Sunday
December 4, 2016

Posts by DrBob222

Total # Posts: 53,737

Ap chemistry
There are 2 mols Al^3+ in 1 mol Al2(SO4)3 so (Al^3+) is twice that of the salt. There are 3 mols SO4^2- in 1 mol Al2(SO4)3 so (SO4)^2- is three times that of the salt.
October 24, 2016

Chem: pH of acids and bases
You started very well. Just go from there. There can be two Ka values because there are two H ions to dissociate. .......H2X + H2O ==> H3O^+ + HX^- I....0.320............0.......0 C.....-x..............x.......x E...0.320-x...........x.......x Now Ka1 = (H3O^+)(HX^-)/(H2X) ...
October 24, 2016

chem
The atom must become excited by absorbing energy from some source.
October 24, 2016

oops--typo--Chemistry - acids & bases
I'm sure you picked it up but that's 0.115 M from the problem and not 0.15. My typo.
October 24, 2016

Chemistry - acids & bases
Nope. You used millimols in this and you should use molarity. Ka is 1.8E-5, yes, but that is Ka = (H3O^+)(Ac^-)/(HAc) and you must substitute M and not mmols. If acetic acid is HAc, then .......HAc+ + H2O ==> Ac^- + H3O^+ I......0.15..........0......0 C......-x................
October 24, 2016

Chemistry
Look up Henry's constant for CO2 in H2O. Be careful because there may be two constants depending upon how the equation is used. I use p = KcC. Substitute and solve for C, then convert to pH.
October 24, 2016

Chemistry
7 in x (2.54 cm/in) x (1 m/100 cm)= ? meters = wavelength Then c = freq x wavlength You know c and wavelength, calculate freq
October 24, 2016

Chemistry
Take 10 mL of the 0.5 M acid and add enough water to make 30 mL
October 24, 2016

Chemistry
A = grams acetone E = grams ethanol dA = density acetone dE = density ethanol VA = volume acetone VE = volume ethanol ------------------ You want the volume to be 1000 mL; therefore, VA + VE = 1000 mL but since volume = mass/density, then A/dA + E/dE = 1000....eqn 1 Two ...
October 24, 2016

Chemistry
Separate this into the net molecular equation first. H^+(aq) + Cl^-(aq) + Li^+(aq) + OH^-(aq) ==> Li^+(aq) + Cl^-(aq) + H2O(l) To turn this into the NET ionic equation, just cancel those species that appear on both sides. So you cancel Cl^-(aq) on the left and right and ...
October 24, 2016

Chemistry
2 m^3 x (100 cm/m)^3 = ? cm^3 1E4 kg x (1000 g/kg) = ? Then density = mass in g/volume in cm^3
October 24, 2016

chemistry
All reactions reach an equilibrium. Some do so at 99.99999% complete while others are at 20% or so and others at 0.000001% or so. Reactions occur if the energy of the products is less than the energy of the reactants and the activation energy is not too high.
October 24, 2016

Chemistry
Convert 0 F to C. C = (F-32)*5/9 = ? That's approx -17.78 delta T = Kf*m 17.78 = 1.86*m Solve for molality. Then m = mol/kg solvent You have m and kg H2O, solve for mols ethanol. Finally, mols ethanol = grams/molar mass. You have molar mass and mols, solve for grams. Post ...
October 24, 2016

Chemistry
Did all of the Fe react? Then mols Fe = grams Fe/atomic mass Fe = ?
October 23, 2016

Chem
What are the units? -6.00 what? 1. dHrxn = (n*Gf products)-(n*dGf reactants). 2. dG = -RTlnK 3. Kp = pO2
October 23, 2016

Chemistry
H2 + 2OH^- ==> 2H2O + 2e Fe^3+ + e ==> Fe^2+ Multiply eqb 1 bt 1 and eqn 2 by 2, then add.
October 23, 2016

Chemistry need asap
a. The equation looks ok to me. b. mols NO = 0.5g/molar mass NO = ? mols O2 = 0.4 g/molar mass NO = ? mols H2O = 12/molar mass H2O = ? Now convert each of the mols above to mols HNO3 produced. This is a limiting reagent (LR) problem and the smaller number of mols will be ...
October 23, 2016

Chemistry
You need to proof your post and correct it.
October 23, 2016

chemistry
First line Lyman Series is transition from n2 = 2 to n1 = 1 E = Eo(1/1^2 - 1/2^2) E = 2.18E-18(1-1/4) E = 2.18E-18(1-0.25) E = 2.18E-18(3/4)
October 23, 2016

