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February 28, 2015

Posts by DrBob222


Total # Posts: 47,308

chemistry
See your other screen names.
November 25, 2014

chemistry
mols = M x L = ?
November 25, 2014

chemistry
See your post under Mackenzie.
November 25, 2014

chemistry
See your other screen names posts.
November 25, 2014

chemistry
Done the same way no matter what your screen name is. See those posts.
November 25, 2014

chemistry
At least you came up with a different kind of problem. M = mols/L solution.
November 25, 2014

Chemistry
Check this to confirm. CuSO4 + 6NH3 + 2H2O = (NH4)2SO4 + Cu(NH3)4(OH)2
November 24, 2014

chemistry 2
The long way is to use PV = nRT and solve for pressure of each gas. n = grams/molar mass or atomic mass when dealing with grams. Then add the partial pressures to find the total pressure.
November 24, 2014

Chemistry
mols = M x L = ? Then mols x molar mass = grams.
November 24, 2014

Chemistry
C + O2 ==> CO2 393.5 kJ x (6g/12g) = kJ heat released to burn 6g C. X grams C = 12 x (39.3/393.5) =
November 24, 2014

Chemistry
........H2 + I2 ==> 2HI E.......x..0.015....0.030 Plug into the Keq expression and solve for x.
November 24, 2014

chemistry-naming
C3H8 probably is propane. KCl is potassium chloride
November 24, 2014

Chemistry
0.60 M Na^+. There are 3 Na atoms in 1 Na3PO4 molecule; therefore, (Na3PO4) must be 0.60/3 = 0.20M Na3PO4.
November 24, 2014

Chemistry
I think Damon worked this below.
November 24, 2014

Chemistry
http://www.nwscc.edu/nsfdc/organicchemistry/constitutional%20isomers
November 24, 2014

chemistry
No and I answered no to the response I gave yesterday. One reason you know 105g can't be correct is because to obtain 160.9 g Au from AuCl3, the AuCl3 must be more than 160.9g because AuCl3 is not 100% Au.
November 24, 2014

chemistry
Frankly, I think the whole idea of valence electrons with transition metals is nonsense unless the rules make sense and most don't. I've spent almost two hours looking at page after page for an explanation of valence electrons. No two sites give the same rules for ...
November 24, 2014

CHEMISTY HOMEWORK HELP ASAP
1. Use the Henderson-Hasselbalch equation. Substitute into the HH equation and calculate pH. 2. Set up an ICE chart using .......CH3COOH + OH^- --> CH3COONa + H2O and substitute the E line of the ICE chart into the HH equation and sole for the new pH.
November 24, 2014

Chemistry Homework Help Please!
See my response above.
November 24, 2014

Chemistry
NaF is the base HF is the acid.
November 24, 2014

Chemistry
millimols NaF = mL x M = approx 100 mmols HF = mL x M = aprox 62.5 mmols HCl added = approx 3.75 You omitted the exponent on Ka. I think that's 7.1E-4, then pKa = 3.14 ................F^- + H^+ ==> HF I..............100....0.......62.5 add.................3.75 C...
November 24, 2014

Chemistry Homework Help
See your post above.
November 24, 2014

chemistry
It works this way. If you multiply the equation you use the same multiplier for dH. If you reverse the equation, change the sign of dH. If you reverse the equation AND multiply it, then multiply by the same multiplier and change the sign.
November 24, 2014

Chemistry Physics
yes
November 24, 2014

Chemistry Physics
c = fw c = speed of light in m/s f = frequency in Hz w = wavelength in m
November 24, 2014

Chemistry
Use PV = nRT and n = grams O2/molar mass O2.
November 24, 2014

soran university
You must have graphs for solubility or tables of solubility. Without those I can't help.
November 24, 2014

chemistry
I can't decipher your post. Please repost and this time use caps where needed, ask your question(s), and don't leave out the adjectives in describing your question.
November 24, 2014

chem/science
It would help if we had the reaction you used.
November 24, 2014

Chemistry 211
I would go with a and b. \
November 24, 2014

Chemistry
Do you mean is 14.6 g CaCO3 is formed? mols HCl = grams/molar mass Convert mols HCl to mols CaCl2. Convert mols CaCl2 to grams. g = mols x molar mass.
November 24, 2014

Chemistry
I think your last step is a little off; I have 82.3 mL. I agree with your numbers up to multiplying by 22.4.
November 24, 2014

