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March 22, 2017

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Posts by DrBob222

Total # Posts: 54,253

chemistry
I don't see a question here.
March 12, 2017

P.S.---Chemistry
The answer will be in J/grams. Convert to J/mol
March 12, 2017

Chemistry
See your post for q below. In this case, q is the same as dHsolution.
March 12, 2017

Chemistry
q = mass Cu x specific heat Cu x (Tfinal-Tinitial) The answer will be in J (if you use 0.385 J/g*K) so convert the answer to kJ.
March 12, 2017

chemistry
It takes a lot of energy to be absorbed by the body to raise the temperature of the body very much.
March 12, 2017

Chemistry
Balance the equation. 2C2H2 + 5O2 ==>4CO2 + 2H2O dHfo rxn = (n*dHfo products)-(n*dHfo reactanta). That will give you dHfo for the rxn which is for 2 mols C2H2. Divide by 2 for kJ/mol.
March 12, 2017

@Scott--Chemistry
Yes, but I believe your reasoning is wrong. The drops actually happen in order to get to the equivalence point BUT you don't count them; therefore, the calculation point (say 10 drops instead of 12 drops) is LOWER which makes M = mols/L higher because the volume number you...
March 11, 2017

Chemistry
M = mols/L so the L would be smaller if you counted fewer drops. That means the M will be ......?
March 11, 2017

CHEM 101 (edited)
Doing what you did is right, as far as you go, BUT it doesn't give you the correct equation. Multiply equation 1 by 2, including dH for equation 1. Reverse equation 2 and change sign as you've done. Add the two. That will give you the equation you want BUT all of the ...
March 10, 2017

CHEM 101
See your other post above.
March 10, 2017

Chemistry
It's much better if you give a problem.
March 10, 2017

Chemistry
2NaOH + H2SO4 ==> Na2SO4 + 2H2O mols H2SO4 = M x L = 1 x 2 = 2 mols NaOH = M x L = 1 x 0.02 = 0.02 All of the NaOH is used; it neutralizes 0.02 x 1/2 = 0.01 mols of H2SO4. That leaves how much H2SO4. That's 2-0.01 = 1.99 What's the volume? That's 2000 mL H2SO4...
March 10, 2017

Chemistry
Isn't this available in your notes/text? http://www.chemteam.info/GasLaw/gas-velocity.html
March 10, 2017

Chemistry
(0.92*28)+(0.05*29)+(0.03*30) = ?
March 10, 2017

Chemistry
Use PV = nRT, substitute the numbers, solve for volume, and compare the two.
March 10, 2017

Chemistry
2,6,8 & 12 are correct. The others are wrong.
March 10, 2017

Chemistry
None of the answers is correct. What you must know is that 1 mol of any GAS (not liquids or solids) will occupy 22.4 L at STP. So ONLY B and E could be correct; BUT a mol of CO2 gas is 44 g and a mol of CH4 gas is 16.04 g. My guess is you made a typo and the answer for B ...
March 9, 2017

Chemistry
mols Cl = M AgNO3 x L AgNO3 = ? Then M Cl^- = mols Cl^-/L H2O = ?
March 9, 2017

Chemistry
I would not be as concerned with the HCl formed from the reaction as I would from the initial H3PO4. FePO4 is soluble in acid. With strong H3PO4 complexes can form AND the H3PO4, although a weak acid, is relatively strong for the first ionization. I would prepare FePO4, if ...
March 9, 2017

@ , Chemistry
What do you mean there are many chem tutors on this site? Ridculous. Most chem questions are answwered within a few hours.
March 9, 2017

Chemistry
m = molality = mols/kg solvent. 1.60 = mols glucose/0.4000). Solve for mols glucose, then mols = grams/molar mass. You know molar mass and mols, solve for grams.
March 9, 2017

chemistry
They want YOUR opinion, not mine.
March 8, 2017

chemistry
34.94 x (atomic mass Au/molar mass AuCl3) = ?
March 8, 2017

Chem
mass CaCO3 ppt is 47.623-46.719 = ? % = (mass CaCO3/1.631)*100 = ?
March 8, 2017

Chemistry
Here is how you work a stoichiometry problem. 1. Write and balance the equation. You have that. 2. Convert what you have (in this case grams NH4NO3) to mols. mols = grams/molar mass = ? 3. Using the coefficients in the balanced equation, convert mols of what you have to mols ...
March 8, 2017

@ Erin---Chemistry
I worked this problem for you this morning at 10:59 A.M. and here you've posted it again about seven hours later. Don't mess up the boards with superfluous questions.
March 8, 2017

