Wednesday
October 1, 2014

Posts by DrBob222


Total # Posts: 44,185

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.
June 24, 2014

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 ...
June 24, 2014

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
June 24, 2014

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&...
June 24, 2014

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.
June 24, 2014

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.
June 24, 2014

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.
June 23, 2014

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 ...
June 23, 2014

Chemistry
PV = nRT Remember T must be in kelvin. R is 8.314 if you use P in kPa.
June 23, 2014

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.
June 23, 2014

chemistry
q = mass x specific heat x (Tfinal-Tinitial) q = 120g x 4.184 J/g*C x (29.2-20) q = ?
June 23, 2014

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".
June 22, 2014

chemistry
a However, I think it plays a role in some cases.
June 22, 2014

chemistry
which do you think and why?
June 22, 2014

Chemistry
And how can I help you with this? How much do you already know how to do?
June 22, 2014

Chemistry
Where is your hang up on this?
June 22, 2014

finite math
That's the problem. That's the end of it. You've multiplied P*r*t, what else is left to do?
June 22, 2014

Chemistry
I think the easiest (but the long) way is to say volume N2 = 0.8 x 1 L = 0.8 L volume O2 = 0.2 x 1L = 0.2 L. Then use PV = nRT and solve for n = mols N2 and mols O2. Then mols N2 = grams/molar mass and mols O2 = grams/molar mass. You know molar mass and mols, solve for grams ...
June 22, 2014

chemistry
Too much typing. Do this (%)(au) + (%)(au) + (%)(au) ........ = au (0.158*91.91) + (0.009*93.90) + ..... = au.
June 22, 2014

chemistry
We can't draw diagrams, Sara/john/robert/et al/ If you can explain what you don't understand about it perhaps I can help you draw it.
June 22, 2014

chemistry
John/Sara/Robert/et al. You must know the rules which are n may be any whole number >1. l may be a whole number from 0 to n-1; i.e., 0, 1, 2, 3, etc. m may be any whole number from -l to +l including zero s may be either +1/2 or -1/2. For example, 1 is allowed but 2 is not...
June 22, 2014

chemistry
mols Mg = grams/molar mass = ? Using the coefficients in the balanced equation, convert mols Mg to mols H2SO4. Then M H2SO4 = mols H2SO4/L H2SO4. You know mols and M, solve for L. Using mols Mg, convert to mols H2 for part 2.
June 22, 2014

chemistry
heat gained by ethanol + heat lost by water = 0 heat gained by ethanol = mass x specific heat x (Tfinal-Tinitial). Use density to convert mL to mass. heat lost by water = mass x specific heat x (Tfinal-Tinitial). Use density to convert mL to mass. Tfinal is the only unknown.
June 22, 2014

oops--chemistry who step by step for me
I made a typo so I've erased my entire response and posted the correct answer. You know your answer can't be right because you have 4 g K2CO3 but the entire sample is only 1.2 g and 4 g is more than the you started with My calculation 20cm3/100cm3 = 0.2 Yes, 0.2 is the...
June 22, 2014

chemistry step by step for me
Do you mean LiCl and BaI2. There is no BaI.
June 22, 2014

Org Chem
Ko/a = amt org layer/amt H2O layer. K is 8 MeCl2 is 30 mL H2O is 30 mL Caffeine is 10g Let X = amount extracted with org layer, then 10-x = amount left in H2O layer. 8 = (x/30)/(10-x)/30 You can cancel the 30 in the denominator. Solve for x. You can do it three times for three...
June 22, 2014

Columbus State
I would have answered much faster if I had seen "chemistry" posted. Instead Writeacher did you a favor and corrected the heading or I never would have looked at "columbus State". The easy way to do this is to change Kc to Kp. Kp = Kc(RT)^delta n. Then run a...
June 22, 2014

chemistry
It works the same way as stoichiometry. rate Cr(SO$)3 x (3 mol C2H6O/2 mol Cr(SO4)3) = 1.24 x 3/2 = ? Note that Cr(SO4)3 cancels but C2H6O stays to change the units to that specie.The coefficients do the job. Same for the other problem. 3.7E-5 x (4/2) = ?
June 21, 2014

