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Posts by drbob222

Total # Posts: 54,515

Chemistry
Use the Henderson-Hasselbalch equation. You SHOULD use M for acid and base BUT you can use a shortcut and save some time by using mols. However, make sure your prof will allow you to do take that shortcut. mols acid = M x L = 0.025 x 0.2 = ? mols base = 0.015 x 0.150 = ? ...

Chem
That's math, not chemistry. :). To make it easy typing let me call the acetic acid, a (for acid) and the sodium acetate, b (for base). So eqn 1 is pH = pKa + log b/a eqn 2 is a+b = 0.05 Substitute into eqn 1 as follows: 5.00 = 4.76 + log b/a 5.00-4.76 = log b/a 0.24 = log ...

Chem
pH = pKa + log (Ac^-)/(HAc) Plug in pH, pKa, and solve for (Ac^-)/(HAc). That is equation 1. Equation 2 is (HAc) + (Ac^-) = 0.05 Solve equations 1 and 2 simultaneously to find (Ac^-) and (HAc). Then mol HAc = M x 0.250 = ? and mols NaAc = M x 0.25 = ? The above gives you the ...

chemistry
Look up these values. Zn(s) ==> Zn^2 + 2e.....E = ? Ag^+ + e ==> Ag(s)......E = ? Add the two E values to find Ecell, then multiply by 4 since they are in series.

A.P Chemistry
dG = dH - TdS If dG = 0, then TdS = dH. Solve for T. Watch the units. dH is in kJ/mol and dS in J/mol

Chemistry
1. Cells in series adds the voltage. 2. You didn't provide enough information about the set up for me to answer.

chemistry
I would think the rxn is amost at 100% now; however, adding more OH^- (from NH3 + H2O ==> NH4^+ + OH^-) would add more OH to the left, the rxn would need to try to reduce the OH^- and it can do that by forming more Mg(OH)2(s). So to the right.

Reposting Chemistry Question -Emergency !!
I don't remember the former post but I think you said to #1, "do I just calculate this from the HCl" and the answer is yes. My assumption is that you used the saturated soln of Ca(OH)2 but it had no solid in it that was titrated. Total millimols OH^- = mL HCl x M...

Chemistry
3Mg + N2 ==> Mg3N2 Look at the coefficients. 3 mols Mg gives 1 mol Mg3N2; therefore, 1 mol Mg will give ..... mol Mg3N2.

Chemistry
First you must calculate the M of the salt, NaAc (sodium acetatate) at the equivalence point. That will be millimols/mL. mmols NaAc = 25 x 0.1056 = approx 2.6 but you should do it more accurately. Since the M NaOH is the same you know it will take 25 mL of the NaOH; therefore...

Chemistry Explanation??
Ca(OH)2 ==> Ca^2+ + 2OH^- and Ksp = (Ca^2+)(OH^-)^2 Ksp is a constant. NaOH is a strong base and ionizes 100%; therefore, NaOH ==> Na^+ + OH^-. Le Chatelier's Principle tells you that when the OH^- increases, due to the NaOH, the Ksp equilibrium of Ca(OH)2 is forced ...

Chemistry
Total of all atoms in C6H12 must be zero. H is +1 and that x 12 = +12. Then 6 C must be -2 each. C = 6*-2 = -12 H = 12*+1 = +12 total = 0 Remember oxidation number is a bookkeeping method.

Chemistry 2202
method 1: NaOH + HCl ==> NaCl + H2O mols NaOH = M x L = ? mols HCl = mols HCl (look at the equation; note 1 mol NaOH = 1 mol HCl) Then M HCl = mols HCl/L HCl = ? method 2: NaOH + HCl ==> NaCl + H2O Note 1 mol NaOH = 1 mol HCl mL NaOH x M NaOH = mL HCl x M HCl Substitute ...

Chemistry
(P1/T1) = (P2/T2) Substitute and solve for P2. Remember T MUST be in kelvin.

Chemistry
If this is REALLY 906 kJ/MOLE that is 906 kJ/17 g NH3. Then 17 x (500/906) = ? g NH3 required.

Chemistry
dHrxn = [(n*dHfo CO2 + (n*dHfo H2O]-[n*dHfo C4H10] You know all of the numbers except for dHo C4H10. Substitute and solve for that.

Chem
7 https://socratic.org/questions/how-do-i-calculate-the-least-number-of-carbon-atoms-in-a-non-cyclic-alkane-molec

Chemistry
1. acetate = Ac ......Ac + HOH ==> HAc + OH^- I....0.25..........0......0 C.....-x...........x......x E...0.25-x.........x......x Kb for Ac = (Kw/Ka for HAc) = (x)(x)/(0.25-x) Solve for x = (OH^-) and covert to pH. The answer is around 8+.

