Sunday
May 1, 2016

Posts by DrBob222

Total # Posts: 52,204

Some Chemistry Questions
1 and 2 are wrong. 3 is ok.
February 29, 2016

Chemistry
acetic acid = HAc NaC2H3O2 is NaAc mols NaAc = grams/molar mass = ? Then mols NaAc/0.250 = ?M mols HAc = molsL. mols = M HAc x L HAc volume = 0.250 L M = mols/L.
February 29, 2016

Chemistry
What is that set up. If can see what you're talking about I can walk you through each step.
February 29, 2016

Chemistry
........HA ==> H^+ + Ac^- I....0.095.....0.....0 C......-x......x.....x E...0.095-x....x.....x The problem tells you that the pH is 5.42 which means you can calculate (H^+) from pH = -log(H^+) and that is x in the above. Then (Ac^-) is the same and you can calculate 0.095-x...
February 29, 2016

Chemistry
That looks ok to me.
February 29, 2016

Chemistry
AgCl(s) ==> Ag^+ + Cl^-. Write Ksp for this. Ag^+ + 2NH3 ==> [Ag(NH3)2]^+ Write Kformation for this one. Overall is is AgCl + 2NH3 ==> [Ag(NH3)2]^+ + Cl^- Wrote Keq expression for this. Then if you will multiply Ksp*Kformation you will get the overall equilibrium ...
February 29, 2016

Chemistry
H2SO4 + 2NaOH --> 2H2O + Na2SO4 mols H2SO4 = M x L = ? Using the coefficients in the balanced equation, convert mols H2SO4 to mols NaOH. Then M NaOH = mols NaOH/L NaOH. You know mols and M, solve for L and convert to mL.
February 29, 2016

Chemistry
The limiting reagent controls the amount of product(s) formed.
February 29, 2016

cHEMISTRY
2AgC2H3O2 + MgCl2 ==> 2AgCl + Mg(C2H3O2)2 mols MgCl2 = grams/molar mass = ? Using the coefficients in the balanced equation convert mols MgCl2 to mols AgCl. Then convert mols AgCl to mass. g AgCl = mols AgCl x molar mass AgCl.
February 29, 2016

Chemistry
.........2CH4 ==> C2H2 + 3H2 I ......0.087......0......0 C........-2x.......x......3x E.....0.087-2x.....x......3x The problem tells you that 3x = 0.012 which allows you to calculate x and 0.087-2x (as well as 3x). Substitute those values into the Keq expression and ...
February 28, 2016

chemistry
First, I wouldn't start that way. Convert torr to atm; i.e., 310/760 = pi = ? pi = MRT. You know pi, R (0.0820), and T (in kelvin please). Solve for M = molarity. Then M = mols/L. You know M and L (or can convert to L), solve for mols. Then mols = grams/molar mass. You ...
February 28, 2016

Chemistry
So delta T = 0-(-3.55) = ? delta T = Kf*m You know delta T and Kf, solve for m = molality
February 28, 2016

Chemistry
mols KCl = grams KCl/molar mass KCl = ? Then M = mols/L solution.
February 27, 2016

Chemistry
I don't think anyone here is likely to do all of your work for you; however, if you will tell us exactly, and in detail, what you don't understand, perhaps we can help.
February 27, 2016

analytical chemistry
mL1 x M1 = mL2 x M2 20 x 0.1 = mL2 x 0.02 Solve for mL2 which gives you the FINAL volume. Subtract the final - initial to find amount to be added. Technically, that will not be right since volumes are not additive but for dilute solutions like this the difference is minuscule.
February 27, 2016

Chemistry
Zn + 2HCl ==> ZnCl2 + H2 mols Zn = grams/atomikc mass = ? Using the coefficients in the balanced equation, convert mols Zn to mols H2. Since this is a 1:1 reaction, mols H2 = mols Zn. Then use PV = nRT to solve for V at the conditions listed. Remember T must be in kelvin ...
February 27, 2016