Chemistry
pH = -log(H^+) Substitute and solve for (H^+). Then (H^+)(OH^-)= Kw = 1E-14. You have Kw and H^+, solve for OH^-?. You need to clarify what you mean by number. If that is mols/L, that is the same the M above.
March 8, 2017

Chemistry Help?
I don't get it. You're given the formula(s) to use. All you need to do is to substitute the values in the problem. For the water. q = mc(Tfinal-Tinitial) q = 1000g x 4.184 J/g*C x (35.65-24.85)= ? q is + so heat is absorbed. For the cal. q = C*(Tfinal-Tinitial) q = 695...
March 7, 2017

Chemistry
(1/A) - (1/Ao) = kt Determine k. A = 50. Ao = 100. t = 16 min. Then use the same equation but A = 18(that's 100-82); Ao = 100; k from above. Solve for t in minutes.
March 7, 2017

Chemistry
1. You have the balanced equation. 2. mols H2CO3 = M x L = ? 3. Using the coefficients in the balanced equation, convert mols H2CO3 to mols Fe2SiO4. 4. Now convert mols Fe2SiO4 to grams. g = mols x molar mass = ?
March 7, 2017

Chemistry
When adding acid, HCOO^- + H^+ ==> HCOOH When adding base, HCOOH + OH^- ==> HCOO^- + H2O
March 7, 2017

chemistry
Let's call the acid HP. a. .......HP ==> H^+ + P^- I.....0.2M....0.....0 C......-x.....x.....x E....0.2-x....x.....x Plug the E line into the Ka expression and solve for x = (H^+), then convert to pH. b is done with the Henderson-Hasselbalch equation. c is the ...
March 7, 2017

chemistry
K^+ is 0.2M ......F^- + HOH ==> HF + OH^- I....0.2............0.....0 C.....-x............x.....x E...0.2-x...........x.....x Kb for F^- = (Kw/Ka for HF) = (x)(x)/(0.2-x) Solve for x = (HF) = (OH^-) You have OH^-, then Kw = (H^+)(OH^-) so you can solve for (H^+). All of ...
March 7, 2017

Chemistry
You don't. You are on the wrong path to the answer. .......2NO(g) + O2(g)---> 2NO2(g) I.......10.0....10.0........0 C.......-2p.....-p.........+2p E.....10-2p.....10-p........2p Substitute the E line into the Kp expression and solve for p and 2p.
March 6, 2017

Chem
I don't get it. The problem gives you specific instructions for working it. You do it step by step. If you need help please explain what you're having trouble with in detail. Show your work you've done and explain what you don't know to do next.
March 6, 2017

Chemistry
What's wrong with using (P1V1/T1) = (P2V2/T2) Remember to use T in kelvin. Convert C to K with K = 273 + C.
March 6, 2017

Chemistry
Here is an activity series table. Use it to answer the question. http://www.grandinetti.org/activity-series Here is how you do it. Any METAL will displace (react with) any METAL ION below it in the activity series. For example, Sn will react with Cu^2+ ion. Sn + CuCl2 ==> ...
March 5, 2017

Chemistry
Sorry but this forum does not allow us to draw.
March 5, 2017

Chemistry
I assume you mean ZnCl2. mols = M x L = ?
March 5, 2017

chemistry
1 ppm = 1 mg/L; therefore, 2500 ppm = 2500 mg/L. You want 250 mL; therefore, 2500 x 250/1000 = ? mg/250 mL. Now convert mg to grams and you have it.
March 5, 2017

chemistry
5% w/w H2SO4 means 5 g H2SO4/100 g solution. So you want 5g H2SO4 and 95 g H2O BUT be sure you add the H2SO4 to the H2O and not the other way around. That gives you 100 g solution. To make 400 mL just multiply everything by 4.
March 5, 2017

Chemistry
Did you work it or someone told you?
March 4, 2017

Chemistry
mols NH3 = grams NH3/molar mass NH3 = ? mols urea = mols NH3 x (1 mol urea/2 mols NH3) = mols NH3 x 1/2 = ? Then grams urea = mols urea x molar mass urea = ?
March 4, 2017

Chemistry
Technically the concentrations go in in molarity. I like to work in mols and since M = mols/L and the value for L in both numerator and denominator is the same the L cancel and one can use mols (actually I use millimols) directly. millimols HAc = 500 mL x 0.3M = 150 mmols...
March 4, 2017

chemistry
P1V1/T1 = P2V2/T2 Remember T must be in kelvin. K = 273 + C
March 4, 2017

