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March 26, 2017

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Posts by DrBob222

Total # Posts: 54,282

chemistry
For 4p. n = 4 l = 1 m can be -1, 0, or +1
October 2, 2016

CHEMISTRY
2C2H6 + 7O2 ==> 4CO2 + 6H2O mols C2H6 = grams/molar mass = ? Using the coefficients in the balanced equation, convert mols C2H6 to mols CO2. That is ?mols C2H6 x (7 mols O2/2 mols C2H6) = ? = ? Now convert mols CO2 to grams. g CO2 = mols CO2 x molar mass CO2 = ?
October 2, 2016

Chemistry
Ba(OH)2 + 2HCl ==> BaCl2 + 2H2O mols HCl = grams/molar mass = ? mols Ba(OH)2 = 1/2 that (from the coefficients) Then M Ba(OH)2 = mols Ba(OH)2/L Ba(OH)2 = ?
October 2, 2016

Chemistry
-3.42 kcal/g x (76g/mol) = approx -260 kcal/mol CS2 + 3O2 ==> CO2 + 2SO2 + 260 kcal/mol
October 1, 2016

Chemistry
The problem doesn't tell you the mass of the sample (nor the volume) and density). As is the problem can't be solved.
October 1, 2016

Chemistry
Sn = 0.00383 mols I = 0.01534. The easy way to find the ratio is to divide the smaller number by itself (thereby assuring you will get 1.000), the divide the other number by the same small number. Sn = 0.00383/0.00383 = 1.00 I = 0.01534/0.00383 = 4.005 Then round to whole ...
October 1, 2016

chem
Instead of me working the problem for you and you checking my work, why not show your work and let us check your work. Be happy to do that for you.
October 1, 2016

chemistry
What you have is a saturated solution since there is solid undissolved. A supersaturated solution will be completely dissolved and will in fact, have more dissolved than it normally can hold. If a single crystal of the solid is put into the solution,or if the sides of the ...
October 1, 2016

chemistry
It is still iodine; therefore, physical change.
September 30, 2016

more dump--Physics
Wouldn't it be better if you showed your work and let us check it for accuracy. That way we're checking you instead of you checking us.
September 30, 2016

Chemistry
Sorry to be so long but I had to leave home. The set up for 3c looks ok but I don't get that answer. Check your arithmetic. I get 9+ for an answer.
September 30, 2016

Chemistry
3a isn't correct. I didn't chck the others. It should be 10.7 x(1 mol O2/32g O2) x (2 mols CO2/1 mol O2) x (44 g CO2/mol CO2) = about 29 or so g CO2. Check your factors. The units don't cancel as they should.
September 30, 2016

Chemistry
pA is unchanged. Ptotal is increased. XB is decreased since total mols is increased.
September 30, 2016

Chemistry
yes
September 29, 2016

Chemistry
Why not draw the Lewis dot structure and see which one is not complete? Try drawing the Lewis structure for BF3 and see what you get.
September 29, 2016

Science
I have a very good question too. With no drawing, how in the world do we even know what you are talking about with distances D and H? We need to be mind readers? Some teachers may be able to do that but I'm not one of them.
September 29, 2016

Science
R = R R1 = R/5*5 = R/25 So (R/R1) = (R/R/25) = R*25/R = 25
September 29, 2016

Science
I think both answers are right. Metallic bonds often are higher melting point but they aren't compounds.
September 29, 2016

Chemistry
(n*BE reactants)-(n*BE products) = BE rxn.
September 29, 2016

Organic Chem
Read under "GC Analysis" https://en.wikipedia.org/wiki/Gas_chromatography
September 29, 2016

Chemistry
HCl + KOH ==> KCl + H2O mols KO = M x L = ? Using the coefficients in the balanced equation, convert mols KOH to mols HCl. (That's a 1:1 ratio you see). Then M HCl = mols HCl/L HCl.
September 29, 2016

Biochemistry
I don't think so. I'll look at your work if you post it.
September 29, 2016

Chemistry
Tough to do on this forum. 92U238. The 92 is a subscript on the left of U and the 238 is a superscript on the left of U.
September 29, 2016

