Thursday
May 5, 2016

Posts by DrBob222

Total # Posts: 52,253

chemistry
Is this a liquid? What's the density?
November 25, 2015

Chemistry
NH4CN NH4ClO3 (NH4)2SO4 etc.
November 25, 2015

Chemistry
You have it. Congrats!
November 25, 2015

Chemistry
Yes, that's what you do.
November 25, 2015

chemistry
Add water, Na2CO3 dissolves, filter, PbCO3 stays in the paper and dissolved Na2CO3 goes through as the solution. Dry the PbCO3 and you have the dry solid.
November 25, 2015

Chemistry
1. Use the Henderson-Hasselbalch equation. KaKb = Kw and you get Ka from that and pKa follows. 2. Ditto for 2. 3. Ditto for 3.
November 25, 2015

Chemistry
2Mg + O2 ==> MgO So 1 mol Mg will take 1/2 mol O2.
November 24, 2015

Chemistry
Which copper oxide; ie., CuO or Cu2O.
November 24, 2015

Chemistry
5% what? w/w or w/v. I'll assume w/v 5% HCOOH is 5 g HCOOH/100 mL. mols in 5g is 5/48 = about 0.1 mol and that in 0.1 L is 1 M. 5% CH3COOH is 5g/100 mL. mols in 5g CH3COOH is 5/60 = about 0.08 and tht in 0.1L is 0.8 M So the reach the eq point you will have mols HCOOH = M ...
November 24, 2015

Chemistry
Because it can dissociate OR add a H^+. As a base: HSO4^- + H^+ ==> H2SO4 As an acid: HSO4^- ==> H^+ + SO4^2-
November 23, 2015

chemistry
Not quite it. mols Zn = grams/molar mass (Zn, not ZnCl2) Convert mols Zn to mols HCl. That 2 is right. Then M HCl = mols HCl/L HCl. You know mols and M, solve for L ad convert to mL.
November 23, 2015

chemistry
XCO2 = mols CO2/total mols.
November 23, 2015

Chemistry
How many mols NaOH in 5.61? That's mols = grams/molar mass = ? How many molos in the solution. That is mols = M x L = ? Total mols NaOH = sum of the two above = ? M = mols/L solution. You know mols. Convert 2.16 gallons to L and add to the 627 for total volume.
November 23, 2015

Chemistry
We can't draw structures on this forum but this may help. https://www.google.com/search?q=lewis+structure+salicylic+acid&ie=utf-8&oe=utf-8
November 23, 2015

Chemistry
n = mols = grams/molar mass = ? Then use pV = nRT. OR you can use the fact that 1 mol of a gas at STP occupies 22.4 L.
November 23, 2015

chem 101
mL1 x M1 = mL2 x M2 mL1 x 18 = 1000 mL x 6 M Take the volume calculated, pipet that into a 1000 mL volumetric flask, make to the mark. Shake thoroughly and stopper.
November 23, 2015

chemistry
We can't draw on this forum.
November 23, 2015

chemistry
The symbols are garbled.
November 23, 2015

Chemistry
Use PV = nRT and solve for n = mols gas. Then n = grams/molar mass. You know grams and n, solve for molar mass.
November 23, 2015

chemistry
No can do diagrams, sketches, pictures, etc on this forum.
November 22, 2015

Chemistry
.........2H2S(g)⇌2H2(g)+S2(g) I.......0.300...0.300....0 C........-2x......+2x...+x E......0.3-2x......2x....x Substitute the E line into Kc expression and solve for x = (S2)
November 22, 2015

Chemistry
F is the most electronegative.
November 22, 2015

Chemistry
Yes, I think it is but I think the question is nonsense.
November 22, 2015

Chemistry
I agree
November 22, 2015

chemistry
Hint: Find the caps key on your keyboard and learn to use it. CO, Co, and co all have different meanings. NaOH + HCl ==> NaCl + H2O
November 22, 2015

Chemistry
See your other post.
November 22, 2015

chem
How many mols CuCl2 do you need? That's M x L = 0.176 x 0.300 = ? How many grams is that? grams CuCl2 = mols CuCl2 x molar mass CuCl2 = ?
November 22, 2015

