Tuesday
July 29, 2014

Posts by drbob222


Total # Posts: 43,211

chemistry
Do you have an equation you want to use?

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?

Chemistry Step by step for me Thank a lot
See your post below.

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 H2...

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.

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

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 conver...

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 HC...

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.

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.

CHEMISTRY
See your post above.

CHEMISTRY
2

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 =...

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.

Chemistry
See your other posts.

Chemistry
See your earlier post.

Chemistry
Brett, I worked these problems for you earlier.

Chemistry
http://www.jiskha.com/display.cgi?id=1404360366

incomplete---Algebra

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

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

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 30.0...

Chemistry
See your other post above.

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

Chemistry
dHrxn = (n*dHf products) - (n*dHf reactants)

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 d...

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

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.

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 H2...

chemistry
Ptotal = pHe + pN2 + pAr You know all but one unknown. Be careful with the units. Ptotal is in atm and the gases are given in torr (and mm but 1 mm = 1 torr)

Chemistry: Conversion
Of course that does all of the work for you and you don't learn to go through the various factors to get from yard^2 to m^2.

Chemistry: Conversion
The easy way is to Google and type in, without the quotation marks, the following: "7 square yards to m^2" and hit the enter key. Up pops 7 sq yards = 5.85289 square meters

chemistry
CH2OHCOOH + NaOH ==> CH2OHCOONa + H2O mols NaOH = M x L = ? Using the coefficients in the balanced equation, convert mols NaOH to mols glycolic acid. That should be 1:1. Then mols glycolic acid = grams/molar mass. You know molar mass and mols, solve for grams.

chemistry
millimols HOCl = mL x M = 225 x 0.283 = estimated 64. mmols KOCl = 225 x 0.456 = 103 add 46 mmols HClO4. ..........OCl^- + H^+ ==> HOCl + H2O I.........64......0........103 add..............46............. C........-46....-46.........+46 E.........18......0........149 Subst...

Organic biochemistry
https://www.google.com/search?q=diethylammonium+bromide&client=firefox-a&hs=oWE&rls=org.mozilla:en-US:official&channel=sb&tbm=isch&tbo=u&source=univ&sa=X&ei=m5OzU6ThC9XEsASbp4DwBA&ved=0CCsQsAQ&biw=1143&bih=688&dpr=0.9

chemistry
For inorganic strong bases use those that end in OH such as NaOH, KOH, Ca(OH)2, Ba(OH)2, CsOH etc. For organic bases use those that have amine groups; either RNH2 (primary amines) or R2NH (secondary amines).

Chemistry
morality? Most H2SO4 solutions are not moral at all. Neither are NaOH solution. H2SO4 + 2NaOH ==> Na2SO4 + 2H2O mols NaOH = M x L = ? mols H2SO4 = 1/2 mols NaOH which you get from the coefficients in the balanced equation. Then M H2SO4 = mols H2SO4/L H2SO4 M is for molarity.

Chemistry
I may have interpreted this all wrong but I think you want 1.2 mL of 100 mM solution. If that is true then 100 mM x 1.2 mL = ? mmols or ?/1000 = mols. mols = grams/molar mass. You have molar mass and mols, solve for grams.

Chemistry
This problem isn't clear to me at all. Is the drug a liquid? density is needed if we are to make 1.2 mL. How much is the stock solution to be diluted?

chemistry
5% glucose means 5 g glucose in 100 mL solution. So in 500 mL there will be 5*5 = 25 g glucose in 500 mL.

science
3e5 N/m2 = 3 bar Sea level is 1 bar Pressure increases 1 bar for every 10.06 m so to go from 1 bar to 3 bar would require 3*10.06 m = ?

Chemistry 1
1/wavelength in m = R(1/4 - 1/n^2) The 1/4 is 1/2^2. R = 1.0973E7 m^-1

Chemistry 1
I don't see a question here. I assume you want to calculate the heat of neutralization (in what units?)