Chemistry
How much heat to you need? That's q = mass H2O x specific heat H2O x delta T. q = 1000 x 4.184 x 10 = 41840 J a. (4J/min*cm^2) x (100 cm/1 m) x (100 cm/1m) x # min = 41840. Solve for # min b. C + O2 ==> CO2 + 393,000 J (393,000/12 g C) x #g C = 393,000 Solve for #g C
September 29, 2016

Chemistry
yes and yes. 8HNO3 + 3Cu ==> mols HNO3 initially = M x L = ? mols Cu = grams/atomic mass = ? Now calculate how much HNO3 is need to dissolve that many mols Cu. mols HNO3 remaining unreacted = initial mols HNO3 = mols needed to dissolve the Du = ?
September 29, 2016

Organic Chemistry
I tried drawing that out. I see the heptane and 4-secbutyl but not the 3,6 dimethyl. I looks like 3,5 dimethyl to me.
September 29, 2016

chemistry
Look up H2O going to oxygen
September 28, 2016

Chemistry
C60 + 60 O2 ==> 60CO2 dE = q + w Combustions are done at constant and W = -pdV. 60 mols CO2 come from 60 mols O2 so there no change in volume and no work. Thus dE = q = dH. dH formation would be the reverse; i.e., 60C --> C60 and dHrxn = dHformation C60. We don't ...
September 28, 2016

Chemistry
Do you want concn in M or g/L. I will assume you want molarity = M mols KCN = grams/molar mass KCN = ? Then ?mols/0.052 L = ? mols/L = M KCN. The NaOH just adds 2 mL to the total volume.
September 28, 2016

CHM 1020
q = mass H2O x specific heat H2O x (Tfinal-Tinitial)
September 28, 2016

chemistry
Assume you have 100 g sample; then, mols C = 74.27/12 = ? mols H = 7.79/1 = ? mols N = 12.99/14 = ? %O = 100-74.27-7.77-12.99 = 4.95% mols O = 4.95/16 = ? Now find the ratio of these elements to one another, round to whole numbers for the subscripts.
September 28, 2016

chemistry
Note: When the question asks for percent composition of a compound, it means to find the percent of EACH element in the compound.
September 28, 2016

chemistry
1.30M x (71/238) x [119/(119+105)] =?M
September 28, 2016

Chemistry
2. It is a double displacement reaction. Some may call it an acid/base reaction, also, but I think you want the first one. 3. H2CO3 ==> H2O + CO2 is decomposition reaction.
September 28, 2016

Chemistry
I believe you're on the wrong track. This is a hydrolysis equation; i.e., at the equivalence point of an acid/base titration, you are left with the salt and water. The salt hydrolyzes (unless it is the salt of a strong base/strong acid such as NaCl, KCl, KBr etc). ......CN...
September 28, 2016

Chemistry
Kayla M, this is done the same way as the HBr/KOH problem I solved for you earlier in the day. If you don;t understand something let me know what it is, in detail, and I can help you through it but after you've seen the process I'm not inclined to do your homework for ...
September 27, 2016

Chemistry
HC2H3O2 + NaOH ==> NaC2H3O2 + H2O mols acetic acid = M x L = ? Using the coefficients in the balanced equation, convert mols aceit acid to mols NaOH. You can see the ratio is 1:1. Then M NaOH= mols NaOH/L NaOH.You know M and mols, solve for L and convert to mL. 2. KHP + ...
September 27, 2016

Chemistry
See your other post.
September 27, 2016

Chemistry
Left to right in the periodic table the electronegativity (EN) increases. F is the most EN.
September 27, 2016

Chemistry
A is right. B is right. C. I would calculate n for each of the gases. You know partial pressure of each, V, R, & T from the first container. Mols Ne can be calculated from P Ne, V of the second container, R & T. Find total mols, use that with R, & T and total volume to find ...
September 27, 2016

AP Chemistry
I answered this 44 minutes after you posted it the first time. http://www.jiskha.com/display.cgi?id=1475010098
September 27, 2016