Chemistry
Do you have a reaction equation? One source gives Fe2O3 as the product; another gives Fe3O4 as the product. The answer to this question depends upon which product is formed. I will assume Fe2O3 and go from there. 2Fe + 3H2O ==> Fe2O3 + 3H2 Use PV = nRT and solve for n = ...
February 27, 2016

chemistry
mols Fe2O3 = grams Fe2O3/molar mass Fe2O3 Then there are 2 mols Fe for every 1 mol Fe2O3.
February 26, 2016

Chemistry
n*lambda = 2d sin angle.
February 26, 2016

Chemistry
+7 K = +1 O = -2 and 4*-2 = -8 What must Cl be for KClO4 to be zero. Remember that all compounds or elements in the free state are zero total. +1 + ? + (-8) = 0
February 26, 2016

Chemistry
I disagree with Nerd. This is a limiting reagent (LR) problem. N2 + 3H2 ==> 2NH3 a. Convert 2 L N2 to mols NH3 produced if we had all of the H2 needed. That is 2 L N2 x (2 mols NH3/1 mol N2) = 2 x 2 = 4 L NH3 b. Convert 2 L H2 to mols NH3 produced if we had all of the N2 ...
February 26, 2016

chemistry
Note the correct spelling of Celsius. .........N2O4 <-> 2NO2 I........1.680.....1.220 C.........-p.......+2p E........1.680-p...2p The problem tells you that 2p = 0.550. You can calculate p from that. That allows you to evaluate 1.680-p Then substitute these values into ...
February 26, 2016

CHE 2B
1. Use the HH equation. pH = pKa + log (KNO2)/(HNO2) 2. Without values of pKa any thing I calculate won't agree with your calculations. Here is what you do. .......HNO2 + OH^- ==> NO2^- + H2O I......12.5....0........9.25 add............2............ C......-2.....-2...
February 26, 2016

chemistry
2C2H2 + 5O2 ==> 4CO2 + 2H2O Use PV = nRT for O2. Plug in 155 atm for P, V = 5.5L, Assume any value for T(in kelvin) and use your chosen value for T throughout. Solve for n = number of mols O2. Knowing you need that many mols O2, use the coefficients in the balanced equation...
February 26, 2016

Chemistry
Why don't you use sodium hydrogen carbonate for the name. Bob Pursley gave you the right procedure and the right numbers. That 84 should be for NaHCO3.
February 25, 2016

Chemistry
79 x 0.225 =
February 25, 2016

Chemistry
C7H16 + 11O2 ==> 7CO2 + 8H2O mols CO2 = grams/molar mass = 37.5/44 = approx 0.85 Convert mols CO2 to mols C7H16 using the coefficients in the balanced equation. approx 0.85 x (1 mol C6H16/8 mols CO2) = approx 0.85 x 1/8 = 0.1 mol C7H16 g C7H16 = mols C7H16 x molar mass ...
February 25, 2016

Chemistry
See your previous post.
February 25, 2016

Chemistry
5. Consider the following reaction: CO2 (g) + H2 (g) CO (g) + H2O (g) Calculate the value of the equilibrium constant, Kc, for the above system, if 0.1908 moles of CO2, 0.0908 moles of H2, 0.0092 moles of CO, and 0.0092 moles of H2O vapour were present in a 2.00 L reaction ...
February 25, 2016

Chemistry
You should post each question separately. Some won't answer posts that too long; i.e., consists of several questions. Calculate the pH of a NaOH solution of concentration 0.5M (Kw = 1.0 x 10-14 mol2dm-6 at 25oC) (H^+)(OH^-) = Kw. Substitute and solve for (H^+) [note that...
February 25, 2016

Chemistry
You want to compare Ksp with Qsp. (AgNO3) = 1E-4 x (200/1100) = ?M (KCl) = 1E-6 x (900/1100) = ?M Qsp = (Ag^+)(Cl^-) = ? If Qsp > Ksp a ppt forms. If Qsp < Ks no ppt forms.
February 25, 2016

educational tec connections academy
pitiful
February 25, 2016

Chemistry
I don't think so. mols you need = M x L = ? Then grams = mols x molar mass = ?
February 25, 2016

