Friday
July 29, 2016

Posts by DrBob222

Total # Posts: 52,781

CHEMISTRY
I would do this. 5% w/v means 5g HAc/100 mL solution which is (5/60) mols/100 and that is 5/60/0.1L or 0.0833 M. Then millimols HAc is 30 x 0.0833 = 25. So acid + base = 25 pH = pKa + log(base)/(acid) 5.75 = 4.74 + log b/a b/a = about 10.3 but you need a better answer than ...
February 18, 2016

CHEMISTRY!!!! HELP
I didn't check 2. #1 is not right but the system is correct. 1. Your calculation for molar mass of Ag2O is not right. The molar mass is closer to 231.8. You obtained that number by 1Ag + 2O and it should be 2Ag + 1 O or (2*107.9)+ 16 = about 231.8. 2. The second error is ...
February 17, 2016

Chemistry
1. Zn + 2AgNO3 ==> Zn(NO3)2 + 2Ag mols AgNO3 = grams/molar mass = ? Using the coefficients in the balanced equation, convert mols AgNO3 to mols Zn. Now convert mols Zn to grams Zn. g Zn = mols Zn x atomic mass Zn. 2. The balanced equation is as follows: (NH4)2SO4 + Ca(OH)2...
February 17, 2016

Chemistry Help please! (:
Answered above.
February 17, 2016

chemistry
D is correct
February 17, 2016

chemistry
The answer is hydrogen bonding in H2O as opposed to H2S; the best answer choice is A. Hydrogen bonding a intermolecular bonding.
February 17, 2016

chemistry
I don't think the question makes any sense. The hands are not anything. I suspect the answer the author wants is A; i.e., chemical energy drives the clock hands to move.
February 17, 2016

chemistry
CaC2 + 2H2O --> Ca(OH)2 + C2H2 mols CaC2 = grams/molar mass = ? Using the coefficients in the balanced equation, convert mols CaC2 to mols C2H2 Then grams C2H2 = mols C2H2 x molar mass C2H2. This the theoretical yield (TY). The actual yield (AY) is 13.5 grams. %yield = (AY/...
February 17, 2016

Chemistry
First determine the constant in p = Kc*C You're given p and C, solve for Kc. Then using that value for Kc, plug in M and Kc and solve for pN2.
February 17, 2016

Chemistry
pH = pKa + log (base)/(acid) You know pH, Ka is calculated from KaKb = Kw = 1E-14 and pKa = -log Ka. You know base is 0.1, substitute into the above and solve for acid. Since the problem asks for mols and grams, the easy to do this is to substitute millimols into (base) and (...
February 17, 2016

Chemistry
None of the equations are balanced.
February 16, 2016

Chemistry
The amount of NaHCO3 depends only upon the starting amount of NH3. 1. You have the equation. Make sure it is balanced. If not, balance it before going further. 2. Convert NH3 to mols. mol = M x L = ? 3. Using the coefficients in the balanced equation, convert mols MJ3 to mols ...
February 16, 2016

chemistry
There is no problem with the NaCl or the AgNO3; the problem exists because of the K2CrO4 indicator solution. In practice the pH is adjusted to between 7 and 10; NaHCO3 is usually used. At lower pH values, the CrO4^2- is converted to HCrO4^-. CrO4^2- + H^+ ==> HCrO4^- ...
February 16, 2016

chemistry
The white ppt is BaCO3. The gas given off is CO2. CO3^2- + 2H^+ ==> CO2(gas) + H2O CO2 + Ba(OH)2 ==> BaCO3(s) + H2O
February 16, 2016

Chemistry
All of the plastics in your car (and your home) are chemistry. The food you eat is chemistry. The clothes you wear are chemistry. The computer you use is chemistry. Bob Pursley is right on target. EVERYTHING is chemistry. The more you understand chemistry the more you ...
February 16, 2016

oops Semisi----Chemistry: stoich
You didn't convert 320 g O2 to mols first. mols O2 = 320/32 = 10; then 10 x 5/4 = 8.00 mols H2O formed.
February 16, 2016

oops Semisi===Chemistry
No that's not right. mols O2 = 2.50g/32 = 0.078 but you should do it more accurately. Convert to mols Fe2O3. That's 0.078 x 2/3 = approx 0.052 Then g Fe2O3 = mols x molar mass = 0.052 x 159.7 = approx 8.3.
February 16, 2016