Chemistry
n = grams N2/molar mass N2 = ? Then use PV = nRT
November 22, 2015

Chemistry
For all of these just follow the definition that M = mols/L solution. a. mols NaCl = grams NaCl/molar mass NaCl Then M = mols L = ? b. M = mols/L. You know mols and M, solve for L. c. Convert 0.08g to mols. mols = grams/molar mass = ? That many mols in 0.1 L means ? mols ...
November 22, 2015

Chemistry
I can do this and you want learn anything. What is it you don't understand about how to do it. Bi goes from 3+ on the left to zero on the right. You should find the arrow key and use it. Co goes from zero on the left to 2| on the right.
November 20, 2015

chemistry
Cu ==> Cu^2+ + 2e Eo ox = ? 2H^+ + 2e ==> H2 Eo red = ? ------------------- Cu + 2H^+ ==> Cu^2+ + H2 Eocell = ? Then Ecell = Eocell - (0.05916/n)*logQ where Q = (pH2)(Cu^2+)/(Cu)(H^+)^2 You know Ecell is 0.070v. You know pH2 = 1 (it's standard H2 electrode). You ...
November 20, 2015

HELP RIGHT AWAY
I don't see a map. And indicate your SUBJECT so the appropriate expert can help you. Help right away doesn't tell anyone anything.
November 20, 2015

Chemistry
1. Balance the equation. 2. Using the coefficients in the balanced equation, convert mols NaN3 to mols Na.
November 20, 2015

General Chemistry
Reverse equation 1 and add to twice eqn 2 and twice equn 3. I didn't add dH to see that it comes out to -170 kJ but the equation you want is right so I assume the numbers will work.
November 20, 2015

CHEMISTRY
With no arrows I don't know where the reactants end and products start; however, dHrxn = (n*dHf products) - (n*dHf reactants) dHformation numbers can be found in your text/notes/web.
November 20, 2015

chemistry
Using the coefficients in the balanced equation, convert mols LiCl to mols Li2O. Then convert mols Li2O to grams by grams = mols x molar mass = ?
November 20, 2015

chemistry
See your other post.
November 20, 2015

Chemistry-Dr.Bob
Yes, the method is right but I think you made a math error for the HCl. 0.001 x 0.05 is 5E-5
November 20, 2015

Chemistry
You worked the Xe/CO; why is this one a problem? I would assume some mass Br2, calculate mols and go from there.
November 19, 2015

Chemistry
Let's make up a number for the rate of Xe gas. Let's call it 10 mL/second. Then (rate CO/rate Xe) = sqrt(M Xe/M CO where M stands for molar mass Xe or molar mass CO. (10/x) = sqrt(131.29/28) Solve for x for rate of CO then calculate how much faster/slower this is than ...
November 19, 2015

chemistry
mass Au + mass Ag = 14.9; therefore, mass Au = (14.9-mass Ag) and you will substitute 14.9-mass Ag for mass Au in the below equation. The general set up is [mass Au x sp.h. Au x (Tfinal-Tinitial)] + [mass Ag x sp.h. Ag x (Tfinal-Tintial)] + [mass H2O x sp.h. H2O x (Tfinal-...
November 19, 2015

Chemistry
See your post below.
November 19, 2015

Chemistry
This is a limiting reagent (LR) problem. You know that because amounts are given for BOTH reactants. mols Zn = grams/atomic mass = ? mols HCl = 0.2 Using the coefficients in the balanced equation, convert mols Zn to mols ZnCl2. Do the same and convert mols HCl to mols ZnCl2 It...
November 19, 2015

Chemistry
Instead of typing in a general question why not type in the problem as is, including numbers.
November 19, 2015

chemistry
Thank you. I'm glad you could do them.
November 19, 2015

chemistry
I can do all of these for you and you won't learn a thing. Tell me what kind of trouble you are having.
November 19, 2015

Chemistry
If I knew how to help I would but you don't have any questions here without referring to some web site that isn't listed. At the equivalence point the pH will be 7 for both titrations. Before the equivalence point for each, determine mols of HCl and mols NaOH from ...
November 19, 2015

Chemistry
mols KOH = M x L = ? Using the coefficients in the balanced equation, convert mols KOH to mols H3PO4. Then M H3PO4 = mols H3PO4/L H3PO4.
November 19, 2015

Chemistry
Mendeleev arranged the elements in columns by increasing atomic mass and in rows by similar chemical properties (opposite to what we do today but the effect is exactly the same). When the next heavier element (higher atomic mass) was to placed in his table, if the element did ...
November 19, 2015