Chemistry
MO + H2 ==>M + H2O 0.090 x (molar mass MO/molar mass H2O) = 0.3975 Solve for molar mass MO, subtract 18 to arrive at atomic mass M.
October 22, 2016

Chemistry
I don't like any of the answers but 2 comes the closest, I think. What actually happens is that the atom absorbs the energy, electrons move from a lower orbit to a higher orbit THEN (and I emphasize THEN) the electron falls back to a lower level and emits electromagnetic ...
October 22, 2016

Chemistry
(1/wavelength) = R(1/1^2 - 1/2^2) Look up R. That's the Rydberg constant. It's about 1.09 E7
October 22, 2016

Chemistry
yes, E divided by h. f = E/h
October 22, 2016

Chemistry
Pick a number. You don't have T or V listed. You need those to answer.
October 22, 2016

Chemistry
2Na + 2H2O ==> 2NaOH + H2 mols Na = 0.05. g Na = mols Na x atomic mass Na = ?
October 22, 2016

BioChemistry
mols = M x L = ?
October 22, 2016

Chemistry
pH = -log(H^+) Substitute and solve.
October 22, 2016

Biochemistry
Your question is not clear to me.
October 22, 2016

Chemistry
I don't think you have enough information. How much PCl5 do you have (pressure or M)?
October 22, 2016

chemistry
(1/wavelength) = RZ^2(1/n^2 - 1/n^2) (1/wavelength) = RZ^2*(1/1^2 - 1/x^2) and solve for x. R = Rydberg constant = 1.0973732 The first n is n = 1 and the second n is n = 2; that's where the 1/1^2 and 1/x^2 come from. Z is the atomic number of the element; in this case that...
October 21, 2016

Chemistry
I don't believe this problem can be solved without using the 0.38 J/g*C as a starting point. I looked that up in a table and found the two closest elements were Zn and Cu. Basically, then, we decide which is the right one. ........M + Cl2 ==> MCl2 ....0.5007 + x .....1....
October 21, 2016

Chemistry
Cu(NO3)2(s) + H2O(l) ==> Cu^2+(aq) + 2NO3^-(aq)
October 21, 2016

chemistry
I presume the 17% means that work from the milk is 3.0 kJ/g x 390 g x 0.17 = ? kJ of work. Then plug this into work = mgh as shown in the problem and solve for h = height in meters.
October 21, 2016

chemistry
First you must determine if the Cu goes through a phase change (i.e., melting) before it reaches 337.3, (it doesn't) so q = mcdT
October 21, 2016

chemistry
Your set up looks ok but I don't get that answer when I do the math using your numbers. I get something like 50.2. By the way, I looked up Fe and found 0.444 but I assume you are using numbers supplied with the problem.
October 21, 2016

chemistry
q = [mass H2O x specific heat H2O x (delta T)] + (Ccal*delta T)
October 21, 2016

CHEMISTRY FOR ENGINEERS
Note that you will need to change A to meters; also, wave number = 1/wavelength
October 21, 2016

Chemistry
You want XNaOH = 0.03. Then 0.03 = mols NaOH/[mols NaOH +(mols H2O-mols NaOH)] If you let y stand for mols NaOH, this becomes 0.03 = y/[y+(100/18)-y] Solve for y = mols NaOH. Post your work if you get stuck.
October 21, 2016

Chemistry
I don't think you typed all of the problem/question. You get mass H2O from mass = volume x density and that will answer your posted question. However, most of these problems want to calculate delta H, usually in kJ/mol. That is done as follows: q = mass H2O x specific heat...
October 20, 2016

Analytical chemistry
A good factor to remember is 1 ppm = 1 mg/L so 1000 ppm would be 1000 mg/L So you want1000 mg (that's 1 gram) MgCO3 in a L of solution.
October 20, 2016

chemistry
1 ppm = 1 mg/L 1 ppm = 1 mg x (25/1000) = 0.025 mg/25 mL. You want 0.02 ppm so 0.02 x 0.025 = ? mg solute in 25 mL solution.
October 20, 2016

Chemistry
I don't know your problem but all you need to do is to think of any sentence starting with that "next" letter. The following won't went a Pulitzer Prize but it answers the question. Now is the time, Or any time for that matter, No matter how little or late, ...
October 20, 2016

chemistry need help
Cr^3+ + 4H2O==> CrO4^2- + 3e + 8H^+ BrO^- + 2e + 2H^+ ==> Br^- + H2O -------------------------------- Multiply eqn 1 by 2 and eqn 2 by 3, then add to obtain the complete balanced redox equation.
October 20, 2016

