Sunday
July 24, 2016

Posts by DrBob222

Total # Posts: 52,747

Chemistry
dGrxn = dGproducts - dGreactants Then dGrxn = -nFEo Solve for Eo.
March 16, 2016

chemistry
The hint tells you how to work the problem. mols NaOH = M x L = ? mols acid = mols NaOH since it is 1:1 ratio. Then M acid = mols acid/L acid = ?
March 16, 2016

Chemistry
This done the same way as you other acid/NaOH problem. The only difference is in this problem the acid is given a name and they want grams and not M. KHP + NaOH ==> NaKP mols NaOH = M x L = ? mols KHP = mols NaOH Then mols KHP = grams KHP/molar mass KHP. You know molar mass...
March 16, 2016

chemistry
I assume you want to prepare 500 cc of the CuSO4. How many mols do you want? That's M x L = 0.1 x 0.500 = ? Then convert to grams. g = mols x molar mass = ?
March 16, 2016

Chemistry DR BOB
I assume you mean the reaction in which electrons flow from the anode to the cathode spontaneously. Anode is on the left, it is oxidized; therefore, Eo oxidation = -0.37 Cathode is on the right so it receives the electrons and it is reduced so Eo redn = 0.67. EoCell = Eox + ...
March 16, 2016

Analytical Chem
Use PV = nRT and solve for pSO3 at the beginning and at equilibrium. I obtained about 1 for pSO3 initially but you need to get a more accurate answer. Then ..........2SO3 ==> 2SO2 + O2 I.........1.0.......0......0 C.........-2x.......2x.....x E........1.0-2x.....2x.....s ...
March 16, 2016

chemestry
Just as an add on, you really need to learn to spell chemistry correctly.
March 16, 2016

chemestry
Let's think about this. If a neutral solution is 1E-7 M for (H^+) and 1E-7 M for (OH^-), that means for the solution to be basic the (OH^-) must be larger than 1E-7 M. Is 4.2E-8 M larger than 1E-7 M?
March 16, 2016

chemestry
The correct answer is "none of these" which is not a choice. The answer your prof wants is B but that isn't correct. Many texts, if you can find the problem addressed, explains this very well but many texts don't even address this segment of chemistry. I have...
March 16, 2016

chemestry
Yes, A is the correct answer. In the acid, HA, it ionizes as HA ==> H^+ + A^- Ka = (H^+)(A^-)/(HA) The acidity of a solution depends upon the (H^+) so the higher that is the stronger the acid. Look at Ka values. If Ka is large then the numerator (the H^+) is larger. For the...
March 16, 2016

Chem
XH2SO4 = 0.2 so XH2O = 0.8 Take 1 mol of the solution. That will contain 0.8 mols H2O. How many grams is that? 0.8 mol x 18 gH2O/mol = 14.4 g or 0.0144 kg. molality = mols H2SO4/kg solvent 0.2/0.0144 = ?m
March 16, 2016

Chemistry
Yes, that final post looks good. Good work.
March 15, 2016

Chemistry
You need to learn to do these by yourself and me doing them will not help you. Here is a site that will help or if you have trouble show what you can do and explain fully what you don't understand about the next step. Cr goes from +6 on the left(for each) to 3+ on the ...
March 15, 2016

Chemistry
The numbers may be slightly different but the process is the same. http://www.jiskha.com/display.cgi?id=1458010856
March 15, 2016

Chemestry
I would convert 100 mM to M and mL to L. Then, how many mols do you need? That's mol = M x L = ? Next step is grams = mols NaCl x molar mass NaCl = ?
March 15, 2016

Chemestry
See your other post. Same process.
March 15, 2016

Chemistry
pH = 9 means pOH = 5 so (OH^-) = 1E-5 Substitute and solve for Qsp. Qsp = (Cd^2+)(OH^-)^2 and compare that with Ksp. If Ksp is smaller there is a ppt. If Ksp is larger there is no ppt.
March 15, 2016