Chemistry
Pick out iron filings with a magnet, add water. Wood ships float to the top and can be picked out. Filter what remains and the sand will be trapped in the filter paper. The salt will remain in the water. Evaporate the water to recover the salt.
February 16, 2016

chemistry
Use PV = nRT and solve for pNH3 initially. Substitute pNH3 from this calculation into the below. pNH3 is approx 1.5 but you need a more accurate number. ...........NH4HS ⇌ NH3 + H2S I.........solid....1.5....0 C.........solid.....+x....x E.........solid....1.3+x...x ...
February 16, 2016

Chemistry
.......4KO2+2CO2⇌2K2CO3+3O2(g) E.....solid..7.33E-2.solid...x Kp = p(O2)^3/p(CO2)^2 Substitute and solve for pO2 Ptotal = pCO2 + pO2
February 16, 2016

Chemistry
See your other post.
February 16, 2016

Chemistry
OK. You changed screen names BUT you also included units. Then heat is added delta H is +. When heat is produced, delta H is -. So for this _+2.4 kcal is delta H.
February 16, 2016

Chemistry, chemical change
Can't answer. You didn't include the units for the 22,000. 22,000 what? The rules are that if it is exothermic, and this reaction is because it tells you it reacts and gives off heat, then delta H is negative. So delta H = -22,000 somethings or -22 somethings. The ...
February 16, 2016

Chemistry
delta P = Xsolute*Poacetone
February 15, 2016

Chemistry
Calculate mole fraction ethylene glycol. Then Psolution = Xsolution *Po H2O You would do well to use the same screen names for your posts.
February 15, 2016

Chemistry
Do you mean NaCl or NaBr. I assume NaBr. 2Na + Br2 ==> 2NaBr mols Na = grams/atomic mass Na = ? Using the coefficients in the balanced equation convert mols Na to mols NaBr. Then grams NaBr = mols NaBr x molar mass NaBr.
February 15, 2016

chem21
2.8 g x (100 mL/27 mL) = ? or if you want to do it by proportion it is (2.8/27) = (x/100) Solve for x.
February 15, 2016

Chem
That melts the ice at zero to liquid water at zero C. Now to heat it from zero C to 60 C is q = mc*delta T. q = 30 x 4.184 x (Tfinal-Tinitial) Then add the two for the total.
February 15, 2016

Chem
4Al + 3H2SO4 ==> 2Al2(SO4)3 + 3H2 Does all of the Al dissolve? Assuming it does, then, how many mols H2 are produced? That's n = PV/RT = (480*0.427)/(8.314*300) = about ? ?mols H2 x (4 mols Al/3 mols H2) = ? = grams theoretical yield. %yield = (grams H2 produced/7.5)*...
February 15, 2016

chem
H2SO4 + 2NaHCO3 ==> Na2SO4 + 2H2O + 2CO2 mass NaHCO3 = 155.00-144.50 = 10.50 g used. mols NaHCO3 = grams/molar mass = about 0.125 If all were to be used it would produce how many mols H2O. That is 0.125 mols NaHCO3 x (2 mols H2O/2 mols NaHCO3) = 0.125 mols CO2. mols H2SO4...
February 15, 2016

@Emma---chemistry
Note that this is a limiting reagent problem.
February 15, 2016

chem
mols Cu initially = grams/atomic mass = about 0.3 but you need a more accurate answer. mols HNO3 initially = M x L = about 1.3 but see note above. Convert mols Cu to mols NO2. That's about 0.3 mols Cu x (2 mols NO2/1 mols Cu) = about 0.6 mols. Convert mols HNO3 to mols NO2...
February 15, 2016

Chemistry
This is a limiting reagent (LR) problem. You know that because amounts are given for BOTH reagents. I suppose you means HCl for HC. 1. Write and balance the equation. 2. Convert grams Mg to mols. mols = grams/atomic mass = ? 3. Convert HCl to mols. mols HCl = M x L = ? 4. ...
February 15, 2016

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

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