CHEMISTRY
a. bubbles b. rxn decreases with time c. ran how of marble chips d. 1. incrase concn HCl 2. increase surface area of chips by breaking them apart into smaller pieces.
October 20, 2016

@ b.k.---chemistry
Yes, you should use 1/50, calculate as shown above but x will be concentration and not mols. Then convert x = concentration in mols/L to mols.
October 20, 2016

Chemistry
You don't have enough information to even estimate an answer, much less obtain a real answer. Also, my crystal ball isn't working today.
October 20, 2016

Chemistry
q1 = heat need to change temperature of solid ice at -45 C to solid ice at 0 C. q1 = mass ice x specific heat solid ice x (Tfinal-Tinitial) q2 = heat needed to change solid ice at 0 C to liquid water at 0 C. q2 = mass ice x heat fusion water. Total q = q1 + q2
October 19, 2016

Chemistry
That's my answer also.
October 19, 2016

Chemistry
I worked this for someone just a day or so ago but I can't find it. Here is a summary. This is a limiting reagent (LR) problem and you know that because amounts are given for BOTH reactants. N2 + 3H2 ==> 2NH3 mols N2 = grams/molar mass = ? mols H2 = grams/molar mass...
October 19, 2016

Chemis6
C6H12O6 → 2C2H5OH + 2CO2 mols ethanol needed = grams/molar mass Using the coefficients in the balanced equation, convert mols ethanol to mols glucose Now convert mols glucose to grams. g = mols x molar mass = ? Post your work if you get stuck.
October 19, 2016

Chemistry
PCl5 ==> PCl3 + Cl2 Is this 100% reaction or must you use the Keq (which you don't list).
October 19, 2016

Chemistry
Here is a similar problem. Just change the numbers. http://www.jiskha.com/display.cgi?id=1442613787
October 19, 2016

Chemistry
See your post above.
October 19, 2016

Chem
Bob Pursley worked this problem for you that I saw this A.M. Look for it. Click on bob Pursley's answers and you can find it.
October 19, 2016

chemistry
The answer by Ashley is correct but the equation is not. Here is the correct equation. Zn + 2HCL-->ZnCl2 + H2
October 19, 2016

Science
distance = rate x time 500 mi = 500 mi/hr x time. Solve for time in hours.
October 19, 2016

Chemistry
for f.p. delta T =i*Kf*m i = 3 for Na2SO4 m you have look up Kf. Subtract delta T from 0 C to find new f.p. for b.p. delta T = i*Kb*m look up Kb. You have m and i, add delta T to 100 C to find new boiling point.
October 19, 2016

chemistry
[mass Pb x specific heat Pb x (Tfinal-Tinitial)] + [mass H2O x specific heat H2O x (Tfinal-Tinitial)] = 0 The only unknown here is Tfinal
October 19, 2016

chemistry
See your previous post. Same kind of problem. Post your work if you get stuck.
October 19, 2016

chemistry
Wouldn't you think N2 < NO2 < KCl?
October 19, 2016

beginning algebra
Plug in 1 for x and solve for y. Plug in 2ffor x and solve for y. Plug in 3 for x and solve for y. Need more? Plug in a number for x or y and solve for the other.
October 19, 2016

Chemistry
(V1/T1) = (V2/T2)
October 19, 2016

Chem
It helps us help you better when you use the same screen name. You didn't do that but see your other post above.
October 19, 2016

chemistry
KCl + Br2 = no reaction
October 19, 2016

chemistry
no reaction. Cl2 and KBr is yes, Br2 and KCl none.
October 19, 2016

chemisty
1 mol of atoms contains 6.02E23 atoms.
October 18, 2016

chemi
See your other post.
October 18, 2016

chemistry
1 mol of molecules contains 6.02E23 molecules.
October 18, 2016

chemistry
See your other posts. All of these are essentially duplicate posts. There are 6.02E23 anythings in 1 mol of anythings.
October 18, 2016

chemistry
Your question is poorly worded in my opinion. By my definitions, if the H2SO4 is neutralized then there will not be ANY H2SO4 left. What the problem means, I think, is after the addition of that much KOH to that much H2SO4, what is the concn of H2SO4. H2SO4 + 2NaOH ==> ...
October 18, 2016

Chemistry
It's tough reading with no caps and no periods and/or question marks. Yes, ice water Ti is 0 and Tf final T of solution. Ti for warm water is unknown. Tf is same for ice water and warm water.
October 18, 2016

Chemistry
heat gained by ice water (you know both Tfinal and Tinitial) + heat lost by warmer water (Tfinal which you know and Tinitial which you don't know) = 0. What's the only unknown in the equation?
October 18, 2016

