Sunday
May 29, 2016

Posts by DrBob222

Total # Posts: 52,449

chemistry
1. Write and balanced the equation. 2. Convert 13.75 g Ba(OH)2 to mols. mols = grams/molar mass = ? 3. Using the coefficients in the balanced equation, convert mols Ba(OH)2 to mols H3PO4. 4. Now convert mols H3PO4 to the volume needed. M = mols/L. You have M and mols, ...
February 15, 2016

chemistry
2KClO3 ==> 2KCl + 3O2 You need how many mols O2? That's n = PV/RT. Substitute and solve for n = mols O2. Using the coefficients in the balanced equation, convert mols O2 needed to mols KClO3. Convert mols KClO3 to g KClO3 needed. That's grams = mols x molar mass = ?
February 15, 2016

Chemistry
2Al + 6HBr ==> 2AlBr3 + 3H2 4 mols Al will produce how much H2? That's 4 mols Al x (3 mols H2/2) mols Al) = ? 3 mols HBr will produce how much H2?That's 3 mols HBr x (3 mols H2/6 mols HBr) = ? This is a limiting reagent problem. The answer to how much is produced is...
February 12, 2016

Chemistry
Energy used to melt ice at zero C to liquid water at zero C. dq = mass ice x heat fusion = (10/18) x 6.02 kJ/mol = 3.34 kJ. Energy remaining to be used is 8.50 kJ - 3.34 = 5.15 kJ. Energy used to raise T of water at zero C to 100 C. q = mass H2O x specific heat H2O x (Tfinal-...
February 12, 2016

chemistry
Limestone rock contains solid calcium carbonate that can react with acid to give products. In one experiment, 1.452 g of limestone rock is pulverised and then treated with 25.00 mL of 1.035 M HCl solution. After the reaction is completed, the resulting mixture is still acidic...
February 12, 2016

Chemistry
How about this? 20Ne + 21Ne + 22Ne = 100% 20Ne + 0.26 + 22Ne = 100% and 20Ne + 22Ne = 100-0.26 = 99.74% Let x = 20Ne and 0.9974-x = 22Ne Set your equation up as usual and solve for x and 0.9974-x.
February 12, 2016

Science (1 question)
Rolling friction is the correct answer. Why not gravity. The question is about REDUCING some force. You CAN reduce the friction since the wheels are not touching the track but you can NOT reduce gravity. That is present in the same amount where ever the wheels are; i.e., above...
February 10, 2016

Chemistry 101
heat lost by granite + heat gained by H2O = 0 [mass granite x specific heat granit x (Tfinal-Tinitial)] + [mass H2O x specific heat H2O x (Tfinal-Tinitial)] = 0 Substitute and solve for specific heat granite, the only unknown.
February 10, 2016

Chemestry
When the next (spoonful, pinch, spatula, etc) was placed into the solution and it did not dissolve.
February 10, 2016

Chemistry
(V1/T1) = (V2/T2) Don't forget C must be in kelvin.
February 9, 2016

AP Chemisty
.......CaSO4 --> Ca^2+ + SO4^2- I......solid......0.......0 C......solid......x.......x E......solid......x.......x Ksp CaSO4 = (Ca^2+)(SO4^2-) Now if we add a large excess of sulfate as Na2SO4, that makes SO4^2- very large, Le Chatelier's Principle says the reaction ...
February 9, 2016

Chemistry
HCl is a strong acid; therefore, it ionizes 100% which means (H3O^+)=(HCl)
February 9, 2016

Chemistry
I don't see a question here, but why not write that "weird" acid as sulfuric (or sulphuric) acid?
February 9, 2016

Chemistry
........HA ==> H^+ + A^- I....0.001.....0.....0 C......-x......x.....x E....0.001-x...x.....x Substitute the E line into the Ka expression and solve for x = (H^+) and convert to pH. Be careful, you may need to use the quadratic equation; i.e., you may not be able to call 0....
February 9, 2016

chemistry
pH + pOH = pKw; then pH = pKw - pOH
February 9, 2016

AP CHEMISTRY
Probably you worked it right and left off the exponents. The answer is 5.27E-4 bar unless that K you list is Kc and not Kp.
February 9, 2016

