Saturday
December 20, 2014

Posts by DrBob222


Total # Posts: 46,145

chemistry
The balanced equation minus the phases to save typing space. 2C8H18 + 25O2 ==> 16CO2+ 18H2O 21.4 mpg x #gallons = 1280 miles Solve for gallons needed. . Convert gallons octane to L octane. Using density convert L octane to grams octane. Convert g octane to mols octane. mol...
December 15, 2014

chemistry
You wrote the choices but not the question.
December 15, 2014

chemistry
Leo, I can't decipher the symbols. BTW, did you omit the exponent on Ka = 3.5 x 10?
December 15, 2014

chemistry
I would like to know what you don't understand about this. It would help answer the questions. H2A ==> H^+ + HA^- HA^- ==> H^+ + A^2- Surely you know how to write Ka1 and Ka2 expressions. If not explain and I can help you through them. b. (H2A) > (H^+) = (HA^-) &...
December 15, 2014

Chemistry 120
KOH = 1.9E-6 pOH = -log(KOH) Then pH + pOH = pKw = 14 You know pOH and pKw, solve for pH.
December 15, 2014

chemistry
I confirm that.
December 15, 2014

Chemistry
I think I worked this yesterday. Let me know if this is not the same problem. http://www.jiskha.com/display.cgi?id=1418542095
December 15, 2014

chemistry
S is 1s2 2s2 2p6 3s2 3p4. You are right with either c or d. I don't know what your study guide is calling 3p1 and 3p4. The 3p configuration is ud u u where up is the spin one way and d is spin the other way. he least amount to ionize with be the two outside (either of the ...
December 15, 2014

Science Help!!!!
! and 2 are ok now.
December 15, 2014

Science Help!!!!
3 is ok.
December 15, 2014

Science Help!!!!
I don't agree with 1 and 2. You didn't answer 3.
December 15, 2014

Science Help!!!!
I agree with your choices.
December 15, 2014

Chemistry
-1. At should have seven (7) electrons in its outer shell and needs 1 more to make eight (8).
December 15, 2014

Science Help!!!!
yes
December 15, 2014

Physical science
If you want to balance what you've written it is MgSO4 + 2NH4OH ==> (NH4)2SO4 + Mg(OH)2 and you are correct that what you have written is a double replacement reaction. Technically that is not correct because NH4OH does not exist. Ammonia is NH3 gas and if you have a ...
December 15, 2014

Chemistry
It's the number of O atoms in the polyatomic ion. Na2SO4 is sodium sulfATE. Na2SO3 is sodium sulfITE. NaNO3 is sodium nitrATE. NaNO2 is sodium nitrITE Na3PO4 is sodium phosphATE. Na3PO3 is sodium phosphITE There is arsenate and arsenite There is chlorate and chlorite There...
December 14, 2014

Chemistry
b was your first choice a few days ago.
December 14, 2014

Chemistry
I think the statement you have written (I assume a quote from your study guide) is very good and states the concept very plainly; however, I don't think it points the way to any of the choices. The quote also does a good job of repeating what I said before; i.e., that it ...
December 14, 2014

Chemistry
mols NaOH = M x L = ? Convert mols NaOH to mols H3A using the coefficients in the balanced equation. Then M H3A = mols H3A/L H3A. for b. M = mols/L solution. Convert mols to grams. g = mols H3A x molar mass H3A to give you grams/L. You want g/100 so divide grams by 10 to give ...
December 14, 2014

chemistry
H2SO4 + 2KOH ==> K2SO4 + 2H2O mols KOH = M x L = ? Convert mols KOH to mols H2SO4 using the coefficients in the balanced equation. Then M H2SO4 = mols H2SO4/L H2SO4
December 14, 2014

Chemistry
Electrons are in the 3d (or 4d or 5d) levels and sometimes some of those 3d electrons are involved in bonding.
December 14, 2014

Science Help!!!!
Does solar power require a turbine to generate electricity?
December 14, 2014

