Sunday
February 26, 2017

Posts by drbob222

Total # Posts: 54,063

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

Chemistry
The problem says nothing about opening a valve so you have the same amount of gas you started with unless there's a leak somewhere.
February 24, 2017

chemistry, science
Please find the caps key and use it. I don't know what he is. Perhaps you meant He. mols = grams/molar mass
February 24, 2017

chemistry
How much H3PO4 is in the sample? That's 75.0 x 0.175 = approx 13g but you need to do it more accurately. How many mols is that? That's about 13/98 = approx 0.13. 2H3PO4 + 3Ba(OH)2 ==> Ba3(PO4)2 + 6H2O mols Ba(OH)2 = approx 0.13 mols H3PO4 x (3 mol Ba(OH)2/2 mol ...
February 24, 2017

Chemistry
mols KOH = grams/molar mass = ? Then M KOH = mols/L. You have mols from above and convert 200 mL to L.
February 23, 2017

Chemistry
E = 2.18E-18 J x (1/1 - 1/0) = 2.180E-18 J x (1 kJ/1000J) x 2.78 mol H atoms x 6.02E23 atoms/mol = ?
February 23, 2017

Chemistry
See your other question above.
February 23, 2017

Chem
delta T = i*Kb*m delta T is what you want. i for MgBr2 is the van't Hoff factor = 3. Kb you can look it up. It't approx 0.5 m = mols/kg solvent. You have g water. Convert to Kg. Then mols MgBr2 = grams/molar mas.
February 23, 2017

Chemistry Help
When equimolar concentrations of base and acid are used, the pH is ALWAYS the pKa. Why? pH = pKa + log (base)/(acid) But if base = acid, then base/acid = 1 and log 1 = 0 so pH = pKa. a is pKa = - log Ka b is pKb = -log Kb, then pKa + pKb = 14
February 23, 2017

Chemistry
You must assume this is a non-volatile compounds AND that it is not ionic. delta T = 100.78-100 = ? delta T = Kb*molality You know delta T, look up Kb (about 0.5), solve for m. m = mols/kg solvent. You kow m and kg waterk solve for mols. mol = grams/molar mass You know grams ...
February 23, 2017

Chemistry
3.65 g HCl in 1 dm3 H2O is 3.65/36.5 = 0.1 M HCl mols HCl = M x dm3 = 0.1 x 0.0227 dm3 = ? Na2CO3 x 2HCl ==> 2NaCl + H2O + H2O mols Na2CO3 = 1/2 mol HCl = ? and that's the mols Na2CO3 in 25 cc. Convert t mols Na2CO3 in 1 dm3 = ?mols Na2CO3 x 1000/25 = ? Convert that to ...
February 23, 2017

Chemistry
14 F. Convert to C. (F-32)*5/9 = C delta T = Kf*molality Substitute delta T and Kf. Solve for m. m = mols/kg solvent. You know m and kg H2O. Solve for mols. mols = grams/molar mass. You know mols and molar mass, solve for grams.
February 22, 2017

Chemistry
How many mols are in 5.00 g NaCl? That's mols = grams/molar mass = ? Then M = mols/L solution. 250 mL = 0.250 L.
February 22, 2017

CHEMISTRY
No. Oxidation is the loss of electrons. Reduction is the gain of electrons. Mg(s) with a zero oxidation number changes to Mg^2+ ion with a +2 oxidation number. From zero charge to +2 charge means it had to lose electrons so Mg is oxidized. Fe^2+ on the left changes to Fe(s) on...
February 22, 2017

CHEMISTRY
The equation ALWAYS tells you. 25 mols O2 = 18 mols H2O or 25:18
February 22, 2017

Chemistry
NH4OH initially = 0.1 mol NH4Cl initially = 0.1 mol When adding HCl the equation is ......NH3 + H^+ ==> NH4^+ When adding NaOH the equation is and I will do this one. ......NH4^+ OH^- ==> NH3 + H2O I.....0.1....0.......0.1....... add........0.02............. C....-.02..-...
February 22, 2017

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

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