Tuesday
May 24, 2016

Posts by drbob222

Total # Posts: 52,411

chemistry
Even though it isn't quite correct since we don't write subscripts on this forum, you should use HPO4- and H2PO42- (I prefer HPO4^- and H2PO4^2-). Most will not know what HPO2-4 is. I responded to this problem a few days ago. Frankly, I don't think 2 and 3 can be ...
April 24, 2016

Chemistry
So you know 2.5 mols CH$ releases 2800 kJ of energy. (By the way that is calorimeter). Look up the energy values for paraffin and the glycol and compare them. That's all there is to it. You can find that information on Google.
April 23, 2016

chemistry
http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/vacfla.html#c2
April 23, 2016

Chemistry
Your post isn't clear to me. I'm confused by the "when THEY dissolve" What is meant by they?
April 23, 2016

Chemistry
CaCO3 ==> CaO + CO2 grams CaCO3 = 250 x 0.8 = 200g. mols CaCO3 = 200/molar mass CaCO3 Using the coefficients in the balanced equation, convert mols CaCO3 5o mols CaO. Now convert mols CaO to g. g CaO = mols CaO x molar mass CaO.
April 23, 2016

chemistry lab
I don't want to appear dumb but how am I supposed to know what you did?
April 23, 2016

chemistry
If you're sure of your numbers all you need is the final concentrations. pH = pKa + log (base)/(acid) pH = 4.76 + log (OAc^-)/(HOAc) but this can't be right. A buffer will have some acetate and some acetic acid. You can't have zero HOAc. If you truly have (HOAc) = ...
April 23, 2016

Chemistry
Your equation is not balanced and Q is not 27; therefore, those initial values you have are incorrect. Correct those and try the last part again. Also, is that -170 what? kJ? kJ/mol? kJ/rxn?
April 23, 2016

Chemistry
This is straightforward. What do you not understand about this? I'll be glad to help you through it but I need to know where the hang up is.
April 23, 2016

Chemistry
See your other posts with different screen names.
April 23, 2016

Chemistry
Too many screen names and you don't fool anyone.
April 23, 2016

Chemistry
See your other posts. Don't expect us to do all your work.
April 23, 2016

BIO chemistry
Use the Henderson-Hasselbalch equation. pH = pKa2 + log (base)/(acid) base is HPO4^-; acid is H2PO4^-
April 23, 2016

Chemistry
NiCl2.6H2O + 6NH3 ==> Ni(NH3)6Cl2 + 6H2O Ni(NH3)6Cl2 + 2NH4BF4 ==> [Ni(NH3)6][BF4]2 + 2NH4Cl Add the two equations to obtain an overall equation if that's what you want. By the way I think your spelling of tetrafluoroborate is incorrect.
April 23, 2016

Chemistry
See your other post.
April 23, 2016

Chemistry
I looked, also, and didn't find an answer in print that answers the question in so many words ut I think you're right and for this reason. If we look at the hydrolysis of each we have CN^- + HOH ==> HCN + OH^- Kb for CN^- = Kw/Ka for HCN. Ka for HCN is approx 10^-10...
April 22, 2016

AP Chemistry
The vapor pressure of pure methanol is 760 mm at this temperature. psolution = Xmethanol*Po 642.3 = Xmethanol*760 Then Xmethanol + Xsolute = 1 Solve for Xsolute.
April 22, 2016

Chemistry
The question is written in such a manner that I can't make sense of it. Sorry.
April 22, 2016

Chemisty
I balanced it for you yesterday and said I didn't understand what you meant by break it down.
April 22, 2016

chemistry
What does all that funny business ater the 200 mean?
April 22, 2016

Chemistry
Your numbers look ok. I suspect the problem is that you are reporting too many significant figures. For example, that first one of 5144.6 is allowed only 3 places. Also, shouldn't you have a - sign for the total. Each of the three are exothermic; i.e.,, the first one is ...
April 22, 2016