Chem please help
I agree with c.
November 24, 2014

Chemistry
The dilution formula is c1v1 = c2v2 c = concentration v = volume
November 23, 2014

Chemistry
K fwd = 0.65 K rvse = 1/0.65
November 23, 2014

chemistry
This is nothing more than plug and chug pH = pKa + log (base)/(acid) base = propanoate acid = propanoic acid You must look up the value for pKa propanoic acid.
November 23, 2014

Chemistry
q = mass H2O x specific heat H2O x (Tfinal-Tinitial)
November 23, 2014

chem
incomplete
November 23, 2014

Chemistry
2KClO3 ==> 2KCl + 3O2 mols KClO3 = grams/molar mass. Using the coefficients in the balanced equation, convert mols KClO3 to mols O2. Now convert mols O2 to grams. g = mols O2 x molar mass O2 = ?
November 23, 2014

chemistry
mols glycerin = grams/molar mass = ? mols H2O = grams/molar mass = ? mols fraction glycerin = Xgly = mols glycerin/total mols. Then pH2O = Xglycerin*PoH2O
November 23, 2014

Chem please help
Yes, C is correct. Gases always have more entropy than liquids.
November 23, 2014

Chemistry - Heat of Fusion of Ice
I don't know exactly how you determined the heat fusion so I can't answer question #3. #1 is No. #2 is No. #3 is I don't know. I don't know how the experiment was done.
November 23, 2014

Biochemistry
I found your other post and saw your non-response BUT you told me what the numbers stood for. Find that post, give me the concns of the HCl and stomach acid, and I can verify your work.
November 23, 2014

Biochemistry
I responded earlier that I couldn't make sense of this because of the spacing (or lack thereof). You haven't helped at all because you haven't changed the spacing. I have used ...... as spacers OR you can write on separate lines but you can't make the page ...
November 23, 2014

Chemistry
(P1V1/T1) = (P2V2/T2)
November 23, 2014

Biochemistry
Apparently you don't get it at all. I know what you're asking and it's a fairly simple question BUT I can't make heads or tails of your post. Look at the post. There are no spaces. I can't tell the difference in your post between the #1, #2 and #3 trial (if...
November 23, 2014

Biochemistry
I can't make head or tails of this. Remember you can't make more than one(1) space. This forum recognizes only 1.
November 23, 2014

chemistry
mols = g/molar mass. Substitute and solve for mols. Then mols = M x L. Substitute and solve for L and convert to mL.
November 23, 2014

Chem
mols Br2 = grams/molar mass Using the coefficients in the balanced equation, convert mols Br2 to mols AlBr3.
November 23, 2014

Chemistry
See your other post.
November 23, 2014

Chemistry
160.9 g Au must have more weight as AuCl3.
November 23, 2014

Chemistry
160.9 g Au x (molar mass AuCl3/atomic mass Au) = ? mass AuCl3.
November 23, 2014

Chemistry
Let's call formate ion for-. It will hydrolyze as follows: .........for- + HOH ==> Hfor + OH^- I........1.19.............0.....0 C.........-x..............x.....x E.......1.19-x............x.....x Kb for for- = (Kw/Ka for formic acid) = (x)(x)/(1.19-x) Solve for x = OH...
November 23, 2014

Chemistry
yes
November 23, 2014

Biochem
See your other post.
November 23, 2014

chemisty
Use the dilution formula. mL1 x M1 = mL2 x M2 or if you prefer c1v1 = c2v2 where c = concentration and v = volume.
November 23, 2014

CHem
Something is missing here.
November 23, 2014

Chemistry
Use the Henderson-Hasselbalch equation.
November 23, 2014

biochemistry
You can dilute 0.1 M HCl (pH = 1) to make pH = 6; however, that will not be a buffer because you have nothing to take up H^+ or OH^- when added to the "so-called" buffer you have prepared.
November 23, 2014

Chemistry
Convert pOH to pH with pH + pOH = pKw = 14. Convert pH to (H^+) with pH = -log(H^+). Then since HNO3 is 100% ionized, H^+) = (HNO3) mols HNO3 needed = M x L = ? mols HNO3 = grams/molar mass. You know mols and L, solve for grams.
November 23, 2014

chemistry
No. Al is the limiting reagent. (and I don't understand what (p) is). And I don't understand your work either for apparently you have omitted division signs and multiplications signs. 54.3/27 = 2.01 is ok. Convert that to mols Cl2 needed. That's 2.01 mols Al x (3 ...
November 23, 2014

