Thursday
May 5, 2016

Posts by DrBob222

Total # Posts: 52,253

Chemistry
Carboxylic acid is correct. The OH group is a phenol group (an alcohol on R group but phenol group when attached to an aromatic ring (AR).
February 23, 2016

Chemistry
Isotonic, hypotonic, hypertonic when compared to what. Iassume you mean when compared with NORMAL saline which is 0.9% NaCl. I would convert 0.9% NaCl to M and use pi = i*MRT to calculate the osmotic pressure. Then convert all of the solution to M and pi. Compart with the ...
February 23, 2016

Chemistry
Let;s call pyridine just B and we know that is a base. ............B + HOH ==> BH^+ + OH^- I........0.02........0.02*0.0003 for BHY and 0.02*0.0003 for OH. Substitute that into the Kb and solve for Kb.
February 23, 2016

Chemistry
H2SO4 + Ba(OH)2 ==> BaSO4 + 2H2O mols Ba(OH)2 = M x L = ? mols H2SO4 = mols Ba(OH)2 M H2SO4 = mols H2SO4/L H2SO4.
February 23, 2016

Chemistry
This done the same way as the BaSO4 problem.
February 23, 2016

Chemistry
Read the problem. It says you started with 147.9 g Mg.
February 23, 2016

chem-1
Use the two equations below. k = 0.693/t1/2 Then substitute k into the below equation. ln(No/N) = kt No = 100 N = 10 k from above. solve for t in min. Something like 66 minutes.
February 23, 2016

Chemistry
You have two equations in two unknowns. Solve the two equations simultaneously. Let X = mass KI and Y = mass NaCl equation 1 is X + Y = 10 (Note: I chose to use 10. You can use ANY number as long as you are consistent.) mm stands for molar mass in equation 2. Equation 2 is X(...
February 23, 2016

Chemistry
4Al + 3O2 ==> 2Al2O3 molsl Al = grams/molar mass = ? Using the coefficients in the balanced equation, convert mols Al to mols Al2O2. Now convert mols Al2O3 to grams. g = mols x molar mass = ?
February 22, 2016

Chemistry
Look at the activity series. The Mg will displace the Ag in AgNO3 but will not react with KNO3.
February 22, 2016

Chemistry
If you remove the electron, that means it is moved to just outside the H atom and that means you use n = infinity. In the equation, then, 1/infinity = 0. In effect you simply have R*[1/(n^2)1-(n^2)2 = R*(16 -0)
February 22, 2016

Chemistry
Please rephrase/rewrite in readable form. It makes no sense as is.
February 22, 2016

chemistry
Cu pan is solid iron nails solid water liquid glass marbles supercooled liquid.
February 22, 2016

Chemistry
1/wavelength = R[1/(N^2)1 -1/(N^2)]2 R = 1.07937E7 in meters N1 = 4 so N^ is 16 N2 is infinity so 1/infinity = 0
February 22, 2016

chemistry
L1 x M1 = L2 x M2 0.03L x 2.5M = 0.050 x M2 Solve for M2.
February 22, 2016

chemistry
80 what? 80 grams 80 bushels 80 gallons 80 baseball fields
February 22, 2016

CHEMISTRY
.......H2CO3 --> H^+ + HCO3^- I......0.025.....0......0 C.......-x.......x......x E....0.025-x.....x......x Plug the E line into the Ka1 expression and solve for H^+ = HCO3^- Then k2 = (CO3^2-)
February 22, 2016

CHEMISTRY
A is true. B is not
February 22, 2016

Chemistry
Use PV = nRT and solve for n = number of mols. Then n = grams/molar mass. You know n and grams, solve for molar mass.
February 22, 2016

Chemistry
The rate of the reaction (from sweet to sour milk) is increased by temperature. In general, the rate of a reaction increases 2x for every 10 degrees increase in T. However, the best answer for this question is that increased T allows the bacteria to grow MUCH faster. More ...
February 22, 2016

Chemistry
Two equations in two unknowns. Solve the two simultaneously. Let X = g NaCl and Y = g KCl equation 1 is X + Y = 1 g Equation 2 comes here. mm stands for molar mass. X(mm AgCl/mm NaCl) + Y(mm AgCl/mm KCl) = 2 g Solve for X and Y in grams NaCl and grams KCl. Then convert g each ...
February 22, 2016

gen chem
Use the Arrhenius equation. ln(k2/k Y1) = Ea(1/T1-1/T2)/R You have k1 and k2; also Ea and T1. Substitute and solve for T2.
February 22, 2016

Chemistry
Tell us your problem here.
February 21, 2016

Chemistry
NH3 + HCl ==> NH4Cl mols NH4Cl = grams/molar mass = approx 12.5/53.5 = approx 0.23 Since 1 mol NH4Cl requires 1 mol NH3, plug 0.23 for mols into PV = nRT and solve for V in L.
February 21, 2016

chemistry
Yes. CH3COOH and C2H5OH makes ethyl acetate or ethyl ethanoate. You want propanoic acid and isoamyl alcohol to make isoamyl propanoate. I gave that ethyl acetate example to show you how it was named and put together. That's how I figure which is the alcohol and which is ...
February 21, 2016

organic chemistry
Other than what? Isopentyl is the same as isoamyl.
February 21, 2016