Chemistry
Step1. Calculate the mols KMnO4 used. mols KMnO4 = M x L = ? Step2. Using the coefficients in the balanced equation, convert mols KMnO4 used to mols Na2C2O4 needed. Step3. Then mass Na2C2O4 = mols Na2C2O4 x molar mass Na2C2O4.
February 9, 2016

Chemistry 101
a. I would convert 35 mpg to km/L. I obtained 14.88 km/L but you should confirm that. Then distance = km/L x 22 L = ? b. 1 gallon = 3.785 L. $1.99/gallon x (1 gallon/3.785 L) x 22 L = ? c. Take the km from part a, convert to miles, then 44 mi/hr x #hr = total miles Solve for...
February 9, 2016

Chemistry 101
volume Pb = mass/density You know mass in pounds, convert that to grams. There are 454.6 g Pb in one pound. You know density. Solve for volume of Pb. The volume of the Pb pushes out that much volume of the water so add 2500 mL + volume Pb in mL to find final volume of water.
February 9, 2016

Chemistry 101
1 mL = 1 cm^3 = 1 cubic centimeter = 1 cc. 7.50 cc x 7.85 g/cc = 58.9 grams. Note that cc in numerator cancels with cc in the denominator.
February 9, 2016

Chemistry 101
mass object = volume x density volume = 57.50-50.00 = ? density = given. Solve for mass object.
February 9, 2016

Chemistry 101
Convert 1" to cm 1 in x 2.54 cm/in = 2.54 cm Volume sphere = (4/3)*pi*r^3 Then density = mass/volume = ? and compare with 1.00 g/cc.
February 9, 2016

Chemistry
delta T = Kf*m You know delta T, Kf is 1.86, solve for molality.
February 9, 2016

chemistry
CaCl2 + Ca(NO3)2 ==> No reaction. CaCl2 + 2AgNO3 ==> 2AgCl + Ca(NO3)2 CaCl2 + AgNO3 + NH3 + H2O ==> Ag(NH3)2Cl + Ca(NO3)2 and you balance.
February 9, 2016

AP Chemistry
.........HF => H^+ + F^- I.......4.7E-2..0....0 C.......-x......x....x E.....4.7E-2....x....x Ka = (x^2)/(4.7E-2 - x) Solve for x = (H^+) and convert to pH. If you are having trouble obtaining the correct answer you may need to solve the quadratic; i.e., don't neglect ...
February 9, 2016

Analytical Chem
NaOH + CO2 ==> NaHCO3 or you can write CO2 + H2O ==> H2CO3, then H2CO3 + NaOH ==> NaHCO3 + H2O
February 9, 2016

Analytical Chem
NaOH absorbs CO2 from the atmosphere and pH decreases.
February 9, 2016

Chemistry
........2A(aq) <--> B(aq) I.......3.10........0 C.......-2x.........x E.....3.10-2x.......x 5.48E-5 = (x)/(3.10-2x) Clear the denominator. 5.48E-5(3.10-2x) = x 5.48E-5*3.10 - 5.48E-5*2x = x Complete the multiplication, combine terms, solve for x.
February 9, 2016

chem,i need someone to explain this definition
Suppose you have a piece of pure aluminum. That means there is no other material(chemical if you will) in that piece of Al. You may treat Al with other chemicals that will make compounds (a compound is composed of two or more elements) BUT you can not treat pure Al (an element...
February 8, 2016

Science 10
distance = 1/2 * gt^2 You know d and g, substitute and solve for t.
February 8, 2016

Chemistry
mols SO3 = grams/molar mass = ? Then M SO3 = mols/L. Let's call this about 0.0075 M but that's just an estimate. You need to do it much more accurately. mols O2 = grams/mola mass = ? Then M O2 = mols/L. Let's call this about 0.003 M. Again, you should do it more ...
February 8, 2016

chemistry
See your post on Al2(CO3)3 to see how to do this one.
February 8, 2016

Chemistry
39 g Al2(CO3)3 mols Al2(CO3)3 = grams/molar mass = ? There are 2 mols Al^3+ for every mole of Al2(CO3)3 There 3 mols of [CO3]^2- for every mole of Al2(CO3)3. There are 9 mols O atoms for every mole Al2(CO3)3
February 8, 2016

Chemistry
p1v1 = p2v2
February 8, 2016

chemistry
Please rephrase your question and/or provide more information. It isn't clear to me what you want.
February 8, 2016