Science Help!!!!
Yes, but fossil fuel emissions are not the only ingredient.
December 14, 2014

P.E. help
Callie, you are guessing again. Surely your study guide doesn't suggest that.
December 14, 2014

chemistry
I don't know. One of the problems with a question of this type is that we are trying to compare micro concepts to macro events. I can see how A might be true if we think in terms of a student spending an hour in English, an hour in history class, an hour in algebra class, ...
December 14, 2014

chem
What do you understand and not understand about this. I can balance it but we need to work so you can.
December 14, 2014

Chemistry
H2SO4 + 2NaOH ==> Na2SO4 + 2H2O mols NaOH = M x L = ? Convert mols NaOH to mols H2SO4 using the coefficients in the balanced equation. Finally, M H2SO4 = mols H2SO4/L H2SO4.
December 14, 2014

Chemistry
NiCl2 + 2KOH ==> Ni(OH)2 + 2KCl mols NiCl2 = M x L = approx 0.006 but you need a more accurate answer. mols KOH = M x L = approx 0.07--again you need a more accurate answer. mols Ni(OH)2 formed if all NiCl2 used will be 0.006 x 1 mol (Ni(OH)2/1 mol NiCl2) = approx 0.006 ...
December 14, 2014

Science
If you have tables or graphs showing the solubility, post that information and we can help. I don't know of anyone who has all of that solubility information memorized.
December 14, 2014

Chemistry
I obtained 251.568. I don't know how many significant figures you have on that 773 but everything else you have is 4 places. If you can have 4 s.f. I would round that to 251.6 J.
December 14, 2014

Chemistry
No. Note the problem specifically suggests you pay attention to the units and you didn't do that. If you use 1.977(2.603) that gives you units for work in L*atma and you want J here. You convert L*atm to J by L*atm x 101.325 = J. Your sign of - is correct. The sign for 773...
December 14, 2014

gen chem (already have answer)
How much (pick any product--I'll pick SO3) mols SO2 will be formed from 0.25 mols P4S6 if we had all of the KClO2 we needed to react with all of the P4S6? That's 0.25 mols P4S6 x (6 mols SO2/1 mol P4S6) = 0.25 x 6 = 1.5 mols SO2 formed. Now how many mols SO2 will be ...
December 14, 2014

basic chemistry
I just looked at Damon's response again and I don't see anything wrong with it. The answer I posted is almost the same as the answer he posted. The only difference is he rounded the molar mass of Fe3O4 from 231.54 (which I used) to 232. Other than that there is no ...
December 14, 2014

basic chemistry
Yes, Damon's response, as noted in that response, is he though it was 1.38E3 L (and not mols). Here is the question again. Fe3O4 + 4 H2 -> 3 Fe + 4 H2O What mass (g) of Fe3O4 would be needed to react with 1.38 x 10^3 mol H2? 1.38E3 mols H2 x (1 mol Fe3O4/4 mols H2) = ...
December 14, 2014

basic chemistry
Do you want me to look at it and repost here if needed?
December 14, 2014

basic chemistry
Damon answered your question on your first post and I answered the one on moles below that. What's the problem?
December 14, 2014

Chemistry
I've never fully understood why students have trouble with conjugate acids/bases. If you want the conjugate acid of something, add a H^+ to what you have. If you want the conjugate base of something, take a H^+ away from what you have.
December 14, 2014

chemistry
Fe3O4 + 4H2 ==> 3Fe + 4H2O 115 mols H2 x (3 mols Fe/4 mols H2) = ?
December 14, 2014

chem
So the volume will be area x thickness = 55 cm x 3E-4 cm = ? mass = volume x density = ?
December 14, 2014

chemistry
No. Consider Na^+ and Na and Cl^- vs Cl2.
December 14, 2014

chemistry
[24.3050*(0.7899)] + [24.9858*(0.1000)] + [25.9826*(0.1101)] = ? = atomic mass Mg
December 14, 2014

