Wednesday
February 22, 2017

Posts by DrBob222

Total # Posts: 54,039

Chemistry
How did you get the initial pH when you don't know how much base/acid you started with.
February 22, 2017

chemistry
NaOH + HCl ==> NaCl + H2O mols NaOH = M x L = ? mols HCl = mols NaOH since the equation tells you 1 mol NaOH = 1 mol HCl. Then M HCl = mols HCl/L HCl = ?
February 21, 2017

Chemistry
mols HCl = M x L = ? From the equation, mols Na2CO3 = 1/2 that. grams Na2CO3 = mols Na2CO3 x molar mass Na2CO3. %Na2CO3 = (grams Na2CO3/0.2638)*100 = ?
February 21, 2017

chemistry
How many mols do you want? That's mols = M x L = 0.1 x 0.1 = ? Then M HCl = mols/L. You know M = 4.0M and you know mols = ? from above, solve for L of the 4.0 M stuff. There is an easier way to do it. You should get the same answer eithr way. mL1 x M1 = mL2 x M2 100 x 0.1...
February 21, 2017

Chemistry
acetate is the base. You need NaOH with HAc (acetic acid). You don't need the HCl. pH = pKa + log (base)/(acid) 5.00 = pKa + log b/a. Look up pKa for HAc. Solve for b/a ratio. That's eqn 1. Equation 2 is b + a = 0.200 Solve those two equations simultaneously for b and ...
February 21, 2017

chemistry
Produce 25.4 g CuCl2 from what? Cu? amd Cl2? Cu + Cl2 == CuCl2 mols CuCl2 = 25.4 g/molar mols Cl2 = same as mols Cu. Then use PV = nRT, substitute mole Cl2 for n, substitute P and T (remember T must be in kelvin) and solve for V in Liters.
February 21, 2017

Chemistry
% w/w = % by mass = [(g solute)/(total grams)]*100 Total grams = grams solute + grams solvent
February 20, 2017

Chemistry
K2SO3 + 2HCl --> 2KCl + H2SO3 mols HCl = M x L = ? Using the coefficients in the balanced equation, convert mols HCl to mols K2SO3. Now convert mols K2SO3 to grams. g = mols x molar mass = ?
February 20, 2017

chemistry
M final solution = total mols/total liters. mols soln 1 = M x L = ? mols soln 2 = M x L = ? total mols = ? volume soln 1 = 0.276 L volume soln 2 = 0.125 L. total volume = ?
February 20, 2017

Chemistry 101
What about them?
February 20, 2017

chemistry
There is a chapter of work here. What do you not understand about each? How much do you know how to do?
February 20, 2017

Chemistry
What's your trouble with this. Concn products/concn reactants and the coefficients in the equation become exponents in the Kc expression.
February 20, 2017

Chemistry
So the polar solvent holds more tightly to the polar solute; the less polar solute has nothing to hold it back so it swishes through the TLC plate.
February 20, 2017

Chemistry
Yes, it does. Is dichloromethane a polar solvent?
February 20, 2017

college chemistry
Alex, I don't quite get it. The problem asks for how much carbon you use. Is that grams carbon. But the rest of the problem tell you to end up with grams CO2. Here is how you do it if you want grams CO2. 2660g/gal x 500 gal/year = approx 1E6 but you need to do it for a ...
February 20, 2017

chemistry
Take a 100 g sample which gives you K = 60 g C = 18.5 g N = 21.5 g Convert to mols. mol K = 60/39.1 = ? mol C = 18.5/12 = ? mol N = 21.5/14 = ? Now find the ratio of each element to each other. The easy way to do that is to divide the smallest number by itself (you know that ...
February 20, 2017

chemistry
See my response to your earlier CxHy question below. I've worked it in detail. I hope things work out for you very well.
February 19, 2017

chemistry
JILLIAN, Alan. We prefer to keep the same screen name. Refer to your other problem. It a little simpler with just CxHy. This one is CxHyOz. The only difference is this. Convert 12.53 g CO2 to g C. Convert 3.849 g H2O to g H. To find g O, it is g O = 8.408 g - g C - g H Then ...
February 19, 2017

Chemistry
Alexander, no go. We HELP you do your home work. We don't do it for you.
February 19, 2017

chem
I showed you exactly how to do it. Please read my response, step by step. You will see I follow what I told you to do. Here it is. mols C = 11.59/44 = 0.263 mols H = 3.164*2/18 = 0.351 I suspect you did not do those calculations. I suspect you read the whole thing, said, Hey ...
February 19, 2017

chem
mols C = 11.59/44 = ? mols H = 3.164*2/18 = ? Now find the ratio of these two numbers with the smallest being 1.00. The easy way to do that is to divide the smaller number by itself and divide the other number by the same small number. Round to whole numbers UNLESS the numbers...
February 19, 2017