Chemistry
Why didn't you show your work so we could figures out what you were doing wrong? You want to add the heat removed in changing T from 35 to zero, to the heat removed @ zero C to convert to ice, to the heat removed in changing T from zero C to -5.
April 22, 2016

Chemistry
......PbCl2 ==> Pb^2+ + 2Cl- I.....solid......0.......0 C.....solid......x.......x E.....solid......x.......x Substitute the E line into Ksp expression and solve for x = solubility PbCl2.
April 22, 2016

chemistry
http://www.jiskha.com/display.cgi?id=1461350333
April 22, 2016

Chemistry
You have looked up all of the boiling point and if you have copied them correctly, then CHI3 must be the right answer. It doesn't matter about intermol forces when you have the boiling points listed. 218 is 218.
April 22, 2016

Chemistry
On the left you have 3 mols of gas. ON the right you have only 2 mols gas. There is more randomness (more random possibilities) in 3 mols than 2 mols.
April 22, 2016

Chemistry
You're on a tight schedule. Most of the times we don't get the answers out that fast. 2Na + 2H2O ==> 2NaOH + H2 mols Na = grams/molar mass = ? M NaOH = mols NaOH/6.8 L = ?
April 22, 2016

Chemistry
Didn't I do parts of this a day or so ago for you. I know i did art 1. What is the trouble you're having.
April 22, 2016

Chemistry
See your other post.
April 22, 2016

Chemistry
Look up the appropriate potentials and post them. We can't get your answer without using your numbers.
April 22, 2016

chemistry
I don't see a question here.
April 22, 2016

chemistry
You don't provide enough information to answer this question. Look up the delta Ho formation and provide that data.
April 22, 2016

chemistry
pH = -log (H^+) (H^+) = ?. I estimate 5E-5 but you need a better answer than that. ...........HA ==> H^+ + A^- I........0.039....0......0 C.........-x......x......x E......0.039-x....x......x The pH tells you the value of x; i.e., approx 5E-5 so you can evaluate x and 0.039...
April 22, 2016

Chemistry
%yield = (4.13/7.10)*100 =
April 22, 2016

Chemisty
2H2S +3O2 = 2H2O + 2SO2 That's balanced. I don't know you mean by "breaking it down".
April 22, 2016

Chemistry
I'm not sure I understand the answers. However, I suspect the answer to this question is b. cold pack + heat = warm Warming the cold pack is endothermic; the cold pack is cooling something else and it absorbs heat to do that.
April 21, 2016

Chemit
34 g/hr x (24 hrs/day) x (30 days/month) = ? grams sucrose /month
April 21, 2016

Chemistry
KHP + NaOH ==> H2O + NaKP mols KHP = grams/molar mass = ? Look at the coefficients in the balanced equation; it is 1:1 so ? mols KPH = same mols NaOH. Then M NaOH = mols NaOH/
April 21, 2016

Chemistry
Yes, I would go with convection but in some cases it could be conduction. That isn't very efficient, though, for gases/liquids.
April 21, 2016

Chemistry
That sounds ok to me.
April 21, 2016

Chemistry
Let's call benzoic acid HB and sodium benzoate is NaB. NaB is the base; HB is the acid. .......HB + NaOH ==> NaB + H2O I......0.1....0.......0.1...... add.........0.01.............. C....-0.01..-0.01......+0.01 E.....0.09.....0.......0.11 Substitute the E line into the ...
April 21, 2016

Chem Please HELP
H2SO4 + 2NaOH ==> 2H2O + Na2SO4 mols NaOH = M x L = ? Using the coefficients in the balanced equation, convert mols NaOH to mols H2SO4. Then M H2SO4 = mols H2SO4/L H2SO4 = ?
April 21, 2016

Chemistry
73 drops x (0.05 mL/drop) x 73 = approx 3.5 mL but that's only an estimate. Recalculate more exactly, then convert to L.
April 21, 2016