Chemistry
I assume the 0.145m is a typo and you meant 0.145 M. Also I assume you meant NaOH and not naoh which means nothing to me. 2NaOH + H2SO4 ==> Na2SO4 + 2H2O mols H2SO4 = M x L = ? Using the coefficients in the balanced equation, convert mols H2SO4 to mols NaOH. That's mols...
March 15, 2016

chemestry
no. A has the least.
March 15, 2016

chemestry
Absolutely no.
March 15, 2016

Chemistry
Ba(OH)2 + 2HNO3 -> Ba(NO3)2 + 2H2O mols Ba(OH)2 = M x L = ? mols HNO3 = 2x that (look at the coefficients). Then M HNO3 = mols HNO3/L HNO3.
March 14, 2016

Chemistry
(mass solute/mass soln) = 0.06
March 14, 2016

Chemistry
How many mols do you need? That's mols = M x L = ? Then mols = grams/molar mass. You know molar mass and mols, solve for grams.
March 14, 2016

Unscramble
You might want to check your spelling/typing.
March 14, 2016

Chemistry
Volumes are not additive.
March 14, 2016

chemistry
Write the molecular equation and balance it. CrBr3(aq) + K3PO4(aq) ==> CrPO4(s) + 3KBr(aq) Separate into the complete ionic equation. It should be obvious that the aq solutions ionize and the solid is shows as the molecule since it doesn't dissolve. Cr^3+(aq) + 3Br^-(aq...
March 13, 2016

Chemistry
How many moles do you need? That's mols = M x L = ? Now mols = grams/molar mass. You know molar mass and mols, solve for grams.
March 13, 2016

chemistry
The problem isn't worded very well. Calculate the concn IN WHAT UNITS. BELOW IS THE COnCN IN M = mols/L For part b M NaOH in 1 L is: 1000 mL x 1.19 g/mL x 0.70 x 1/molar mass NaOH = ? approx 33 M Then use the dilution formula for part C. mL1 x M1 = mL2 x M2 250 x 0.1 = mL2...
March 12, 2016

chem 121
2HClO4 + Ba(OH)2 ==> Ba(ClO4)2 + 2H2O mols HClO4 = M x L = ? mols Ba(OH)2 = 1/2 mols HClO4 (from the coefficients in the balanced equation) Then mols Ba(OH)2 = M x L. You know mols and M, solve for L.
March 12, 2016

Chemistry- DrBob222
........HA <----> H+ + A- I.....0.05........0.....0 C....-5E-5........5E-5..5E-5 E......?..........5E-5..5E-5 Substitute the E line (after evaluation 0.05-5E-5) and solve for Ka.
March 12, 2016

Chemistry
I suggest you check the numbers.
March 12, 2016

Chemistry-DrBob222
Close but not there. Since that other problem was close, too, perhaps you are not rounding right. Post your work here and I will check it. MY answer is 63.2 mL.
March 12, 2016

Chemistry -DrBob222
Looks ok to me.
March 12, 2016

Chemistry-DrBob222
I get 167 but that difference may be due to rounding errors.
March 12, 2016

Chemistry
A and B look ok to me but I don't agree with C.
March 12, 2016

chem 12
right
March 12, 2016

General Chemistry
I think the secret is "assuming that all dissolved CO2 is present as H2CO3". .......H2CO3 ==> H^+ + HCO3^- I.......0.12......0.....0 C.......-x........x.....x E......0.12-x.....x.....x Set up the E line into k1 and solve for H^+ and convert to pH.
March 11, 2016

Chemistry
No, of course not. It depends upon how much of each reactant is present.
March 11, 2016

Chemistry-DrBob222
I'm not sure I understand the question. The assumptions don't change the way you work the problem; i.e., no heat is lost is obvious and it means density of the solution is 1.00 g/mL which means mass of the solution is 30.0 grams.
March 11, 2016

