Saturday
April 19, 2014

Posts by DrBob222


Total # Posts: 41,793

Chemistry
Zn is almost always 2 as its placement in the periodic table would suggest. Same for Sc at +3. All of the others are variable. At least ONE valence will be the period; for example, Mn has bunches of numbers but +7 is one of them. Cr has several but at least one of them is +6. ...

Chem
Does relative mean concentrations are not needed; only a ranking? You know H2O is the most prevalent. You know HNO3 is the least. Can you fill in the others. What are your thoughts and "I don't have a clue" is not acceptable.

Chemistry
HCl is a strong acid; i.e., it ionizes 100%. Same for HBr. So the combined M in the solution is 0.5+0.085. pH = -log(H^+), then pH + pOH = pKw = 14.

Chem
If we define "valence electrons" as simply the number of electrons in the outer shell of an atom, these can be found in the periodic table. Xe has 8, Rb has 1, I is 7, etc. Just look up the electron configuration of each.

Chemistry
Look at the equation. The equation tells you 1 mol CaO reacts with 1 mol H2O to yield 1 mol Ca(OH)2.

Chemistry
Your mistake is you didn't take into account the van't Hoff factor, i. The equation is delta T = i*Kf*m is for CsX is 2.

Chemistry
I agree with the last answer.

Chemistry
See your post above.

Is the Cations and Anions right?
No. None are completely correct. 1. Fe^3+ and SO4^2- 2. Co^2+ and 2Cl^- I don't understand your problem. Perhaps you cn explain it to me. For #2. when you write Co(II) you KNOW WITH CERTAINTY that Co is 2+. And if Co is 2+ and you have two Cl with it, then Cl must be -1 an...

Chemistry
E = hc/wavelength Substitute wavelength and solve for E = ? J/photon. 7 kJ/s/m^2 x 8.40 cm^2 x *(1 m/100 cm)^2 x (1 kJ/1000J) = Joules striking 8.40 cm^2 area. Then ? J/photon x # photons = J striking 8.40 cm^21 area. Solve for # photons.

Quick math help please!!!
You can tell if it is right or not by substituting your values for x and y into either equation. If you get -19 for the first one OR -30 for the second one your answers are right.

Chem
What you have is arranged properly. FeO difference in electronegativity is 1.7 and should fit between OH and NaCl. FeC difference is 0.7 and should fit after CH and before HCl.

College Chemistry
J = mass x specific heat x (Tfinal-Tinitial)

College Chemistry
See this. http://www.jiskha.com/display.cgi?id=1392734601

chemistry 112
For an 80% yield you will need 1.6 mols SO3. .........2SO2 + O2 ==> 2SO3 I........2 mols..2.......0 C........-2x.....-x......2x E.......2-2x.....2-x.....2x Then an 80% yield gives SO3 = 1.6 mol; therefore, 1.6 = 2x and x = 0.8 Solve for 2-2x = 0.4 mol SO2 2-x = 1.2 mols O2 ...

chemistry
Pick any convenient mass, say 100 g, then mass = volume x density Substitute and see which has the larger voluem.

chem
mols Li = grams/atomic mass Using the coefficients in the balanced equation, convert mols Li to mols H2. Use PV = nRT, substitute the conditions and mols and solve fr V in liters.

chemistry
You didn't list any but the ions present will be Na^+ and SO4^2-

chemistry
%O = 100 - %C - %H Take a 100 g sample which gives 53.4g C 11.1g H 35.5g O mols C = 53.4/12 = ? mols H = 11.1/1 = ? mols O = 35.5/16 = ? Now find the ratio of the atoms to each other (as whole numbers) with the smallest number being 1.00. The easy way to do that is to divide t...

AP Chem
The (H^+) for a weak acid/weak base salt is (H^+) = sqrt (KwKa/Kb). So you look up a Ka that is smaller than Kb. You know Kb is about 1.8E-5 so any acid that is smaller than that should produce a basic solution. Look in your Ka tables for an acid smaller than 1.8E-5 and if the...

chem 102
p = KcC p = 0.21 when saturated and Kc = about 769 atm*L/mol but you should look this up in your tables and use that number here. Also, I have estimated all of my other answers; you definitely should go through the calculations yourself and refine each of the steps. C for the ...

chemistry
mol CuSO4 = grams/molar mass M = mols/L solution.

Chemisty
1. Write and balance the equation. 2NaOH + H2SO4 ==> Na2SO4 + 2H2O 2. mols NaOH = M x L = ? 3. Using the coefficients in the balanced equation, convert mols NaOH to mols H2SO4. ? mols NaOH x (1 mol H2SO4/2 mols H2SO4) = ? mols H2SO4. 4. Now convert mols H2SO4 and volume to ...

