Tuesday
July 28, 2015

Posts by DrBob222


Total # Posts: 49,557

chemistry
It does and the answer is the same either way. However, I'm curious, if you knew the answer why did you ask? Or why not show your work and ask if that's the right way?
June 10, 2015

chemistry
You must have a table or a graph or something like that which will tell you the number of grams of NaI in a saturated solution. From the data you should get something like grams/mL or grams/L. Whatever you get change that to grams/L then convert grams to mols. mols = grams NaI...
June 10, 2015

chemistry
This is a menu item; it covers many subjects--just click on a item. Don't be fooled by the title--this is a good site. http://www.chemteam.info/ChemTeamIndex.html
June 10, 2015

chemistry
http://www.chemteam.info/Redox/Redox.html
June 10, 2015

chemistry
http://www.chemteam.info/Redox/Redox-Rules.html
June 10, 2015

chemistry
Before I retired I taught all of these subjects in freshman chemistry. It took about 2 months to cover all of these. I'm not prepared to sit down and write two month's of notes; however, if you can be more specific about what you know and what you don't understand ...
June 10, 2015

Chemistry
1.162 kJ = 0.688 mol x specific heat x (Tf-19.6) Solve Tf after substituting specific heat. Note that must have units of kJ/mol; otherwise you must change kJ or mols (or both).
June 10, 2015

oops--careful--Chemistry
I believe Sofia has the right idea but has answered the wrong question. If one uses H3PO4/NaH2PO4 (that's the question, not H3PO4/K2KPO4), the optimum operating range for the system is +/- 1 pH unit of pk3 (not k2). pK3 for H3PO4 is 12.35. Since the cell operational range ...
June 9, 2015

science
35*120 = 30x
June 9, 2015

incomplete--Kainantu sec..science(chemistry)
no above sample information.
June 9, 2015

Chemistry
CaCO3 + 2HCl ==> H2O + CO2 + CaCl2 NaOH + HCl ==> H2O + NaCl mols HCl initially = M x L = estimated 0.013 but you need a better number than this. All of the other numbers that follow are estimates, too. mols excess HCl = M x L = estd 0.0027 mols HCl used to neutralize ...
June 8, 2015

Chemistry
Yes, or you could have converted 20g to mols which is 20/17 = 1.176, then 1168 kJ/4mol = 292 kJ. Then 292 x 1.176 = 343 kJ
June 8, 2015

Chemistry
H2SO4 + 2NH3 ==> (NH4)2SO4 What's the concentration of the H2SO4?
June 8, 2015

Chemistry
eqn 1 as is. Eo = 0.90 Reverse eqn 2. Eo = 0.10 sum eqn 1 and reverse eqn 2 Eo = 1.00 A + voltage means the products are favored so N2H4 will be produced.
June 7, 2015

chemistry
What's your trouble with this. Substitute the concentrations into Kc expression and solve for K.
June 7, 2015

chemistry
(ICl)/(I2)(Cl2) = ?
June 7, 2015

chemistry
Fe3O4 + 4H2 + 36 kcal ==> 3Fe + 4H2O 36 kcal x 64/3*atomic mass Fe = ? kcal required. mols Fe needed = grams/atomic mass = ? Use the coefficients in the balanced equation to convert mols Fe to mols H2. Now convert g H2 to mols H2. g = mols x molar mass.
June 7, 2015

chemistry
2CH3OH + 3O2 => 2CO2 + 4H2O dH = -174 kcal/mol and that x 2 = -348 kcal/rxn and I'm taking you at your word that this is -174 kcal/mol and not -174 kcal/reaction for the 2 mols. -348 kcal x 33.0/64 = ?
June 7, 2015

chemistry
If dH is - heat is released and not absorbed. Is that kcal/mol or kcal/2 mols.
June 7, 2015

chemistry
You have a chapter here. It would help if you told us exactly what you don't understand. I'll get you started. 2C8H18 + 25O2 ==> 16CO2 + 18H2O + heat or you may write it as 2C8H18 + 25O2 ==> 16CO2 + 18H2O dH = -239.5 kcal Note that this is the reaction for the 5....
June 7, 2015