Chemistry
NH4^+ + H2O ==> H3O^+ + NH3
September 27, 2016

Chemistry
But that isn't ferrous ammonium sulfate. The correct formula is Fe(NH4)2(SO4)2. IN YOUR COMPOUND, (NH4)^+ is 0.360 so (SO4)^2- = 0.360 x (3 mols SO4/2 mols NH4) = 0.360 x 3/2 = ?
September 27, 2016

Chemistry
Look at your post below under Taylor. This is the same kind of problem. By the way we prefer that you use the same screen name on Jiskha. We can help you better that way.
September 27, 2016

too many typos---AP Chemistry
I made several typos. Here is the corrected. -3226.7 = [7*-393.5)+(3*-285.8)] - [dHbenzoic acid)-0] I get 385.2 kJ but a NEGATIVE sign. Check that.
September 27, 2016

AP Chemistry
dHrxn = (n*dH products) - (n*dH reactants) -3226.7 kJ = [(3*-393.5)+(3*-385.8)] - [(1*dHbenzoic acid) - (0)] and solvle for dHbenzoic acid.
September 27, 2016

Chemistry
HBr + KOH ==> KBr + H2O mols KOH = M x L = 1.569 x 0.51 approx 0.8. mols HBr = 0.8 (look at the coefficients in the balanced equation; 1 mol HBr to 1 mol KOH.) M HBr = mols HBr/L HBr = approx 0.8/0.635 = approx 12.6M mols HBr initially = 0.8 mols KOH added with 141 mL = M x...
September 27, 2016

AP Chemistry
A multistep problem. q1 = heat needed to raise T ice from -50 to zero C. q1 = mass ice x specific heat ice x (Tfinal-Tinitial) q2 = heat needed to change solid ice at zero C to liquid water at zero C. q2 = mass ice x heat fusion ice. q3 = heat needed to raise T of liquid H2O ...
September 27, 2016

chemistry
NaCl BeF2 KI What's the problem here? What do you not understand about this? The periodic table almost TELLS you what to write.
September 27, 2016

Chem
Stoichiometry 101. 2CH4 + 2NH3 + 3O2 --> 2HCN + 6H2O What mass of NH3 is required for the synthesis of 1.5 × 105 kg of HCN if the reaction has a 97.5% yield? mols HCN = 150,000g/molar mass HCN = ? Using the coefficients in the balanced equation, convert mols HCN to ...
September 27, 2016

Chem
See your other post.
September 27, 2016

chemistry
5.75 g CuSO4.5H2O ==> CuSO4 + 5H2O 5.75 g x 0.36 = ? g H2O in 5.75 g CuSO4.5H2O
September 27, 2016

Chemistry
Maria--I tried to find your initial post and my response but failed. Here is what I remember about it. This is the most head scratching question I've seen in my career. The I^- is oxidized to IO3^- so you can write that half reaction easily. It is I^- + 3H2O ==> IO3...
September 26, 2016

Chemisty
2H2 + O2 ==> 2H2O mols H2 = grams/molar mass H2 = ? mols H2 x 1 = mols H2O grams H2O = mols H2O x molar mass H2O
September 26, 2016

chemistry
Lyman Series is from n = ? to n = 1; therefore, for 4th line, that is n = 5 to n = 1. E = 2.180E-18(1/1^2 - 1/5^2) = ?
September 26, 2016

chemistry
right
September 25, 2016

Chemistry
I wouldn't worry about the volume. p*molar mass = density*RT You know P, molar mass, density,and R.Solve for T (in kelvin).
September 25, 2016

Chemistry
Why not post the complete problem?
September 25, 2016

Chemistry
OK. I'm going with the flow. ...Ag(OH)2 + 2HBr ==> AgBr + 2H2O mols Ag(OH)3 = grams/molar mass = ? initial mols HBr = M x L = ? mols HBr used = 2*mols Ag(OH)2 mols HBr remaining = initial mols - mols used = ? Then M HBr left = mols/L and pH = -log (HBr) = ?
September 25, 2016

Ap Chemistry
Convert pKa to Ka. pKa - -log Ka Let's call saccharin just HS. M HS = grams/molar mass which I've estimated to be about 0.03 but you need a closer answer than that. .....HS ==> H^+ + S^- I..0.03.....0.....0 C....-x.....x.....x E..0.03-x...x.....x Substitute the E ...
September 25, 2016