Chem
I would rank these Br < P < Na < Ca
December 14, 2014

chemistry
I2 is held together by covalent bond; therefore, you would expect it to dissolve in a non-polar solvent (cyclohexane) and not be very soluble in a polar solvent (H2O).
December 14, 2014

Science Help!!!!
I think A is the answer but I'm not a land manager. I think mining anything from underground, replacing the soil and replacing the plants sounds like land reclamation (reclaiming the land) to me. B is cutting all the timber, not doing anything to the land, and letting it ...
December 13, 2014

Science Help!!!!
Do you know what desertification means?
December 13, 2014

chemistry
If solubility is 39 g/100 mL, how many grams will dissolve in 250 mL? That's 39 g x (250 mL/100 mL) = 97.5 g. The problem states that 83 g has been dissolved; the solution can hold 97.5 so the solution is .......?
December 13, 2014

chem
Mg + 2HCl ==> MgCl2 + H2 mols Mg = grams/molar mass = ? Using the coefficients n the balanced equation, convert mols Mg to mols MgCl2. Now convert mols MgCl2 to grams. g = mols MgCl2 x molar mass Mgcl2.
December 13, 2014

Chemistry
That might work but it's the long way around AND you don't know mols KCl in the mixture, although you can calculate mols KCl but only after you've worked the problem. I would use the equation you have to convert mL O2 gas to mols O2 and convert that to mols KClO3. ...
December 13, 2014

chemistry
Three equations will work most of the heat problems. When you are heating WITHIN a phase (raising a liquid @ one T to liquid at another T; solid at one T to solid at another T; gas at one T to gas at another T) use q = mass x specific heat in that phase x (Tfinal-Tintitial) ...
December 13, 2014

chemistry
I believe the way to approach this problem is through mole fraction. With all materials in the gaseous phase one can use volume as mols; first determine the limiting reagent. 100 mL NO will give you 100 x (2 mol NO2/2 mols NO) = 100 mL NO if we had all of the O2 needed. For ...
December 13, 2014

science
My personal opinion is that orientation make sno difference. Also I think the type of light is relevant. A bright white light vs a yellow light vs a uv light I think would make a huge difference. I don't know about C since I don't know the behavior of young vs old ...
December 13, 2014

Chemistry
Yes, heed Bob P's advice. CO means carbon monoxide, Co means cobalt, co is a abbreviation for company.
December 13, 2014

Chemistry
c1v1 = c2v2 5.2M x v1 = 0.04 x 81.0 Solve for v1.
December 13, 2014

Chemistry
E = h*freqency or E = hc/wavelength in m
December 12, 2014

chemistry
That is correct for those mentioned.
December 12, 2014

To Drbob222
Thank you clarifying that.
December 12, 2014

Chemistry
I think the photoelectric effect shows that A is true. (B) Electrons can be thought of as particles or as waves; certainly they have a wave nature but i wouldn't call them composed of light. C and D are not reasonable.
December 12, 2014

chemistry
(x g solute/150.0)*100 = 1.30% Solve for x grams and subtract from 150. 150-x = grams H2O
December 12, 2014

chemistry
(15g/x g)* 100 = 20.0%
December 12, 2014

L.A. Not really important but want an answer. . .
I Googled "types of poems" and obtained a bunch of hits. Try it.
December 12, 2014

Chemistry
First determine the molarity of the HCl. mols NaOH = M x L = ? mols HCl = mols NaOH M HCl = mols HCl/L solution. You know mols and L(convert mL to L), solve for M. M HCl means mols/L solution Convert mols HCl to grams HCl. mols = grams/molar mass. You know molar mass and mols...
December 12, 2014

Chemistry
1. Balance the equation. 2. This is a limiting reagent (LR) problem. Determine the LR. 3. Convert mols reactants to heat produced. This is the theoretical yield.
December 12, 2014

