an accurate answer but usually these problems would indicate about 4-6 grams. If this is a titration problem you want enough to use about 35-45 mL of the titrant. If a grqavimetric procedure it depnds upon what kind of balance you used...

chemistry
25 mi/gal x (1 km/0.6214 mi) x (1 gal/3.78L) = ? km/L ? km/L x # L = 142 km Solve for # L needed for the 142 km trip. Then convert from L to gallons . #L x (1 gal/3.78L) = ? gallons. Note: It's probably easier to do it this way. How many miles is 142 km? That's 142 km ...

Science~!
This is out of my field but I think turbines is the right answer. I have done some geothermal work (the chemistry of it and not the engineering part) and in all cases the pressure was to run turbines which in turn generated electricity. Water and wind also run turbines to gene...

physical science
2000m/8.6s = ?m/s

Analytical Chemistry
0.1067M x (25/250) x (10/1000) = ? or you can do this in you head. 25 to 250 is 1/10 and 10 to 1000 is 1/100 so the final concn is just 1/1000 x 0.1067 = 0.0001067M

Science~!
I agree with 2 and 3 but not 1.

Chemisry
1. You have the balanced equation. 2. How many mols H2 do you want? That's mols = grams/molar mass. 3. Using the coefficients in the balanced equation, convert mols H2 to mols H2SO4. 4. Then M = mols/L. You know M H2SO4 and mols H2SO4, solve for L H2SO4. This four step met...

College Chemistry
You can do this one of several ways. Some are longer than others but all give the same answer. The easy way I think is to just recognize that the initial concn of EACH reagent in the mixture is diluted and solve it that way. What's the total volume? That's 3.00 + 6.00 ...

chemistry
You're on the ball. Go to the head of the class. :-)

chemistry
I don't believe density has anything to do with it. The density of n-propanol is less than that of water, also (although it is slightly greater than that of ethanol). Thanks for the clarification of the experiment in the follow up. If I read this right, you made standards ...

chemistry
When I come up with that dilemma I put doen the formula I need, plug in the values, see which unknown I don't have and work it from equation to equation. Here is the order you need. delta T = Kf*m. You have delta T (or can calculate it) and Kf so solve for m. molality = mo...

Chemistry
I'm assuming the question is "How many g CH4 are required to produce 50 g CHCl3?" I think the equation you wrote is screwed up (or that CH4+Cl3 may be a typo); anyway, here are the steps. 1. Write and balance the equation. 2. Convert 50 chloroform to mols. mols =...

Chemistry
When gases are involved you may use a shortcut; i.e., use volumes as if volume = mols. 19.8 L SO3 x (1 mol O2/2 mols SO3) = ? L O2. Then grams = mols x molar mass.

Chem
(S2) = 11.0mols/5.20L = approx 2 but you need to be more accurate. .........S2 + C ==> CS2 I mols...2..xs...0 C.......-x..xs...x E......2-x..xs...x Kc = (CS2)/(S2) note:C doesn't appear in the Kc exprssion because it is a solid. Substitute the E line into Kc expression ...

CHEM
(PCl5) = 0.229/3.20 = approx 0.072 but you should start over and calculate more accurately. ......PCl5 -------> PCl3 + Cl2 I.....0.072..........0......0 C.......-x...........x......x E....0.072-x.........x......x Substitute the E line into Kc expression and solve for x = (P...

science
r earth = 6,000 km d satellite from earth = 900. r satellite's orbit = 6900 km 2*pi*r = circumference = distance traveled around earth. distance/2 = speed satellite in km/hr d/hr x (1 hr/60 m) x (1 min/60 s) = ? km/s

chemistry
0.22 mL + 2.67 mL = ? mL assuming the density of H2O is 1.00 g/mL. If that isn't so you can calculate the volume of 2.67g from v = m/d using the density.

chemistry
C2H6 + O2 ==> CO2 + H2O You balance.

chemistry
3.50E21 x (1 mol/6.02E23) = ?

Chemistry:Important!!!!!!!
I don't know what a copper cycle lab is. a. mols Cu(NO3)2 = M x L = ? 1 mol Cu in 1 mol Cu(NO3)2 g Cu = mols x atomic mass = theoretical yield b. 0.075 from the problem. c. (actual/theoretical)*100 = %yield

chemistry
6.5E9 people x (4 particles/second) x (60 s/min) x (60 min/hr) x (24 hr/day) x (365 d/yr) x # yrs = 8.10E23. Solve for #yrs.

chemistry
See your other post.

