Tuesday
September 30, 2014

Posts by DrBob222


Total # Posts: 44,143

pharmacy calculations
I answered this for you earlier.
July 8, 2014

ph
I'm not a pharmacist but if that means take 250 mg every 8 hours for 7 days, the total dose is 250 mg/dose x 3 doses/24 hrs x 24 hours/1 day) x 7 days = ?
July 8, 2014

questions
So you want 15 tablets for 1/2 the month (30/2 = 15 days) and another 15/2 day supply so that is 15 + 7.5. You dispense 15 + 8 = 23 tablets unless you want to cut one of the tablets into two. I don't know if you are allowed to cut tablets or not. If so then you want 22.5 ...
July 8, 2014

Chemic
mL1 x %1 = mL2 x %2 mL1 x 98% = 50 mL x 5% Solve for mL 1. Add that amount to 50 mL volumetric flask and make to the mark with distilled H2O.
July 8, 2014

CHEMISTRY
You're right. I turned it around. Sorry about. Just reverse everything and you will have that half reacted. For KPb(OH)3 the cation is K^+ and the anion is Pb(OH)3^- So I would write PbO2 ==> Pb(OH)3^- I assume this is a basic solution. Pb is +4 on the left and +2 on ...
July 8, 2014

CHEMISTRY
In acid solution.? 2H^+ + ClO^- + 2e ==> Cl^- + H2O In basic solution? H2O + ClO^- + 2e --> Cl^- + 2OH^- The way to learn this is to do them. Looking at what someone else has done won't get it. If you will share what your problem(s) is/are in doing these perhaps I ...
July 8, 2014

Chemistry
Yes, and if your prof is picky about the number of significant figures you whould round that to 514 mL. You are limited to 3 from the 325 to start.
July 8, 2014

Chemistry
When it's an all gas sample and the T and P don't change, you may use a shortcut and use volume directly as if they were mols. 2C6H14(g) + 19O2(g) -> 12CO2(g) + 14H2O(g) 325 mL CO2 x (19 mols O2/12 mols CO2) = 325 mL x (19/12) = mL O2 consumed.
July 8, 2014

Chemistry
Use PV =nRT and convert NH3 and O2 (each) to mols = n. Find the limiting regent Convert to mols N2 formed, the use PV = nRT and convert to mL at the conditions listed.
July 8, 2014

Chemistry
I don't think you did anything wrong. v1 = 683 mL p1 = 0.792 atm t1 = 19C = 273+19 = 292K v2 = 733 mL p2 = ? in atm. t2 = 76C = 273+76 = 349K (0.792*683/292) = (p2*733/349) If I used 292.15 and 349.15 the answer is 0.8819 which rounds to 0.882 atm. Usually when something ...
July 8, 2014

Chemistry
(P1V1/T1) = (P2V2/T2)
July 8, 2014

Chemistry
Since they threw that T as 27.2 then I would add to 273.2 to convert to K (I missed that above) so I would use 300.4 and not 300.2. That gives you n = number of mols. The problem asks for grams methane. g methane = mols x molar mass CH4 = mols methane x 16 = ? Note: Check your...
July 8, 2014

Chemistry
P in atm (741/760) = ? atm V in L. 200 mL = 0.200 L T in kelvin. K = 273 + 27.2 = ? With all of those, R = 0.08205.
July 8, 2014

Chemistry
If P is changed to atm [(741/760) = ?] then R is 0.08205 L*atm/mol*K
July 8, 2014

Chemistry
Use PV = nRT and solve for n = number of mols CH4. Then n = grams/molar mass. You have molar mass and n, solve for grams.
July 8, 2014

Chemistry
Ptotal = pN2 + pO2 + pCO2 You have only one unkinown; solve for that. However, note that the units are not the same. Since you want pCO2 in torr (mm Hg), I suggest you change the others to mm Hg.
July 8, 2014

Chemistry
density = mass/volume
July 8, 2014

chemistry
I have no idea which experiment you are conducting or what this problem is about.
July 8, 2014

CHEMISTRY
Here is a simplified set of oxidation state rules. http://www.chemteam.info/Redox/Redox-Rules.html You must understand that oxidation rules are arbitrary rules mostly for bookkeeping. When H is with a metal, such as CaH2, I always give it an oxidation state of -1 because it&#...
July 8, 2014