Chemistry
I worked c the same way you did and another way and got the same answer each way. Then I used both ways to to do A and came up with your answer. I assume the others are ok. Here is the OTHER way to do density. Density at STP is 32/22.4 = about 1.43 g/L. Not convert from STP to...
March 11, 2016

Chemistry
No. The temperature increased from 15 to 26.5 and that makes it an exothermic reaction so dH is -.
March 11, 2016

Chemistry- DrBob222
See above
March 11, 2016

Inorganic Chemistry
q = mass H2O x 4.184 x 4.63 x 1/1000 = ? kJ heat produced. That is for 0.680 x 0.07 mols H2O = ? So dHrxn is q/mols = ?. I think the answer is about 56 kJ/mol or so.
March 11, 2016

chemistry
os h what What does 6m mean?
March 10, 2016

chemistry
Use the Henderson-Hasselbalch equation.
March 9, 2016

Chemistry
What's the density?
March 9, 2016

Chemistry
You need more information than that. density? molarity? molality? something. The stuff sold in grocery stores is approximately 3-5%.
March 9, 2016

chemistry
pH = pK3 + (K3PO4^3-)/(K2HPO4^2-) Plug in the numbers and solve for (K2HPO4^2-) in M = mols/L. Then mols = M x L = ? and mols = grams/molar mass. You know molar mass and mols, solvle for grams.
March 9, 2016

chemistry
Saturated.
March 9, 2016

chemistry
mols Sb2S3 = 3.87E23/6.02E23 = ? Then mols Sb2S3 x (3 mols FeS/1 mol Sb2S3) = ? Finally, grams = mols x molar mass
March 9, 2016

chemistry
Use the coefficients to tell you. 13.7 mols N2 x (4 mols NH3/5 mols N2) = ? mols NH3 13.7 mols N2 x (6 mols NO/5 mols N2) = ? mols NO
March 9, 2016

chemistry
EMF = ? Add the oxidation half to the reduction half. Use pH = -log (H^+) for the other two.
March 9, 2016

chemistry
I don't see a question here.
March 9, 2016

chemistry
q1 = heat needed to raise T ice froom -20 to zero C. q1 = mass ice x specific heat ice x (Tfinal-Tinitial) q2 = heat needed to melt ice @ zero C to liquid water @ zero C. q2 = mass ice x heat fusion ice. q3 = heat needed to raise T water at zero to 100 C. q3 = mass water x ...
March 9, 2016

Chemistry-DrBob222
mols Mg = grams/molar mass = ? Using the coefficients in the balanced equation, convert mols Mg to mols H2. That is a 1:1 so mols Mg = mols H2. Then use PV = nRT to solve for volume in L and convert to mL. For n use mols from above. R and T are the usual. For P use Ptotal = ...
March 8, 2016

Chemistry
A is ok but you didn't calculate the total pressure. Of course, it's 2.2 atm. B. You want XO2 to be 0.5 (pO2/Ptotal) = 0.5 What must total pressure be. (1.6/y) = 0.5 Solve for y and you get 3.2 for the total pressure; i.e., that way, 1.6/3.2 = 0.5 So what pAr is needed...
March 8, 2016

Chemistry
q = mass H2O x heat vaporization = ?
March 8, 2016

Chemistry
See your post above.
March 8, 2016

Chemistry
Do you know the definition. M = mols/L. You know mols and you know L. Substitute and solvle for M.
March 8, 2016

chemistry
mass pure CaCO3 initially. 200 x 0.95 = 190 g. Then 190 g CaCO3 x (molar mass CaO/molar mass CaCO3) = ?
March 8, 2016

Chemistry
mL1 x M1 = mL2 x M2 10 x 12 = 250 x M2. Solve for M2.
March 8, 2016

Chemistry
This is not a chemistry problem to me. Frankly, I call this a stoichiometry problem but I don't know that it makes any difference what one calls it. Many students call it a "I don't know how to work this problem" problem.
March 7, 2016