Chemistry
See your other post.
March 4, 2017

chemistry
0.1 M x (3 mL/10 mL) = ?
March 3, 2017

Chemistry
Use PV = nRT Watch the units.
March 3, 2017

CHEMISTRY
SrCl2 => Sr^2+ + 2Cl^- m = mols solute/kg solvent If SrCl2 is 0.15 m then Sr^2+ must be 0.15 m and Cl^- must be 0.30 m
March 3, 2017

Chemestry
I don't see a question here but you need to learn how to spell chemistry.
March 3, 2017

chemistry
What, pray tell, is Cl2Cl2.
March 3, 2017

Chemistry
With good technique and good equipment, it is possible to get very close to 100%. Your theoretical yield is 0.52 and you obtained 0.52 for CO2 so that is 100% yield. If you had weighed to two more places it may (or may not) have been exactly 100%. If you use 44.01 for molar ...
March 2, 2017

chemistry
3.05 g - 1.94 = 1.11 g H2O abd 1.94 g CuSO4 mols H2O = grams H2O/molar mass H2O mols CuSO4 = grams CuSO4/molar mass CuSO4. Now fine the ratio of the two to each other. The easy way to do that is to divide the smaller number by itself (thereby making sure it is 1.00). Then ...
March 2, 2017

Chemistry
I think you're guessing (big time) but your guessing gene is pretty good. We don't do quizzes but I just confirmed your guess.
March 1, 2017

Chem
Heat lost by water + heat gained by Pt = 0 We call Pt 1; then H2O = 32 [mass H2O x 32 x (Tfinal-Tinitial)] + [mass Pt x 1 x (Tfinal-Tinitial) = 0 Substitute and solve for Tfinal.
March 1, 2017

Chemistry
mols CH3OH = grams/molar mass = ? 1 mol CH3OH contains 6.02E23 molecules. Then there are 4x that number of H atoms..
March 1, 2017

Chemistry
N = 14 O = 16 NO = 30. Therefore, 30 g NO will contain 6.02E23 molecules mols NO in 2.5E20 molecules = 2.5E20/6.02E23 = ? mols NO. 1 mol has a mass of 30 g so ? mols will have a mass of .....
March 1, 2017

Chemistry
Ge has an atomic mass of 72.6; therefore, 1 mol (72.6g) will contain 6.02E23 atoms of Ge. How many mols do you have? That's grams Ge/72.6 = ?
March 1, 2017

Chemistry
Do you have an equation for this. Are you sure you didn't go through an extra step with iodide ion?
March 1, 2017

Chemistry
See my question and response above.
March 1, 2017

Chemistry
You need to be careful how you write questions; I think you meant that 10 mL H2SO4 was diluted TO 250 mL with DW. I'll assume that's what you meant. 2NaOH + H2SO4 ==> Na2SO4 + 2H2O mols NaOH = M x L = 0.1 x 0.01 = 0.001. mols H2SO4 in that 25 mL aliquot = 1/2 x 0....
March 1, 2017

Chemistry
Sarah, I worked this for you below. It's a waste of our time to answer twice AND you posted under Lauren also. I assumed no water vapor in the flask.
March 1, 2017

Chemistry
This is a limiting reagent (LR) problem. mols Zn = 0.01 mols HCl = M x L = 0.03 x 1 = 0.03 mols H2 produced from Zn if we had all of the HCl we needed = 0.01 (from the 1 mol Zn gives 1 mol H2. molsl H2 produced from 0.03 mols HCl if we had all of the Zn we needed = 0.03 x 1/2...
March 1, 2017

chemistry
2NaOH + H2SO4 ==> Na2SO4 + 2H2O I think for (b) you means how many mols H2SO4 were used. All of ot was meeded. mols H2SO4 = M x L = ? (c) Using the coefficients in the balanced equation, convert mols H2SO4 you had to mols NaOH neutralized. (d) usually these problems want ...
March 1, 2017

Chemistry
See above under a difference screen name. Sarah, you continue to use difference screen names and I've asked you several times to use the same screen name. It really slows us down in getting the answers out to you AND it serves no useful purpose.
March 1, 2017

Chemistry
k = 0.693/2 min = ?. Then subsitute k into the below equation. ln (Ao/A) = kt Let Ao = 100, then A = 25. Substitute Ao, A, and k into the equation and solve for t in minutes.
February 28, 2017