Chemisty
Usually this is called Ksp. ..........Mg(OH)2 ==> Mg^2+ + 2OH^- I.........solid.......0.........0 C.........solid.......x.........2x E.........solid.......x.........2x Plug the E line into the Ksp expression and solve for x = (Mg^2+)
November 19, 2015

Chemistry
Don't the P4 and O2 concentrations at equilibrium depend upon their initial concentrations and/or the concn of P4O6 initially.
November 19, 2015

Chemistry
1. m = mols/kg solvent m = 0.610/1.35 = ? 2. 0.200 mg KBr = 0.0002 g. mols = grams/molar mass = 0.002/119 = 1.68E-6 m = mols/kg solvent = 1.68E-6/0.0055 = ? etc.
November 19, 2015

Chemistry
The density you use should be that of the SOLUTION. Do you want to make a solution that is 50 g PEG/1000 g H2O? Then you take 25 g PEG and dissolve it in 0.5L H2O (not solution) and that will be 50 g PEG/kg H2O won't it and you don't need density for that. I don't ...
November 18, 2015

chemistry
You may have a different equation but this is what I have. 2NH3 + 6F2 → 6HF + 2NF3 mols HF = 4.65 g/molar mass HF = ? Using the coefficients in the balanced equation, convert mols HF to mols NH3. Then remember that 1 mol NH3 at STP occupies 22.4 L.
November 18, 2015

chemistry
What are you reacting the NH3 with?
November 18, 2015

Chemistry
millimols HCl = mL x M = 10 x 0.17 = 1.7 mmols NH3 = 50 x 0.16 = 8 ..... HCl + NH3 ==> NH4Cl I.....1.7....8.......0 C....-1.7..-1.7......1.7 E......0....6.3.....1.7 Therefore, the resulting solution consists of 6.3 mmols NH3 and 1.7 mmols NH4^+ in 60 mL. (NH3) = mmols/mL = ...
November 18, 2015

chemistry
I assume you really meant CuNO3 and not Cu(NO3)2. mols CuNO3 = grams/molar mass = ? Then M CuNO3 = mols CuNO3/L CuNO3 solution. You know M and mols, solve for L.
November 18, 2015

chemistry
Neither problem makes any sense to me. With Ksp = 6.47E-6, the solubility of Ca(IO3)2 is 0.0117 in a saturated solution. Therefore, you can't have a 0.13M solution. You don't need to add any KIO3; Ca(IO3)2 is already pptd.
November 18, 2015

Chemistry
The work done by Nick is interesting but it doesn't answer the question. Fe + 2HCl ==> FeCl2 + H2 mols Fe = grams/molar mass = ? Using the coefficients in the balanced equation, convert mols Fe to mols HCl. That's mols HCl = twice mols Fe. Now convert mols HCl to ...
November 18, 2015

Chemistry
No, I think your first answer is the one. Look at it this way. Draw a cell with a salt bridge between. Make it Zn metal dipping into Zn(NO3)2 solution on the left and Cu metal dipping into Cu(NO3)2 solution on the right. When the reaction starts, Zn goes to Zn^2+ + 2e on the ...
November 18, 2015

Chemistry
http://www.wikihow.com/Determine-Screening-Constant-and-Effective-Nuclear-Charge
November 18, 2015

Chemistry
Look up reduction potentials for these two. E = Eo - (0.05916/n)*log[(red)/(ox)] for Ag. E = Eo - etc etc for Zn. Reverse one of the Eo values(change sign, too) and add to the other. Do this in such a fashion that the Ecell = + value volts. That gives you the Eocell.
November 18, 2015

Chemistry
Write the molecular equation and balance it. Convert the molecular equation into an ionic (total ionic) equation. The rules are as follows: solids(insoluble materials formed) are written as the molecule, gases are written as the molecule, weak electrolytes are written as the ...
November 18, 2015

Chemistry
See your other post.
November 18, 2015

chemistry
Did you use dGo formation for your values. I don't have those values. Were the two values separate calculations or is the question asking for two different values? I don't see but one question.
November 18, 2015

Chemistry
First you need to be sure part a is right. Did you get AgCl pptng first? Ksp/0.1 is Ag^+ needed for pptn AgCl but sqrt (Ksp/0.1) is Ag^+ needed for pptn of Ag2CrO4. Adding AgNO3 drop wise to the mixed solution will ppt AgCl first. B. AgCl will continue to ppt (with no Ag2CrO4...
November 18, 2015