Chemistry
12% m/v (w/v) means 12g solute/100 mL solution. How many mols is 12 g Na2SO4? That's mols = grams/molar mass = approx 0.08 but you need a more accurate answer than that. What volume? That's 100 mL or 0.1L M = mols/L. I don't think the density is needed.
December 12, 2014

chemistry
As for the Na question. I've not made a secret that I think some of the questions are not very good, some of the answers are not very good, but mostly, as this one, there is no clear answer or the answers are muddled. At any rate, here is my take on this one. A is true. ...
December 12, 2014

chemistry
Thanks!. One more. Are these questions you post test questions? I'm working on the answer to the Na question.
December 12, 2014

chemistry
OK, so I'll repeat some of them. What do you have as resource material for study? Is the material explained thoroughly? Where do these questions come from? Are they test questions?
December 12, 2014

chemistry
You answered one question but not the others. Please fill me in on the others.
December 12, 2014

chemistry
Did you see my note from last night? Here is a link. I would like some answers please. http://www.jiskha.com/display.cgi?id=1418364644
December 12, 2014

Equations and Inequalities
Links do a better job of explaining than I can ever do. Here is another link. Read it and put it in your own words. his isn't purple math although I think that web site is very good. http://www.ehow.com/info_8382315_difference-between-inequality-equation.html
December 12, 2014

Chemistry
0.557 mol x atomic mass Ag = mass Ag (mass Ag/mass sample)*100 = % Ag Substitute and solve fo mass samle.
December 12, 2014

Chemistry
Use PV = nRT Remember T must be in kelvin
December 12, 2014

Chemistry
If I read this problem correctly it provides numbers that are entirely unrealistic and I don't want to tackle it. For example, 0.365 mol H2O = approx 6.6 grams. If the density is 1.0 g/mL that is about 0.0066 liters which makes the HCl about 0.250/0.0066 = approx 38 M and ...
December 12, 2014

Chemistry
A solubility of 36.0 g NaCl/100 g H2O is 36.0/58.44 = 0.616 mol NaCl. 100 g H2O is 100/18 = about 5.55 mols H2O so the solubility in terms of mols/mols is 0.616 mols NaCl/5.55 mols H2O. 5.55 mols H2O x (0.263/0.616) = ? mols H2O to prepare a saturated solution.
December 12, 2014

To Morgan
Where are you getting all of this stuff? What university/college? Where do the exercises(questions) come from? What sources to you have for study? What percentage are you getting from Jiskha? Thanks. I'm just curious.
December 12, 2014

Chemistry
Na2SO4 + BaCl2 ==> BaSO4 + 2NaCl mols Na2SO4 = M x L = ? mols BaCl2 needed = same as mols Na2SO4 since the reaction coefficients are 1 mol Na2SO4 to 1 mol BaCl2. Then M BaCl2 = mols BaCl2/L BaCl2. You know M and mols, solve for L and convert to mL.
December 12, 2014

chemistry
q = heat = mass x specific heat x (Tfinal-Tinitial)
December 12, 2014

chemistry
Nope. You have it backwards (actually you want the reciprocal of what you wrote). Its grams/molar mass = mols Then mols/2.5 = m
December 12, 2014

Chemistry
The one electron in the H atom is in the n = 1 shell in its ground state. It can be moved from the n = 1 shell to n = 2 or n = 3 or n= 4 etc by absorbing energy. Thus we can expose H atoms to energy and cause the electron to move to higher levels BUT not just any amount of ...
December 12, 2014

chemistry
The ppt is Ca3(PO4)2. You have 8.16E25 atom Ca ions. That's 8.16E25 x (1 mol/6.02E23) = ? mols Ca and divided by 3 = mols Ca3(PO4)2. From there you know you have twice that mols P atoms (mols P x 6.02E23 = atoms P) and 8x that number of mols O atoms (atoms O = mols O x 6....
December 11, 2014

chemistry
OK but I disagree. b can be right in certain cases, as in the case of the H atom, but for other atoms the orbitals(s,p,d,f) determine the energy of the electrons. The answer d is correct for n of any element. Here is a graph of such a function. http://en.wikipedia.org/wiki/...
December 11, 2014

chemistry
I would go with d.
December 11, 2014

chemistry
d It is quantized.
December 11, 2014

chemistry
What do you not understand about this? Anytime you are within a phase it is q = mass x specific heat x (Tfinal-Tinitial) Phase changaes are different. At the melting point it is q = mass x heat fusion. At the boiling point it is q = mass x heat vaporization. Those three ...
December 11, 2014