Chemistry (Urgent)
First things first. Learn how to spell celsius. 1. The equilibrium equation is just the solubility in water. PbI2(s) ==> Pb^2+(aq) + 2I^-(aq) 2. Surely you know how to write the Ksp. 3. From the equation is (1), solve for the solubility. .....PbI2 ==> Pb^2+ + 2I^- I......
February 28, 2017

Chemistry
Use wavelength = h/mv. That's the De Broglie equation.
February 28, 2017

Chemistry
What's wrong with substituting into n = m/M? n = 140/28 = ?
February 28, 2017

chemistry
Al^3+(aq) + 3OH^-(aq) ==> Al(OH)3(s)
February 28, 2017

homework
NO. Why divide by 4. Didn't Scott say times 4 weeks. And what did you do with the 7 days per week.
February 28, 2017

Chemistry
[H2O2] before = 0.88M volume H2O2 before mix is 4 mL total volume after mix is 5 (4 from H2O2 + 1 from KI) so the H2O2 has been diluted from 4 to 5 mL.' 0.88 x 4/5 = ? KI before mix is 0.500. volume KI before mix is 1 mL. total volume after mix is 5 (1 from KI + 4 from ...
February 28, 2017

chemistry
Almost. You were asked to calculate the mass CO2 generated. The last line should read "0.5 g of carbon dioxide" 05 g/mol is not right. The unit /mol canceled in your previous step.
February 28, 2017

Chemistry
Note you have the wrong formula for fluorapatite. It is Ca5(PO4)3F. 2Ca5(PO4)3(OH) + SnF2 ==> 2Ca5(PO4)3F + SnO + H2O This is just like the problem I did for you last night. These stoichiometry problems are done the same way. A four step process. 1. Write and balance the ...
February 28, 2017

chemistry
Your full equation is ok. The half equations are Zn ==> Zn^2+ + 2electrons O2 + 4 electrons ==> 2O^2- For the full equation you multiply equation 1 by 2 and add to equation 2.
February 27, 2017

Chemistry
Ksp = (2x)^2(0.1) You can look up the Ksp for Ag2CrO4. It's approximately 9E-12 but you should use the value in your book's table of Ksp values. 9E-12 = 4x^2(0.1) 9E-12/0.1 = 4x^2 9E-11 = 4x^2 9E-12/4 = 2.25E-11 = x^2 x = sqrt 2.25E-11 = 4.47E-6 M In 2L that is 4.47E-6...
February 27, 2017

chemistry
I use this most often but it's a couple of equations put together. mL x M x (molar mass/1000) = grams You don't list mL in the problem and you must have that. M - 0.272. Molar mass acetylsalicyclic acid you can look up. Calculate grams. Then % ASA = (grams ASA/0.726 ...
February 27, 2017

Chemistry
dG = dGo + RTlnQ Write the equation. Determine the limiting reagent. Q = (NaNO3)^2/[Pb(NO2)] Determine the concentrations for Q and calculate. Post your work if you get stuck.
February 27, 2017

Chemistry
When dG is - (i.e., <0) the reaction is favored. Therefore, if dGo is >0 it must be + and that means the system is not favorable for a reaction. That is the equilibrium lies to the left. That takes care of 1 and 5. 2. Knowing that the equilibrium lies to the left means ...
February 27, 2017

Chemistry
This looks like a limiting reagent (LR) problem. SiO2 + 2C ==> SiC + CO2 mols SiO2 = grams/molar mass = approx 50/60.1 = approx 0.0832 mols C = 50/12 = approx 0.0416 mols SiC formed using just SiO2 = 1:1; therefore, 0.0832. mols SiC formed using just C = 0.0416 x 1/2 = 0....
February 27, 2017

Homework
You ask questions, we provide answers BUT the emphasis is on HELPING you and not doing all of your work. We try to teach you how to do it rather than doing it for you. It is not a place to type in your tests and make 100% score. Here are the tips you should do. Homework ...
February 27, 2017

Chemistry
Ag2CrO4 ==> 2Ag^+ + CrO4^2- Ksp = (Ag^)^2(CrO4^2-) mols CrO4^2- = mols x L = ? Substitute into Ksp expression and solve for (Ag^+). That is (AgNO3). Convert M to mols in the 2.0 L and convert to grams. g = mols x molar mass. Post your work if you get stuck.
February 27, 2017

add on----Chemistry
You have the two solubilities. You will need to calculate the ratio from that.
February 27, 2017