Chemistry
Reacted with what? O2? 2C2H2 + 5O2 ==> 4CO2 + 2H2O mols C2H2 = grams/molar mass = ? Then H2O = mols C2H2 x (2 mols H2O/2 mols C2H2) = ? mols H2O Convert mols H2O to grams. grams H2O = mols H2O x molar mass H2O
October 18, 2016

chemistry
I don't understand what you want with a skeleton equation. But here is the equation. CuCl2 + Li ==> LiCl + Cu You can balance it?
October 18, 2016

chemistry
See your other post.
October 18, 2016

Chemistry
Ksp AgI = (Ag^+)(I^-) You know Ksp and I^-, solve for Ag^+. Same for AgBr and AgCl. b part. What is Ag^+ when AgBr first ppts. You calculated that above. Plug Ag+ from the AgBr when it first ppt into Ksp for AgI to find the I^- concn when AgBr starts. Then %I left at that ...
October 18, 2016

Chemistry
ok
October 18, 2016

chemistry
dq = mass Au x heat fusion
October 18, 2016

chemistry
q = mass ethyl alcohol x heat vap
October 18, 2016

Chemistry
You didn't quit soon enough. The answer is 25 cc = volume. That's the end of the problem. The problem DID NOT ask for the volume of the sides and even if it had the problem didn't say it was a cube with equal dimensions.
October 18, 2016

chemistry
See your posts above.
October 18, 2016

Chemistry
Almost. I arrived at 14.77 on my calculator, also, but you are allowed only three significant figures. So that 14.77 is rounded to 14.8 g
October 18, 2016

CHEM 1411
g CaSO4 = 0.0.6168 x (molar mass CaSO4/molar mass BaSO4) = ? Then % CaSO4 = (g CaSO4/mass sample)*100 = ? mass of sample is 0.4550g
October 18, 2016

Chemistry
0.177, not 0.1777. Then 0.000522 = 0.177/x x = 0.177/0.000522 = 338.9 which rounds to 339. Your line three doesn't follow from line 2. Line 2, except for the extra 7 in the grams is ok. I don't know where the 380 came from. If you had finished and shown how you ...
October 17, 2016

Chemistry
You leave us in the dark with this. Instead of saying you tried everything, post what you tried and let us find the error. This we're playing guessing games.
October 17, 2016

Chemistry
I don't see any answer you posted; I see only questions. NaOH + HA ==> NaA + H2O 1 mol NaOH = 1 mol HA so mols NaOH from above = mols HA. Then mols = grams/molar mass or molar mass = grams/mols. If you did g/mols, I suggest you post your work and let us look at it.
October 17, 2016

Chemistry
mols = M x L = ?
October 17, 2016

Chemistry
You need to provide us information on what you were doing.
October 17, 2016

Chemistry
Are you sure that was 0.7374 g Ca? or was it CaCO3. The answer below is for 0.7374 g Ca. 0.7374 x (molar mass Ca citrate/atomic mass Ca) = ? For other metals look for other carbonates that are insoluble; ;i.e., Mg might be one.
October 17, 2016

honors chem
(0.8020*11.01)+(0.1980*x) = 10.81 Solve for x
October 17, 2016

Chemistry Plz Help!
Starting with what?
October 17, 2016

Thermochemistry
What reaction?
October 17, 2016

chemistry
0.5 what? KCO3. No such animal.
October 17, 2016

chemistry
Kd = 4.0 = [(x/20)/(100-x)/50] Solve for x = amount in the methylene chloride layer. 100-x is the amount in the water.
October 17, 2016

chemistry
% mass w/w means (gsolute/total g)*100 = ? [17.35/(17.35+x)]*100 =22.5 Solve for x
October 17, 2016

Chemistry
A two-step problem. First, determine the specific heat of Co from sample A. q = mass Co x specific heat Co x (Tfinal-Tinitial). The only unknown in this equation is specific heat Co in sample A. Specific heat doesn't change. NHow use the same formula for sample B of Co. q...
October 17, 2016

Chemistry
I worked a problem just like this last night. Post your work if you run into trouble. http://www.jiskha.com/display.cgi?id=1476638100
October 17, 2016

Chemistry
See your other post above.
October 17, 2016

Chemistry
glad you figured it out.
October 17, 2016

Inorganic Chemistry
1.577 M is 1.577 mols/L solution. With density = 1.220 g/mL, then substitute volume and density to find mass of the solution. 1.577 mols AgNO3 x molar mass AgNO3 = grams AgNO3. Then mass solution - g AgNO3 = mass solvent. Convert that to kg. m = 1.577 mols AgNO3/kg solvent
October 16, 2016

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