Chemistry
It has an alkane (the ethyl) and a phenol
February 25, 2016

Chemistry
See your other post.
February 25, 2016

chemistry
2H2C2O4 + O2==> 2H2O + 4CO2
February 25, 2016

Chemistry
I didn't know they were. Have you measured the temperature of the liquids in those containers? That is, how do you know the liquids are colder?
February 25, 2016

Chemistry
The lactate ion is hydrolyzed by the water in the solution. L^- + H2O ==> HL + OH^- so the solution will be alkaline.
February 25, 2016

chemistry
Which means what?
February 24, 2016

Chemistry
Let mass urea = X mass H2O = 50.9-X mols urea = X/molar mass urea = ? mols H2O = (50.9-X)/molar mass H2O = ? Total mols = X + (50.9-X)/molar mass H2O Substitute and solve for X. I believe X is approx 11 grams. Then mols urea/total mols = 0.769
February 24, 2016

Chemistry
I assume you mean Ni(NO3)2. In chemistry you need to find the caps key on your keyboard and use it. CO, Co, and co are not the same. mols Ni(NO3)2 = grams/molar mass = ? Then M = mols Ni(NO3)2/L solution = ?
February 24, 2016

chemistry
I would prefer you call them nitrate and not that gibberish. 4 LiNO3 → 2 Li2O + 4 NO2 + O2 2 KNO3 ↔ 2 KNO2 + O2 2 Ca(NO3)2 → 2 CaO + 4 NO2 + O2
February 24, 2016

AP Chemistry
This is a limiting reagent. HCl + NaOH ==> NaaCl + H2O mols HCl = M x L = ? = approx 1.4 mols NaOH = M x L = ? = approx 0.46 So the amount of NaCl formed is 0.46 mols. The volume is 400 + 200 = 600 mL = 0.6 L M = mols/L
February 24, 2016

Chemistry
All I can do is to balance these for you and that won't help you at all. If you want to show what you have, especially for the one you know, perhaps we can help. Here is a site that may help, also. http://www.chemteam.info/Redox/Redox.html In 1, Cr goes from zero on the ...
February 24, 2016

Chemistry lab
1. By reaching constant weight you know you have driven off all of the water it contains. 2. If allowed to stand in air the alum will reabsorb, from the air (which contains some water), some of the water diven off by previous heating. Cooling it in a desiccator keeps it from ...
February 23, 2016

Chemistry (balancing equations)
No it isn't and you should never need to ask because you can count atoms on both sides. They will be the same if balanced. I see 6 O atoms on the left (2*3 = 6) and only 3 on the right. Also 2 N on the left and 1 on the right. Not balanced.In addition the formula for ...
February 23, 2016

Orgo
Can't draw pictures on this forum.
February 23, 2016

Chemistry
Technically you can't calculate this because, technically the volumes are not additive. In practice they are with very little error in this case so assuming the volume are additive do it this way. Follow the same procedure for the second problem you posted. mL1 x M1 = mL2 ...
February 23, 2016

chemistry
This is a limiting reagent (LR) problem and you know that because amounts are given for both reactants. 3Mg(NO2)2 + 2Li3PO4 ==> Mg3(PO4)2 + 6LiNO2 mols Mg(NO2)2 = grams/molar mass = ? mols Li3PO4 = grams/molar mass = ? Using the coefficients in the balanced equation, ...
February 23, 2016

chemistry
See your post above.
February 23, 2016

CHEMISTRY! HELP
#2 is easy. There is no reaction. #1. This is a limiting reagent (LR) problem. You know that because amounts are given for both reactants. First you need to balance the equation. 2CuNO3 + MgCl2 ---> 2CuCl + Mg(NO3)2 mols CuNO3 = grams/molar mass = ? mols MgCl2 = grams/molar...
February 23, 2016

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

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