Chemistry
CaSO4 ===> Ca^2+ + SO4^2- For pure water, Ksp = (Ca^2+)[(SO4)^2-] So (Ca^2+) = x and [(SO4)^2-] = x. Solve for x and that is the solubility of CaSO4 in pure water. For the 0.1M Na2SO4 solution. Ksp is the same expression. (Ca^2+) = x [(SOr)^2-] = 0.1 + x. [Note: that is 0....
February 27, 2017

chemisrty
mols KOCl = 6.22g/90.55 = 0.0687 or 68.7 millimols. ......OCl^- + H^+ ==> HOCl I....68.7.....0........0 add..........16............. C...-16.....-16........16 E....52.7.....0.........16 You can substitute to find the pH of this solution is 8.05 Out of the buffer range for ...
February 27, 2017

Chemistry
mols N2 = 2.0/28 = about 0.07 (N2) = 0.07/1.3L = about 0.05 mols O2 = 3.0/32 = about 0.09 (O2) = a0.09/1.L = about 0.07 All of the above need to be recalculated more accurately. .......N2 + O2 ==> 2NO I....0.05..0.07......0 C.....-x...-x.......2x E..0.05-x..0.07-x....2x ...
February 27, 2017

Chemistry
Take a 100 g sample to give you 57.8g C, 3.6g H and 38.6 g O. Convert to mols. 57.8/12 = ? 3.6/1 = ? 38.6/16 = ? Now find the ratio of CHO to each other with the lowest being no smaller than 1.00. The easy way to do this is to divide the smaller number by itself, then divide ...
February 27, 2017

Chemistry
mols C = 7.961/44 = ? mols H = 1.164 x (2/18) = ? mols N = 1.551/30 = ? Now find the ratio in small whole numbers to one another. The easy way to do that is to divide the smallest number by itself (which gives you 1.000), then divide the other numbers by the same small number...
February 26, 2017

Chem
Cindy, Tiffany, et al. See your other posts. We prefer you stick to one screen name. Posting with more than one name often delays help.
February 26, 2017

Chemistry
Your Ksp for AgBr is eqn 1. Your Kf for Ag(S2O3^-2)^3- is eqn 2. Add equn 1 to eqn 2 to get AgBr(s) + 2(S2O3)^3- ==> Br^- + [Ag(S2O3)2]^3- Write the equilibrium expressiion for that which equals Ksp*Kf. Then substitute 0.02 for Br^- and 0.02 for [Ag(S2O3)]^3- and solve for...
February 26, 2017

Chemistry
You don't need the gas equation. Mg + 2HCl ==> H2 + MgCl2 mols Mg = grams/atomic mass = ? This could be a limiting reagent problem so watch that.
February 26, 2017

CHEMISTRY
mols Na2CO3 = grams/formal mass = ? L = 2.25 M Na2CO3 = mols/L. (Na^+) = ? ppm 1 ppm = 1 mg/L g Na^+ = 2.22E-4 x 2 = 4.44E-4 g/2.25 L = ?g/L. Convert to mg/L to obtain ppm. (CO3^2-) in ppm is 1/2 that.
February 26, 2017

Chemistry
1/A - 1/Ao = kt A = 0.0174 M Ao = 0.0693 M t = 489 s Solve for k.
February 24, 2017

Chemistry
mols SO2 = 38000/molar mass SO2 = ? mols H2SO4 produced = same as mols SO2 becaue 2 mol SO2 = 2 mol H2SO4. Then grams H2SO4 = mols H2SO4 x molar mass H2SO4 = ? g, then convert to kg. That's if the process were 100% efficiency. It isn't so that answer x 0.70 = the ...
February 24, 2017

Chemistry
How many mols do you need? That's M x L = mols. 0l00 x 0.558 L = ? Then grams = mols x molar mass = ? That's grams you need if the SrCl2 is 100%. It isn't so you need ?g from above/0.586 = ??
February 24, 2017

Chemistry
You got an error message because 1/0 is an indeterminate. I didn't know how to write 1/infinity but that's what it should have been and 1/infinity is 0. As to the other, I guess I don't know what the second excited state is. I assumed it was with the electron in n...
February 24, 2017

Chemistry
E = 2.180E-18(1/2^2 - 1/0)
February 24, 2017

Chemistry
The energy of the H atom in its ground state is -2.18E-18. Find the difference in the energy, change the negative sign to a positive sign then E = hf and solve for f = frequency. Is that something like 10^15 Hz? You should confirm that.
February 24, 2017

Chemistry
Would you look at your post and proof it please. That 10^20? Is that right?
February 24, 2017

Chemistry
a. T goes up. E goes up. b. T goes down ..... c. V goes down so P goes up which means more collisions. d. More mols Ne means higher P so .....
February 24, 2017

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