Chemistry
0.998 is ok. 20.0 is not. 0.1 mol x (3 mols O2/2 mols O3) = 0.1*1.5 = 0.15 and if you substitute 0.15 for n in the equation surely you don't get 20 atm. Wouldn't the correct answer logically be P2 = 1.5*P1 = 0.998*1.5 = about 1.5?
November 18, 2015

Chemistry
mols O3 = g/molar mass = 4.8/48 = 0.1 Pressure before O3 decomposes is then P = nRT/V = ? After decomposition you have 2O3 ==> 3O2 0.1 mol O3 x (3 mols O2/2 mols O3) = ? and use P = nRT/V again to find the O2 pressure.
November 18, 2015

Chemistry (Check)
1.3 L is right. I expect you used, as you should, (V1/T1) = (V2/T2)
November 18, 2015

Chemistry
Yes it is but I don't know how you arrived at the 0.8252. We may have used slightly different numbers. P*Molar mass = d*RT (956/760) x 16/(0.08206*298) and I get 0.8230 which is 0.823 to there s.f. You may have used a slightly different molar mass than 16.
November 18, 2015

Chemistry - radioactivity
According to this table it appears to me that 78Pt200 is subject to beta decay while 192 and 196 are stable and 188 is electron capture. https://en.wikipedia.org/wiki/Isotopes_of_platinum
November 17, 2015

Chemistry (Help)
I don't get 35,120. I get 75,520 for the balanced equation. If you take the question literally you divide by 2 but that gives my number still higher. I normally don't divide by 2 UNLESS the problem states that they want kJ/mol but I don't know the context of your ...
November 17, 2015

Chemistry (Help)
I am really embarrassed. I completely ignored that coefficient of 2 for the first material. Ok so the equation is ok. Let me recalculate the dH.
November 17, 2015

Chemistry (Help)
Yes it is. 2C57H110O6 (s) + 163O2(g) --> 114CO2(g) + 55H2O(l) You have 110 H on the left and 110 on the right.
November 17, 2015

Chemistry (Help)
The equation isn't balanced. You have (163*2)+(2*6) = 338 O on the left and (114*2) + 110*2) = 448 on the right. You can make it balance with 55 H2O and not 110 H2O.
November 17, 2015

Chemistry (Help)
That's what I obtained.
November 17, 2015

Chemistry (Help)
If you show each step perhaps I can figures out what you're doing wrong. For example: 6*-393.5 = ? 6*-285.84 = ? Total = ? etc.
November 17, 2015

Chemistry (Help)
I think it is set up right but I don't get that answer. It is exothermic and the equation is balanced.
November 17, 2015

Chemistry
Note here that you obtained 75520 for dHrxn but on page 1 you are not using half of that if you are doing for 1 mole. And the 75520 agrees with the number I had (before dividing by 2) for 1 mole. Here, I obtained 890 for the molar mass but I used 12 for C, 16 for O and 1 for H...
November 17, 2015

Chemistry
I don't get that. The best way you can do this is to show the balanced equation, then show step by step what your math is like and I can find the error if you've made one. I think we're wasting time with your multiple answers and my no that isn't right.
November 17, 2015

Chemistry
Balance the equation. dHrxn = (n*dHf products) - (n*dHf reactants) in units of kJ/mol q = dHrxn x (578/2*molar mass tristearin) = ?
November 17, 2015

general chemistry
mols Na2CO3 = grams/molar mass = ? Then M Na2CO3 = mols/L (but the problem SHOULD SAY in 1.50 L of SOLUTION). (Na^+) = 2 x (Na2CO3) (CO3^2-) = (Na2CO3) For ppm, convert 2.57E-4 g Na2CO3 in 1.50 L to mg/L and that will be the ppm.
November 17, 2015

Chemistry
m^-1 means per meter and since R is measured in per meter the wavelength comes out in meters. So solve as you have suggested and convert the answer for wavelength in meters to nanometers. By the way, you want to substitute 1 for n1 and solve for n2.
November 17, 2015

