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March 25, 2017

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Posts by DrBob222

Total # Posts: 54,273

Chemistry
I agree EXCEPT that isn't B.
March 24, 2017

chemistry
Use V = nRT. Substitute and solve for n.
March 24, 2017

chemistry
I will assume the Keq given is for the reaction Fe^3+ + SCN^- ==> [FeSCN]^2+ K = [FeSCN]^2+/[Fe^3+][SCN^-] Substitute the numbers in the problem and calculate the only unknown there.
March 24, 2017

Chemistry
See your other post under Coolest.
March 24, 2017

Chemistry
See your other post.
March 24, 2017

chemistry
Qp = (SO3)^2/(SO2)^2(O2) = 3.70E7 so reverse is correct.
March 24, 2017

Chemistry
q = mcdT 1.4E3J = mass sand*specific heat sand*(Tfinal-Tinitial). You need to know the specific heat of the sand. Then plug in the numbers and solve for mass sand.
March 24, 2017

chemistry
q = mols ether x Hvap. mols = grams/molar mass = ? You know Hvap and can solve for mols. Substitute and solve for q.
March 24, 2017

chem
(P1V1/T1) = (P2V2/T2) Remember T must be in Kelvin.
March 23, 2017

chemistry
P1V1 = P2V2 V1 = 0.5 V2 - 2.0
March 23, 2017

chem
You can do also by using P1V1 = P2V2 P1 = 1.08 atm and P2 = 1.08+0.25*1.08 = ? V1 is given. Solve for V2
March 23, 2017

Chemistry
I didn't check the math but the method looks ok to me.
March 23, 2017

Chemistry
I don't believe you can do that. C(s) + H2O(g) ==> CO2(g) a. The equation is not balanced. b. In those equations to be used you don't have H2O(g) anywhere but only H2O(l) c. The equation you have posted isn't balanced. You're OK with C but O doesn't ...
March 23, 2017

Chemistry
I disagree with both of you. A) 2CH3OH(l) + 3O2(g) --> 4H2O(l) + 2CO2(g) 3 mols gas goes to 2 mols. Not expanding so it isn't A. B) S(s, rhombic) + O2(g) --> SO2(g) Can't be B. 1 mols gas on left goes to 1 mol gas on the right. Volume stays the same. Not ...
March 23, 2017

Chemistry
Step 1. Write and balance the equation. The one you have is incorrect. I have corrected it. 2Pb(NO3)2 ==> 2PbO + 4NO2 + O2 Step 2. Convert what you have to mols. mols Pb(NO)2 = grams/molar mass = ? Step 3. Convert mols of what you have to mols of what you want. Use the ...
March 23, 2017

Chemistry
I suppose you want to know the mass of H2O but you don't ask it directly. Heat lost by Fe + heat gained by H2O = 0 Note: sph = specific heat [mass Fe x sph Fe x (Tfinal-Tinitial)] + [mass H2O x sph H2O x (Tfinal-Tinitial)] = 0
March 22, 2017

Chemistry (Ochem)
I don't think so. Sterocenter refers to the "atom" that causes the molecule to be a stereoisomer while stereochemistry refers to the SUBJECT.
March 22, 2017

Chemistry
I think both of you are right.
March 22, 2017

Chem
The shape of the water molecule is what makes it polar.
March 22, 2017

Chemistry
Good for you. Keep up the good work.
March 22, 2017

Chemistry
Won't work. Check your post. c is not balanced; i.e., no H on the left. Check the others, too. I didn't check them.
March 22, 2017

chemistry
Write and balance the equations for H2 + O2 ==> C + O2 --> CH4 + O2 ==> Reverse 3 and add to 1 and 2. See if you don't get C + 2H2 ==> CH4.
March 22, 2017

Chemistry
a. mols PbO2 = grams/molar mass = ? b. 1 mol PbO2 produces 1 mol Pb; therefore, mols Pb = mols PbO2. c. grams Pb = mols Pb x atomic mass Pb. Remember this. This will work all of your stoichiometry problems. Step #1 is to write the balanced equation but you already had that.
March 22, 2017

Chemistry
Helium is the lighter gas (density less and atomic mass/molar mass less) so it will pass through the whole faster. You don't need a pinhole, either. Helium is small enough that it will pass through the pores of the balloon over a day or so.
March 22, 2017

Chemistry
mols N = 0.606/14 = about 0.043 mols O = 1.39/16 = about 0.087 Now find the ratio. The easy way to do that is to divide each number by the smaller number. N - 0.043/0.043 = 1.00 O = 0.087/0,043 = 2.02 and rounds to 2. It may come out a little closer if you do the calculations ...
March 21, 2017

chmistry
What about it.
March 21, 2017

chemistry
PV = nRT and solve for n = mols. Then mols = grams/molar mass. You have mols and grams, solve for molar mass. Remember K must be in kelvin and P must be in atm if you use R as 0.08206
March 21, 2017