Chemistry
q = mass(grams) x Hvaporization (J/g) This will give q in J/g, then change J to kJ.

chemistry
What units?

Chemistry
0.01M means 0.01 mols H3PO4/1000 mL solution. The molar mass is 98; therefore, there are 0.98 grams H3PO4/1000 mL solution. mass solution is 1000 mL x 1.11 g/mL = 1110 grams. mass % = (gH3PO4/g solution) = (0.98/1110)*100 = ? % w/w

Chemistry
Heating NaHCO3 to what temperature? If to about 270 C or so it is 2NaHCO3 ==> CO2 + Na2CO3 + H2O mols NaHCO3 = grams/molar mass Using the coefficients in the balanced equation convert mols NaHCO3 to mols CO2. Then 22.4L x ?mols = ? L at STP

Chemistry
How can we help you with this assignment short of doing your homework for you. I recommend color for Ni. The Al and Sn are colorless while most Ni solutions are green or blue. Co solutions are pink to blue. Remember that Al is amphoteric; i.e., it forms a white gelatinous ppt ...

chemistry
mols methanol = grams/molar mass Then m = mols/kg solvent

chemistry
You provided no information for the question. My crystal ball is hazy today.

Chemistry
CuSO4 + 2KOH ==> Cu(OH)2 + K2SO4 You have 150 x 1.50 = 225 millimols CuSO4 and 450 mmols KOH q = mass solution x specific heat x (Tfinal-Tinitia) I would use 300 mL = 300 g for mass soln. Specific heat H2O is 4.184 J/g*C Tfinal and Tinitial are given. q is Joules/225 mmols....

CHEMISTRY
I will do the first one in detail. The others follow the same pattern. Look up the activity series in your text/notes/Google/etc. If the METAL is above the metal ION, the metal will displace it; otherwise, there is no reaction. 3Mg + Al2(SO4)3 --> 3MgSO4 + 2Al Mg is ABOVE A...

Chemistry
See your post above. For oxidizing agent and reducing agent here is what you do. Oxdn is loss of electrons--that substance is the reducing agent. Reduction is the gain of electrons--that substance is the oxidizing agent.

chm101
high

CHEMISTRY
0.15g/molar mass = mols M = mols/6.5L pH = -log(HCl)

science
You have posted a number of these multiple guess questions recently; have you given any thought to telling us what you think the answer is and why you chose that answer.

chem
You don't give enough information about the question to be sure but I assume this is a 10 eletcron system with 2e in the n = 1 and 8e in n = 2. So out of the 10 possibilities, 2 of them are from the n = 1 shell (2/10) and 8 of them are from the n = 2 (8/10).

Chem Help :(
1. pH = -log(H^+) 2. (H^+)(OH^-) = Kw = 1E-14. You know Kw and OH, solve for H^+, then use pH equation in #1.

Chemistry
Mg + 2HNO3 ==> Mg(NO3)2 + H2 mols Mg = grams/molar mass mols Mg(NO3)2 = mols Mg (look at the mole ratio) which is 1 mol Mg to 1 mol Mg(NO3)2. Then grams Mg(NO3)2 = mols x molar mass. For HNO3 needed, convert mols Mg to mols HNO3 and convert mol HNO3 to grams as in the above.

Chemistry Help Please!!!
First you must recognize that k1 is the largest K of the group and the pH of the solution will be due largely to the first dissociation. The second and third don't produce enough to concern us too much. .......H3PO3 ==> H^+ + H2BO3^- I......0.05M.....0.......0 C......-x...

science
Does this last post have anything to do with the first? An object traveling in a straight line in space will continue in a straight line unless acted upon by an outside force.

science
I would go with D.

science
??

science
A

chemistry
??

science
B

Ap chem-Bases
I did this for you yesterday.

college chemistry
C = p*k k = C/p Convert 321.9 torr to atm. atm = torr/760 Convert 0.02538 g/L to mols/L = M mols = grams/molar mass Substitute into equation and solve for k.

chemistry
Larger and more complicated structures have more entropy than their lesser cousins. NaNO3 has more atoms, more bonds, higher molar mass, etc.

Chemistry
Solid phosphorus pentachloride yields phosphorus trichloride gas plus chlorine gas.

AP Chemistry
First you must calculate (H^+) for 0.90M acetic acid (HAc). .........HAc ==> H^+ + Ac^- I.......0.90.....0......0 C........-x......x......x E.....0.90-x.....x......x K = 1.8E-5 = (H^+)(Ac^-)/(HAc) Plug in the E line and solve for x = (H^+). So you want (H^+) in HCl to be th...