Chemistry
It would have been so much easier if you had shown your work; then I could have found your error. First, you didn't balanced the equation. 2Na2O2 + 2CO2 ==> O2 + 2Na2CO3 mols Na2O2 = grams/molar mass = ? I have approx 0.3 but that's just an estimate. Use PV = nRT ...
September 25, 2016

Chemistry
For the metal.
September 25, 2016

Chemistry
What are your results in? grams nitrate? if so, then g N = g nitrate x (atomic mass N/molar mass NO3^-)
September 25, 2016

Chemistry
IO3^- + 3H2O ==> IO3^- + 6e + 6H^+ O3 + 2H^+ +2e ==> O2 + H2O --------------------------- You can get the molecular equation by multiplying equn 1 by 1 and eqn 2 by 3, then cancel ions common to both sides and you end up with this. 3O3 + I^- ==> 3O2 + IO3^-
September 24, 2016

biology
There is a C2H4 and a C2H6 but there is no neutral C2H5 atom. If it is C2H5^- then it is polar.
September 24, 2016

Chemistry
CuSO4(aq) + K2CO3(aq) ==> CuCO3(s) + K2SO4(aq)
September 24, 2016

CHEMISTRY HELP
I don't understand the question with your use of symbols. M stands for molarity but I think you mean molar mass NH3 is 17. I have no idea what M(NH3)= 8.5 g means nor H n(NH3) formed = 5 mol.
September 24, 2016

Chemistry (Help!)
See your post above.
September 24, 2016

chemistry
phex = Xhex*Pohex ppen = Xpen*Popen eqn1 Then Xpen = 1-Xhex eqn2 phex + ppen = 252 Substitute and solve these two equations for Xhex and Xpen. I worked through them and got about 0.4 for pentane and about 0.6 for hexane. Post your work if you get stuck.
September 24, 2016

chemistry
Sounds like a math problem to me. The way I read it, there is an excess moisture content of 10% so the $40/ton is reduced by $4/ton to make it $36/ton. It cost $1.00/100 lb or $20.00/ton for shipping [$1.00 x (2000 lbs/100 lb)] and 10% of the $20.00 is $2.00/ton so 40-4-2 = $...
September 24, 2016

Chemistry
The atomic mass of an element is the weighted average of the mass of all of the isotopes. 63(0.5) + 65(0.3) + 67(0.2) = ?
September 24, 2016

chemistry
CaC2O4 = 0.253 g 0.253 x (molar mass K2C2O4.H2O/molar mass CaC2O4) = ? g K2C2O4.H2O
September 23, 2016

chemistry
q needed to heat the water is q = mass H2O x specific heat H2O x (Tfinal-Tinitial). Note that if you use specific heat listed you must change 110 kg H2O to grams. 1 lb x (? J needed/2.2E7 J/lb) = lbs oil needed. Convert to kg oil.
September 23, 2016

Chem
1 g carbohydrate = 4 kcal 5.9 g x (3500/100) = ?g glucose. 4 kcal/g x ?g glucose = ?
September 23, 2016

Chemistry
0.5 kg x [2 molar mass NH3/molar mass (NH4)2SO4] = ?
September 23, 2016

chemistry
That certainly is true for water. What about other substances? Here is a table for heats of fusion and heats of vaporization. Compare them and see. http://chempaths.chemeddl.org/services/chempaths/?q=book/Quick%20Resources/1251/table-molar-enthalpies-fusion-and-vaporization
September 23, 2016

12
Is 12 REALLY the subject? You will get more and quicker results if you type in the subject here. I would suggest math.
September 23, 2016

chemistry
Doesn't that answer depend upon where you started; i.e., solid ice and solid ethanol or liquid water and liquid ethanol?
September 23, 2016

Chemistry
See your other posts.
September 23, 2016

Chemistry
Follow Dr Rebels answer for your other problem.
September 23, 2016

Chemistry
You really should be more careful in writing these problems. cc or cm^3 and not cm. silver nitrate solution and not silver nitric, etc. HCl + AgNO3 ==> AgCl + HNO3 mols AgNO3 = M x L = ? mols HCl = mols AgNO3 Convert mols HCl to volume using PV = nRT. The answer will be in ...
September 23, 2016