CHEMISTRY
I'll play your game. What about them? You add H^+ if acid and OH^- if basic along with H2O in the appropriate amounts.
July 8, 2014

CHEMISTRY
You look at the activity series. Here is one on the web. http://www.cod.edu/people/faculty/jarman/richenda/1551_hons_materials/Activity%20series.htm Any metal will displace any ion BELOW it in the activity series. So Al(s) + Ni^2+(aq) ==> Ni(s) + Al^3+(aq) then balance it; ...
July 8, 2014

science
q1 = heat removed to lower T from 10C to zero C. q1 = mass H2O x specific heat H2O x (Tfinal-Tinitial) q1 = 200g x 4.184 x (10) = ? q2 = heat removed to freeze the H2O (change from liquid to solid phase). q2 = mass H2O x heat fusion H2O. q2 = 200 x heat fusion = ? Look up heat...
July 8, 2014

CHEMISTRY
...........AB2 ==> A^2+ + 2B^- I..........solid...0.......0 C..........solid...s.......2s E..........solid...s.......2s Ksp = (A^2+)(B^-)^2 Ksp = (S)(2S)^2 Ksp = 4S^3
July 8, 2014

CHEMISTRY
Ca5(PO4)3F--> 5Ca^2+ + 3PO4^3- + F^- I..solid.......0.........0.......0 C..solid.......5x......3x........x E..solid.......5x......3x........s Ksp = (Ca^2+)^5*(PO4^3-)^3*(F^-) 1E-60 = (5x)^5*(3x)^3*(x) Solve for x = solubility in mols/L.
July 8, 2014

chemistry
You use the water as a way of knowing how much heat was lost or gained. So the salt changed T from zero c to -1.0 C. Since it cooled the water you know the reaction is endothermic; i.e. it took heat away from the water so the rxn required heat and that is endothermic. Rxns ...
July 7, 2014

chemistry
salt + H2O ==> solution - heat or salt + H2O + heat ==> solution. endothermic for #1 and #3. Exothermic for #2. Therefore, for the salt, q is + for 1 and 3 and - for #2. Do you want q/g? You don't have the molar mass so you can't get q/mol. qH2O = mass H2O x ...
July 7, 2014

chemistry
Will this get you started. S on the left is +4; on the rght is +6 Mn on the left is +7 and on the right is +2. I think you failed to add the charge to MnO4. It should be MnO4^-.
July 7, 2014

chemistry
And how would you like for us to help you? The directions are there, the formulas are there, the only thing left is for you to substitute the numbers into the formula to obtain the answers. We shall be happy to check your work.
July 7, 2014

chemistry
This must be a question associated with an experiment you performed. What experiment did you conduct? What was your experience?
July 7, 2014

chemistry
Frankly I don't know what you are asking? The left hand side (Mg and HCl) are the reactants. The right hand side (H2 and MgCl2) are the products. HCl is hydrochloric acid Mg is magnesium H2 is hydrogen MgCl2 is magnesium chloride.
July 7, 2014

chemistry
I've shortened the equation. HAc is acetic acid, RCH2OH is the alcohol and RCOOR is the ester. ..........HAc + RCH2OH --> RCOOR + H2O I.........1.0....1.0........0.......0 C..........-x.....x.........x.......x E.........1.0-x..1.0-x......x.......x Substitute the E line ...
July 7, 2014

chemistry
q = mass concrete x specific heat concrete x (Tfinal-Tinitial)
July 7, 2014

CHEMISTRY
AgCl --> Ag^+ + Cl^- Ksp = (Ag^+)(Cl^-) = about1.8E-10 Compare Qsp with Ksp. In soution (and I'm assuming that adding the salts to 200 mL H2O is the same as producing 200 mL solution). Ag^+ = 1.7/170 = about 0.01 mols. You should go through these calculations yourself; ...
July 7, 2014