Chemistry pls clearly step step for me
And I can't calculate to obtain that answer either. I don't think the problem is worded correctly. Here is why I think that. If the sample is 56.7% NaHCO3 then it is 43.3% Na2CO3. g Na2CO3 = 2 x 0.433 = 0.866g Na2CO3 g NaHCO3 = 2 x 0.567 = 1.134g NaHCO3 total = 1.134+0...
June 21, 2014

chemistry--NCCU
I would have answered this much quicker if you had typed in the subject instead of something obscure like NCCU.
June 21, 2014

chemistry---NCCU
millimols benzoic acid = mL x M = about 27 but that's an estimate and you should redo the math. Then pH = pKa + log (base)/(acid) 4.30 = pKa benzoic acid + log benzoate/27 Look up the value of pKa for benzoic acid, substitute, solve for base. That will be millimols sodium ...
June 21, 2014

intro to chem
q = mass Au x specific heat Au x (Tfinal-Tinitial) q = 3000 g x 0.128 J/g*c x 37C = 1.4 E4 J to two s.f. If you multiply 3 x 0.128 x 37 you don't get 3.6. You get 14.2 BUT that 3 is not right. It is in kg and your specific heat unit is in J/g*c so you must change the 3 kg ...
June 21, 2014

intro to chem
I don't understand how you get 3.6 anything. 3000 x 0.128 x 37 = ?
June 21, 2014

intro to chem
I'm guessing here since I don't know what you used for specific heat Au and what units you want the answer. But my guess is you used specific heat in cal/g*C and that's about 0.032. delta T is 60-23 = 37. Then I think you failed to convert 3 kg Au to g Au so 3 x 0....
June 21, 2014

intro to chem
What did you use for specific heat Au? with units?
June 21, 2014

intro to chem
q needed = mass Au x specific heat Au x (Tfinal-Tinitial)
June 21, 2014

chemistry Please who helps me stpe by step
mass sample titrated = 2 g x (25/250) = 0.2 g. You have two unknowns which will require two equations and you solve those simultaneously. Let X = mass Na2CO3 and Y = mass NaHCO3 ------------------------ Equation 1 is : X + Y = 0.2 Then # milliequivalents = grams/...
June 21, 2014

chemistry
pH of the original solution before NaOH is added is pH = pKa + log (base)/(acid) pH = 9.26 + log (0.1/0.1) = 9.26 millimols NH3 = 0.1 x 1000 = 100 mmols NH4Cl = 0.1 x 1000 = 100 mols NaOH added = 1.8/40 = 0.045 mols or 45 millimols. .............NH4^+ + OH^- = NH3 + H2O I...
June 21, 2014

Chemistry
%by mass = (mass solute)/(mass solution) % w/w = 19.7g NaOH in 100 g solution. % w/w = 19.7 g NaOH in [19.7g NaOH + (100-19.7)g H2O].
June 21, 2014

CHEMISTRY
W = nRT*ln(Vfinal/Vinitial) If you want W in joules use R = 8.314
June 21, 2014

Chemistry
That's probably right. If I use 4.76 for pKa for acetic acid and plug in 1.82 for mols base and 1 for mols acid, I get pH 5.02. Using pKa 4.74 gives 5.00.
June 20, 2014

Chemistry 10As
16% w/v means 16 g ethanol in 100 mL solution. So add 5*16 = 80 g ethanol, place in a 500 mL volumetric flask, and make to the mark with distilled water.
June 20, 2014

chemistry
Look up refrigeration or air conditioning on google.
June 20, 2014

Chemistry
11=4+2+m+2 Solve for m
June 19, 2014

Chemistry
I don't think any of us memorized all of the solubility tables for all of the salts in the universe. If you have a graph or a table that gives you the solubility at various temperatures, post them and I can help. If you don't have that information I may be able to find...
June 19, 2014

chemistry
b although I don't like the way it is stated.
June 19, 2014

Chemistry
(H^+)(OH^-) = 1E-14 So smaller H^+ means higher OH^- or higher H^+ means lower OH^-
June 19, 2014

chemistry
mols HCl = grams/molar mass mols C6H6 = grams/molar mass total mols = mols HCl + mols C6H6 Xbenzene = mols benzene/total mols.
June 19, 2014

algebra
g/9 = ?
June 18, 2014

Chemistry
I would classify these as a redox reaction.
June 18, 2014

Chemistry
(V1/T1) = (V2/T2) Remember T must be in kelvin.
June 18, 2014

Chemistry
Multiply equation 1 by 2 and reverse it. Add to equation 2. That will give you the equation you want but you need to go through the steps to confirm that. When you multiply an equation, do the same to delta H. When you reverse and equation change the sign of delta H.
June 18, 2014

chemistry
What water has hydrated the H2SO4, the reaction is exothermic so heat is evolved.
June 18, 2014