Chemistry<--------
What makes you think the numbers I have are any better than the number you get on the internet?
April 21, 2016

Chemistry -Dr.Bob222
I don't know if you are to calculate these or not. Approx pH values are NaOH is about 12, NaHCO3 is about 8, NaCl is about 7, NH4Cl is about 5. You will need to calculate the pH of NH4ClO2. I don't remember those Ka or Kb values. (H^+) = sqrt(Kw/KaKb) and fit that into...
April 21, 2016

Chemistry
All are gases therefore, you may use as a shortcut that the L is directly the same as mols. 0.3L C2H2 x (2 H2O/2 C2H2) = ?L H2O produced. 0.3L C2H2 x (4 mols CO2/2 mols C2H2) = ? L CO2 produced. 0.3 L C2H2 x (5 mols O2/2 mols C2H2) = ? mols O2 used.
April 21, 2016

Chemistry
You made a typo; the atomic mass of Ag is 107.8(rounded). This is a limiting reagent (LR) problem and the way you know that is because amounts are given for BOTH reactants. 2Ag + S ==> Ag2S mols Ag = 2.16/atomic mass Ag = ? mols S = grams/atomic mass S = ? Using the ...
April 21, 2016

Chemistry
mL1 x M1 = mL2 x M2 25 x 6.0 = 1750 mL x M2 Solve for M of diluted HCl. Then pH = -log (HCl)
April 21, 2016

Chemistry
(P1/T1) = (P2/T2)
April 21, 2016

chemistry
There must be a question here but I don't see it.
April 21, 2016

Chemistry
Sr(NO3)2 + Na2CO3 ==> SrCO3(s) + 2NaNO3 As long as Na2CO3 is available (not all of it has reacted) adding Sr(NO3)2 forms more and more of the ppt of SrCO3. But even after all of the Na2CO3 is used, then increasing Sr(NO3)2 becomes a common ion and the Ksp dictates that the ...
April 21, 2016

chemistry
Do you want Kc or Kp? Kc = (NOBr)^2/(NO)^2(Br2)
April 21, 2016

chemistry
20 cm is a length. How much H2 gas is there?
April 21, 2016

Chemistry
HCl + NaOH ==> NaCl + H2O mols NaOH = M x L = ? mols HCl = mols NaOH (look at the coefficients; 1:1) Then M HCl = mols HCl/L HCl.
April 20, 2016

chemistry
q = mass H2O x heat fusion
April 20, 2016

chemistry
q1 = heat needed to raise T of liquid water from 40 C to liquid water at 100 C. q1 = mass H2O x specific heat H2O x (Tfinal-Tinitial) q2 = heat needed to convert water at 100 C to steam at 100 C. q2 = mass H2O x heat vaporization. Total q = q1 + q2. By the way, it helps us ...
April 20, 2016

Chemistry
By arbitrary rules the system is exothermic if the sign for delta H is negative, endothermic if the sign for delta H is +. Pretty simple, right?
April 20, 2016

chemistry
What reactions?
April 20, 2016

Chem
Are you sure it is CO2 and not CO?
April 20, 2016

Chemistry
q1 = heat needed to melt the ice at zero to form liquid water at zero. q1 = mass ice x heat fusion = ? q2 = heat needed to raise T of liquid H2O at zero to liquid water at 100 C. q2 = mass H2O x specific heat H2O x (Tfinal-Tinitial) q3 = heat needed to turn liquid water @ 100 ...
April 20, 2016

Chemistry- Dr.Bob222
Take a 1000 mL sample. 1000 mL x (1.01 g/mL) x 0.00655 x (1/molar mass HNO3) = Molarity of the HNO3 solution. Since HNO3 is a strong acid (it ionizes 100%) then (H3O^+) = (HNO3) and pH = -log(H3O^+) Since pH + pOH = pKw = 14, you can get pOH from that and OH comes from pOH = -...
April 20, 2016

