# Posts by DrBob222

Total # Posts: 54,975

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...

chemistry
I use this most often but it's a couple of equations put together. mL x M x (molar mass/1000) = grams You don't list mL in the problem and you must have that. M - 0.272. Molar mass acetylsalicyclic acid you can look up. Calculate grams. Then % ASA = (grams ASA/0.726 ...

Chemistry
dG = dGo + RTlnQ Write the equation. Determine the limiting reagent. Q = (NaNO3)^2/[Pb(NO2)] Determine the concentrations for Q and calculate. Post your work if you get stuck.

Chemistry
When dG is - (i.e., <0) the reaction is favored. Therefore, if dGo is >0 it must be + and that means the system is not favorable for a reaction. That is the equilibrium lies to the left. That takes care of 1 and 5. 2. Knowing that the equilibrium lies to the left means ...

Chemistry
This looks like a limiting reagent (LR) problem. SiO2 + 2C ==> SiC + CO2 mols SiO2 = grams/molar mass = approx 50/60.1 = approx 0.0832 mols C = 50/12 = approx 0.0416 mols SiC formed using just SiO2 = 1:1; therefore, 0.0832. mols SiC formed using just C = 0.0416 x 1/2 = 0....

Homework
You ask questions, we provide answers BUT the emphasis is on HELPING you and not doing all of your work. We try to teach you how to do it rather than doing it for you. It is not a place to type in your tests and make 100% score. Here are the tips you should do. Homework ...

Chemistry
Ag2CrO4 ==> 2Ag^+ + CrO4^2- Ksp = (Ag^)^2(CrO4^2-) mols CrO4^2- = mols x L = ? Substitute into Ksp expression and solve for (Ag^+). That is (AgNO3). Convert M to mols in the 2.0 L and convert to grams. g = mols x molar mass. Post your work if you get stuck.

You have the two solubilities. You will need to calculate the ratio from that.

Chemistry
CaSO4 ===> Ca^2+ + SO4^2- For pure water, Ksp = (Ca^2+)[(SO4)^2-] So (Ca^2+) = x and [(SO4)^2-] = x. Solve for x and that is the solubility of CaSO4 in pure water. For the 0.1M Na2SO4 solution. Ksp is the same expression. (Ca^2+) = x [(SOr)^2-] = 0.1 + x. [Note: that is 0....

chemisrty
mols KOCl = 6.22g/90.55 = 0.0687 or 68.7 millimols. ......OCl^- + H^+ ==> HOCl I....68.7.....0........0 add..........16............. C...-16.....-16........16 E....52.7.....0.........16 You can substitute to find the pH of this solution is 8.05 Out of the buffer range for ...

Chemistry
mols N2 = 2.0/28 = about 0.07 (N2) = 0.07/1.3L = about 0.05 mols O2 = 3.0/32 = about 0.09 (O2) = a0.09/1.L = about 0.07 All of the above need to be recalculated more accurately. .......N2 + O2 ==> 2NO I....0.05..0.07......0 C.....-x...-x.......2x E..0.05-x..0.07-x....2x ...

Chemistry
Take a 100 g sample to give you 57.8g C, 3.6g H and 38.6 g O. Convert to mols. 57.8/12 = ? 3.6/1 = ? 38.6/16 = ? Now find the ratio of CHO to each other with the lowest being no smaller than 1.00. The easy way to do this is to divide the smaller number by itself, then divide ...

Chemistry
mols C = 7.961/44 = ? mols H = 1.164 x (2/18) = ? mols N = 1.551/30 = ? Now find the ratio in small whole numbers to one another. The easy way to do that is to divide the smallest number by itself (which gives you 1.000), then divide the other numbers by the same small number...

Chem
Cindy, Tiffany, et al. See your other posts. We prefer you stick to one screen name. Posting with more than one name often delays help.

Chemistry
Your Ksp for AgBr is eqn 1. Your Kf for Ag(S2O3^-2)^3- is eqn 2. Add equn 1 to eqn 2 to get AgBr(s) + 2(S2O3)^3- ==> Br^- + [Ag(S2O3)2]^3- Write the equilibrium expressiion for that which equals Ksp*Kf. Then substitute 0.02 for Br^- and 0.02 for [Ag(S2O3)]^3- and solve for...

Chemistry
You don't need the gas equation. Mg + 2HCl ==> H2 + MgCl2 mols Mg = grams/atomic mass = ? This could be a limiting reagent problem so watch that.

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.

Chemistry
1/A - 1/Ao = kt A = 0.0174 M Ao = 0.0693 M t = 489 s Solve for k.

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 ...

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 = ??

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...

Chemistry
E = 2.180E-18(1/2^2 - 1/0)

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.

Chemistry
Would you look at your post and proof it please. That 10^20? Is that right?

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 .....

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.

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

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 ...

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

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 = ?

Chemistry

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.

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

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 ...

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 ...

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.

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.

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...

CHEMISTRY
The equation ALWAYS tells you. 25 mols O2 = 18 mols H2O or 25:18

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..-...

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

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 = ?

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 = ?

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...

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 ...

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.

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

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 = ?

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 = ?

Chemistry 101

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

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

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.

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

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 ...

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 ...

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.

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 ...

Chemistry

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 ...

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...

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

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.

chemistry
No. See my response below. m = mols solute/kg solvent.

chem
I don't see a question here.

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.

Chemistry-Urgent
The answer is approx 0.12 or so.

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 ...

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...

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

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 = ?

Chemistry-Urgent
Of course not. 11.1/142 is 1?

Chemistry-Urgent
ok. Now what is 11.1 grams Na2SO4 converted to mols?

Chemistry-Urgent
No. What's the molar mass of Na2SO4?

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

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.

Chemistry-Urgent
m = mols solute/kg solvent

Chemistry-Urgent
Didn't I do one just like this for you.

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.

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.

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

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

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 = ?

Chemistry
1911.9 x 0.0362 = ?

Chemistry
I obtained 0.126 L.

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.

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.

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

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...

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

Organic Chemistry
Can't draw on this forum.

Organic Chemistry

Chemistry
http://www.jiskha.com/display.cgi?id=1487548876

Chemistry
http://www.jiskha.com/display.cgi?id=1487548953

Chemistry
http://www.jiskha.com/display.cgi?id=1487548953

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.

Chemistry
I worked this exact problem above.

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

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

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