Chemistry
If you take the ideal gas law of PV = nRT and modify it to P*molar mass = density*RT (745/760)*M = 1.2*0.08206*293 Solve for M = molar mass.
February 21, 2016

Chemistry
See your post above and use P*M = dRT
February 21, 2016

chemistry functional groups
I think this site may explain it better than I can. Apparently it can be used one of three ways. In the sense of your question I believe methylene bridge is the correct usage. But see the other uses at this Wikipedia site. https://en.wikipedia.org/wiki/Main_Page
February 21, 2016

chemistry
I'm not an organic chemist so I must figure these things out as I go. It is done this way. Think about how one makes ethyl acetate. acetic acid + ethyl alcohol = ester. CH3COOH + C2H5OH => CH3COOC2H5 so the ethyl of ethyl acetate comes from the alcohol and the acetate ...
February 21, 2016

Chemmistry
%F = (atomic mass F/molar mass CuF2)*100 = ? Then g F in 54.0 g CuF2 = 54.0 x %F/100 = ? g F.
February 21, 2016

science1002
I am assuming you intended to write 0.1 M and not 0.1 m. M stands for molarity; m stands for molality. Chemistry is more exact than writing sentences with no cap and formulas with no caps. CO, Co, and co all mean different things. May I suggest you find the caps key on your ...
February 21, 2016

Chemistry
Titration with phenolphthalein adds 1 H^+ to the CO3^2- to make HCO3^-. You are right with mols K2CO3. That titrates none of the HCO3^- The methyl orange end point adds another H^+ to the HCO3^- formed from the CO3^2- in the first end point. It adds a H^+ to the HCO3^- that ...
February 21, 2016

Chemistry
Damon's estimate is quite good (and reasonable) and the answer is correct. If you want to do it without assuming it is 22.4 L/mol, it is done this way. Use PV = nRT and solve for n = number of mols of the gas. (758*58.4)/(760*0.08206*275.6) = 0.257 = n. Then mols = grams/...
February 21, 2016

chemistry
Remember like dissolves in like. Both are non-polar.
February 20, 2016

chemistry
Convert 273.7 mg CO2 to mg C, then to %C. 273\.7 mg x 12/44 = ?, then (?/255) x 100 = about 29.3% C. Convert 130.6 mg H2O x (2/18) = ? Then (?/255)*100 = about 5.7% H. The halogen must be 100%-29.3%-5.7% = about 65% halogen. Which halogen? The cream colored ppt PROBABLY MEANS ...
February 20, 2016

Chemistry
I have no idea what experiment or determination you performed.
February 20, 2016

Chemistry
What's the pKa? You have two equations. #1 is pH = pKa + log (base)/(acid) 6.8 = pKa + log b/a #2 is a + b = 0.1 Solve these two equations for (acid) and (base). Calculate grams base needed, add to 100 mL of water, place in a pH meter, add HCl to the desired pH.
February 20, 2016

Chemistry
Law of conservation of mass. Fe + H2O ==> Fe3O4 + H2 168 + 72 = ...232 + 8 ........240 = 240 Matter is noither created nor destroyed.
February 20, 2016

AP Chemistry
Tyra, you really need to help by answering the questions we ask. I need to know WHAT you don't understand about a problem. 1. For strong acids like HCl which ionize 100%, then pH = -log HCl) 3. Convert 5.6 g to mols. mols = grams/molar mass. Then the definition of molarity...
February 20, 2016

AP Chemistry
I know that. What is your problem in understanding these. Be specific. I need to know what you don't understand so I'll know where to start explaining.
February 19, 2016

AP Chemistry
All of these are the pH values for strong or weak acids. What is it you don't understand. Be specic.
February 19, 2016

Chemistry
1. Absolutely not a good idea to use different thermometers. You want the DIFFERENCE in temperature. If either thermometer reads only slightly different than the other, then that error will be the final calculation. 2. m = mols/kg solvent = 0.150/1.2 = ? Then delta T = Kf*m ...
February 19, 2016

Chemistry
Stoichiometry and Henderson-Hasselbalch equation. You have 100 mL of 0.1M NaHC2O4 = 10 millimols sodium bioxalate ..HC2O4^- + OH^- ==> C2O4^2- + H2O I..10........0........0 add..........x.............. C..-x.......-x........x E..10-x......0........x Plug the E line into the...
February 19, 2016

Chemistry-Dr.Bob 222
I copied this from Wikipedia. "The units of the pre-exponential factor A are identical to those of the rate constant and will vary depending on the order of the reaction. If the reaction is first order it has the units s−1, and for that reason it is often called the...
February 19, 2016

