Saturday
July 4, 2015

Posts by drbob222


Total # Posts: 49,393

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

Chemistry
PV = nRT Remember T must be in kelvin. n = grams/molar mass He = 27800g/molar mass He.
May 27, 2015

Chemistry
See your post above. Same PV = nRT
May 27, 2015

Chemistry
M x L x molar mass = grams.
May 27, 2015

Chemistry
mols Na2CO3 = M x L = ? mols Na^+ = twice that since there are two Na ions in 1 molecule of Na2CO3. mols NaHCO3 = M x L = ? Total Na = mols Na from Na2CO3 + mols Na from NaHCO3. M Na = mols Na/total volume in L
May 27, 2015

Chemistry
CH3COOH + NaOH --> CH3COONa + H2O millimols CH3COOH = 50 x 0.150 = ? millimols NaOH = 49 x 0.150 = ? mmols CH3COOH left = the difference. M CH3COOH = mmols/total mL = ? Then convert to pH.
May 27, 2015

chemistry
What is ,300m7^3?
May 27, 2015

Chemistry
2.5L is right for a. I don't agree with 3.00 L for b. What you want is ?Lair x 0.2 oxygen = 2.5 L oxygen. ?Lair = 2.5 Loxygen/0.2 oxygen = ? which I think is 12.5 L air. Check it. 12.5 L air x 0.2 oxygen = 2.5 L oxygen. Do c the same way.
May 27, 2015

chemistry- titration
I don't understand what you've done but the HH equation should be pH = pKa + log (base)/(acid). After you know the Ka value, assuming it is monoprotic, then mLacid x Macid = mLbase x Mbase
May 27, 2015

chemistry
First you need to correct the typos and make sue you have the correct numbers. They can't be right because they don't add to 100%
May 27, 2015

chemistry
I don't see a question. If you want an answer you should explain what you hav written.
May 27, 2015

Chemistry
dG = -nFEo
May 27, 2015

chemistry
First step. Cu2S ==> 2CuO Cu changes from total of +2 on the left to total of +4 on the right. S changes from +6 in SO4^2- to +4 in SO2. Now you balance the two half reactions.
May 27, 2015

science
1. (1/16)*6.02E23 = ? 2. (1/32)*6.o2E23*(2 atoms O/molecule O2) = ? 3. (1/48)*6.02E23*(3 atoms o/molecule O3) = ?
May 27, 2015

college chemistry
q1 = heat needed to change phase of ice from solid to liquid(i.e., to melt ice)? q1 = mass ice x heat fusioin q2 = heat needed to raise T of liquid water from zero C to 100 C. q2 = mass H2O x specific heat H2O x (Tfinal-Tinitial) q3 = heat needed to change phase of liquid ...
May 26, 2015

Chemistry
Without Figure 13.7 how am I supposed to help you? In the absence of Figure 13.7, you can use the Clausius Clapeyron equation of ln(P2/P1) = (dHvap/R)(1/T1 - 1/T2) P2 is 330 P1 is 760 dHvap is whatever in jouls/mol R is 8.314 T1 is 100C (remember that's 373 K) T2 is ? and ...
May 26, 2015

Chemistry
From your previous post. q1 to melt ice + q2 to heat melted ice to final T + q3 to cool 90 C water to final T = 0 q1 to melt ice is that mass ice x heat fusion. (That change the phase) q2 to raise T of melted ice is that mass H2O x specific heat H2O x (Tfinal-Tinitial). (That ...
May 26, 2015

Chemistry
Look at your ice to steam problem above. This is the same concept. After you have one of these worked you should be able to follow the template and work the others. In these problems there are two formulas. 1. When changing T WITHIN A PHASE (i.e., one T in ice to another T in ...
May 26, 2015

Chemistry
I showed you how to do this yesterday. Why are you posting again?
May 26, 2015

Chemistry
C2H4 + 3O2 ==> 2CO2 + 2H2O 10.0 what? Change 10? to mols if it isn't already in mols. dH = 1410 kJ/mol x (# mols) = ?
May 26, 2015

CHEMISTRY
Use the Henderson-Hasselbalch equation. KH2PO4 is the acid and K2HPO4 is the base.
May 26, 2015

chemistry
Do you know the solubility of I2? Do you have an equilibrium constant. A distribution constant? Any other information available. I just don't have thousands (millions?) of solubility data memorized. No one does.
May 26, 2015