Chemistry
Dream on. What is your main issue with these. I can give you a web site or you can tell me what your main problem is. I will glad to help you through these but I won't balance them for you.
March 21, 2017

chemistry
sph = specific heat heat lost by Fe + heat gained by Au = 0 [mass Fe x sph Fe x (Tfinal-Tinitial)] + [mass Au x sph Au x (Tfinal-Tinitial)] = 0 Solve for Tfinal
March 21, 2017

Chemistry
You do this the same way as the Tom post. We prefer you don't change screen names.
March 21, 2017

chemistry
Mg + 2HCl ==> H2 + MgCl2 mols Mg = grams/atomic mass = ? Using the coefficients in the balanced equation, convert mols Mg to mols HCl.That's 1 mol Mg = 2 mol HCl Now M HCl = mols HCl/L HCl. You know mols HCl and M HCl, solve for L HCl and convert to cc3 (mL).
March 21, 2017

chemistry
I responded to your question about how to solve the two equations simultaneously at the initial post. The answer is there.
March 21, 2017

Chemistry
(S2) = mols/L = 8.9/5.00 = approx 1.8 but you need a better number than that. Recalculate all that follows. ......S2 + C(s) ==> CS2 I....1.8............0 C.....-x............x E....1.8-x..........x Note that C does not appear in the Kc expression because it is a solid. Kc...
March 20, 2017

Chemistry
Where did you come up with the Kc expression? It should be Kc = [FeSCN]^2+/(Fe^3+{)(SCN^-). Kc = [3.49E-5]/[4.39E-4][1.93E-5]\ 411.9 which rounds to 412. :-)
March 20, 2017

chemistry
See your previous post. Make sure P1 and P2 are in the same units. 1 atm = 760 mm. Post your work if you get stuck.
March 20, 2017

Chemistry
(P1V1/T1) = (P2V2/T2) Make sure V1 and V2 are in the same units. I would change 2 atm and use P1 as 760 x 2 = ? torr. That way the asnwer will come out in torr.
March 20, 2017

Chemistry
mols CaCl2 = M x L = ? mols X2CO3 = mols CaCl2 from the 1:1 ratio. mols (CO3)^2- = mols X2CO3 = mols CaCl2.
March 20, 2017

chemistry
Na2CO3 + 2HCl ==> 2NaCl + H2O + CO2 Going to the methyl orange end point titrates ALL of the Na2CO3. Titrating to the phenolphthalein end point titrates just 1/2 of it; i.e., to NaHCO3.
March 20, 2017

Chemistry
Pb(NO3)2(aq) + Na2SO4(aq) ==> PbSO4(s) + 2NaNO3(aq)
March 20, 2017

chemistry
Write some of the hydrocarbon rxns with oxygen. All give CO2 + H2O. The problem would be easier if you were given cc H2O (as a gas) but if you don't have that I would do this. CH4 + 2O2 ==> C2 + 2H2O C2H6 + 7O2 ==> 4CO2 + 6H2O C3H8 + 5O2 --> 3CO2 + 4H2O 2C4H10 + ...
March 20, 2017

chemistry
mols HCl - M x L = ? Equn is HCl + NaOH ==>NaOH + H2O so the ratio is 1 mol HCl to 1 mol NaOH. That means mols NaOH = mols HCl and you have that from above. Then M NaOH = mols NaOH/L NaOH. you have M and mols, solve for L and convert to mL.
March 20, 2017

chemistry
Wouldn't that be X2O3? X + O2 ==> X?O? 1.0L 1.5L Two ways: 1 short, 1 long. 1/22.4 = 0.446 mols X 1.5/22.4 = 0.067 mols O2 or 0.134 O Find the ratio. 0.0446/0.0446 = 1.00 0.134/0.0446 = 3.00 XO3. Short way: When dealing with gases we get mols by dividing by 22.4L (at ...
March 20, 2017

chemistry
I've gone through this time and time again and something isn't clicking. Here is the way to do it BUT the answers are not reasonable. %B = (6.1/29)*100 = 21.03 %Cl = (22.9/29)*100 = 78.97 Take 100 g sample which then gives you 21.03 g B and 78.97 g Cl. mols B = 21.03/...
March 20, 2017

Chemistry
Please use the same screen name. First we get confused. Second it takes us longer to sort things out. Third you're asking the same type question which is a waste of time. delta T = Kf* molality You know delta T. Look up Kf for benzene. Substitute and solve for molality. ...
March 20, 2017