Science
This is a limiting reagent problem and you know that because amounts are given for BOTH reactants. I worked a problem just a few minutes ago and here is a link. Just follow the same steps. http://www.jiskha.com/display.cgi?id=1418356094
December 11, 2014

Chemistry
See your other post.
December 11, 2014

Chemistry
I have rewritten the equation without phases to save space. This is a limiting reagent (LR) problem and you know that because amounts are given for BOTH reactants. 2NaCl + H2SO4 --> 2HCl + Na2SO4 Usint 2.00 mols H2SO4 and all of the NaCl needed will give you 2.00 x (2 mols ...
December 11, 2014

Chemistry
.......H2C2O4 + H2O --> H3O^+ + HC2O4^- I......0.175.............0.......0 C........-x..............x.......x E.....0.175-x............x.......x Substitute the E line into Ka1 expression and solve for x = (H3O^+) = (HC2O4^-). That gives you H3O^+ and HCO4^- and note they ...
December 11, 2014

Chemistry
All waves have same speed in a vacuum of 3E8 m/s. All have a wavelenth although each is different. All have a frequency although each is different. All have energy although each is different. They all have amplitude that depends upon intensity. In short all could be true. I ...
December 11, 2014

chemistry
Exactly. The only difference is the definition. M = mols/L solution m = mols/kg solvent At very low concentrations M is about equal to m.
December 11, 2014

chemistry
q1 = heat to raise T from -20 to zero. q1 = mass ice x specific heat ice x (Tfinal-Tinitial) where Tf is 0 and Ti is -20. q2 = heat to convert solid ice at zero to liquid water at zero C. q2 = mass ice x heat fusion q3 = heat to raise T of liquid water at zero C to 90 C. q3 = ...
December 11, 2014

chemistry
Experimentally you can try dissolving polar and non-polar solids in the solvent. Since like dissolves like polar solids are soluble in polar solvent and vice versa. Remember, however, that advice sometimes fails. Theoretically, you compare the electronegativity of the elements...
December 11, 2014

chemistry
I worked this problem just below just a short time ago. The formula for obtaining mols hasn't changed since then. mols = M x L = ? http://www.jiskha.com/display.cgi?id=1418348915
December 11, 2014

chemistry
mols NaNO3 = grams/molar mass Then m = mols/kg solvent. 2.5 L is 2.5 kg if the density of H2O is 1.00 g/mL.
December 11, 2014

chemistry
Theoretically I would do it this way. You want how many mols? That's M x L = mols. Then mols = grams/molar mass. You have molar mass and mols, solve for grams. Place that many grams in a 1L volumetric flask, add some water, swirl until dissolved, then make to the mark with...
December 11, 2014

chemistry
jim, dd, et al. We prefer you keep the same screen name. We can help you better if you do that. q = heat absorbed = mass H2O x specific heat H2O x (Tfinal-Tinitial)
December 11, 2014

chemistry
Here it is by FF but with you using so many screen names one never knows. As I said above, using the same screen name helps us help you and changing names helps no one. http://www.jiskha.com/display.cgi?id=1417667658
December 11, 2014

chemistry
I think I worked this problem for you about a week or so ago.
December 11, 2014

chemistry
Increasing P has little effect on the solubility of solids but it increases the solubility of gases. Increasing surface area of solids increases solubility and increased agitation helps also. Increasing temperature increases the solubility of most solids but decreases some. ...
December 11, 2014

vy? in Physics
I suggest you repost your COMPLETE problem under the title of physics. I think it will be easier for a physics prof to answer a real rather than a hypothetical question.
December 11, 2014

Chemistry
yes. Do you have an answer you know is correct for the delta G problem?
December 11, 2014

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