Chemistry
(CO) = mols/L = ? (H2) = mols/L = ? (CH3OH) = mols/L = ? Substitue the concentrations into the Kc expression and sole for Kc. Convert to Kp by Kp = Kc(RT)^delta n. 6.22E-3 is the right answer.
June 7, 2015

Chemistry
gases have no shape; i.e., they take the shape of the container.
June 7, 2015

Chemistry
2. mL1 x M1 = ml2 x M2 mL1 x 3.6 = 350 x 3.6 3. mols NH4Cl = M x L grams = mols x molar mass.
June 7, 2015

Chemistry
5% SO4 w/w = 5g SO4/100 g solution. (x g solute/1200) = 0.05 Solve for x g SO4^2- and convert to g K2SO4, then to mols K2SO4. 2. 3.6 what? 3. See 2.
June 7, 2015

Chemistry
I expect you are reporting too many significant figures. You're allowed just three; therefore, I would round the answer to 11.7 g. By the way, you will have some trouble making 1.26 M solution of H2CO3. A saturated solution isn't that strong.
June 6, 2015

Chemistry
This is a limiting reagent (LR) problem. You know that because an amount is given for BOTH reactants. I work these the long way. Na2O2 + CO2 ==> Na2CO3 + O2 Use PV = nRT and solve for n = number of mols CO2 at the conditions listed. mols Na2O2 = grams/molar mass Use the ...
June 6, 2015

Chemistry
..............2NO(g)←−→N2(g)+O2(g) I...........0.220......0.....0 C............-2x.......x.....x E..........0.220-2x....x.....x Substitute the E line into Kc expression and solve for x, then evaluate 0.220-2x.
June 6, 2015

chemistry
This is a mixture problem. It requires two equation to be solved simultaneously. Let X = mass BaO ad Y = mass CaO ---------------- equation 1 is X + Y = 10g The second equation comes from the reaction with HCl. 2HCl + BaO ==> BaCl2 + H2O 2HCl + CaO ==> CaCl2 + H2O You ...
June 6, 2015

chemistry
This means you want a procedure, likely taking at least a page or more. You write it and we will critique it for you.
June 6, 2015

chemistry
millimols HAc = mL x M = 25 x 0.01 = 0.25 mmols Ac^- = mL x M = 25 x 0.1 = 2.5 mmols HCl = 10 x 0.01 = 0.1 ---------------------- ......Ac^- + H^+ ==> HAc I....2.5.....0........0.25 add.........0.1............... C...-0.1...-0.1......+0.1 E.....?......?.........? Complete ...
June 5, 2015

chemistry
http://www.jiskha.com/display.cgi?id=1433438216
June 5, 2015

Chemistry
x kJ/(6.02E23*0.02) = ?
June 5, 2015

science
50 what? 50 ohms? rho = sp resistivity = R*A/l A = 60E7 m^2 R = 50 ohms l = 15 m Solve for rho
June 5, 2015

science
http://www.jiskha.com/display.cgi?id=1433438216
June 5, 2015

Chemistry
Na2CO3 ==> Na2O + CO2 look up delta Hformation for each at 25 C. Assuming delta H doesn't change that much, then dHrxn = (n*dHf products) - (n*dHf reactants) That will give you the heat required to decompose 106 grams. Then dHrxn x (32.5/106) =? I don't have those ...
June 4, 2015

Chemistry
H3PO4 + 3KOH ==> K3PO4 + 3H2O mols H3PO4 = M x L = ? Use the coefficients in the balanced equation to convert mols H3PO4 of mols KOH. Now M KOH = mols KOH/L KOH. You know M and mols, solve for L. Convert to whatever volume units you wish.
June 4, 2015

Chemistry
By the way those are estimates. You should recalculate to get more exact numbers.
June 4, 2015

Chemistry
Difference in p of solvents = 256-55.3 = 200.7 (256-213)/200.7 = about 0.2 (213-55.3)/200.7 = about 0.8 So the 0.2 is closer to the Xmethanol. The 0.8 must be XH2O
June 4, 2015

Chemistry
It isn't. That's 22.4 L/mol and not 22.4 mols/L. So you want 2/22.4 = ? mols H2 produced.
June 4, 2015