Chemistry
a. 134 g MgSO4.7H2O x (7*molar mass H2O/molar mass MgSO4.7H2O) b. 134 g MgSO4.7H2O x (molar mass MgSO4/molar mass MgSO4.7H2O) = ?
May 26, 2015

chemistry
a. q = mass Al x specific heat Al x (Tfinal-Tinitial) b. Look at your specific heat problem just before this as a hint (if you need a hint).
May 26, 2015

chemistry
heat lost by metal + heat gained by water = 0 [mass metal x specific heat metal x (Tfinal-Tinitial)] + [mass H2O x specific heat H2O x (Tfinal-Tinitial)] = 0 Substitute and solve for the only unknown in the set up.
May 26, 2015

chemistry
q1 = heat needed to raise T of ice from -22 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 H2O at zero C. q2 = mass ice x heat fusion q3 = heat needed to raise T of liquid water from zero C to 22.0 C. ...
May 26, 2015

chemistry
Three hints. 1. You need to find the caps key and use it. 2. You need to use proper sentence structure so we know when one sentence ends and the next one starts. 3. You need to rewrite this question and rephrase it so it makes sense. As is it makes no sense whatsoever.
May 26, 2015

Chemistry
Look up the Ka for HF and compare it with the Ka for acetic acid. Use 0.1M for the two solution and calculate the (H^+) and the pH. You will see the difference.
May 26, 2015

Chemistry
q = mass solution x specific heat solution x (Tfinal-Tinitial) mass solution = 75 + 75 = 150 mL and that is 150 g since density is 1.00 g/mL. You have the specific heat and Tfinal andTinitial. Calculate q. Then delta E = q + w You have q from above. I believe w is zero. It is ...
May 26, 2015

Chemistry
Convert 6.6g NaOCl to mols. mols = grams/molar mass. Then M = mols/L solution
May 25, 2015

chemistry
The is a limiting reagent (LR) problem and you know that because amounts are given for BOTH reactants. 1. Write and balance the reaction. The products are CO2 and H2O. 2. Convert grams C6H6 (use caps) to mols. mols = grams/molar mass 3. Do the same and convert g O2 to mols. 4...
May 25, 2015

Chemistry check my answers
1. Synthesis is right. You should note the color of the oxide produced. A red or yellow color denotes the formaton of Cu2O. A black color is CuO. Generally if Cu is heated in air it forms both. 4. There is nothing wrong with what you wrote; however, I wanted you to know that ...
May 25, 2015

Chemistry check
No
May 25, 2015

Chemistry
1. Convert 73.1 g CsXeF7 to mols. mols = grams/molar mass = ? 2. Using the coefficients in the balanced equation, convert mols CsXeF7 to mols CsF. 3. Now convert mols CsF to grams. g = mols x molar mass.
May 25, 2015

ap chemistry
Ecell = Eocell - (0.05916/n)*log Q You have Ecell and Eocell. n is 2 and Q = (Fe^2+)^3/(Fe^3+)^2 Substitute and solve for (Fe^2+). 0.047M is the correct answer.
May 25, 2015

Chemistry
mL1 x M1 = mL2 x M2
May 25, 2015

science
The half life of insulin is prolonged due to less degradation. http://clinical.diabetesjournals.org/content/25/3/90.full
May 25, 2015

chemistry
How many mols NO3^- do you want. That's M x L = mols = 0.25 x 0.5L = 0.125 How many mols do you have in the NaNO3? That's mols = grams/molar mass = 5.0/85 = approx 0.06 but you need a more accurate answer that the estimate. How many more mols do you need to be ...
May 25, 2015

chemistry
15 g Ca(OH)2 = ? mols. That's 15/molar mass Ca(OH)2 = 15/74 = estimated 0.2 You used how many mols for the neutralization? That's 0.2 x (300/500) = estimated 0.12 mol Ca(OH)2. The equation is Ca(OH)2 + 2HCl ==> CaCl2 + 2H2O If you neutralize 0.12 mols Ca(OH)2 it ...
May 25, 2015

chemistry
How about this? volume of Hg is mass/density or in dimensional analysis it is 20g x (1 cc/13.6 g) (g cancels and leaves cc which is volume) of Hg. . Now we want to convert to grams alcohol. 20 g x (1 cc/13.6 g) x (0.9 g/cc) = ? cc on top cancels with cc on bottom. g on top ...
May 25, 2015

Chemistry
Substitute into the HH equation. HF is the acid; NaF is the base.
May 25, 2015

Chemistry
That's right. Think what temperature H2O condenses from gas to liquid (or freezes to a solid) vs temperature CO2 condenses from gas to solid.
May 25, 2015

chemisrty
I don't know where you have it but the sum of the partial pressure of each is the total pressure. 1.5 + 1.6 + 1.3 = ? atm. You have a tough time getting 1.3 atm H2O vapor unless the container is sealed since the vapor pressure at boiling point is 1 atm.
May 24, 2015