Chem
I thought I worked this a couple of days ago. 4H ==> 2H2 So 435 kJ/mol x 2 mol = 870 kJ. 870,000J = mass H2O x specific heat H2O x (Tfinal-Tinitial) Plug and chug. Solve for mass H2O

Chemistry
Balance the redox part first. You don't need to write the entire equation, just the redox part. C2O4^2- + Cr2O7^2- ==> 2Cr^3+ + 2CO2 C in C2O4 changes from +6 (for 2C) to +8 (for 2C) which is a change of 2e. Cr in Cr2O7^2- changes from +12 (for 2Cr) to +6(for 2 Cr) whic...

Chemistry
mols KOH = M x L = ? Since aspirin is a monoprotic acid then mols aspirin = mols KOH. g aspirin = mols aspirin x molar mass aspirin. % aspirin = (mass aspirin/0.534)*100 =

Chemistry
(35.9675*0.003365) + (37.9627*0.000632) + (39.9624*0.99600) = ?

Chemistry
1 ton = 2000 lbs. 261 tons x (2000 lbs/1 ton) x 0.014 x (molar mass (CH3)2Hg/atomic mass Hg) =

Chemistry
If that is 7.04% N (and not N2), you have 7.04g N in 100 g of the fertilizer. To convert to g urea just multiply by the chemical factor (which usually isn't taught in schools now). 7.04 x (molar mass urea/2*atomic mass N) = ?

chemistry
Did you make typo? If Kp is at 160 C then it will be different at 100 C. Assuming you mean Ptotal at 160 C... ....2NaHCO3(s)=>Na2CO3(S)+CO2(g)+H2O(g) I...solid.......solid......0......0 C...solid.......solid......p......p E...solid.......solid......p......p Kp = pCO2 * pH2O...

Soil Chemistry
Yes you are, STP means standard temperature and pressure. So P is 1 atm standard, T is 273 K standard and you are to calculate standard V.

Soil Chemistry
(P1V1/T1) = (P2V2/T2) Whatever units you use for the left side use the same units for the right side.

Soil Chemistry
I don't see a question here.

Chemistry
Two rules to follow in chemistry problems. 1. Work in mols. You get mols two ways. The first is when you have grams; that's mols = grams/molar mass. The second is when you have a solution; then mols = M x L. 2. When you have mols you can convert mols of anything in the equ...

Chemistry
Ba(NO3)2 + 2NaIO3 + H2O ==> Ba(IO3)2*H2O + 2NaNO3 Ba(NO3)2 is the limiting reagent with either number. mols Ba(NO3)2 = M x L = 0.4912 x 0.030 = 0.014736 = mols Ba(IO3)2.H2O g Ba(IO3)2 = mols x molar mass = theoretical yield (TY). Actual yield (AY) = 6.895g in the problem. %...

Chemistry
See you other post.

Chemistry
See your post below. Same procedure.

Chemistry
See your post below. You calculate mols to calculate grams.

Chemistry
See your post below. BTW, you would get faster responses if you didn't change screen names. Joe, Steve, Chris, ?

Chemistry
This is a limiting reagent (LR) problem. 2NH4F + Ca(NO3)2 ==> CaF2 + 2NH4NO3 1. Write and balance the equation as above. 2. Convert numbers to mols. mols = M x L = ? mols Ca(NO3)2 = M x L = ? mols NH4F = M x L = ? 3a. Using the coefficients in the balanced equation, convert...

chemistry
2AgNO3 + CaCl2 ==> Ca(NO3)2 + 2AgCl mols CaCl2 = grams/molar mass = ? Use the coefficients in the balanced equation to convert mols CaCl2 to mols Ca(NO3)2 (That should be mols CaCl2 x 2 = ?). Then g Ca(NO3)2 = mols Ca(NO3)2 x molar mass Ca(NO3)2 = ?

Soil Chemistry
You must pay attention to units no matter what problem you are working. Here, use PV = nRT and solve for n P must be in atm and 755/760 = ? atm. V in L n = number of mols. Solve for this. R = 0.08205 L*atm/mol*K T = 24C + 273 = ?K. T must be in kelvin. Then n = mols = grams/mo...

Soil Chemistry
No big problem. Just remember the definitions. Oxidation is the loss of electrons. Reduction is the gain of electrons. In the problem Mn goes to Mn^2+, so Mn ==> Mn^2+ + 2e is the loss of electrons and is oxidation. A is the only answer that fits for Mn. I don't see the...