chemisrty
So you reacted 1.2M x 0.050L = 0.06 mols HCl with 0.06 mols NaOH in 100 mL solution. mass solution = 100 mL x 1.05 g/mL = 105 grams. delta T = dT = 29.8-24.1 = 5.7 degrees. q = (mass soln x specific heat x dT) + (Ccal x dT) q = (105 x 4.184 x 5.7) + (32.5 x 5.7) = ? J for 0.06...
June 18, 2014

algibra
y1-y2/x1-x2 -10-(-2)/1-(-7) -8/8 = -1 = m
June 18, 2014

Chemistry
(CO3^2-) = k2. The reasoning is this but it's a little long. I wish we had a board and I could talk. ...........H2CO3 ==> H^+ + HCO3^- I..........0.18......0.......0 C...........-x.......x.......x E.........0.18-x.....x.......x k1 = 4.3E-7 = (x)(x)/(0.18-x) and solve ...
June 18, 2014

chemistry
mols HCl = grams/molar mass Then M = mols/L solution.
June 18, 2014

Chemistry
On a relative scale we often say the mass of a proton is 1, a neutron is 1 and an electron is 0 BUT that's a relative scale so we don't need to keep repeating those 10^- numbers for the exponents. The rest mass of a proton is 1.672E-27 kg. It is 1.007 amu. It is not 1g.
June 18, 2014

Chemistry
q = Ccal*(Tfinal-Tinitial) + [mass H2O x specific heat H2O x (Tfinal-Tinitial)] Solve for Ccal Watch the units. If you use 4.184 J/g*C for H2O and you want Ccal in J/C, then you must substitute q in J, not kJ.
June 18, 2014

chemistry
(V1/T1) = (V2/T2) Remember T must be in kelvin. (210/200) = (360/T2) Solve for T2 in K
June 18, 2014

physical chemistry
X = 0.444*Y X = 2.96*12 Y = ?
June 18, 2014

chemistry
A lost of writing but no numbers. You can't calculate anything without numbers.
June 18, 2014

physical chemistry
mols Fe = grams/atomic mass = ?. There are 6.02E23 atoms in 1 mol so there will be ..... atoms in ? mol.
June 18, 2014

physical chemistry
Reason this out. mols = grams/atomic mass mols A = x/40 mols B = 2x/80 = x/40 Since there are the same number of mols of A and B there must be the same number of atoms of A and B. Therefore, since A contains y atoms then B must contain y atoms.
June 18, 2014

physical chemistry
mols C = 12g/12 = 1 1 mol contains 6.02E23 atoms. 98% of those will be C-12 and 2% will be C-14; therefore, number atoms C-14 = 6.02E23 x 0.02 = ?
June 18, 2014

physical chemistry
See your posts above.
June 18, 2014

physical chemistry
See your other posts.
June 18, 2014

physical chemistry
mols (NH4)3PO4 = 3.18 mols H x (1 mol (NH4)3PO4/12 mols H) = ? Then mols O is 4x that since there are 4 atoms O in 1 molecule (NH4)3PO4
June 18, 2014

physical chemistry
1 atm = 760 mm Hg = 101.325 kPa Make the conversion.
June 18, 2014

physical chemistry
mols CO2 = grams/molar mass There are 6.02E23 molecules in 1 mol CO2.
June 18, 2014

physical chemistry
no answer choices. abundance first isotope = 95.72% abundance other isotope is 100-95.72 = 4.28% Let x = mass other isotope (114.9041*0.9572) + (x*0.0428) = 114.82 Solve for x
June 18, 2014

physical chemistry
If 99% is 20 the the total must be approximately 20. Note: I stated at the top and worked down before realizing you had writer's cramp from all of your questions. This is not a place to dump your homework but for today I have helped with each one. In the future you need to...
June 18, 2014

chemistry
If plot ln k vs 1/T then slope = -Ea/RT
June 18, 2014

chemistry
Use the Arrhenius equation. Substitute k1 and k2 rates at the appropriate T and solve for Ea (activation energy); then use the same equation with Ea you found to solve for the new k.
June 18, 2014

chemistry
(1/A) - (1/Ao) = akt Let Ao = 100; A = 5; a = 1
June 18, 2014

Chemistry - Electroplating - URGENT
I believe you should have divided 52 by 3; the electroplating probably goes from Cr^3+ to Cr which is a change of 3 electrons. Then coulombs needed = 96,485 x (200/17.3) = ? C = amps x seconds but you have two unknowns. You don't know amps (usually given in the problem) or...
June 17, 2014

