# Posts by DrBob222

Total # Posts: 54,973

Chemistry
17. If the solubility of a gas is 5.6 g/L at 505 kPa pressure, what is the solubility of the gas when the pressure is 1010kPa? * The solubility of a gas is directly proportional to the pressure; i.e., the more pressure the higher the solubility. So 5.6 g/L x 1010 kPa/505 kPa...

chemistry
I = initial; i.e., start C = change E = equilibrium; end .......HCl + NaOH ==> NaCl + H2O I......1.2...3.9.......0......0 C.....-1.2..-1.2......+1.2...+1.2 E......0.....2.7.......1.2....1.2

Chemistry
How many mols KI do you want? That's mols = M x L = ? Then mols = grams/molar mass. You know mols and molar mass, solve for grams.

OChem
You need more information that what you posted. You need to know the solubility of SA at 75 C and at 10 C. Technically you can't answer the first part of the question BECAUSE it is crude SA and not pure. So you CAN calculate how much will dissolve IF you have the ...

Chemistry
HAc = acetic acid HAc + KOH ==> KAc + H2O mols KOH = M x L = ? Convert mols KOH to mols HAc. Since 1 mol HAc = 1 mol KOH (from the coefficients), then mols HAc = mols KOH. Then M HAc = mols HAc/L HAc = ?

Chemistry
See your post just above. All of these are done the same way. 1. Write and balance the equation. H2SO4 + 2LiOH ==> Li2SO4 + 2H2O 2. mols = M x L = ? 3. Convert mols of what you have to mols of what you want. In this case it is mols LiOH to mols H2SO4. 4. M os what you want ...

Plate tectonics
Scroll to just below the first large colored picture for the explanations. http://crack.seismo.unr.edu/ftp/pub/louie/class/100/plate-tectonics.html

Chemistry
Oxidation is loss of electrons; therefore, these are reducing agents. For example, Zn ==> Zn^2+ + 2e so these (metals) would be reducing agents. non metals, like Cl2. Cl2 + 2e ==> 2Cl^- so these are oxidizing agents. Noble gases very reactive at all. See Cl2 for halogens.

Mrs Sue History
All of this is interesting but the answer MUST be A and for the reasons cited by Ms Sue and M, S, E. As the epitome of a non-historian I disagree with B also. You can't tell me, and make me agree with that logic, that more volume can be transported through the canal than ...

chemistry

chemistry
See my comments below. I gave you two freebies but no more.

chemistry
You have a steady stream of posts with no effort to answer any of them. I'll be glad to help with the others if you show your work and/or explain in detail what you don't understand about them.

chemistry
volume NaOH = 30.5-0.50 = 30.0 mols NaOH = M x L = ? mols HCl = mols NaOH since 1 mol NaOH - 1 mol HCl in the titration. Then M HCl = mols HCl/L HCl.

chemistry
Depends upon the M of the HCl to begin with.

chemistry
Depends upon how much 0.01 M was diluted. You should proof your posts.

Chemistry
I GUESS that weird name you have above is sulfuric acid. H2SO4 + 2NaOH ==> Na2SO4 + 2H2O

chemistry
I looked in the archive section of 2014 and was unable to find the post to which you refer. Sorry.

chemistry
mass C = 18.1 mg CO2 x (atomic mass C/molar mass CO2) = ? %C = (Mass C/mass sample)*100 = ?

Chemistry
This is a limiting reagent (LR) problem; basically you go through the usual stoichiometry steps twice. 1. Write and balance the equation. Ba(NO3)2 + Na2SO4 ==> BaSO4(s) + 2NaNO3 2a. mols Ba(NO3)2 = M x L = ? 2b. mols Na2SO4 = M x L = ? 3a. Convert mols Ba(NO3)2 in 2a to ...

Chemistry
0.1% w/v means 0.1 g glucose/100 mL blood. Therefore, there will be 1 g glucose in 1000 mL (1L) blood or 0.1 g x (1000 mL/100 mL) = 1 g.

chemistry
coulombs = amperes x seconds = approx 50 x 50min x (60 sec/min) = about 150,000 but check that. We know 96,485 coulombs will deposit 107.9 g Ag so 107.9 x (150,000/96,500) = ?g g deposited.

chemistry
Be patient. See my next response at the initial post.

Chemistry
It would help if you told us exactly what you don't understand about this. The words are there; you need to convert them to formulas etc.

chemistry
https://en.wikipedia.org/wiki/Carbon_monoxide#Laboratory_preparation Look under lab preparation. Zn + CaCO3 ==> ? By the way, CO is a gas, not a solid. My best guess is that you have a problem/task and this is just one part of it. Instead of posting the entire problem you ...

chemistry
I don't see a question here.

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

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

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.

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

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.

@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...

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

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 ...

CHEM 101

Chemistry
It's much better if you give a problem.

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...

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

Chemistry
(0.92*28)+(0.05*29)+(0.03*30) = ?

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

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

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 ...

Chemistry
mols Cl = M AgNO3 x L AgNO3 = ? Then M Cl^- = mols Cl^-/L H2O = ?

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 ...

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

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.

chemistry
They want YOUR opinion, not mine.

chemistry
34.94 x (atomic mass Au/molar mass AuCl3) = ?

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

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 ...

@ 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.

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.

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...

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.

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 = ?

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

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 ...

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 ...

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.

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.

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

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 ==> ...

Chemistry
Sorry but this forum does not allow us to draw.

Chemistry
I assume you mean ZnCl2. mols = M x L = ?

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.

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.

Chemistry
Did you work it or someone told you?

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 = ?

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...

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

Chemistry

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

Chemistry
Use PV = nRT Watch the units.

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

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

chemistry
What, pray tell, is Cl2Cl2.

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 ...

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 ...

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.

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.

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

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 .....

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 = ?

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

Chemistry
See my question and response above.

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....

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.

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...

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 ...

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.

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.

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......

Chemistry
Use wavelength = h/mv. That's the De Broglie equation.

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

chemistry
Al^3+(aq) + 3OH^-(aq) ==> Al(OH)3(s)

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

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 ...

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.

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 ...

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.

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...

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