Chemistry
The question is somewhat confusing to me. Here is what I think the question is about. What volume of 75% (w/w) HNO3, density 1.41 g/mL is required to prepare 1 L of 0.1M HNO3. First determine the M of the 75% HNO3 starting material. That is 1.41 x 1000 x 0.75 x (1/63) = approx...
February 19, 2016

chamistry
What's with the same post five times. 24000 what?
February 19, 2016

chemistry!
You will see the solution become brownish (if the solution is water) or purple (f the solvent is hexane or carbon tetrachloride).
February 19, 2016

CHEMISTRY HELP
You had this in math. It isn't chemistry. 5.75 = 4.74 + log b/a 1.01 = log b/a 10^(b/a) = 1.01 Plug into the calculator; a/b = 10.23
February 19, 2016

chemistry
The tutors here are sharp people but few of us have the heats of solution for thousands of chemical compounds memorized. We may be able to help if you supplied that data.
February 19, 2016

Chemistry
But why don't you learn to do it right so when you have a number that isn't an even multiple, you will know how to do it. For this problem, that is 21 mols O2 x (4 mols CO2/7 mols O2) = 21 x 4/7 = 12
February 19, 2016

chemistry
63(0.691) + 65(0.309) = ? S is done same way.
February 19, 2016

Chemistry
That is correct but check my response to this question posted separately. I would strongly suggest you do it through the coefficient process so you can do it easily if the numbers are not even multiples as they were in the previous problem or in this new one.
February 18, 2016

Chemistry
How do you know which numbers goes on top and which on the bottom? Look at the units. By placing O2 on the top and C2H6 on the bottom, the mols C2H6 cancel to leave mols O2 as the unit and that's what you want. If you put mols C2H6 on top and mols O2 on the bottom, the ...
February 18, 2016

Chemistry
That is absolutely correct and your reasoning is sound. But if the numbers didn't come out so even could you do it? Here is the way itis done for ALL problems. You use the coefficients. 4.0 mols C2H6 x (7 mols O2/2 mols C2H6) = 4.0 x (7/2) = 28/2 = 14 mols O2.
February 18, 2016

Chemistry
1% w/w = 1 g coke/100 mL solution = 1 g coke/(1 g coke + 99 g H2O). Now if you knew the density you could go further but I don't see a density listed. If you wish to assume the density of the solution is 1.0 g/mL (and it should be close to that since this is such a dilute ...
February 18, 2016

CHEMISTRY PLEASE HELP APPRECIATE IT LOTS!
Most of these stoichiometry problems are worked the same way. Here is a step by step procedure. 7.) How many moles of fluorine are required to react with 12 g of sodium iodide? I already balanced it but am confused to go from here F2 + 2 NAi ---- 2 NaF + I2 12 g NaI + 2 mol ...
February 18, 2016

chem
2HgO ==> 2Hg + O2 mols HgO = 15.22/molar mass HgO Using the coefficients in the balanced equation, convert mols Hg to mols O2.
February 18, 2016

chemistry
p1v1 = p2v2
February 18, 2016

Chemistry
Yes, the data is there to calculate that. The spacing is not good since this forum messes up the spacing; however, you are given the initial concentrations for both NO and O2. Then you are given the concentrations after certain times. That allows you to know the rate in M/s.
February 18, 2016

Chemistry
So what's the rate law? I don't know the exponents but you have that you say. Rate = k(NO)^x*(O2)^y where x and y are the exponents you have determined. Look at any run in the experiment, substitute rate, (NO) and (O2), then calculate k.
February 18, 2016

chemistry
Is that 200 g of H2? Watch the typos. Is that at STP. You don't give the P or T so I'm assuming STP. mols H2 = grams/molar mass - ? Then 1 mol H2 occupies 22.4 L at STP
February 18, 2016

Chemistry
I posted the answer above. Let me know if you can't find it.
February 18, 2016

Chemistry
Do you have k1 and k2 for H2C2O4? We can't get the same answer unless we use the same values for the two constants.
February 18, 2016

Chemistry
What you've done is almost correct assuming the spacing is ok. The numbers are but some are in the wrong place. This forum doesn't do spacing very well. I'll try to improve that. .......... AgCl ==> Ag^+ + Cl^- I.........solid.....0.......0 C.........solid.....x...
February 18, 2016

Chemistry
If that is 5 g then you have only one significant figures so the answer is 0.1 and you're correct. However, the second part can't be done that way. You have assume, I suppose, that Br2 is a gas and it occupies 22.4 L/mol. If that were true your answer of 2.44 would be ...
February 18, 2016

Chemistry
see your other post above.
February 18, 2016

chemistry
See your other post above.
February 18, 2016

Chemistry
Technically any number you choose. I'm sure the author of the problem meant (but didn't say) how much HCl is need to react COMPLETELY with the 5.8 g Al(OH)3 3HCl + Al(OH)3 ==> AlCl3 + 3H2O mols Al(OH)3 = grams/molar mass = ? Using the coefficients in the balanced ...
February 18, 2016

Chemistry
If the energy is 2.93E-19/photon, the multiply by 6.02E23 to find the energy of a mole of them.
February 18, 2016

chem
C = KpP C = 4.48E-5*(760mm-23.8mm) = ? mols/L. Then ? x 44 = grams/L. Convert to g/mL.
February 18, 2016

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

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