Chemistry
sulfur trioxide ==> sulfur + oxygen The second equation will not react to produce anything. The names are potaqssium iodide + magnesium chloride --> Magnesium iodide + potassium chloride.
March 7, 2016

Chemistry
http://academics.wellesley.edu/Chemistry/chem211lab/Orgo_Lab_Manual/Appendix/ClassificationTests/phenol_amine_nitro.html#IronChloride
March 7, 2016

Chemsistry
H3O^+(aq) + CaCO3(s) => Ca^2+(aq) + (HCO3^-)(aq) + H2O(l)
March 7, 2016

Chemistry
I don't get all of the mumbo jumbo at the end of the question. I assume you want this. ..........NH4Cl --> NH3 + HCl If pNH3 is 1.51 atm then pHCl is 1.51 atm. Plug These numbers into the Kp expression and solve. Kp = pNH3*pHCl Kp = (1.51)(1.51) = ? Note that NH4Cl ...
March 7, 2016

Chemistry
delta T = i*Kb*m delta T = 4.4 i for CaCl2 = 3 Kb for water you know solve for m.
March 7, 2016

Chemistry
20 x (2*atomic mass Na/molar mass Na2CO3) = ?
March 7, 2016

CHEMISTRY HELP
mols Al = grams/molar mass = ? Using the coefficients in the balanced equation, convert mols Al to mols H2. Then remember that 1 mol H2 occupies 22.4 L at STP.
March 6, 2016

chem
A word to the wise. When you answer a question with JUST an answer you don't help us find the error. ALWAYS show your work of how you obtained that answer so we can go through the math with you. I suspect you either substituted incorrectly or you made a math error.
March 6, 2016

chem
.......NiO(s)+CO(g)⇌Ni(s)+CO2(g) I......solid..0.1....solid..0 C......solid...-x....solid..x E......solid..0.1-x..solid..x Substitute the E into the Kc expression and solve for x. Remember that NiO and Ni are NOT included in the Kc expression.
March 6, 2016

Chemistry
According to this web site the cardboard (coated with plastic) is better. Read about it here. http://www.slate.com/articles/health_and_science/the_green_lantern/2011/03/disoriented_in_the_dairy_aisle.html
March 6, 2016

Chemistry
1a. 5 mL added. (HCl) = 0.1M x 5 mL/105 mL = ?. Convert to pH. 10 mL and 100 mL are done the same way. 1b. millimols HCl added = 5 x 0.1 =0.5 mmols HAc = mL x M = about 150 mmols Ac&- = about 120 .......Ac^- + H^+ ==> HAc I......120....0........150 add..........0.5...
March 6, 2016

Chemistry
See your other post above.
March 6, 2016

Chemistry
I don't see a question here.
March 6, 2016

Chemistry
What does this mean? "Name each compound by ionic, hydrogen, or molecular compound."
March 6, 2016

Chemistry
Dalton's Law of Partial Pressure. Ptotal = 1.023 atm from problem. pH2O = 42.2 mm Hg from problem. Depending upon how the answer is to be displayed (mm Hg or atm),convert one of the above into the other unit and use Dalton's law. Ptotla = pH2 + pH2O You know Ptotal and...
March 6, 2016

Chemistry
HC2H3O2 = HAc. [C2H3O2]^- = Ac^- It is easier to work in millimoles which I will do. Technically it isn't proper to use mols or millimols in the HH equation; however, since M = millimoles/mL and you have mmols/mL in numerator and denominator of the HH equation, the answer ...
March 6, 2016