Chemistry Please Help Thanks!
mols galactose = 200.3/180 = approx 1.1 Psoln = XH2O*PoH2O 25.8 = XH2O*26.4 Solve for XH2O 1-XH2O = Xgal Xgal=ngal/(ngal+nH2O) Solve for nH2O nH2O = grams/molar mass H2O Solv for grams. Convert g to volume using density.
June 4, 2015

math practice help
You can add or subtract like terms; i.e., like terms are the X^2 or the X or the numbers. Adding we get 2x^2+(-7x^2) = -5x^2 6x+(+2)2x = 8x 1+(-3) = -2 So the answer for the addition is -5x^2+8x-2 For subtraction you do them this way 2x^2 -(-7x^2) = 2x^2+7x^2 = 9x^2 6x-(+2x...
June 4, 2015

Chemistry
Dey are not. Don't forget to convert 1.59 kg to grams.
June 4, 2015

Chemistry
mols = grams/molar mass
June 4, 2015

Science
ln(No/N) = kt No = 100 N = 85 t = 5 days solve for k Then ln(No/N) = kt No = 100 N = ? solve for this amount remaining. k = from above t = 25 days N is what is left. (N/100)*100 = % remaining
June 4, 2015

Chemistry
I believe Dalton did but I think Thomson did not. Dalton talked about atoms being the smallest "particles" of an element and didn't go into how they were constructed (electrons, protons, neutrons were not known then) but Thomson discovered the first subatomic ...
June 4, 2015

science
I would think after I went to the trouble of numbering your questions (as well as checking the answers you gave) that you would at least post again WITH NUMBERS. How in the world do you expect anyone to tell you which question is being answered? Also I note you didn't ...
June 3, 2015

CHEMISTRY
See your Ag2CO3 post.
June 3, 2015

CHEMISTRY
Ag2CO3 ==> 2Ag^+ + CO3^2- Write Ksp H2CO3=> H^+ + HCO3^- Write k1 expression HCO3^-=>H^+ + CO3^2-.Write k2 expression H^+ = 4.187E-4 Solubility = S, then S = (CO3^2-) + (HCO3^-) + (H2CO3) Substitute H^+ into k2 expression and solve for HCO3^- in terms of CO3^2-; i.e...
June 3, 2015

Chemistry
Your problem is that you don't recognize what you have at this point. If 20 mL is half-way to the equivalence point, then 40 mL must be AT the equivalence point; therefore, the pH at this point will be determined by the hydrolysis of the salt; i.e., the KF. The HH equation...
June 3, 2015

Chemistry
mols NaCl in 1L of 1M = M x L = 1 mols Cl^- = 1 since there is 1 Cl ion in 1 mol NaCl. 0.5L of 1 M MgCl2 contains mols = M x L = 0.5 x 1 = 0.5 mols MgCl2.' mols Cl^- will be twice that (2*0.5 = 1) = 1 mol Cl ions.
June 3, 2015

chemestry
NaH2PO4 + 2NaOH ==> Na3PO4 + 2H2O mols NaH2PO4 = grams/molar mass = ? Use the coefficients in the balanced equation to convert mols NaH2PO4 to mols NaOH used. Then M NaOH = mols NaOH/L NaOH. You know mols NaOH and M NaOH, solve for L NaOH. Convert to mL if that is the unit ...
June 3, 2015

Chemistry
2.9 mg/mL x 430 mL = ? mg K^+ needed. ? mg K^+ x (molar mass KNO3/atomic mass K) = mg KNO3 needed. mg KNO3 x (1 g/1000 mg) = g KNO3 needed.
June 3, 2015

Chemistry
We help do homework. You're asking us to write a 1-2 page essay (procedure) for your from scratch. I have a better idea. You write it and we will critique it for you.
June 2, 2015

Dividing Decimals
No. The way to do this (by hand) is to move the decimal on the 0.64 to 64. So add two zeros to the 8 to make 800 so that's the same as 800/64 = ? If you're using a calculator just punch in the numbers. But if you're using a calculator how could you come up with the...
June 2, 2015

Chemistry
At what conditions? The volume of CO2 varies with both T and P. I'll assume STP. 2C4H10 + 13O2 ==> 8CO2 + 10H2O mols CO2 = 7.64/22.4 = ? Using the coefficients in the balanced equation, convert mols CO2 to mols C4H10. Then convert mols C4H10 to grams. g = mols C4H10 x ...
June 2, 2015