Chemistry
I don't know the details of the experiment so I don't know if the results are high or low (or no change). Frankly, I don't agree with the term human error as different from experimental error. In my view, any error in the experiment is experimental error. If I ...
April 20, 2016

Chemistry
volume ethanol that is pure ethanol is 2.00 mL x 0.95 = ? mL. Then grams ethanol = ? mL x density = grams ethanol. Convert g ethanol to mols. mols = grams/molar mass = ? mols ethanol. Using the coefficients in the balanced equation, convert mols ethanol to mols CO2 and mols ...
April 20, 2016

Chemistry
You have made a typo (maybe two typos). You mean either FeSO4 or Fe2(SO4)3 and also, the equation is not balanced. I will assume FeSO4 but if my assumption is wrong, you will need adjust the molar mass of the product accordingly. First and second, correct the products, then ...
April 20, 2016

Chemistry
(V1/T1) = (V2/T2) Don't forget T must be in kelvin.
April 20, 2016

Chemistry
p1v1 = p2v2
April 20, 2016

chemestry
You may want to spell chemistry right. E = hc/wavelength for one atom. That x 6.02E22 atoms for 0.1 mol.
April 20, 2016

Chemistry-Dr.Bob222
Treat this as just another ammonia, NH3, problem. Remember, NH3 + HOH ==> NH4^+ + OH^- and you know how to solve those problems. This is the same thing. See here for the structure. https://en.wikipedia.org/wiki/Pyridine Let's call pyridine a simple PN. Then ......PN + ...
April 19, 2016

Chem
q = mass H2O x specific heatH2O x delta T. Solve for q. Since the temperature rose you know the heat was generated by the combustion of the butane so it was an exothermic reaction. That q is in J/3.00 g. Change to kJ/3.00 g, then kJ/3.00 g x (molar mass butane) = kJ/mol.
April 19, 2016

Chemistry
I don't see a question here. I assume you want directions for preparing the buffer. Let's say you want 1 L of the buffer. pH = pKa + log (base)/(acid) 7.40 = pK2 + log (base)/(0.0100) You will need to look up pK2 for H3PO4. solve the equation for (base). Knowing you ...
April 19, 2016

Chemistry
Ba(OH)2 + 2HCl ==> BaCl2 _ 2H2O mols Ba(OH)2 = grams/molar mass = ? Using the coefficient sin the balanced equation, convert mols Ba(OH)2 to mols HCl. Now convert mols HCl to grams. grams = mols HCl x molar mass HCl.
April 19, 2016

Chemistry
It really would have been nice if you told us how much ethanol (I presume that is number of mL) but you didn't type that in. Can't work the problem without proper information.
April 19, 2016

Chemistry
Not much to go on here. If you have delta H, I assume the next step is to calculate delta S and delta G. Then dGrxn = -RTlnK.
April 19, 2016

pre-ap chemistry
How many mols do you need? That's mols = M x L = ? Then mols = grams/molar mass. You know molar mas and mols, solve fo grams. Place that many grams in a 100 mL volumetric flask, add some water and swirl until all of the CuSO4 is dissolved, add DI water to the mark of the ...
April 19, 2016

Chemistry
I don't understand why it couldn't hold 19L or 30 L or for that matter 100 L if it were strong enough to resist bursting. 15.7 L is the answer for the problem that says v1 is 19L under certain conditions and you want to know v2 at different conditions but this problem ...
April 19, 2016

Chemistry
Cr2O3 Here is how you do it in a very simple way. Write CrO Over the Cr place a 3 Over the O place a 2 Place a . beside Cr at the bottom. Place a . beside O at the bottom. The bottom will look like this. Cr.O. and along the top (I can't do it because of spacing issues) ...
April 19, 2016

Chemistry
Kelly, I don't get it. How does Na2SO4 fit in. How does NaCl fit in. Where do they go? And where does the H2O go? When you write Pair of compounds, I see benzene and hexane but that leaves out Na2SO4.
April 19, 2016