Chemestry
Where's the arrow. I can't tell the products from the reactants. 1. Balance the equation. 2. mols I2 produced = grams/molar mass = ? 3. Using your balanced equation, convert mols I2 to mols I^- 4. Convert mols I^- to mols KI (which will be the same) 5. Convert mols KI ...
November 23, 2014

chem
Mn usually +2, +4. +7 Rh I would expect +2, +3
November 23, 2014

Chemistry
To be frank about it I can't remember all of that stuff about which is the anode/cathode and I'm not sure it matters in this case. You're looking for Ecell and my philosophy is to calculate Ecell and not worry about the anode and cathode. But I do remember ONE ...
November 23, 2014

Chemestry
Find your arrow key and use it. 1. Balanced the equation. 2. mols Fe^2+ = M x L = ? 3. Using the coefficients in the balanced equation, convert mols Fe(II) to mols Cr2O7^2-. 4. Then M Cr2O7^2- = mols/L. You have M and mols, solve for L, convert to mL if you wish.
November 22, 2014

Chemistry
mols BaSO4 = grams/molar mass Convert mols BaSO4 to mols K2SO4. The easy way to do this is to recognize there is 1 mol SO4 in BaSO4 and 1 mol in K2SO4 so mols BaSO4 = mols K2SO4. Then convert mols K2SO4 to grams. g = mols x molar mass Next convert mols K2SO4 to grams K2SO4. g...
November 22, 2014

Chemistry
That sounds good. Remember that anytime you use a formula you should define the terms. Therefore, I would writae KE = 1/2 mv^2 where KE is kinetic energy in joules, m is mass in kg, and v is velocity of the particles in m/s.
November 22, 2014

Chemistry
I would say so far so good. You might want to mention something about KE = 1/2 mv^2
November 22, 2014

Chemistry
There is no way out of memorizing the solubility rules for things like PbI2, PbSO4, BaSO4, CuI, etc. You can Google solubility rules and look for the one you like best. I always told my students to memorize them. Frankly, I never did BUT I used them so often when I was in high...
November 22, 2014

Chemistry
Or post the two and see if we know.
November 22, 2014

Chemistry
8.01E24 atoms O x (1 mol/6.022E23) = # mols O. Then mols (NH4)2SO4 = mols O atoms x (1 mol (NH4)2SO4/4 mols O atoms) = ? Then g (NH4)2SO4 = mols x molar mass = ?
November 22, 2014

Chemistry
All you need to do is to substitute the numbers into the formula. mL1 x M1 = mL2 x M2 mL x 17M = 939 x 6.7 solve for mL. And it doesn't make any difference which one you call mL1 and mL2 as long as you're consistent;i.e. you could have 939 x 6.7 = mL x 17 and solve for...
November 22, 2014

Chemistry
mL1 x M1 = mL2 x M2
November 22, 2014

Chemistry
right. liquid water + heat ==> steam adds heat so it is endothermic. Note that many thing freezing water to ice is endothermic too but it is exothermic and one equation like the one above will show it. ice cubes + heat ==> liquid water is an endothermic process because ...
November 22, 2014

chemistry
A calorimeter may be used to determine the specific heat of an unknown substance and I think also to determine the T of a chemical reaction; however, I think the answer to the question is B. You want to measure the energy change (q) of a chemical reaction. If done at constant ...
November 22, 2014

chem please help
I obtained 3538; I suspect D is the correct answer since the 0.70 mols restricts the answer to 2 significant figure and 3100 is that. Technically the 50 number of grams H2O has only 1 s.f. but I guess they ignored that.
November 22, 2014

Gen Chem
1. You must have data to use to do the calculation. 2. Are you sure that's not CO3^2- (carbonate) they want to know.
November 22, 2014

chemistry
I would go with d.
November 22, 2014

chemistry due soon
Yes, c is correct.
November 22, 2014

Chem
I looked up the neutral atom and ionic species and this is what I found from smallest to largest. It isn't what I expected. Ar < Cl^- < Ca^2+ < K^+ I thought in an isoelectronic series (which this is since all atoms/ions have 18 electrons) that Cl^- would be ...
November 22, 2014

chemistry Thank a lot help
I solved this for you twice last week.
November 22, 2014

chemistry
dG = dH - TdS Max value for dG is 0. Then TdS = dH dS = dH/T = 19,000/(273+72) dS = ?
November 22, 2014