Chemistry
A and B dilute each other when mixed so the final solutions as they are mixed, but before they react is 0.050M x 45/70 = about 0.032M for A. but you should confirm this an all others that follow and do them more accurately than I. 0.100 M x 25/70 = about 0.0357M for B. ....A(a...

Chemistry
Fe(s) + Cu^2+(aq) ==> Cu(s) + Fe^2+(aq)

Chemistry
I don't see a procedure so I can't be too helpful; however, here are some common errors if you used a solution. 1. Weighing errors. 2. Did you filter anything? If so some could have splattered out. Same thing for boiling away liquid such as water from a solution. 3. If...

Chemistry
1. If all you are doing is identifying meal ions, the contamination of the HCl with Al will not affect the results at all UNLESS the Al energy overlaps one of those from the unknown. Why? Because it takes a certain amount of energy for the Al lines to appear and it takes A DIF...

Chemistry
mols Al = grams/atomic mass = ? Using the coefficients in the balanced equation, convert mols Al to mols Fe. That is the theoretical yield. If you want it in grams then g = mols x atomic mass.

Chemistry check and help
Yes, if no subscript is shown it is understood to be 1. For the first part all are ok except these two. SO2 = Tin(I)Oxide S is sulfur (not tin) and I would name this sulfur dioxide but I believe the IUPAC name would be sulfur(IV) oxide. BrF7 = Bromine(VI)Fluoride Wouldn't...

Can someone please answer my question
done

Ap chem-Bases
..(C2H5)3N + HOH ==> (C2H5)3NH^+ + OH^- I...0.2M................0...........0 C....-x.................x...........x E...0.2-x...............x...........x Substitute the E line into the Kb expression and solve for x = (OH^-), then convert that to H^+ by (H^+)(OH^-) = Kw = 1E...

Science
When you have H2 gas in a tube and you test it, you usually ignite the H2 gas with a flame. The reaction is 2H2 + O2 ==> 2H2O. I expect that you SEE no H2O because the combustion gives a gas (steam) and you don't see that. But it's there. Perhaps if you cooled the t...

Science
Yes, elements can be separated from compounds. It takes a reaction of some kind; i.e., they can not be separated by physical means. The gas, H2, is lighter than air; therefore, holding the tube upright with no stopper and the gas will float out. Holding the tube upside down, w...

AP Chemistry
The easy way to do this is to assign some convenient rate to SF6, then multiply that number by 1.5 to know the rate for X. Then plug into the formula for Graham's Law and calculate the molar mass of X.

AP Chemistry
Use PV = nRT and calculate n. P in torr wet H2 = 966 torr P H2O torr = 22 torr PH2 dry = 966-22 = ? PH2 in atm = ?/760 V = 1.277 L n = unknown--Solve for this. R = 0.08206 L*atm/mol*K T = 297K Find n, then n = grams/molar mass. You know n and molar mass, solve for grams.

AP Chemistry
The long way of doing this, but the easier to explain, is as follows. Use PV = nRT and solve for n N2 in the 2L tank. Use PV = nRT and solve for n Ar in the 11 L tank. Then add nN2 + nAr = nTotal and use PV = nRT with a volume of 13 L (the sum of the 11 and 2 L tanks). That gi...

AP Chemistry
Here is the formula for solving theser stoichiometry problems. 1. Write the equation and balance it. 2. Convert what you have into mols. mols = grams/molar mass. 3. Using the coefficients in the balanced equation, convert mols of what you have (from step 2) to mols of the prod...

AP Chemistry
Use PV = nRT and solve for n. Then n = grams/molar mass. Solve for molar mass.

AP Chemistry
You can add the PV = nRT equation to the density and come up with P*molar mass = density*RT

AP Chemistry
Use PV = nRT. For n find n for each and add for the total. n = grams/molar mass.

AP Chemistry
See your post on stoichiometry and solve with that process. When you find mols of each product, add together, use PV = nRT to solve for volume under the conditions listed.

AP Chemistry
(V1/T1) = (V2/T2)

Chemistry
.......CO + Cl2 ==> COCl2 I.....319...220......0 C......-x....-x......x E...319-x...220-x....x Substitute the E line into the Kp expression and solve for x, 319-x, and 220-x. Then add mols of each to find total mols. XCO = nCO/total mols XCl2 = nCl2/total mols XCOCl2 = nCOC...

Chemistry
Zn + 2HCl ==> ZnCl2 + H2 mols Zn = 0.10 mols HCl = M x L = 1 x 0.150 = 0.150 First you must determine the limiting reagent (LR). You know this is a LR problem because amounts are given for BOTH reactants. a. Convert 0.10 mol Zn to mols H2. That's 0.10 mol Zn x (1 mol H2...

Chemistry
That's right. In fact that is the whole concept behind balancing redox equations. You count up the electrons lost from one side to the other; count up electrons gained from one side to the other, then multiply by whatever numbers you need to make electrons gained equal ele...