Chemistry
Ptotal = p(drygas) + pH2O 750 = pdrygas + 20 Solve for p dry gas.
February 7, 2016

chemistry
I have not used the triiodide ion (I3^-) below but you may convert to that if you wish. KIO3 + 5KI + 3H2SO4 ==> 3H2O + I2 + 3K2SO4 2S2O3^2- + I2 ==> S4O6^2 + 2I^- mols KIO3 = M x L = ? mols I2 produced = 3 x that = ? mols S2O3^2- needed = 2 x mols I2 = ? Then M S2O3^2...
February 7, 2016

organic chemistry
First, determine K. Ko/a = 20/13.3 Then K = (org layer)/(aq layer) For part b. Let x = grams in org layer; then 40-x = grams in aq layer. Then (organic layer) = x/300 (aqueous layer) = (40-x)/300 K = (x/300)/(40-x)/300 Solve for x and 40-x. For part a use the same set up but ...
February 7, 2016

chem 12
I don't see that you have gone astray. I don't see anything wrong.
February 6, 2016

chemistry
Fe2O3 + 3C → 2Fe + 3CO mols Fe2O3 = grams/molar mass = ? mols C needed = 3x that. Look at the coefficients. g C = mols C x atomic mass C = ?
February 6, 2016

chemistry
A non-polar solvent? such as hexane.
February 6, 2016

Chemistry
mols Br2 gas = grams/molar mass = ? Then PV = nRT and solve for P.
February 6, 2016

Chmistry
mols HNO3 = grams/molar mass = ? Then M HNO3 = mols HNO3/0.1L = ? Then pH = -log(HNO3)
February 6, 2016

SyEd
The right most C has only three bonds; it needs another one to be a viable compound.
February 6, 2016

Chemistry
pi = i*M*RT. i is 2 for NaCl (the van't Hoff factor) M = grams NaCl/molar mass/0.1L R as usual T given Solve for pi in atm if R is 0.08206 L*atm/mol*K
February 6, 2016

Chemistry
delta P = i*Xsolute*Po delta P is 9.2-8.0 = > Po = 9.2 i = 3 for MgCl2. Solve for Xsolute and use nsolute/(nsolute+nsolvent) = X (Note that n solvent is 500/18). Solve for nsolute, convert to grams MgCl2.
February 5, 2016

Chemistry
I think you need to re-word the question. I find it difficult to believe that a solution boiling at 0.125C is greater than that of pure benzene. Do you know the b.p. of pure benzene. I think it's about 80 C.
February 5, 2016

Chemistry
It isn't possible for us to draw mechanisms on this forum but here is one from the web. http://www.chemguide.co.uk/physical/catalysis/esterify.html
February 5, 2016

@Bob PursleyChemistry
Check this step. hen reactant is moles=11.205/(10.8*2+3*48) Is that 3*16?
February 5, 2016

chemistry
https://www.google.com/search?q=bond+order+oxygen&ie=utf-8&oe=utf-8
February 5, 2016

Chemistry
H2SO4 ==> H2O + SO3 ...x......4.52 + 20.09 x = 4.52 + 20.09 = 24.61 Law of Conservation of mass. Starting mass = ending mass.
February 4, 2016

chemistry
In your book the reaction between iron and oxalic acid to produce iron(II) oxalate. Then they go through a decomposition of iron(II) oxalate to form iron(II) oxide. This is a two-step synthesis. Bob Pursley gave you the direct one-step process which is far easier to do.
February 4, 2016

Gen Chem
This a multistep problem involving simultaneous equations. pi = i*M*R*T. I is the van't Hoff factor. Substitute and solve for M = molarity. Then you have two equations. Let X = grams NaCl and Y = grams sucrose = SU equation 1 is X +Y = 10.2 Then mols NaCl + mols SU = total...
February 4, 2016

Chemistry- Dr. Bob222
I obtained 109.22 but I think the 37.4 kJ number allows only 3 sig figures.
February 4, 2016

Chemistry
2F2(g)+2H2O(l)= 4HF(aq) + O2(g)
February 4, 2016

Chemistry
See your other post.
February 4, 2016

Chemistry
If it is heated enough to boil off some of the water it will become more concentrated in the acid and that will lower the pH. If it is heated slightly and you use a regular pH meter, most meters have an adjustment to correct for that so the pH should be correct as measured.
February 4, 2016