General Chemistry
What's the problem here? You have the equation. Just plug in the numbers.
February 19, 2017

chem
I posted it below. Just follow the steps. Do each step and show your work. I'll see what you're doing wrong. There's no understanding to it. All you need to do is to substitute the numbers into the steps I've shown.
February 19, 2017

chemistry
No. See my response below. m = mols solute/kg solvent.
February 19, 2017

chem
I don't see a question here.
February 19, 2017

Chemistry-Urgent
mol fraction. I didn't do the molality. It's done the same say as the last one. m is approx 7 if I didn't screw up.
February 19, 2017

Chemistry-Urgent
The answer is approx 0.12 or so.
February 19, 2017

Chemistry-Urgent
Just follow the steps. 1. XHCOOH = mole fraction HCOOH. 2. XHCOOH = mols HCOOH/total mols. 3. mols HCOOH = grams HCOOH/molar mass HCOOOH 4. total mols = mols HCOOH + mols H2O. How much water is there? If you have 100 sample and it is 25.5% HCOOH, then 25.5 grams must be HCOOH ...
February 19, 2017

Chemistry-Urgent
Sometimes students type in the wrong numbers in the calculator. Sometimes they misread the atomic masses and/or the molar masses of atoms/molecules. But most of the time they don't think clearly about what they are doing. When I say m = mols/kg solvent you should recognize...
February 19, 2017

Chemistry-Urgent
Yes. What were you doing wrong and why did this take so long?
February 19, 2017

Chemistry-Urgent
OK. So mols = grams/molar mass mol Na2SO4 = 11.1 g/142.04 = 0.0782 Now m = mols/kg solvent. you know mols = 0.0782 You know kg solvent = 2.269 So m = ?
February 19, 2017

Chemistry-Urgent
Of course not. 11.1/142 is 1?
February 19, 2017

Chemistry-Urgent
ok. Now what is 11.1 grams Na2SO4 converted to mols?
February 19, 2017

Chemistry-Urgent
No. What's the molar mass of Na2SO4?
February 19, 2017

Chemistry-Urgent
Yes, that is kg solvent. Now convert 11.1 g Na2SO4 to mols. mols = grams/molar mass = ?
February 19, 2017

Chemistry-Urgent
No. m = mols solute/kg solvent. molsl Na2SO4 is not 11.1. The problem lists that as grams. and 2269.2 is not kg. I didn't write 100 anywhere in my instructions. You're not thinking straight.
February 19, 2017

Chemistry-Urgent
m = mols solute/kg solvent
February 19, 2017

Chemistry-Urgent
Didn't I do one just like this for you.
February 19, 2017

Chemistry-Urgent
Henry's Law says concn is proportional to pressure; therefore, 0.12 x (3E-4/4) = ? M = ? mols/L. Convert to grams/L.
February 19, 2017

Chemistry
Daryll, "Explain it further" doesn't help much. Did you try following each of the formulas I gave. Exactly what do you not understand. Do it step by step, show your work, and explain each part you don't understand.
February 19, 2017

Chemistry
You should look before you leap. I answered this for you half an hour ago at your earlier post.
February 19, 2017

Chemistry
KI, KBr, KCl are neutral. You're right. F^- + HOH ==> HF + OH^- and it's the OH that gives it the higher pH.
February 19, 2017

Chemistry
In a 100 g sample, you will have 30.1 g HCOOH and 69.9 g H2O. mols HCOOH = 30.1/molar mass = ? Then m = mols HCOOH/0.1 kg solvent = ? XHCOOH = mols HCOOH/total mols. You have mols HCOOH. mols H2O \ grams H2O/molar mass = ?
February 19, 2017

Chemistry
1911.9 x 0.0362 = ?
February 19, 2017

Chemistry
I obtained 0.126 L.
February 19, 2017

Chemistry
NH4CN (NH4)2SO4 Make the charges add to zero. You see +1 charge for NH4 and -1 charge for CN. You see +2 charge for NH4 and -2 charge for SO4.
February 19, 2017