Chemistry
It isn't a hard question if you remember that in a balanced equation the number of mols electrons lost ALWAYS equals the mols gained. There is a second but more work way of doing it like this. Oxidation state Fe on the left is 0. On the right is +6 (2*3+ = 6+) and going fr...

science
density = mass/volume Just make up some numbers and see. For example suppose A = 20g and B = 10 g for mass. Then they both have the same volume of 5 cc. Substitute those numbers and see which has the higher density.

chemistry
volume = 64.8-22.9 = ? mL = ? cc. Then density = mass/volume = ? g/cc or g/mL.

chemistry
See your other post.

chemistry
volume = length x width x height = ? cc. Then density = mass/volume = ? g/cc

AP Chemistry
mmols = millimols = mL x M. mmols CH3COOH = 500 x 0.1M = 50 mmols NaOH = 500 x 0.167 = 83.5 Total volume = 500 + 500 = 1000 mL ....CH3COOH + Na^+ + OH^- --> CH3COO^- + Na^+ + H2O I......50.....83.5........0........0 C.....-50.....-50........+50......+50 E......0......33.5....

Chemistry
If you are given a name that has a metal with a multivalent possibility, the Roman numerals will tell you which to use. For nickel(I) oxide, that tells you Ni is I (i.e., +1) and not II (i.e., +2. the other common valence). Oxygen usually is -2 so you write Ni2O. For nickel(II...

Chemistry
How can we help you with this assignment? One similarity is that both yield the same products. One difference is that the temperature rises rapidly in combustion but over a longer period of time for metabolism (although the heat generated is the same).

CHEMISTRY
See your other question.

chemistry
You must have tables or graphs from which to obtain these data. I certainly don't have these things memorized. If you don't have this information in your text/notes, Google them and see if you can't find the numbers that way.

General Chemisty
H2SO4 + 2NaOH ==> Na2SO4 + 2H2O mols NaOH - M x L = ? Using the coefficients in the balanced equation, convert mols NaOH to mols H2SO4. Then M H2SO4 = mols H2SO4/L H2SO4

Chemistry
40% is 40 g sucrose/100 g solution. Use density to convert 100 g solution to volume in cc and convert that to L. Convert 40 g sucrose to mols. mol = grams/molar mass. Then M = mols/L

Chemistry
A. E/photon = hc/wavelength. wavelength = 1.350E-9 m B. I obtained 40.08 using 6.022E23 for Avogadro's number. C. looks ok to me. D. c = freq x wavelgnth

Chemistry
(P1V1/T1) = (P2V2/T2)

chemistry
What is the question? The empirical formula? Convert 4.23g CO2 to g C and convert that to %C. Here is how you do that. 4.23g CO2 x (atomic mass C/molar mass CO2) = 4.23 X 12/44 = about 1.15g C, then %C = 1.15/mass sample)*100 = about 45.8%C For g H it is 1.01g H2O x (2*1/18) =...

Chemistry
This is (P1V1/T1) = (P2V2/T2) The must be in kelvin. What else is there to show? Substitute the numbers form the problem and solve for the only unknown.

Chemistry 106 ch 11
q1 = heat released when steam @ 122 moves to 100. q1 = mass steam x sp h steam x (Tfinal-Tinital) q2 = heat released when steam condenses. q2 = mass steam x heat vap q3 = heat released when H2O @ 100 moves to 39 C. q3 = mass H2O x sp h H2O x (Tfinal-Tinitial) Then add q1 + q2 ...

analytical chemistry
How many moles do you want? That's M x L = mols. How many grams is that? That's mols = grams/molar mass. Calculate grams. Weigh the grams, add to the 200 mL volumetric flask, add some water, swish to dissolve the solid, make to the mark with distilled water and mix tho...

analytical chemistry
mols = M x L = ? mols = grams/ molar mass. Solve for grams.

Chemistry
yes

Chemistry
Use delta T = i*Kf*m and calculate m. Then use pi = i*mRT and solve for pi

Chemistry
See this. http://www.jiskha.com/display.cgi?id=1392408518

chemistry
The smaller melting range is the higher purity. That's because of colligative properties (the decrease in melting point with added impurity)

chemistry
When you've made a typo and typed 9 instead of 8. :-)

chemistry
mass % = [(mass solute)/mass solution)]*100 = ? mass solute = 7.084g mass solution = 7.084g + 123.0g = ?

Science
I believe the answer is c but I think most modern CRTs use deflection by magnetic coils. Some electrostatic devices are also used and this may be where the word "plate" comes from.

chemistry
Use PV = nRT Remember T must be in kelvin for use in the formula, then must be converted back to C for the answer.

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