Chemistry
See your other post above.
March 6, 2016

chemistry
H2SO4 + 2NaOH ==> Na2SO4 + 2H2O mols H2SO4 = grams/molar mass = ? Using the coefficients in the balanced equation, convert mols H2SO4 to mols NaOH. Then g NaOH = mols NaOH x molar mass NaOH = ?
March 6, 2016

chemistry12_1
N2 is 28 x 0.80 = approx 23 O2 is 32 x 0.20 = approx 6 Total approx 29
March 6, 2016

chemistry
Ca(HCO3)2 + 2HCl ==> CaCl2 + 2CO2 + 2H2O
March 6, 2016

chemistry
That are these? What are the units? H20=-228.6 NO= 86.69 N2H4= 159.3 02 = 0 If this is delta G, then dGrxn = (n*dGproducts)-(n*dG reactants) Then dGrxn = -RTlnK YOu know dGrxn, R, T, solve for K.
March 5, 2016

chemistry
You need to learn how to type the arrow. --> or ==> See your post under Lia. Same process. Post your work if you get stuck.
March 5, 2016

@Lia--chemistry
My guess is that's the red cabbage indicator question.
March 5, 2016

Chemisrty
HClO4 is strong acid. pH VERY low. HBrO is a weak acid. pH higher than HClO4 but still lower than 7. NH3 is a weak base. pH slightly more than 7 (maybe 8.5-10). Ca(OH)2 is strong base. Greater than NH3 but less than KOH. KOH is a very strong base and is VERY much higher than ...
March 5, 2016

chemistry12_2016
See your other post.
March 5, 2016

chemistry12
CaCO3 ==> CaO + CO2 mols CaCO3 = grams/molar mass = ? Using the coefficients in the balanced equation, convert mols CaCO3 to mols CaO. That's 1:1 so mols CaCO3 = mols CaO. Then g CaO = mols CaO x molar mass CaO.
March 5, 2016

chemistry
See your other posts with different screen names.
March 5, 2016

chemistry
You're asking the same question and apparently not doing much work of your own. Yes, it is a simple lab. No, it isn't a simpler answer. I searched Google, which you could do too, and finally came up with this equation. Red cabbage has a flavenoid in it. The particular ...
March 5, 2016

Chemistry
I may have missed something here but I don't think equilibrium ever stops working. If the equilibrium is disturbed, it MUST redirect itself so as to reach equilibrium again. And that will continue as long as something is changing.
March 5, 2016

Chemistry
What were you titrating? HOAc? What were you titrating with? NaOH or similar? Take the volume of base you added, add 20 mL to that and that is the final volume. The OAc^- then will be (in molarity) mols HOAc you started with divided by the final volume in L.
March 4, 2016

Chemestry
mols acetic acid (HAc) = grams/molar mass = ? mols KOH = mols HAc (look at the coefficients in the balanced equation. M KOH = mols KOH/L KOH. You know mols and M, solve for L and convert to mL if needed.
March 4, 2016

Chem
Are you assuming all form compounds with Pb^4+ Pb(CN)4 Pb(SO4)2 Pb(ClO3)4 Pb(H2PO4)4
March 4, 2016

chemistry
You're making it harder than it is. Mo(NO3)2.5H2O. 1 mole salt to 5 mols H2O. CaSO4.2H2O 1 mol salt to 2 mols H2O
March 4, 2016

Chemistry
Frankly, I don't know what you did in the red cabbage experiment. Without knowing what you did it's tough to answer any questions about it. That's why I gave you a link. If you google it you can find a lot of information.
March 4, 2016

Chemistry
You've done the hard part. (Na2SO4.6H2O) = 1.2 M. Now there is 1 sulfate/1 Na2SO4 so (SO4^2-) must the same as (Na2SO4). Right? Right. Now there are 2 Na/1 Na2SO4 so (Na^+) = 2 x (Na2SO4) = 2*1.2 = 2.4. Right?
March 4, 2016

Chemistry 101
See your other post.
March 4, 2016

Chemistry
mols = M x L = ? Then mols = g/molar mass. You know mols and molar mass, solve for grams.
March 4, 2016

Chemistry
It seems obvious to me that if you put more molecules together there must be a better and increasing chance that they will bump into each other. Right?
March 4, 2016

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