CHEM HELP PLEASE
https://www.youtube.com/watch?v=riMzriytw40
February 3, 2016

chemistry
Like dissolves like. That is, polar solvents dissolve polar solutes but not non-polar solutes and non-polar solvents dissolve non-polar solutes.
February 3, 2016

Chemistry
delta T = i*Kf*m i = van't Hoff factor, which for KNO3 is 2. So -0.744. b. Have you had anything about the Debye-Huckel theory/law. That says the 0.2 m is not quite 0.2 and as the concn increases there is more attraction between solvent/solute molecules. The net result is ...
February 3, 2016

Chemistry
2AgNO3 + Cu ==> Ag + Cu(NO3)2 Cu metal is more easily oxidized than silver metal so the Cu metal is oxidized and the Ag ion is reduced to silver metal.
February 3, 2016

chem 12
I think you are using some of the numbers incorrectly. .........N2 + O2 ==> N2O4 I......0.04..0.04.....0 C.......-x...-2x......+x E...0.04-x...0.04-2x...+x The problem states that the N2 consumed (that's x) is 0.0059 so the new (N2)is 0.04-0.0059 = ? New (O2) is 0.04-[2...
February 3, 2016

Chemistry
ppmv = (2E-8/100)*10^6 = ?
February 3, 2016

Chemistry
Sc 1s2 2s2 2p6 3s2 3p6 3d1 4s2 Basically the 3d and 4s levels are so close in energy for Sc that energy necessary to remove 4s2 and 3d1 are about the same so you see only +3 oxidation state.
February 3, 2016

Chemistry
There may be a number of reasons. One is that the electrons in Mn and O are shared and not transferred but this may not be the answer you are looking for.
February 3, 2016

Chemistry
Mn has 25+ and 23- for +2 net. Fe has 26+ and 24- for +2 net. Therefore, Fe^2+ has a higher + charge pulling on those outside electrons.
February 3, 2016

Chemistry
The 41 drops is correct but not the 14. That's for water. You want HIO3 so it is 0.010 x (6/41) = ?
February 2, 2016

Chemistry
The other halogen (I,Br, Cl) are large enough to accommodate 5 or 7 F atoms and have enough space for the extra pair of electrons (there are more than 8 around the B atom). However, note that IBr5 and BrCl5 (and others) are not "invariably" F.
February 2, 2016

chemistry
I would do a melting point.
February 2, 2016

Chemistry
That looks good to me but you have too many significant figures if you posted the problem correctly. 7.5 L allows only two places and I would round to 22 g.
February 2, 2016

Chemistry
(HI) = 16.7/10 = 1.67 M .....H2 + I2 ==> 2HI I.....0....0......1.67 C.....x....x......-2x E.....x....x.....1.67-2x Plug the E line into the Kc expression and solve for x
February 2, 2016

Chemistry
Use the Clausius-Clapeyron equation. You can use the "other" p/t numbers as 273 K at 760 torr. Remember to use the correct value for R.
February 2, 2016

Chemistry
Mike, what is your trouble with this?
February 1, 2016

chemistry
I would like to clarify Steve's answer a little. Since the question is so detailed about the phases I suspect the author of the question wants you to include the phases like this. HCl(aq) + NaHCO3(s) --> H2O(l) + NaCl(aq) + CO2(g)
February 1, 2016

chem
q = mass x specific heat x (Tfinal-Tinitial).
February 1, 2016

chemistry
v1/t1 = v2/t2
February 1, 2016

chemistry
This is a limiting reagent (LR) problem and you know that because amounts are given for BOTH reactants. 2C2H6 + 7O2 ==> 4CO2 + 6H2O mols C2H6 = grams/molar mass = ? mols O2 = grams/molar mass = ? Using the coefficients in the balanced equation, convert mols ethane to mols ...
January 31, 2016

Chemistry
It would help if you gave an example of what you're asking.
January 31, 2016

chem
I didn't check the math but the numbers and substitution are correct.
January 31, 2016

chemistry
AgNO3 + NaCl ==> AgCl + NaNO3. You quote all of those numbers BUT ask only for the equation. Two observations. 1.This is a limiting reagent problem if you want to do the math and determine the amount of AgCl formed. 2. I call that silver nitrate and sodium nitrate. In my ...
January 31, 2016

Chemistry
1 no. PV = nRT and solve for n = number of mols. Then n x 6.022E23 = number He atoms. Same at both temperatures. 2. density = P*molar mass/RT gives density in g/L. Convert to g/L.
January 31, 2016