Chemistry
Proof your question. You've made a typo. I think you must have meant -0.73 C.
March 20, 2017

chemistry
c. mols HCl = M x L = ? mols CaCO3 = 1/2 that grams CaCO3 = mols x molar mass = ? d. See my other response and plug in the numbers.
March 20, 2017

chemistry
The problem is a little more complicated because it wants mL (not mols or millimols). a. Excess acid = millimols NaOH = mL x M = 15.3 x 0.7034 M NaOH. I'll leave it to you to calculate how many mL HCl that is. b. mL HCl used in the neutralization was 30 mL - mL from part a...
March 20, 2017

Chemistry
How much Pb(NO3)2 is contained in the 4.5 dm^ at 70 C? That's 2.25 mols x 4.5/1.33 = approx 7.5 but you need a more accurate number. Now you have 4.5 dm^3 containing about 7.5 mols Pb(NO3)2 at 70 C. You cool it to 18 C where the solubility is lower. How much can that 4.5 ...
March 20, 2017

Chemistry
Yes. Isn't that what the equation says? Ca(OH)2 ==> Ca^2+ + 2OH^- So if you know the OH from Ca(OH)2 then 1/2 that is Ca^2+. By the way you should write Ca(OH)2 right; the way you write it is not right and I know what it is only because I've been working with the ...
March 20, 2017

Chemistry
I'll try to take care of both questions but it may be confusing to try t answer both with one post. For #3, yes, solubility Ca(OH)2 is (Ca^2+). You have total OH and you have OH from the NaOH. The difference is the OH from the Ca(OH)2 itself. 1/2 the OH from Ca(OH)2 gives ...
March 20, 2017

Chemistry
http://www.jiskha.com/display.cgi?id=1489957110
March 20, 2017

Chemistry
mL1 x M1 = mL2 x M2 40 x 0.045 = mL2 x 2.1 Solve for mL2 of the stock to take.
March 19, 2017

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 = ? ...
March 19, 2017

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 ...
March 19, 2017

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 ...
March 19, 2017

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.
March 19, 2017

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
March 19, 2017

Chemistry
1. Cells in series adds the voltage. 2. You didn't provide enough information about the set up for me to answer.
March 19, 2017

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.
March 19, 2017

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...
March 19, 2017

Chemistry
3Mg + N2 ==> Mg3N2 Look at the coefficients. 3 mols Mg gives 1 mol Mg3N2; therefore, 1 mol Mg will give ..... mol Mg3N2.
March 19, 2017

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...
March 19, 2017

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 ...
March 19, 2017

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.
March 19, 2017

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 ...
March 19, 2017

Chemistry
(P1/T1) = (P2/T2) Substitute and solve for P2. Remember T MUST be in kelvin.
March 19, 2017

Chemistry
If this is REALLY 906 kJ/MOLE that is 906 kJ/17 g NH3. Then 17 x (500/906) = ? g NH3 required.
March 18, 2017

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.
March 18, 2017

Chem
7 https://socratic.org/questions/how-do-i-calculate-the-least-number-of-carbon-atoms-in-a-non-cyclic-alkane-molec
March 18, 2017

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+.
March 18, 2017

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.
March 18, 2017

Chemistry Titration-emergency :(
Also, I suggest you post the Ksp you are using for Ca(OH)2.
March 18, 2017

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 ...
March 18, 2017

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).
March 18, 2017

chemistry
rate for y = 1 rate for H2 = 8 (rate H2/rate y) = sqrt(mm y/mmH2) Substitute and solve for mm y.
March 18, 2017

Chemistry
from what?
March 18, 2017

chemistry
You also need the solubility of ASA at 25.
March 18, 2017

chemistry
What's wrong with substituting the numbers into the Henderson-Hasselbalch equation? HCO3^- is the acid ad CO3^2- is the base.
March 17, 2017

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
March 17, 2017

more---Chemistry
Note that work in the above is in L*atm. You must change this to joules.
March 17, 2017

Chemistry
work = -pdV a. If p is zero, then pdV is 0 b. substitute into the equation. dV is V2-V1.
March 17, 2017

Chemistry
http://www.jiskha.com/display.cgi?id=1489708172
March 17, 2017

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.
March 17, 2017

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 ...
March 16, 2017

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.
March 16, 2017

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....
March 16, 2017

chemistry
H2CO3 is the stronger acid and will react with the strong base.
March 16, 2017

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...
March 16, 2017

Chemistry
4Bi + 3O2 ==> 2Bi2O3
March 16, 2017

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.
March 16, 2017

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.
March 16, 2017

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.
March 15, 2017

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 ...
March 15, 2017

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...
March 15, 2017

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.
March 15, 2017

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...
March 14, 2017

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...
March 14, 2017

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
March 14, 2017

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.
March 14, 2017

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 ...
March 14, 2017

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