CHEMISTRY
This is done the same way as the AgCl problem. Compare Qsp with Ksp.
July 7, 2014

chemistry
See above.
July 7, 2014

Science
15% w/v means 15 g solute in 100 mL solution. [(x g solute)/250 mL] = 0.15 x g solute = 250 x 0.15 = 37.5g HCl Therefore, (37.5g HCl)/(mL HCl + mL H2O) = 0.15 Since mL HCl + mL H2O = 250, you can solve for mL H2O if you know the volume occupied by 37.5g HCl. There is no date ...
July 7, 2014

chemistry
I don't see a question here.
July 7, 2014

Science
no question.
July 7, 2014

Science
See your methyl alcohol problem.
July 7, 2014

Science
% v/v means (volume solute/total volume)*100 = ? = (80/154)*100 = ?
July 7, 2014

Chemistry
........HCHO2 --> H^+ + CHO2^- I........0.2......0......0 C.......-0.006..0.006...0.006 E......0.2-0.006..0.006..0.006 Ka = (H^+)(CHO2^-)(HCHO2) Ka = (0.006)(0.006)/(0.2-0.006) Ka = ? pH = -log(H^+) = -log(0.006) = ? HCHO2 --> H^+ + CHO2^- Le Chatelier's Principle ...
July 7, 2014

Science
% w/w means (grams solute/grams solution)*100 = ? [(15g NaCl/(70+15)]*100 = % NaCl {(70g H2O/(70+15)]*100 = % H2O
July 7, 2014

Science
See your NaCl problem. Same thing.
July 7, 2014

general chem
Don't forget to multiply by 100 to convert to %.
July 7, 2014

chemistry solution preparations
To begin, I don't think this is possible using standard volumetric equipment. I'll explain below. Let's first determine the N of the 37% stuff. The density of 37% HCl is 1.19g/mL so the N is 1000 mL x 1.19 g/mL x 0.37 x (1/36.5) = about 12N for the 37% HCl. How ...
July 7, 2014

CHEMISTRY
Here is the first one in detail (for CO2). 1) 2CO + O2 <==> 2CO2 + 167 kJ and I will rewrite the problem to more clearly show how the heat is treated. Basically the heat is made to look just like an added product (if an exothermic rxn) or a reactant (if an endothermic ...
July 7, 2014

CHEMISTRY
See you last post for that detail explaination I gave for CO2
July 7, 2014

chemistry, biology
I believe you can use the Henderson-Hasselbalch equation for this pH = pKa + log (base)/(acid) You have the zwitterion at the isoelectric point and you are taking away the H^+ from the NH3^+ group. Acid + OH ==> base + H2O etc. You have 480 x 0.02M = 9.6 millimols to start...
July 6, 2014

science
q = mass iron x specific heat iron x (Tfinal-Tinitial) q = 114
July 6, 2014

chemistry
Use PV = nRT and sole for n = number of mols. You must convert 1.00 MPa to kPa.
July 6, 2014

chemistry
I would use PV = nRT. You know n, R, T, and P. Solve for V. Or you may use the other bit of information given that 1 mol at STP occupies 22.4L. So you know that at STP you will have 14 x 22.4L, then use (p1v1/t1) = (p2v2/t2)
July 6, 2014

chemistry
(P1V1/T1) = (P2V2/T2)
July 6, 2014

chemistry
Use PV = nRT and solve for n = number of mols. You must convert cubic meters to L. Then n = grams/molar mass. You know molar mass and n, solve for grams.
July 6, 2014

Chemistry
0.0900M = 0.0900 mols/L solution. g = mols x atomic mass = 0.0900*19 = 1.71g. mass solution = volume x density = 1000 mL x 1.0 g/mL = 1000 grams. mass % = (g solute/grams soln)*100 = ? Convert to mg/L and that is ppm
July 6, 2014

investing
The interest of 6% compounded quarterly is 6/4 = 1.5% each quarter. There are 20 quarters in 5 years. (1.015)20*4,000 = ? = final value of thd $4,000. Interest earned is ?-4000 = ?
July 6, 2014

chemistry step by step for me thank a lot
1 mol Ca(OH)2 removes 1 mol Ca(HCO3)2; therefore, to remove 100 ppm harness (as CaCO3) will require (100 x 74/100) = 74 ppm Ca(OH)2. (Note: To convert harness in ppm CaCO3 to Ca(OH)2, use the coefficients in the balanced equation. That is a 1:1 mole ratio in which 1 mol Ca(OH)...
July 6, 2014

