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Posts by DrBob222

Total # Posts: 54,751

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

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 = ?

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.

chemistry
Look up H2O going to oxygen

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 ...

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.

CHM 1020
q = mass H2O x specific heat H2O x (Tfinal-Tinitial)

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.

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

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

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.

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...

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 ...

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 + ...

Chemistry
See your other post.

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

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 ...

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

Chemistry
NH4^+ + H2O ==> H3O^+ + NH3

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 = ?

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.

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.

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.

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...

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 ...

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.

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 ...

Chem
See your other post.

chemistry
5.75 g CuSO4.5H2O ==> CuSO4 + 5H2O 5.75 g x 0.36 = ? g H2O in 5.75 g CuSO4.5H2O

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...

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

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) = ?

chemistry
right

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).

Chemistry
Why not post the complete problem?

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) = ?

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 ...

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 ...

Chemistry
For the metal.

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

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^-

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

Chemistry
CuSO4(aq) + K2CO3(aq) ==> CuCO3(s) + K2SO4(aq)

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.

Chemistry (Help!)
See your post above.

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.

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 = $...

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) = ?

chemistry
CaC2O4 = 0.253 g 0.253 x (molar mass K2C2O4.H2O/molar mass CaC2O4) = ? g K2C2O4.H2O

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.

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

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

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

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

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

Chemistry
See your other posts.

Chemistry
Follow Dr Rebels answer for your other problem.

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 ...

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 = ? ...

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

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

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.

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.

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 = ?

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.

ANUENUE
I'll bet Ms. Sue DOES know it.

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 ...

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.

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 = ?

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

chemistry
false

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

Chemistry
Awkward question. Awkward answers. The best answer in the list is 3.

Chemistry
See the other post.

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...

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 ...

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

Chemistry
It is a chemical property because the CaCO3 is changed into something different. The equation is CaCO3 + 2HC2H3O2 ==> Ca(C2H3O2)2 + CO2 + H2O

Organic chemistry
The melting point of a mixture is lower than the melting point of either pure compound.

analytical chemistry
I assume you mean ppmw (ppm by mass and not by volume) So mass H2O in that 1 L is 1000 g and that added to the 0.361 gives you a mass of solution of 1000.361g. 0.361g x (1E6/1000.361) = ? ppmw and you round that off to three significant figures and you get the same answer as ...

Chemistry
http://chemicals.etacude.com/c/more/cuso4.html

Chem
(V1/T1) = (V2/T2)

Chem
Actually HF is approximately 50% ionic/50% co-valent character. In fact, Linus Pauling, when he developed his electronegativity scale (F = 4.0 arbitrarily), I understand that he used 50% for HF

Math for Ms. Sue
I believe any number one chooses (over two) will be the correct number of pizzas to buy; the problem doesn't say there can't be any pieces left over. So anything over 2 pizzas will, in my opinion be right. 2 pizzas will give 16 slices and 16/14 = 1+. So each student ...

@ Reiny & Steve--Math - check answer
As well as for the tutors. :-)

chemistry
30 x (atomic mass Fe/molar mass FeSO4) = ?

College Chemistry
mols MgCl2 = grams/molar mass = ? M MgCl2 = mols MgCl2/L = ? Technically, there isn't any MgCl2 since all of it is ionized completely; however, I think the spirit of the question is to give the concentration of the salt, MgCl2. You will have 2.39E-4 g Mg ^2+ there and that...

chem
Your best bet is to get a 250 mL beaker that is marked every 25 mL and look to see about how close you think you can come to estimating the volume. I'm not looking at one, but I might guess at 5 mL but that is strictly a guess.

Chemistry AP
Is that Kc or Kp? I will assume it is Kp since the pressures are given but the problem is worked the same way for each (Kp is used with partial pressures; Kc with concentrations in mols/L) K = 1.9 Q = p(PCl5)/p(PCl3)*p(Cl2) Q = (0.5)/(0.5)(0.5) = 2 Looking at Q = 2, that is &...

Chemistry
http://www.jiskha.com/display.cgi?id=1474173035

Chemistry
.......Ca(OH)2 ==> Ca^2+ + 2OH^- I......solid.......0........0 C......solid........x.......2x E......solid.......x........2x Ksp = (Ca^2+)(OH^-)^2 Substitute the E line into the Ksp expression and solve for x. That will give you the solubility of Ca(OH)2 in mols/L. That is ...

Chemistry
mols NaOH in 5.52 grams is mols = grams/molar mass = ? mols NaOH in the solution of NaOH is mols = M x L = ? Total mols NaOH = mols in the 5.52g + mols in the solution = ? Convert 1.52 gallons to L. 1 gallon = 3.785 L. total volume is L in 1.52 gallons + 659 mL(convert to L ...

Biochem
I think you need the total concentration of the buffer; i.e., you want 20 mL of what? 0.05M, 0.01M, what M. Here is a problem just like that which I worked earlier last week. http://www.jiskha.com/display.cgi?id=1470250931

Chemistry
That looks good to me.

Chemistry
The mass of an empty container is 91 g. The mass of the container filled with water is 111 g. What is the volume of the container? The density of water is 1 g/cm3 .Answer in units of cm3 20cm3 right 016 (part 2 of 5) 1.0 points The container was emptied, dried, and a piece of ...

Chemistry
The polarity of H2O causes the H2O molecules to "stick" (more or less) to each other. It also has adhesive properties and you can see that if you suck water up into a glass tube. The tube needs to be about 1/2 inch in diameter. You will see the edges of the water ...

chem
I would convert to g first.

science chemistry
CuS + 6H^+ + 3SO4²- = CuO + 4SO2 + 3H2O

chemistry
mass # = #p + #n 16 = #p + 7 p = 9 So it must have 9 electrons so the charge must be -1 when the anion is formed. 9F^16. 9 is the subscript; 16 is the superscript and goes at the top left.

chemistry
What you did, and you needed to that, is convert 1.4E2 pm to cm. Then (1.4E-5 cm/atom) x # atoms = 1 cm. Solve for # atoms in the 1 cm.

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