Chemistry
In a hurried calculation I got 0.9841 for pH and I carried it out to 4 significant figures and used all of the digits in the numbers themselves.

Chemistry Titration-emergency :(
Also, I suggest you post the Ksp you are using for Ca(OH)2.

Chemistry Titration-emergency :(
I know how to work the problem but I'm confused by the data. What volume of saturated Ca(OH)2 solution did you use? Was that 25.00 mL? What was "it". The 0.05349 M was the concentration of what? Was that the NaOH concn or the Ca(OH)2. It might help if you ...

Chemistry Titration-emergency :(
I dont get it. It appears that something is missing here. I don't know the solubility of Ca(OH)2 in NaOH. Without that I don't see how the amount of HCl can be apportioned between NaOH and Ca(OH)2 (or perhaps more information about the HCl titration).

chemistry
rate for y = 1 rate for H2 = 8 (rate H2/rate y) = sqrt(mm y/mmH2) Substitute and solve for mm y.

Chemistry
from what?

chemistry
You also need the solubility of ASA at 25.

chemistry
What's wrong with substituting the numbers into the Henderson-Hasselbalch equation? HCO3^- is the acid ad CO3^2- is the base.

Chemistry
heat lost by warm water + heat gained by cold water = 0 [mass warm water x specific heat H2O x (Tfinal-Tinitial)] + [mass cool water x specific heat H2O x (Tfinal-Tinitial)] = 0 Substitute and solve for Tfial

more---Chemistry
Note that work in the above is in L*atm. You must change this to joules.

Chemistry
work = -pdV a. If p is zero, then pdV is 0 b. substitute into the equation. dV is V2-V1.

Chemistry
http://www.jiskha.com/display.cgi?id=1489708172

Food analysis
m is molality. M is molarity. If you actually mean m, that is mols/kg solvent. So add 0.5 mol HCl to 1 kg H2O. For 0.5 mol, weigh out mol = grams/molar mass or 0.5 mol = grams/36.5 and solve for grams.

Chemistry
No. You were asked for mols. That's mols = grams/molar mass and that's what you have done. Placing it in water has nothing to do with the number of mols. For example, suppose you have a pound of bananas and each banana weighs 1/4 pound. That means you must have four ...

Chemistry
This is involved and I could write a book on it. Tell me what you don't understand about the problem and we can go from there.

Chemistry
millimols HI = mL x M = about 9.9 but you need a better answer on this AND all that follows. My numbers are just estimates. mmols NaOH = approx 6.5 ......HI + NaOH ==> NaI + H2O I....9.9...0.........0.....0 add........6.5............... C...-6.5..-6.5......6.5...6.5 E... 3....

chemistry
H2CO3 is the stronger acid and will react with the strong base.

Chemistry
mols Na2CO3 = grams/molar mass = about 2.35/106 = about 0.02 but you need a better answer than that. M Na2CO3 = mols/L = about 0.02/0.1L = about 0.2 M ....CO3^2- + H2O ==> HCO3^- + OH^- I...0.2...............0.......0 C...-x................x.......x E..0.2-x..............x...

Chemistry
4Bi + 3O2 ==> 2Bi2O3

organic chemistry
Take a mixed melting point with pure benzoic acid. If the unknown is benzoic acid the mixed melting point will not change from the pure stuff. If the unknown is lower it isn't benzoic acid.

Science
I suggest you look up each of the words of the answers in a dictionary. After you know what each means you should be able to answer the question.

chemISTRY
Let's assume the time is 1 sec. Then rate O2 = 5.36 mL/sec. rate unknown gas = 3.60 mL/sec rate O2/rate unk) = sqrt(mm unk/mmO2) Solve for mm unk.

Chemistry help!!
Use the coefficients in the balanced equations to convert any value to any other value. In this case, 2.34 mol H3PO4 x (1 mol P4O10/4 mol H3PO4) x (1 mol P4/1 mol P4O10). Note how the unit cancel. The P4O10 cancels, and the H3PO4 cancels to leave what you want that looks like ...

Chemistry
q rxn = mass H2O x specific heat H2O x (Tfinal-Tinitial) mass H2O = 22.5 + 22.5 = ? sp. h. is given So q = approx 1200 (but that's just an estimate)and it is approx -1200 J since the reaction is exothermic. That is delta H per 0.0225 mols. Then dH in J/mol = approx -1200/0...

Organic Chemistry
Kd for caffeine is about 8 between methylene chloride and water was the only reference I could find. You can google it too and might find other numbers to confirm this.

Chemistry
This is relatively simple so I'm trying to understand what is troubling you. What is it you don't understand about this question? Do you know the symbols? how to balance an equation? Please clear this up. If you're stuck on this I know you will be quite confused as...

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
Ditto. I answered two freebies below. See my other comments.

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
See your other post above.

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 ...

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