Chemistry
Yes, or a net ionic equation. NaCl and Pb(NO3)2 will do it.
April 19, 2016

Chemistry
Your question is not clear. What solid?
April 19, 2016

chemistry
Write and balance the equation. Then dSo rxn = (n*dSo products) - (dSo reactants) Substitute and solve for dSo rxn.
April 19, 2016

Chemistry
Have you made a typo? Is that supposed to be AsO4^3-
April 19, 2016

Chemistry
Here is the NO3^- half. 1. Write it down. NO3^- ==> NO 2. Oxidation state of N on left is +5; on the right is +2. Change in oxidation state is gain of 3e. Do that as step 3.[5+ +(-3) = 2+] 3. NO3^- +3e ==> NO 4. Count up the charge on both sides. I see -4 on the left and...
April 19, 2016

Chemistry
What are the other reactions?
April 19, 2016

Chemistry
572 kJ x (54.0/2.00) = ? kJ
April 18, 2016

Chemistry
(32.6 bil bar/yr) x ?yrs = 1526 bil Solve for ? yrs in billions of barrels.
April 18, 2016

Chemistry
2H2(g) + O2(g) --> 2H2O(g) + 483.6 kJ. You want to go backwards with 5.00 mols H2O vapor instead of 2.00 mols. 483.6 kJ x (5.00/2.00) = ?
April 18, 2016

chemistry
dGo = =nFE
April 18, 2016

chem
In my 75 yrs if working with chemistry I've never run across Hal.
April 18, 2016

Chemistry
......Mg(OH)2 ==> Mg^2+ + 2OH^- I......solid.......0.......0 C......solid.......x.......2x E......solid.......x.......2x Then NH3 + HOH ==> NH4^+ + OH^- I....0.1...........0........0 C....-x............x........x E....0.1-x.........x........x First, determine the OH^- ...
April 18, 2016

Chemistry
See other post.
April 18, 2016

Chemistry
You're a genius if you can do this. You don't have enough information. You've omitted the joules necessary to raise the temperature by 5 C.
April 18, 2016

Chemistry
Use 1.047 g to calculate mols He. mols = grams/atomic mass. Then use PV = nRT and solve for P. This will be in atm; I would conert that to mm Hg. atm x 760 = pHe in mmHg. Then Ptotal = pHe + phexane You know Ptotal = 739.6 mm You know PHe from PV = nRT; solve for phexane.
April 18, 2016

Chemistry
I'm assume the solution is one of sucrose and water. delta T = Kb*m Solve for delta T, then add to the normal boiling point to find the new boiling point.
April 18, 2016

Chemistry
Mg + 2HCl ==> MgCl2 + H2
April 18, 2016

AP Chemistry
Ditto Bob Pursley and his comments.
April 18, 2016

chem
mols Al2(SO4)3 = grams/molar mass = ? There are 12 O atoms per 1 mol Al2(SO4)3 so there are 12 x mols Al2(SO4)3 there. Convert mols O to grams O. g = mols x 16 = ? I assume the question means grams O (atoms) and not O2 (molecules).
April 18, 2016

chem
"full mineralization of toluene???"
April 18, 2016

chemistry
0.717 g KH2PO4 in 500 mL to ppm. You want to convert to mg/L. 717 mg/500 mL = 1434 mg/L = 1434 ppm.
April 18, 2016

chemistry
1000 mL x 1.18 g/mL x 0.37 x (1/36.5) = ? mols/L = ? M concd HCl. b. M = mol/L. You know mols and M, solve for L and convert to mL. mass = volume x density. You know density and volume, solve for mass.
April 18, 2016

Chemistry
120 W = 120 J/s. For 1 hour that is 120 J/s x 60 s/hr = 7200 J. 7200 = mass H2O x delta H vaporization. Substitute and solve for mass H2O (sweat)
April 18, 2016

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