chemistry
Write the hydrolysis equations. For x it will be ........X^- + HOH ==>HX + OH^- I......0.1...........0.....0 C......-x............x.....x E.....0.1-x..........x.....x Kb for X^- = (Kw/Ka for HX) = (x)(x)/).1-x Since pH = 7 that makes pOH = 7 and (OH^-) = x = 1E-7. Solve for...
November 22, 2014

chemistry
.............PbCl2 ==> Pb^2+ + 2Cl^- I............solid......0......0.15 C............solid......x........x E............solid......x......0.15+x Ksp = (Pb2+)(Cl^-)^2 Ksp = (x)(x+0.15) Solve for x.
November 22, 2014

Chemistry
Yes, dS for the system is 79.0 J/K*mol but I would use T at boiling point of 98C (371K) to solve for this because you're using dHvap and it makes sense to use T at the vapor point. I note the problem asks for dSuniv at 298. I think you can get that by dG = -dH/T = (dSuniv...
November 22, 2014

Chemistry
dSsys = dH/T I think you should look at your dH value. Isn't 21.6 kJ/mol = 21600 J/mol
November 22, 2014

Chemistry
No. You don't have 2.10 mols HCl. Did you read my response? mols HCl = M x L = 2.10 x 0.035 = ? Then convert to mols H2 and from thre to L.
November 22, 2014

Chemistry
Do you mean delta Hf? If dHf<0 doesn't that mean dHf = negative and doesn't that mean it is exothermic and wouldn't that mean it gets hotter?
November 22, 2014

chemistry
mols HCl = M x L = ? Using the coefficients in the balanced equation, convert mols HCl to mols H2 gas. Now convert mols H2 gas to L. L H2 = mols H2 x 22.4 L/mol = ? L.
November 21, 2014

Ratio - proportion - unit rate
$71.88 doesn't appear to be a question to me. Answer Ms. Sue's question.
November 21, 2014

Chemistry
Here is my response to your earlier question. Although you didn't explain what you didn't understand, I think you must understand it ok for the equation is balanced. Read my response and redo this one and see if that doesn't help. If it doesn't, repost and this...
November 21, 2014

Chemistry
C2H5OH + 3O2 ==> 2CO2 + 3H2O heat of combustion ethanol = 3600 kJ/mol x (3.78/molar mass ethanol) = ? ? = Ccal(Tfinal-Tinitial)
November 21, 2014

Chemistry
I answered under Sam. Re-post with a follow up if the "mole" isn't clear.
November 21, 2014

Chemistry
Look at your post under Sam. These are worked almost the same way but if you don't understand please show what you know and tell me exactly what you don't understand about the question. As for mols of benzene, the answer is none although your teacher may count that ...
November 21, 2014

Chemistry
That is a constant. It's just another unit like a dozen of something (12) or a gross of sometihig (144 or 12 dozen) or a ream (500 sheets paper). In this case there are 6.022E23 molecules in a mole of molecules, 6.022E23 atoms in a mole of atoms, 6.022E23 bananas in a mole...
November 21, 2014

Chemistry
You made a typo wring sodium sulfate but typing Li2SO4. I assume you meant Li2SO4. 1 mol contains 6.022E23 molecules so 6.78E23 molecules x (1 mol/6.022E23 molecules) = mols Li2SO4. There are two Li^+ per 1 molecule Li2SO4; therefore, there must be twice mols Li&+ must 2x mols...
November 21, 2014

Science- Skin
I see measurements here. Perhaps this will help. http://dermatology.about.com/cs/skinanatomy/a/anatomy.htm
November 21, 2014

Chemistry
Instead of me guessing what you know (or don't know) about this why don't you tell me exactly what your problem is in redox equations and let me help you through it?
November 21, 2014

oops--Chemistry
I used 22.4 L/mol for O2 and that is true for 273 C but for 298 I should have used 24.45 L/mol. That is, mols O2 x 24.45 L/mol = ? L O2 and that's the theoretical yield.
November 21, 2014

Chemistry
You need to calculate the theoretical yield. 2H2O ==> 2H2 + O2 mols H2O = grams/molar mass = 10,000/18 = ? Using the coefficients in the balanced equation, convert mols H2O to mols O2. That's ? mols H2O x (1 mol O2/2 mols H2O) = ? mols H2O x 1/2 = ? Then convert mols O2...
November 21, 2014

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