College Algebra I
I don't see a question here.
July 6, 2014

chemistry step by step thank a lot
Is that m or M (molality or molarity) M is molarity m is molality Did you make a typo? Is that question for molarity of the H^+. That is 0.888M (not m). Total molarity, however, is much more than 0.888M.
July 6, 2014

Chemistry
pi = MRT pi = 869/760 = ? M solve for this R = 0.08205 L*atm/mol*k T = 273 + 21 = ? M gives you part b. Then M = mols/L solution, you know L solution and M, solve for mols and that is part c. Part a is mol = grams/molar mass. You know grams and mols, solve for molar mass.
July 6, 2014

Soil Chemistry
I don't get it. There are no carbon-halogen bonds in any of those molecules.
July 6, 2014

chemistry
wavelength = h/mv Convert 1A to m.
July 6, 2014

CHEMISTRY
dG = dH - TdS 0 = 8000 - 298(dS)
July 6, 2014

CHEMISTRY
q = mass In x specific heat In x (Tfinal-Tintial) q = 23J mass = atomic mass In solve for sp.h.
July 6, 2014

chemistry
CO2 is the gas evolved. It is colorless and odorless but will extinguish a burning flame.
July 6, 2014

chemistry step for step thank a lot
1. Why do you think 1000 ppm is the correct answer for #1? 2. Balance the redox part. The other parts of the equation (H2O, H^+, SO4^2-, etc) do not need to be balanced. a. KMnO4 + 5FeSO4 ==> Mn^2+ + 5Fe^3+ (Mn changes from +7 on the left to +2 on the right for the gain of ...
July 5, 2014

uos
universal optimum science? university optional science? university optimal services? unrealized optical scans?
July 5, 2014

chemistry
The easy way to do these is to assume some convenient number for the rate of effusion. The number 1 is an easy one to use. unknown gas rate = 1L/min oxygen gas rate = 2.5*1L/min = 2.5 L/min (rate O2/rate unk) = swrt(MMunk/MMO2) (2.5/1) = sqrt(MMunk/32) Solve for molar mass (MM...
July 5, 2014

Chemistry
This is just like the HBr problem. Just follow the format.
July 5, 2014

Chemistry
As in the HCl problem, start with the definition. m = mols/kg solvent mass of 1 L = 1000 mL x 1.38 g/mL = 1380 g. Not all of that is HBr. HBr present is 40% so 1380 x 0.40 = 552g. mols in 552g HBr is mols = grams/molar mass = 552/about 81 (but you need to do it more accurately...
July 5, 2014

Soil Chemistry
I presume it's just like any other hydrocarbon; i.e., products are CO2 and H2O
July 5, 2014

Chemistry
M = mols/L so you want to know how many moles HCl there are in 1 L. 1000 mL weighs how much? That's 1000 mL x 1.19 g/mL = 1190 g How much of that is HCl? Only 36%; therefore, g HCl = 1190 x 0.36 = estimated 428g How many mols is that? mol = g/molar mass mols = 428/36.5 = ...
July 5, 2014

chemistry
There is some information here but you must assimilate your knowledge of chemistry to be useful. http://en.wikipedia.org/wiki/Polyethylene
July 5, 2014

chemistry
How about one of each? We're supposed to help with your homework, not do all of your homework. silt in water--suspension colloidal gold in water--colloid http://chemistry.about.com/od/lecturenotesl3/a/colloids.htm
July 5, 2014

chemistry
Do you have an equation you want to use?
July 4, 2014

chemistry Step for step for me thank a lot
Ken, I did step by step and explained every step as I went. Step by step what do you not understand?
July 4, 2014

Chemistry Step by step for me Thank a lot
See your post below.
July 4, 2014

chemistry step by step for me Bob
Saponification number is the number of mg KOH required to react with 1g fat (in this case peanut oil). mols KOH initially added to 2g oil = M x L = 0.4M x 0.025L = 0.0100 mols. Then H2SO4 is added to neutralize the excess amount of KOH. H2SO4 + 2KOH ==> K2SO4 + 2H2O mols ...
July 4, 2014