Chemistry
You need three things: a. What is the change in oxidations state? b. Were electrons lost of gained. c. the definitions: oxidation is the loss of electrons. Reductions is the gain of electrons. Here is a. Zn has an oxidation state of zero on the left and +2 on the right. Loss o...

chemistry
http://en.wikipedia.org/wiki/Hard_water

Chemistry
q = 4 mol x 435 kJ/mol = ? kJ = ? x 1000 J. q = mass x specific heat x (Tfinal-Tinitial). YOu know Tfinal, Tinitial, specific heat, and q, solve for mass

Chemistry
Convert 1 L to gallons. Convert Canadian $ to U. S. $. 0.771 CD/L x (1 USD/1.401 CD) x (1 L/0.264 gallons) = ? USD/gallon.

Chemistry
Explain your trouble. You set up Ca(s) --> Ca(g) dH = +192 kJ Ca(g) --> Ca^+ + e dH = + 589.5 kJ Ca^+(g) --> Ca^2+ + e dH = + 1146 kJ Cl2(g)--> 2Cl(g) dH = 242.6 kJ 2*Cl(g) + 2e -->2*Cl^-(g) dH =2*-348 kJ Ca^2+(g) + 2Cl^-(g) --> CaCl2 dH = lattice -----------...

Chemistry
1/wavelength = R(1/4 - 1/n^2) 1/4 is 1/2^2

Chemistry
E for 3.00 mm is E = hc/wavelength. Convert wavelength in mm to m. That gives E for 1 photon which is q/photon q needed to raise T H2O is q = mass H2O x specific heat H2O x delta T = 1.45g x 4.184 x 1 = estimated 6 J Then q/photon x # photons = estimated 6 and solve for # phot...

Chemistry
You have a typo in the equation. 6HCl + Fe2O3 -> 2FeCl3 + 3H2O g Fe2O3 reacted = 37.5-5.5 = 32.0g mols Fe2O3 = grams/molar mass = estimated 0.2 a. mols HCl used = 0.2 x (6 mol HCl/1 mol Fe2O3) = estimated 1.2. M HCl = mols/L = estd 1.2/0.240 = ? b. mols FeCl3 = mols Fe2O3 x...

Chemistry 12
KOH ==> K^+ + OH^- mols KOH = grams/molar mass = ? M KOH = mols KOH/L solution = ? pOH = -log(KOH) Then pH + pOH = pKw = 14. You know pKw and pOH, calculate pH.

Chemistry
pi = MRT pi = 0.138 atm M = ? R = 9.08205 L*atm/mol*K T = 273.15 + 28 = ? Solve for M. Then M = mols/L. You know L and M, solve for mols. Then mols = grams/molar mass. You know mols and grams, solve for molar mass.

Chemistry 108
mass benzene = volume x density = ? mols benzene = grams/molar mass = ? m benzene = mols benzene/kg solvent For f.p.: delta T = Kf*m, then subtract delta T from 0C to find new f.p. For b.p.: delat T = Kb*m, the add delta T to 100 C to find new b.p.

science
I don't see a question here.

Chem
CH4 + 2O2 ==> CO2 + 2H2O 16g CH4 releases 802 kJ so 16 x 542 kJ/802 kJ = ?

Chem
2Mg + O2 ==> 2MgO + 1203 kJ (although I can't tell if you meant that to be a + or a -). You know from the equation that 2 mol Mg (which is 2*24.3 g Mg) liberates 1203 kJ/ So 1203 kJ x 7.01/(2*24.3) = ? and you place the right sign on it.

Chemistry
I looked up the enthalpy of solvation for NH4Cl and CaCl2. I can work this problem for you now. If you still need help, please repost as a new question and I will get to it.

Chemistry
Do you have any other data given such as heat solvation etc?