Chemistry
1. p1v1 = p2v2 p1= 5 atm v1 = 1 L p2 = ? v2 = 11 Solve for p2 = partial pressure Ar in the combined system. Do the same and calculate pN2. Ptotal = pN2 + pAr pN2 = XN2*Ptotal. Substitute and solve for XN2. pAr = XAr*Ptotal. Solve for XAr. 3. If XAr = 0.5, then XN2 must be 0.5 ...
January 31, 2016

Chemistry
I THINK your problem is that the value of 0.87 is two significant figures (s.f.) but your answer is 5 s.f. and that isn't kosher. Try rounding your answer to 2 s.f. (1.8) and see if that works.
January 28, 2016

chemistry
29.568 g = mass bkr and alcohol. -24.568 g = mass empty bkr ----------- 5.000 g = mass alcohol Then volume = mass/density. Substitute and solve for volume in cc.
January 27, 2016

Chemistry
I don't know how you obtained that answer but the unit is %. The molar mass of Al2(SO4)3.18H2O is 666.429 and 18 mols H2O = 324.275 so %H2O = about (324/666)*100 = ?%. You can do it more accurately.
January 27, 2016

chemistry
This is a lot of writing. I shall be happy to critique your thoughts. If you don't know the process in each, look on google, read your text/notes, ask here and explain what you don't understand.
January 27, 2016

chem 101
q = mass H2O x specific heat H2O x (Tfinal-Tinitial)
January 27, 2016

Chem
Use PV = nRT P = unknown to be calculated. V = 500 mL but convert to L. n = grams He/molar mass He. R = 0.08206 L*atm/mol*K T = 77 K. Note this calculation does not involve H2. Dalton's Law tells us that EACH gas exerts its own partial pressure regardless of other gases ...
January 27, 2016

Chemistry
I think this is just what you're looking for. BCC is 2, FCC us 4, simple cubic is 1. http://chemed.chem.purdue.edu/genchem/topicreview/bp/ch13/unitcell.php#determ
January 27, 2016

Chemistry
More than likely it is F2.
January 27, 2016

Chemistry
2H2 + O2 --> 2H2O mols H2O = grams/molar mass = ? Using the coefficients in the balanced equation, convert mols H2O to mols O2. If you want amount O2 in grams, then g O2 = mols O2 x molar mass O2.
January 27, 2016

Chemistry 102
M Fe^3+ = 1.11E-3 x (16/26) = ? and lets calls this a. M SCN^- = 1.11E-3 x (10/26) = ? and let's call this b. ......Fe^3+ + CN^- --> FeCNS^2+ I.....a........b.........0 C....-x.......-x.........x E....a-x.......b-x.......x Substitute the E line into the Kc expression ...
January 27, 2016

Chemistry
Use PV = nRT You know P (1 atm), v(55 cm but change that to L), n (solve for this), R (0.08206 L*atm/mol*K), T (20 C but change that to kelvin). n = number of mols. grams CO2 = mols x molar mass CO2 T(kelvin) = celsius T + 273
January 27, 2016

Chem
mols glucose = 1.50 mols water = 3.50 total mols = 1.50 + 3.50 = ? X(mol fraction) H2O = mols water/total mols. Psolution = Xsolvent*Po solvent
January 27, 2016

Chemistry
m is molality and M is molarity; however, I understand Osm is the osmolarity of the solution. I will answer on that assumption. MgCl2 has a van't Hoff factor of 3; i.e., MgCl2 ionizes in solution to three particles. How many OSm do you want? That's 0.4 x 2/3 = ? grams...
January 27, 2016

Chemistry 101
mass = volume x density
January 27, 2016

Chemistry 101
No. Yes, mass = volume x density so volume = mass/density = 2/0.785 = ?
January 27, 2016

Chemistry
2H2 + O2 ==> 2H2O + heat So 4.5 g gives 72 kJ, heat for the reaction above is -72 kJ x 36 g/4.5 g = -576 kJ. That's for 2 mols so for 1 mole is it -576/2 = ?
January 27, 2016

Chemistry
There are 5 mols C in each mol of C5H12; therefore, in 10.5 mols C5H12 there must be 5*10.5 = ? mols C.
January 27, 2016

Chemistry
Please post ALL of problem.
January 27, 2016

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