Chemistry
The question is a little confusing to me but I would answer that they have different number of protons, different number of neutrons, and different number of electrons. But your question MAY means copper arsenide, germanium arsenide, silicon arsenide etc.
July 4, 2014

chemistry Ben step by step for me
What's the question? 1000 ppm is 1000 mg/L.
July 4, 2014

chemistry please step by step for me
I did it step by step. Here it is again with more explanation. Write and balance the equation. Zn + 2HCl ==> H2 + ZnCl2 How many mols H2 do you want to generate. mols = grams/molar mass g H2 = 4g. molar mass H2 = 1*2 = 2 g/mol. mol H2 = 4g/2 = 2 mols H2 in 4g H2. Now ...
July 4, 2014

chemistry
What is the molarity of the HCl solution? That's 1000 mL x 1.2 g/mL x 0.0365 x (1 mol/36.5g) = 12M Zn + 2HCl ==> ZnCl2 + H2 How many mols is 4g H2. mol = grams/molar mass = 4/2 = 2 2 mols H2 = 2*2 = 4mols HCl M HCl = mols HCl/L HCl. You know M HCl from above and mols ...
July 4, 2014

CHEMISTRY
I don't understand the question. 1 is the conjugate base of HPO4^2-. 2 is the conjugate base of H3O^+. 3 is the conjugate acid of H2PO4^- 4 is the conjugate acid of HPO4^2- and the conjugate base of H3PO4.
July 4, 2014

Science
I don't understand the question. A 2% isotonic solution seems to be an oxymoron to me. An isotonic solution is about 0.9% NaCl/100 mL solution.
July 4, 2014

CHEMISTRY
See your post above.
July 4, 2014

CHEMISTRY
I think you meant to say that the freezing point of the pure water as read on your thermometer was 0.25. Therefore, the freezing point of the original solution KNO2 was -1.40. Then 1.40 = i*Kf*m 1.40 = 2*1.86*m m = about 0.376 0.415g KNO3 = 0.415/101.1 = about 0.0041 mols. m...
July 4, 2014

Chemistry
See your earlier post. I'll explain something here if you don't understand it but I'm not about to rework four problems just for the fun of it.
July 3, 2014

Chemistry
See your other posts.
July 3, 2014

Chemistry
See your earlier post.
July 3, 2014

Chemistry
Brett, I worked these problems for you earlier.
July 3, 2014

Chemistry
http://www.jiskha.com/display.cgi?id=1404360366
July 3, 2014

CHEMISTRY
At 60C 200 g H2O will hold 18 x 200/100 = 36g and that is a saturated solution. At 20C it will hold 12 x 200/100 = 24. Difference is 36-24 = ?g
July 3, 2014

Cattle ranching
I disagree. http://animals.pawnation.com/country-introduced-cattle-us-7162.html
July 3, 2014

Chemistry
I worked this a couple of days ago but that problem didn't included the water washing as described here. There is so much superfluous information here it makes the problem a little confusing. Here is what I will work with. Calculate theoretical yield of Ba(IO3)2 using 30....
July 3, 2014

Chemistry
See your other post above.
July 3, 2014

Chemistry
See you last post. dHrxn = (n*dHf products) - (n*dHf reactants)
July 3, 2014

Chemistry
dHrxn = (n*dHf products) - (n*dHf reactants)
July 3, 2014

Chemistry
multiply equation 1 by 2 and dH x 2. Reverse equation 2 and change sign dH. Balance equation 3(it isn't balanced now). Add the three equations and add dHs. This will get 2NO2 + 2N2O ==> 6NO which is twice what you want. So divide the final equation by 2 and divide sum ...
July 3, 2014

Chemistryq
Use PV = nRT and solve for P. n for O2 = grams O2/molar mass O2
July 3, 2014

Chemistry
mols KMnO4 = M x L = ? Use the coefficients in the balanced equation to convert mols KMnO4 to mols H2O2. Then M H2O2 = mols H2O2/L H2O2 I'll be glad to check your answer.
July 3, 2014

chemistry
heat loss by Cu + heat gained by H2O = 0 heat loss by Cu is [(mass Cu x specific heat Cu x (Tfinal-Tinitial)] heat gain by H2O is [mass H2O x specific heat H2O x (Tfinal-Tinitial)] Add those and set to zero as follows: [mass Cu x specific heat Cu x (Tfinal-Tintial)] + [mass ...
July 2, 2014

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