Chem URGENT
By the way you will get faster answers if you don't change screen names.
June 17, 2014

Chem URGENT
Do this in steps. 1. heat released in lowering steam from 114.5 to steam at 100 c. q1 = mass steam x specific heat steam x (Tfinal-Tinitial) q2 = heat released in changing steam at 100 C to liquid H2O at 100 C. q2 = mass x heat vap q3 = heat released in moving liquid H2O at ...
June 17, 2014

CHemistry
0.5M x (3 SO4^2- ions/1 Al2SO4)3 molecule) = 0.5 x 3/1 = ?
June 17, 2014

chemistry
mols = grams/molar mass 0.007g/14 = ? mols C14 atoms There are 7 neutrons/atom; therefore, # mols x 7 = ? mols neutrons. There are 6.02E23 neutrons for each mol of neutrons; therefore, mols neutrons x 6.02E23 neutrons/mol = # neutrons. mass of those neutrons = # neutrons x ...
June 17, 2014

chemistry
1 mol U weighs 238g There are 6.02E23 atoms in 1 mol. 1 atom x (238g/6.02E23 atoms) = ?g/a atom
June 17, 2014

chemistry
#/sec x #sec = 6.02E23 10^10/sec x #sec = 6.02E23 Solve for #sec and convert to years.
June 17, 2014

chemistry
Something is askew here. If you have 79% of one isotope and 21% of the other, that adds to 100% so there is no room for any other isotope.
June 17, 2014

chemistry
See your post on water answered by steve.
June 17, 2014

chemistry
Your question makes no sense.
June 17, 2014

chemistry
mols = grams/molar mass There are 6.02E23 molecules in a mole.
June 17, 2014

chemistry
Look the atomic mass up on the periodic table and add them. The answer is about 100.
June 17, 2014

chemistry
mols CO2 = grams/molar mass There are 6.02E23 molecules in a mol. Subtract 1E10^21 to find number left.
June 17, 2014

chemistry
What's your problem here. Are you dumping your homework?
June 17, 2014

chemistry
I'll be glad to help if you will explain what you don't understand. "None of it" is not an acceptable answer.
June 17, 2014

chemistry
2NaN3 ==> 2Na + 3N2 mols NaN3 = 88.8g/molar mass NaN3 = approx 88.8/65 = about 1.4 but that's an estimate. mols N2 produced = 1.4 mols NaN3 x (3 mols N2/2 mols NaN3) = 1.4 x 3/2) = estimated 2. Substitute n (2) into PV = nRT at the conditions listed and solve for V in ...
June 17, 2014

Chemistry
I think you can take your answer to the bank.
June 16, 2014

Chemistry
CuSO4.5H2O is soluble in water. With time the CuSO4 dissolves and begins to diffuse throughout the beaker. Left undisturbed, even after a long time, the bottom of the beaker will be quite blue and the upper portions will be much less blue in color.
June 16, 2014

chemistry
There are far too many chemicals for me to remember the solubility of each of them. If you have a table or a graph that gives solubility I can help. Otherwise, look up the solubility KClO3 and correct to 100 g.
June 16, 2014

chemistry
%H2O = (mass H2O/mass sample)*100 = ?
June 16, 2014

chemistry
https://www.google.com/search?q=ketohexose&client=firefox-a&hs=hp1&rls=org.mozilla:en-US:official&channel=sb&tbm=isch&tbo=u&source=univ&sa=X&ei=sDmeU-MezbawBLbBgLAH&ved=0CCYQsAQ&biw=1099&bih=679&dpr=0.9
June 15, 2014

chemistry
http://en.wikipedia.org/wiki/Ketohexose
June 15, 2014

analytical chemistry
0.2810g Fe(NH4)2(SO4)2 x (1000 mg/g) x [1 mol Fe/1 mol Fe(NH4)2(SO4)2] x (1 mol Fe(NH4)2(SO4)2/284g) x (55.85g Fe/1 mol Fe) = ? Or without all the mishmash it is 0.2810 x (atomic mass Fe/molar mass Fe(NH4)2(SO4)2) x 1000 = 0.2810 x (55.85/284) x 1000 = ?
June 15, 2014

algebra
Here is how you do this with algebra. Let x = 10s digit and y = units digit. So the number is 10x + y and you know that if you reverse the number it is 10y + x. The problem tells you that 10x + y = 10y+x+18 which simplifies to 9x-9y=18 The second equation is x + y = 8. Solve ...
June 15, 2014

chemistry
http://www.jiskha.com/display.cgi?id=1402851831
June 15, 2014

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