Chemistry
See your other posts.

Chemistry
See your other posts.

chemistry
http://www.jiskha.com/display.cgi?id=1391878825 Post your work if you get stuck.

Chemistry Urgent
3 is the easiest. The others are the same kind but are a little more complicated. This will get you stated on #3. CH4 + 2O2 ==> CO2 + H2O 2C2H6 + 7O2 ==> 4CO2 + 6H2O If O2 is 90 cc initially and excess O2 was 32 cc, then 90-32 = 58 cc O2 used. Let x = volume CH4 and (24-...

Chemistry Help
Here are questions quite similar to yours. Post your work if you still have questions about any of these. http://www.jiskha.com/display.cgi?id=1391994083

Chemistry
C3H8 + 5O2 => 3CO2 + 4H2O a. Use the coefficients in the balanced equation to convert anything to anything. 1.5 mols C3H8 x (5 mols O2/1 mol C3H8) = ? b. same process. c. grams = mols x molar mass but you didn't say grams of what. d. Remember 1 mol of anything occupies ...

Physical Chemistry
Really this is analytical chemistry. It will take twice as much to reach the second as it did to reach the first.

Chemistry
How many mg do you want? That's 0.100 L x 500 mg/L = 50 mg. So weigh out 50 mg, place in a 100 mL volumetric flask, dissolve in a little water and make to the mark. Mix. Not so hard. eh?

chemistry
mols Ba(OH)2 = grams/molar mass mols H2O = grams/molar mass Find the ratio of H2O molecules to 1 molecule Ba(OH)2. Post your work if you get stuck.

CHEMISTRY
The Bohr model does a fairly good job with both but a correct must be made for the Be^3+ because of the increased mass of the Be vs H. You would not expect the line spectra to overlap line for line.

CHEMISTRY
I'll do my best for the work but you get the answers. E = hc/wavelength E = h*c/700E-9. h is 6.626E-34 J.s c is 3E8 m/s This gives the energy of ONE photon of red light. Then Efrom above x #photons = 2.0E-17 Solve for # photons. Do the same for the blue light.

Chemistry
Stage 1 is Fe(s) + heat ==> Fe(g) State 2 is Fe(g)==> Fe^3+(g) + 3e and since the loss of electrons is the definition of oxidation, the Fe is oxidized. Note that the mass specrometer may or may not remove three electrons, you could make Fe^+ or Fe^++ or Fe^+++. Why is th...

Chemisty
2AgNO3 + K2Cr2O7 ==> Ag2Cr2O7 + 2KNO3 mols K2Cr2O7 = M x L = ? mols Ag2Cr2O7 =mols K2Cr2O7 Then g Ag2Cr2O7 = mols Ag2Cr2O7 x molar mass A2Cr2O7

chemistry
This is a limiting reagent (LR) problem. I know that becsuer amounts are given for BOTH reactants. 2H3PO4 + 3Ca(OH)2 ==> Ca3(PO4)2 + 6H2O 1. mols H3PO4 = M x L = ? Do the same for mols Ca(OH)2. 2a. Using the coefficients in the balanced equation, convert mols H3PO4 to mols ...

chemistry
The idea of predicting which is ionic, which covalent, which polar covalent depends upon some man made definitions and how to interpret them. Look up the value for the electronegativity (EN) for each element. If the difference is about 1.9 or so it is about 50% covalent/50% io...

Chemistry
(P1/T1) = (P2/T2)

Chemistry
See your other post.

chemistry
4. mols = grams/molar mass 5. At what pressure? If you mean standard pressure of 760 mm Hg then you need to remember that 1 mol of gas occupies 22.4 L at STP 6. Take a 100 g sample which will be 36.2g Al 63.8g S. Convert these to mols by mols = g/atomic mass. 36.2/27 = about 1...

chemistry
volume of sphere = (4/3)*pi*r^3 Plug into mass = volume x density I assume you either have or can look up the other information.