Chemistry 121
So you have 31.304 kJ/mol. How many mols are in 3.0 g Mg? That's mols = grams/molar mass = ? Then 31.304 kJ/mol Mg x ? mols Mg = ? kJ heat given off.
February 19, 2017

chemistry
H2(g) + I2(g) -> 2HI (g) 2.33 mols H2 x (2 mol HI/1 mol H2) = 2.33 x 2/1 = ? mols HI
February 19, 2017

chemistry
If you had shown your work I could have found the error in half the time it takes to write all of this out. 2CH3OH(I) + 3O2 (g) ? 2CO2(g) + 4H2O(I) mass CH3OH = volume x density mass CH3OH = 0.79 g/mL x 11.25 mL = ? mols CH3OH = grams CH3OH/molar mass CH3OH = ? mols CO2 = mols...
February 19, 2017

Chemistry-Urgent
% v/v = (mL solute/mL solution)*100 % v/v = [26/(26+113)]*100 = ? or (26/139)*100 = ?
February 19, 2017

Organic Chemistry
Can't draw on this forum.
February 19, 2017

Organic Chemistry
See your other post.
February 19, 2017

Chemistry
http://www.jiskha.com/display.cgi?id=1487548876
February 19, 2017

Chemistry
http://www.jiskha.com/display.cgi?id=1487548953
February 19, 2017

Chemistry
http://www.jiskha.com/display.cgi?id=1487548953
February 19, 2017

chemistry
We prefer you use the same screen name. Brianna and John? Posting with different screen names doesn't help. Look for answers under other posts.
February 19, 2017

Chemistry
I worked this exact problem above.
February 19, 2017

chemistry
CaCO3 + 2HCl ==> CaCl2 + H2O + CO2 3 mols HCl x (1 mol CO2/2 mols HCl) = ?
February 19, 2017

chemistry
Kate didn't answer all of the question. mols SO2 = grams SO2/molar mass SO2 = ? Then there are 6.02E2 molecules in 1 mol
February 19, 2017

college chemistry
Will they react?
February 18, 2017

Chemistry
K2CO3(s) + 2HCl(aq) ==> 2KCl(aq) + H2O(l) + CO2(g)
February 18, 2017

Chem
3.5 mols O2 x (4 mols H2O/5 mols O2) = 3.5 x 4/5 = ?
February 17, 2017

Molarity question!! please help urgently!
pH = 8.7 so pOH = 14-8.7 = 5.3 5.3 = -log(OH^-) and (OH^-) = approx 5E-6 but you need to that more accurately. ........NO2^- + HOH ==> HNO2 + OH^- I.......M................0......0 C......-x................x......x E......M-x...............x......x Kb for NO2^- = (Kw/Ka for...
February 17, 2017

Equilibrium concentrations, please help!!!
...Pb(s)+2Cr3+(aq)?Pb2+(aq)+2Cr2+ I.......0.150.......0.........0 C.......-2x.........x.........2x E.....0.150-2x......x.........2x Kc = (Pb^2+)(Cr^3+)^2/(Cr^3+)^2 Substitute and solve for x = (Pb^2+). Note Pb(s) doesn't appear in the Kc expression since it is a pure ...
February 17, 2017

science, chemistry
See my response above.
February 17, 2017

Chemistry
q = [mass H2O x specific heat H2O x (Tfinal - Tinitial) YOu know mass H2O, look up specific heat H2O in calories/grams*C, you know Tfinal and Tinitial. Substitute and solve for q in calories.
February 17, 2017

physical science
One never knows.
February 17, 2017

physical science
7.0 what? inches, feet, miles?
February 17, 2017

Stoichiometry
I don't see a question here.
February 17, 2017

Chem
Here are two links. Read about each, then write about the differences https://en.wikipedia.org/wiki/Peroxide https://en.wikipedia.org/wiki/Oxide
February 17, 2017

Chemistry
Aqueous solutions of element in period 3 are basic. I wonder if you meant GROUP 3A?
February 17, 2017

Chem
There are 6.02E23 molecules in 1 mol of anything; therefore, there are 6.02E23 x 1.4 = ? molecules of your compound. You must know what compound you have (or the formula) before you can calculate the number of C atoms.
February 17, 2017

chemistry
Use the Henderson-Hasselbalch equation. pH = pKa + log (base)/(acid) (base) = 0.2 M (acid) = 0.1 M Look up pKa CH3COOH. I think it's close to 4.74.
February 17, 2017

Chemistry
This set of rules will get the right answer for you. http://www.chemteam.info/Redox/Redox-Rules.html
February 16, 2017