Chemistry 12
The average volume is not right because you threw away one of the 11.8 volumes. Volumes are 11.80, 11.80 abd 14.10 Sum those and divide by 3. Then mols NaOH = M NaOH x L NaOH = ?
June 2, 2015

Chemistry
mols you need = M x L = ? Then mols = grams/molar mass. You know mols and molar mass, solve for grams.
June 2, 2015

Chemistry
v = m/d
June 2, 2015

science
http://www.cliffsnotes.com/cliffsnotes/sciences/how-do-electrical-charges-interact
June 2, 2015

CHEMISTRY
You need to rephrase your question. As written it makes no sense.
June 2, 2015

Science Help Plzz
1. The images above show particles in a medium. Which of the following shows the worst conditions for a sound wave travel? A B C D is the answer A? I don't see any images. I recopied all of this since you didn't number them. 2. Which of the following correctly ...
June 2, 2015

Science
The plane is traveling at 215 m/s horizontally. The package is traveling at 215 m/s horizontally. The package is falls directly under plane until the package hits the ground and it's horizontal speed is slowed.
June 1, 2015

Chemistry
The mass of an object is the same no matter where you are. The weight changes due to the gravitational attraction but the mass stays the same.
June 1, 2015

Chemistry
I would write it this way since you added the gaseous state to O2. S(s) + O2(g) ==> SO2(g) Also I don't know how your prof handles S; some show that S actually is S8 in the normal state. If that is the case then the equation would be S8(s) + 8O2(g) --> 8SO2(g)
June 1, 2015

chemistry
I don't know what definition your prof is using. In relation to H2 or in relation to air. If H2 it is this. dx = 4dy Mx = 8dy so if Mx = m, then My is 8m.
June 1, 2015

Chemistry
heat lost by Al + heat gained by H2O = 0 [mass Al x specific heat Al x (Tfinal-Tinital)] + [mass H2O x specific heat H2O x (Tfinal-Tinitial)] = 0 Substitute and solve for mass H2O.
June 1, 2015

chemistry
Also see this. http://chemistry.about.com/od/matter/f/Is-Dissolving-Sugar-In-Water-A-Chemical-Or-Physical-Change.htm
May 31, 2015

chemistry
For years I think the answer has been physical for the reason you note but let me give you some food for thought. What about HCl gas dissolving in water to form a solution? HCl + H2O ==> H3O^+ + Cl^- and actually the Cl^- is hydrated also. Or how about when NaCl dissolves ...
May 31, 2015

Chemistry
I don't think so. I don't know why you converted anything to mass although it can be done that way but not by your calculation. (For example, the volume is not 0.05). You want the molarity and that is mols/L. You already have it as 5% w/v which means 5 g/100 mL or 50 g...
May 31, 2015

chemistry
nope. 1. The number 2 is the only significant figure. The zeros are place holders only; i.e., they are they in order to set the decimal point.
May 31, 2015

chemistry
Yes, the lowest part.
May 31, 2015

chemistry
Wouldn't that be 15.95/100 = 0.1595 g/mL?
May 31, 2015

Chemistry
I don't have the same electronegativity values you have because we are using different sources but isn't SiCl4 the highest?
May 31, 2015

Science
I would look at C as a possibility
May 31, 2015

Chemistry
You're ok as far as you went. Who ever made up this problem forgot to tell us how much solution is being prepared. It makes sense, doesn't it, that we can get more AgCl if we made up 5L than if we made up 1L. So I guess we assume we make 1 L solution. ........Ag^+ + Cl...
May 31, 2015

chemistry
7.89 what
May 31, 2015

pennfoster
And when you get the numbers straight, please do NOT write your answers in a straight line. Mathematically it is not correct. For example, If the account were 25.00 and you wrote a check for 10.00 and added 5.00 to the account the new balance is NOT 25.00-10.00 = 15.00+5.00 = ...
May 31, 2015

nuclear chemistry
I believe that answer should be -4.43E-13 J/nucleon. 0.55433 amu x 1.6605E-27 kg/amu x c^2 = ? for 187 nucleons. Divide by 187 for 4.42E-13 J/nucleon.
May 31, 2015

chem
H. H has 1 electron in the neutral state. Add 1 electron gives it a -1 charge. So H^- is the ion and that's the hydride ion.
May 31, 2015