Chemistry
The correct name for the ionic compound Al2Se3 is? I would name this aluminum selenide but some might prefer the name aluminum triselenide. The correct name for the ionic compound Fe2Se3 is? I would name this iron(III) selenide; some may prefer iron(III) triselenide. the Roma...

Science
I suppose one should ask WHICH experiment by Lavoisier but I agree with your answer.

AP Chemistry- Equilibrium
MgCl2 + 2NaOH ==> Mg(OH)2 + 2NaCl millimols MgCl2 = 10.0 x 0.18 = 1.8 mmols NaOH = 20.1 x 0.56 = about 11.3 but you should do these more accurately. The remaining steps are approximations too. 1.8 mmols MgCl2 will use 3.6 mmols NaOH and form 1.8 mols Mg(OH)2. The solubility...

AP Chemistry- Equilibrium
See your other post.

chemistry
AgOH ==> Ag^+ + OH^- Mg(OH)2 ==> Mg^2+ + 2OH^- Ksp Mg(OH)2 = (Mg^2+)(OH^-)^2 Ksp AgOH = (Ag^+)(OH^-) Calculate (OH^-) in a saturated solution of Mg(OH)2. That is .........Mg(OHO2 ==> Mg^2+ + 2OH^- I........solid........0.......0 C........solid........x.......2x E........

chemistry
I would go with d but you should know how to do these.

Science
I agree.

Science
For NaOH, this is 100% dissociated; therefore, (OH^-) = (NaOH) OH^- = 2 M pOH = -log(OH^-) pH + pOH = pKw = 14. You know pOH, solve for pH. The H2SO4 isn't as simple as it lookis. If you are an advanced student, (0.39+x)/(0.39-x) = k2 for H2SO4. Solve for x and evaluate 0....

Science
See your post above.

chemistry
Did you finish your post? I would write for this particular compound Tl2Te3 which I would name thalium(III) telluride

physical science
Mass is the same no matter where. Weight is greatest on planet with largest G and smallest on planet with smallest G.

physical scief = nce
f=ma or a = f/m = 10/1 = ?

Chemistry HELP
With 1:2.24 you can't round to 1:2. Multiply by a whole number until you get two whole numbers (or at least to close whole numbers). 1:2.24 2:4.48 3:6.72 4:8.96 which I would round to 4:9 for the formula C4H9. Having done that I don't know what to do except look at you...

Chemistry
How many moles do you want? That'x M x L = ? Then mols = grams/molar mass.

Chemistry
CaCO3 ==> CaO + CO2 mols CaCO3 = 0.01 mol. You get 1 mol CO2 for each mol CaCO3; therefore, you can produce a maximum of 0.01 mol CO2. How many grams is that? g CO2 = mols CO2 x molar mass CO2.

Chem
Does this reaction go to completion or do you have a Keq?

Chemistry
N2 + 3H2 ==> 2NH3 mols NH3 = grams/molar mass = 42800/17 = ? Using the coefficients in the balanced equation, convert mols NH3 to mols H2. Now convert mols H2 to grams. g = molx x molar mass.

chemistry
I need clarification. Group I and II are cations, not anions.

chemistry
5.13 g CO2 x (1 mol CO2/44g) x (1 mol C/1 mol CO2) = ? and I don't believe that is 0.117 2.10g H2O x (1 mol H2O/18) x (2 mol H/1 mol H2O) = ?

science
BC: d = rate x time 40,000 = 2500*t t = 8 hours for the first half. 40,000 = 1000*t t = 20 hours for the second half. Total time = 28 hours. There are ways to go here. The first is to see if half the time (14 hours) at the FC speeds will come up more or less than 40,000. d = r...

Chemistry
K3PO4(s) ==> 3K^+(aq) + PO4^3-(aq) I don't know the level of chemistry for you, but I assume you're not expected to know that the PO4^3- ion will hydrolyze in H2O as PO4^3-(aq) + HOH(l) ==> HPO4^2-(aq) + OH^-(aq)

Science
In a perfect world I suppose I agree with you. Although it isn't part of the problem, remember that preservation means from all influences, not just those by man.

Chemistry (Analytical) followup
I assume this is the CaC2O4 problem. If the pH is reduced to 2, that makes the H^+ MUCH larger (by a factor of 10,000,000 which is really MUCH larger) and the solubility of the CaC2O4 is increased significantly. The reason is that you add a competing reaction (actually two rea...

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