Chemistry
Unless I missed something, aren't all of them true?
February 16, 2017

chemistry
Here is a table showing the solubility of NH4Cl vs temperature. Solubility NH4Cl vs Temperature. That's about 65 g at 80 C. That should allow you to calculate how much must be added to 25 g to make it saturated. https://en.wikipedia.org/wiki/Solubility_table
February 14, 2017

chemistry
C3H8 + 5O2 ==> 3CO2 + 4H2O mols C3H8 = grams/molar mass = ? Using the coefficients in the balanced equation, convert mols C3H8 to mols O2. That's ?mols C3H8 x (5 mols O2/1 mol C3H8) = ? Now convert mols O2 to grams. grams = mols x molar mass = ?
February 14, 2017

chemistry
https://en.wikipedia.org/wiki/Solubility_table
February 14, 2017

Chemistry
What charge? Do you mean how many coulombs? coulombs = 2.5 A x 3 min x *(60 s/min) = ?
February 14, 2017

oops---Chem
I made a typo. That last sentence should read as follows: Does that tell you that 0.1M AlCl3 contains 0.1 M Al^3+ and 0.3M Cl^-?
February 13, 2017

Chem
AlCl3 ==> Al^3+ + 3Cl^- So 1 mol AlCl3 contains 1 mol Al^3+ ions and 3 mols Cl^-. Does that tell you that 0.1M AlCl3 contains 0.1 mol Al^3+ and 0.3M Cl^-?
February 13, 2017

Chem
mols KOH = M x L = ? 1 mol KOH = 1/2 mol H2SO4 (from the equation) M H2SO4 = mols H2SO4/L H2SO4
February 13, 2017

Chemistry
I don't get the problem you have. Can't you substitute into PV = nRT (the question tells you how to solve it).
February 13, 2017

chemistry
How (why) did you get O2 into your calculations. The problem asks for grams CO2. mols C2H2 = 104/26 = 4.0 Convert mols C2H2 to mols CO2. That's 4.0 mols C2H2 x (4 mols CO2/2 mols C2H2) = 8 mols CO2. Now convert mols CO2 to grams. That's grams = mols CO2 x molar mass ...
February 13, 2017

chemistry
Substitute into PV = nRT and solve.
February 13, 2017

chemistry
1. With a magnet. 2. OR, add H2O, NaCl dissolves, filter to remove the iron (not soluble in water), then evaporate the water to recover the NaCl.
February 13, 2017

Chemistry
I presume the % is by volume; therefore, mole fraction He is 0.5 pHe = XHe*Ptotal SHe = 0.5 Ptotal is given. Solve for for pHe.
February 13, 2017

Chemistry
Do you have a list or you want the one of millions of compounds known?
February 13, 2017

Chemistry (ap)
And CV stands for what?
February 13, 2017

Chemistry
I see math here; not much chemistry. 20.7 L/min x 107 min x 0.7949 = ?L. Convert L to quarts. 1.0 L = 1.057 quarts.
February 12, 2017

Chemistry
mL1 x M1 = mL2 x M2 mL1 x 12.1M = etc
February 12, 2017

Chemistry
How many mols do you need? That's M x L = ? Then grams = mols x molar mass
February 12, 2017

chemistry
Look in your text/notes about how to solve limiting reagent problems.
February 12, 2017

Chemistry
heat lost by Pb + heat gained by water = 0 [mass Pb x specific heat Pb x (Tfinal-Tinitial)] + [mass H2O x specific heat H2O x (Tfinal-Tinitial)] = 0 The only unknown is sp. h. Pb.
February 12, 2017

@ Sarah--that won't do itChem
Add them all together, THEN DIVIDE THE NUMBER OF DIMES BY THE TOTAL. Multiply the answer by 100 to convert to percent. Round to the ones place; i.e., a whole number.
February 12, 2017

Chemistry 2
NH + H2O = NH3(aq) + 30.50 kJ/mol So this tells you that the solution becomes warmer.
February 12, 2017

Chemistry
(3.5L*xM) + (2.0L*0.5M) = (10L*1.5M) Solve for x molar.
February 12, 2017

CHEM
A = ebc. A = Absorbance e = molar absorptivity = constant b = cell length c = concn in mols/L Measure A of a known concentration. Knowing b and c, solve for e. Then measure A of an unknown. Plug in b and e, solve for c in mols/L. Convert to ppm or whatever units you want.
February 12, 2017

chemistry
11.1 M x (25.0 mL/500 mL) = ? OR use the dilution formula. mL1 x M1 = mL2 x M2 25.0 x 11.1 = 500 mL x M2. Solve for M2.
February 12, 2017

Chem
You didn't give the yield for the second reaction (and it isn't balanced either). First equation is not balanced either.
February 12, 2017

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