Chemistry
How can we help you with this assignment short of writing out a textbook procedure for you? I'll be glad to answer any questions or critique what you write.
May 24, 2015

Chemistry
2KOH + H2SO4 ==> K2SO4 + 2H2O mols KOH = M x L = ? mols H2SO4 = 1/2 that looking at the coefficients in the balanced equation. Then M H2SO4 = mols H2SO4/L H2SO4. You know mols and M, solve for L.
May 24, 2015

CHEM
q = mass H2O x specific heat H2O x (Tfinal-Tinitial) You know q, mass H2O, specific heat and Tfinal. Solve for Tinitial.
May 24, 2015

chemistry
You must know how to do parts of this. What about the problem do you not understand? a. m = mols/kg solvent. You have volume and density. That's how you determine kg solvent. b. XNaCl = n/total mols XH2O - n/total mols c. % NaCl w/w = grams NaCl/100 g solution. d. Take the...
May 24, 2015

chemistry
See your other post.
May 24, 2015

ap chem
96,485 Coulombs can plate out approx 209/3 grams Bi. You need a better answer than that estimate. How many coulombs do you have? That's C = amperes x seconds = approx 5.60 x 23.8 x 60 s/min = ? 209/3 x ?coulombs/96,485 = g plated out.
May 22, 2015

AP Chem ---
k = 0.693/t1/2 Solve for k and substitute into the below. ln(No/N) = kt No = 100 N = 25 k from above Solve for t in days.
May 22, 2015

AP Chem ---
See your post above.
May 22, 2015

AP Chem ---
zXw ==> 11Na24 + 2He4 z = 11 + 2 = ? (13 and that is Al) w = 24 + 4 = ? So the equation is 13Al28 ==> 11Na24 + 2He4
May 22, 2015

Chemistry
24Cr51 ==> 25Mn51 + -1eo So that must be a beta decay.
May 22, 2015

Chemistry
Pb is +2 on the left and +2 on the right O is zero on the left and -2 on the right. S is -2 on the left and +4 on the right.
May 22, 2015

Chemistry
Oxidation is the loss of electrons. Cu is +2 on the left and zero on the right. H2 is zero on the left and +1 on the right.
May 22, 2015

is the ph= o for the H+
10^-0.249 = 0.56 so from these numbers the pH = 0.56.
May 21, 2015

is the ph= o for the H+
If you will show your work I can check it.
May 21, 2015

CHEMISTRY ( I NEED HELP AGAIN QUICK )
The first question is a limiting reagent problem. You work it the same way as the previous LR problem. The second one is not a LR problem but a simple stoichiometry problem. So instead of converting two reactants to mols of product and choosing which one to use you have only ...
May 21, 2015

chem 100
a. .........PbI2 ==> Pb^2+ + 2I^- I........solid.....0.......0 C.........-x.......x.......2x E........solid.....x.......2x Sustitute the E line into Ksp expression and solve for x = (Pb^2+) b. You need Kc for the reaction and you can get that from the sum of the two ...
May 21, 2015

Chem 100
http://www.chemistry.wustl.edu/~edudev/LabTutorials/naming_coord_comp.html
May 21, 2015

Chemistry (I NEED HELP REAL QUICK)
This is a limiting reagent (LR) problem and you know that because amounts for BOTH reactants are given. I work these the long way. BaCl2 + MgSO4 ==> MgCl2 + BaSO4 mols BaCl2 = M x L = ? mols MgSO4 = M x L = ? Use the coefficients in the balanced equation to convert mols ...
May 21, 2015

chem
You don't have a workable equation.
May 21, 2015

Chemistry
NF3 is trigonal pyramidal; therefore, it is not symmetrical in three dimensions. NF4^+ is tetrahedral and is not polar because the N-F polar bonds balance each other. That is not true for NF3.
May 21, 2015

science
I would choose a,b,d with a note that heat energy is the only end product of the transfer. The others are USING electrical energy to make the transfer from an electromagnetic wave in space that contains the video and audio signals into light and sound.
May 21, 2015

science
I don't think much of this question. It's worse than the one above it. The answer is it depends upon where you place it. If you place it on the stove top burner it is mostly conduction. If you place it in the oven it is mostly convection but with some radiation.
May 21, 2015

  1. Pages:
  2. <<Prev
  3. 1
  4. 2
  5. 3
  6. 4
  7. 5
  8. 6
  9. 7
  10. 8
  11. 9
  12. 10
  13. 11
  14. 12
  15. 13
  16. 14
  17. 15
  18. Next>>

Members