Chemistry
I think I can answer your question but your phrasing is bad. You don't ask a question, really, and that word "is" is out of place. Delta G is zero but not because it is standard but because it is in equilibrium at the boiling point (I assume that is the b.p. for ...
November 17, 2015

chem
millimols AgNO3 = mL x M = 25*0.1 = 2.5 millimols Na3PO4 = 50 x 1.5 = 75 ......3AgNO3 + Na3PO4 ==> Ag3PO4 + 3NaNO3 I......2.5......75..........0........0 C.....-2.5.....-2.5/3......2.5/3....2.5 E.......0.......74.17.......0.8333..2.5 For solubility product with the PO4^3- ...
November 17, 2015

chem
Refer to your other problem with Ag3PO4.
November 17, 2015

Chemsitry
And you can't do this for what reason(s)?
November 17, 2015

chem
I have seen you write tsp twice. What in the world is tsp? Do you mean Ksp. ...........SrCrO4 --> Sr^2+ + CrO4^2- I..........solid.......0........0 C..........solid.......x........x E..........solid.......x........x Ksp = (Sr^2+)(CrO4^2-) You must determine the ...
November 17, 2015

Chemistry
grams O2 = density x volume = 1.118 g/cc x 1 cc = ? mols O2 = n = grams/molar mass = ? Then use PV = nRT and solve for P. Remember to use K for temperature and L for volume.
November 17, 2015

Chemistry
NH4Cl is a salt that ionizes completely; therefore, (NH4^+) = 1.50 M. NH3 is a weak base that has a Kb. ...........NH3 + H2O ==> NH4^+ + OH^- I.........0.50............0.......0 C..........-x.............x.......x E.......0.50-x............x.......x Kb = look it up = (NH4...
November 17, 2015

Chem
M CaSO4 = mols/L. You have 1 L and mols = grams/molar mass. Solve for M. Ksp = (Ca^2+)(SO4^2-). Plug in M Ca^2+ and SO4^2- and solve for Ksp.
November 17, 2015

Chemistry
heat lost by Cu + heat gained by H2O = 0 [mass Cu x specific heat Cu x (Tfinal-Tinitial)] + [mass H2O x specific heat H2O x (Tfinal-Tinitial)] = 0
November 17, 2015

Chemistry
40 mL of 0.1 M HCl obviously will take exactly 40 mL of 0.1 M NaOH to arrive at the equivalence point. So a and b are before the eq pt and c is after the eq pt. For a. HCl + NaOH ==> NaCl + H2O. millimols HCl = 40 x 0.1 = 4 mmols NaOH = 28 x 0.1 = 2.8 Difference [which is ...
November 17, 2015

Chemistry
C6H12O6 + 6O2 ==> 6CO2 + 6H2O dHrxn = (n*dHf products) - (n*dHf reactants) and dHrxn will be in kJ/mol. Divide by 1 and divide by molar mass C6H12O6 to get kJ/gram. To convert to fuel value change the negative sign to a + sign. Do the same for tristearin. The equation is ...
November 17, 2015

chemistry
1. It appears the problem states the single dose is 1g per 10 mL. mols of the stuff = grams/molar mass = ? Then M = mols/0.010 L = ? 2. Sure is a funny way of stating the problem but it is mL1 x M1 = mL2 x M2 mL1 x 6 = 75 mL x 0.5 Solve for mL 1. 3. mL1 x M1 = mL2 x M2
November 17, 2015

chem
1. 148 ng/L = 148E-9 g/L. Then g/L is 1.48E-9 g/L x #L = ? 2. mols NaF = grams/molar mass M = mols/L 3. You have 0.030 g in 48,000 g and you want to convert that to g in 1000. So 0.030 g x 1000/48000 = ? 4. mols = grams/molar mass Then M = mols/L 5. 5 ug x (1 mg/1000 ug) = ? ...
November 17, 2015

Chemistry (Help)
No. mols CO2 = 114 mol H2O = 110 so dHrxn = [(114*-393.5) + (110*-285.84)] - [ etc.
November 17, 2015

Chemistry (Check)
Go back to the C57 compound and see how I did that. You are using TOTAL mols and that isn't the right way to do it.
November 17, 2015

chem
I suggest you repost this at the top of the page but add what you don't understand about the question or what numbers you have to show in your work.
November 17, 2015

chemistry
You want how many mols? That's mols = M x L = ? with M = 0.01 and L = 0.015 Then grams = mols x molar mass. You know molar mass and mols, solve for grams.
November 17, 2015

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