Chemistry
KOH + HNO3 ==> KNO3 + H2O Do you mean 1M HNO3 or 1m HNO3. There is a difference, you know. I will assume you meant 1 M. Also you must mean 20 cm^3 and not 20 cm. mols HNO3 = M x L = 0.1M x 0.0242 L = 0.00242. mols KOH = same = 0.00242 g KOH = mols KOH x molar mass KOH = ? ...
September 23, 2016

Chemistry
mols Na2SO4 = M x L = ? mols Pb(NO3)2 = M x L = ? It should be obvious that Na2SO4 is the limiting reagent. 1 mol Na2SO4 produces 1 mol PbSO4; therefore, mols PbSO4 = mols Na2SO4. Then grams PbSO4 = mols PbSO4 x molar mass PbSO4
September 22, 2016

Chemistry
Couldn't you have followed the Pb/water problem Bob P worked for you?
September 22, 2016

oops--Chem equilibrium
Well, I looked at your numbers and not the problem. You ARE allowed three s.f. I think your answer of 75.8% is correct. Some round to 75.7%. Other than that I don't know.
September 22, 2016

Chem equilibrium
I wonder if you are trying to report too many significant figures? You are allowed only two; therefore, that 75.76 should be rounded to 76%. I assume are reporting to a data base. Often too man s.f. is the problem with these problems.
September 22, 2016

Chemistry G.12
I would have done it this way/. 0.068 x *6 mols H2O x 4 mols NH3) = 0.068 x 6/4 = ?
September 22, 2016

AP Chemistry
The dissolution of X is exothermic since T increased. What was q? q = mass H2O x specific heat H2O x (Tfinal-Tinital) Then q = delta H and that is negative. That is delta H/1.97 g and you convert that to mols by (-dH/1.97g) x 141 g/mol = -dH/mol. Post your work if you get stuck.
September 22, 2016

ANUENUE
I'll bet Ms. Sue DOES know it.
September 22, 2016

Chemistry
In order to find g oxygen you need to first convert CO2 to C and H2O to H. g C = 0.1601 x (12.01/44) = ? g H = 0.05243 x (2*1/18) - ? g O = 0.06120 - g C - g H = ? mols C = g C/12.01 = ? mols H = g H/1 = ? mols O = g O/16 = ? Now find the ratio of these three elements to each ...
September 22, 2016

Chemistry
Is that 0.06120 g sample; 0.1601 g CO2 and 0.05243 g H2O? I may not be reading those funny symbols correctly.
September 22, 2016

Chemistry
You came close but it isn't balanced. 2C2H6O2 + 5O2 ==> 4CO2 + 6H2O mols C2H6O2 = grams/molar mass = ? Then mols H2O = ?mols C2H6O2 x (6 mols H2O/2 mols C2H6O2) = ?mols C2H6O2 x 6/2 = ?
September 22, 2016

Science am i correct?
I think Bob P's answer meant you were right.
September 22, 2016

chemistry
false
September 22, 2016

analytical chemistry
Angel, you didn't like my answer? I workedd this for you last night. http://www.jiskha.com/display.cgi?id=1474502380
September 22, 2016

Chemistry
Awkward question. Awkward answers. The best answer in the list is 3.
September 22, 2016

Chemistry
See the other post.
September 22, 2016

Chemistry
Yes, %M = (5.65/12.47)*100 = ? about 45% but you need a more accurate number than that. Then what do you do to identify the metal. I will use estimates BUT you must get accurate numbers yourself. %Cl then must be 100%-45.?% = about 55%. Be sure and get good numbers to at least...
September 21, 2016

Chemistry
I assume this means you want a phosphate buffer of pH = 7.5 containing 0.3M mannitol. So the mannitol part is to weigh out 0.3 mol mannitol/L or you will want 0.3/4 mols for the 250 mL. Then grams mannitol = mols mannitol x molar mass mannitol. Place that in a 250 mL ...
September 21, 2016

Chemistry
I don't know what you mean for a "beaker diagram" but yes, that's the way NaHCO3 dissociates.
September 21, 2016

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