Chemistry
[Pb2+] = (1.1x10^-4 mol/L x 0.02L)/(0.02L + 0.08L) = 2.2x10^-5 mol/L This is right for Pb^2+. [I-] = (4.45x10^-2 mol/L x 0.08L)/0.1L = 3.56x10^-2 mol/L This is right for [CaI2] but [I^-] is twice that or 7.12E-2 Qsp = [Pb2+][I-]^2 = (2.2x10^-5)(3.56x10^-2)^2 = 2.7x10^-8 This ...
May 31, 2015

Chemistry
CaCO3 ==> CO2 + CaO 2 mols CaCO3 will produce 2 mols CO2 and grams = mols x molar mass = ?
May 30, 2015

Science
delta T = Kf*molality delta T = normal freezing point of 1,4-dichlorobenzene - 49.2. Kf is the freezing point constant for 1,4 dichlorobenzene. Substitute in the equatiohn and solve for m. m = molslity = mols/kg solvent. You have kg solvent (0.040g) and you have m. Substitute ...
May 30, 2015

IT
I can't answer either; however, I can tell you that you won't get an answer unless you clean up the question. Your one sentence is too long and it contains too many identical phrases.
May 30, 2015

chemistry
It depends upon the units you want for pressure in the answer. If you want the pressure in units of kPa use 8.31. If you want the pressure in units of atm use 0.08206.
May 30, 2015

Chemistry
1. The 53.1 you quote is kJ/mol and you need to change that to J/mol. 2. You have calculated the mols but you don't have as much as a whole mole. Therefore, 53,100 J/mol x # mols in reaction = J and that is Q. 3. This is an exothermic reaction and q goes in this equation ...
May 30, 2015

chemistry
http://www.jiskha.com/display.cgi?id=1432930774
May 30, 2015

chemistry
How many moles do you want? That's M x L = ? Then mols = grams/molar mass. YOu know molar mass and mols, solve for grams.
May 30, 2015

chemistry
I don't know what molecules are tried to draw. You might try writing the condensed structure.
May 29, 2015

chemistry
The modified form of the gas equation is P*molar mass = density*RT Substitute and solve for d.
May 29, 2015

Science
yes 88.82% which rounds to 89%
May 29, 2015

general chemistry
This is meant to be your explanation of this experiment and not mine. How can I help you?
May 29, 2015

chemistry
See your other post above.
May 29, 2015

Chemistry
ln(No/N) = kt Solve for k using 100 for No and 40 for N(i.e., if it was 60% completed and you started with 100, you would have 40 left. Then ln(No/N) = kt again, use k from above and solve for t.
May 29, 2015

Chemistry
Substance A is hot and substance B is cold. They come together. The hot material loses heat and the cold material gains heat but the heat lost - heat gained so heat (energy) is not created or destroyed but relocated (moved around).
May 29, 2015

chemistry
Do you intend for that to be Cl^-(aq) or Cl2(aq). It isn't balanced. If you write what you intended and balance it we can change to whatever you need.
May 28, 2015

Chemistry
Assuming you meant 0.2 M and not 0.2 m, then HNO3 + OH^- ==> NO3^- + H2O mols HNO3 = M x L = 0.02 x 0.2 = 0.004 mols OH- = the same since 1 mol HNO3 reacts with 1 mol OH-. Then M OH- = mols OH-/L OH- = 0.004/0.04 = 0.1 M. Now let's be careful here. That 0.1M is the (OH...
May 28, 2015

chemistry
Use (P1V1/T1) = (P2V2/T2) For P1 use 750-14 = ? V1 = 50 cc T1 = 273+17 = ? P2 and T2 ae STP V2 = solve for this in cc.
May 28, 2015

Chemistry
PV = nRT and solve for n = number of mols. Then n = grams/molar mass. You know molar mass and n, solve for grams.
May 28, 2015

Chemistry
Is that 60 g? q = mass NH3 x heat vaporization NH3
May 28, 2015

chemistry
I don't understand the question. Do you mean 0.3 cc LiOH neutralizes 0.2 M H2SO4. How much H2SO4 was neutralized?
May 28, 2015

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