Chemistry
Not balanced. MnO4^- + C2O4^2- + H^+ ==> 10CO2 + H2O + Mn^2+

chemistry
It depends upon what 1:2 means. There is confusion among even experienced on this. If 1:2 means 1 part NaHCO3 + 2 parts water, then the concn is 0.6M x (1/3) = ? If you mean 1 part NaHCO3 + 1 part (to make 2), then the concn is 0.6M x (1/2) = ? The following is a good web site...

math
I think "would be produced" is superfluous wording. I read it as what is the greatest odd number after rounding 660 to the nearest hundreds. 660 rounds to 700 and that's an odd number

Chemistry
No idea what the set up was. max P = 1.4094 what? initial P = what unit? atmosphere probably. Did the system gain weight? If so due to what?

analytical question
I would call this the near infrared although this is the upper end of that region. E = hc/wavelength in meters. E is J/photon. Multiply by 6.02E23 to convert to J/mol photons and change that to kJ/mol.

Analytical chem
If I read this right, you have 3 mg Cu initially, you place it in 250 mL, withdraw 15, add 15 more of something else and take 25 of that 30. So you should have 0.003/63.55 mol = ? initially and at the end it will be (0.003/63.55) x (15/250) x (25/30) = ? and that is in 30 mL o...

Chemistry
a 9% by mass means 9g ethanol in 100 g solution or 9g ethanol/(9g ethanol + 91g H2O). m = mols/kg solvent convert 9g ethanol to mols. mol = grams/molar mass. Then m = mols/0.091 = ? b delta T = Kf*m c You don't have but one solution here; what are you comparing?

Chemistry
what reaction?

Chemistry
2Al + 6HCl ==> 2AlCl3 + 3H2 mols Al = grams/molar mass Using the coefficients in the balanced equation, convert mols Al to mols H2. Then use PV = nRT and convert mols H2 to L at the conditions listed. Change L to mL.

chem school
Find your caps key and use it. m stands for molality; M stands for molarity. I assume M is what you want? And I doubt you mean 880 m or M. 3H2SO4 + 2Al(OH)3 ==> Al2(SO4)3 + 6H2O mols H2SO4 = M x L = ? Convert mols H2SO4 to mols Al using the coefficients in the balanced equa...

Chemistry
S + O2 ==> SO2 SO2 + Cl2 ==> SO4^2- mols S = grams/atomic mass = ? 1 mol S = 1 mol SO4^2- 1 mol SO4^2- = 1 mol BaSO4 I believe that is D

Chemistry
We can't draw diagrams/graphs on this forum. Plot the data, as the problem asks, zero, first, second order reactions look different. Here are some images. https://www.google.com/search?q=graphically+order+reactions&client=firefox-a&hs=LiV&rls=org.mozilla:en-US:official&ch...

chemistry
Did I miss something here? According to the first part of your post the volume of the unknown liquid is exactly 25 mL. According to the last part it is 50-3.25 = 46.75 mL. d = m/v but I don't know which volume to use.

chemistry
E = hc/wavelength Plug in E in J, h is Planck's constant, c is speed of light in m/s. Answer for wavelength is in meters, change to nm.

chemistry
Pb(NO3)2 + 2NH4I ==> PbI2 + 2NH4NO3 mols Pb(NO3)2 = M x L = estimated 0.16 mols NH4I needed = estd 2*0.16 = about 0.32 M NH4I = mols NH4I/L NH4I. You know mols and M, solve for L.

college chem
Here is the hint you should need to work the problem. You have two equations and you solve them simultaneously (which I think is the easier way) but there are other ways to do it. pH = pKa + log (base)/(acid) Take the Ka of k1, k2, and k3. The closes one to 6.9 is the one you ...

Chemistry
PV = nRT Remember T must be in kelvin. R is 8.314 if you use P in kPa.

Science
What acid/base? What indicator? You should be able to look up the pH range of the indicator but if you give me the name of the indicator perhaps I can find a place on the web that will gives the color changes vs pH.

chemistry
q = mass x specific heat x (Tfinal-Tinitial) q = 120g x 4.184 J/g*C x (29.2-20) q = ?

science
The mirror is a piece of glass with a silver backing on it(for back surface mirrors) that reflects light. The wall doesn't reflect enough light to "see yourself in a wall".

chemistry
a However, I think it plays a role in some cases.

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