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March 28, 2017

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Posts by DrBob222

Total # Posts: 54,303

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

Chemistry
Take a 100 g sample. That will be 14.1 grams Cu and 85.9 g Sn. mols Cu = 14.1/63.55 = 0.222 mols Sn = 85.9/118.7 = 0.724 atoms Cu = mols x 6.02E23 = 0.222 x 6.02E23 = 1.34E23 atoms Sn = 0.724 x 6.02E23 = 4.36E23 %Cu by atoms = (atoms Cu/total atoms)*100 = ? Check all of those ...
February 12, 2017

Chemistry
M = mols solute/L solution. mols solute = grams/molar mass = ? L solution = 0.2 L
February 12, 2017

chemistry
10.5 g KNO3 in 5 g solvent. Convert to g KNO3/100 g solvent. That's 10.5 x 100/5 = ? g KNO3/100 g solvent Isaac, you can convert grams solvent to dm-3 without knowing the density of the solvent
February 12, 2017

@ eimer---chemistry
Note that the problem says "this substance" which leads me to believe you are adding coconut oil to the benzene. If that is the case, you can't determine the molar mass of lauryl alcohol this way. I will assume "this substance" means you are adding that...
February 12, 2017

@ Isaac---chemistry
Isaac, don't piggy back on another question. Post your own.
February 12, 2017

chemistry
multiple proportions.
February 12, 2017

Biochemistry
pH = pKa + log (base)/(acid) (acid) = mols benzoic acid/1 L = ? (base) = mols sodium benzoate/1 L = ? Substitute and solve for pH. Final concentration of buffer = total mols/total L = mols acid + mols base/total mols = 3 mol/L = ?
February 12, 2017

Chemistry
If NaHS is the base, then H2S must be the acid. If you have 1.0L of 1.0M NaHS, you will need to add 0.5 mol HCl. That will give you 0.5 mol of NaHS and 0.5 mol H2S.
February 11, 2017

Chemistry
I think you're on the wrong track. Kf has the units of *C/molal pel = pelargonic acid lau = lauric acid mols pel = grams/molar mass = ? m = molality pel = mols/kg lau = ? dT = Kf*m. You know Kf and m, solve for dT. Subtract dT from 43.2 to arrive at the new freezing point.
February 11, 2017

thermodynamics
I would convert the dimensions of the room to m and calculate the volume in m^3. 46 x 0.2 m^3 = ? volume occupied by the people and that subtracted from the total volume gives you the volume of air in the room. Convert 14.7 psi to 1 atm. Convert 60.8 F to C. You know P, V of ...
February 11, 2017

Chemistry
dU = q + work q = -4215 kJ/mol x 2 mol = ? 2C6H14 + 19O2 ==> 12CO2 + 14H2O work is pdV. I assume p = 1 atm. dV is -7 mol x 22.4 L/mol = ? Since the volume is contracting then the surroundings are doing work on the system; therefore, work will be negative. Substitute and solve.
February 10, 2017

Chemistry
As Bob P points out, Kion may be called the van't Hoff factor, i and for KCl it is 2.
February 10, 2017

Chemistry
I don't understand--molecular and empirical formula? When you have grams of a substance, then mols = grams/molar mass = ? If it is an element and you have grams then mols = grams/atomic mass = ? For solutions, mols = M x L = ?
February 10, 2017

Chemistry
L1 x M1 = L2 x M2 2.5 x M1 = 10.0 x 1.5 M1 = ? = 10*1.5/2.5 = 6.0 M Now convert 6.0M to % w/v. M = mols/L = 6.0 mols/L. 1 mol = 101 g, then 6 mols must be 6 mol x 101 g/mol = ?
February 9, 2017

here's a better answer--Chemistry
millimoles = mmols. Pb(NO3)2 + 2KCl ==> PbCl2 + 2KNO3 mmols Pb(NO3)2 = mL x M = 25.5 x 4.5 = 114.75 mmols PbCl2 formed if you had all of the KCl you needed = 114.25 mmols KCl = mL x M = 35.5 x 3.0 = 106.5 mmols PbCl2 if you had all of the Pb(NO3)2 you needed = 53.25. So KCl...
February 9, 2017

Chemistry
delta T = i*Kf*m You have delta T = 10.4 i is the van't Hoff factor which is 2 for NaCl. Kf = 1.86 for water. Solve for m. Then m is molality = mols NaCl/kg solvent. You have kg solvent. Solve for mols. Then mols = grams/molar mass. You have mols and molar mass NaCl; solve...
February 8, 2017

chemistry
q = 115 = mass H2O x specific heat H2O x (Tfinal-Tinitial). Solve for Tfinal
February 8, 2017

chemistry
How many mols do you need? That's M x L = 0.5 x 0.250 = ? Weigh out that many grams of Na2CO3, place in a 250 cc volumetric flask, add some distilled water and swirl until all of the Na2CO3 is dissolved, then add distilled water to the mark on the flask, stopper, mix ...
February 8, 2017

chemistry
See your post above.
February 8, 2017

chemistry
2Mg + O2 ==> 2MgO mols Mg = grams/atomic mass = ? Convert mols Mg to mols MgO. Use 1 mol Mg = 1 mol MgO. Now convert mols MgO to grams MgO. grams = mols x molar mass
February 8, 2017

chemistry
5 mol CH3OH x (3 mols O2/2 mol CH3OH) = 5*3/2 = ? mols O2. grams O2, if you need it = mols O2 x molar mass O2.
February 8, 2017

Chem!
SO2 was used at one time but isn't being used now. Ditto for NH3. Both are good refrigerants but both are lethal if a gas leak occurs in the system. Freon 134a is being used now. Here is a link that discusses CO2. It isn't as good as the others but has some benefits. ...
February 8, 2017

chemistry
Bromothymol blue is yellow in acid and blue in basic solution.
February 8, 2017

Chemistry
Don't you usually neutralize acid solutions?
February 8, 2017

Chemistry
mols acid = grams/molar mass. You know grams and mols, solve for molar mass
February 8, 2017

Chemistry
See your post below. mol = M x L
February 8, 2017

Chemistry
mols NaOH = M x L = ? mols HCl = mols NaOH (from the problem) mols acid = grams/molar mass. You know molar mass and mols acid, solve for grams acid. Round to two s.f.
February 8, 2017

Chemistry
Let x = mass Al2O3, then 0.53*x = 26.5 x = ? = mass Al2O3 and ?-mass Al = mass O. I get 50 g for mass Al2O3 and 23.5 = mass O2.
February 8, 2017

Chemistry
mass = density*volume mass benzene = 0.88 g/mL x 125 mL = ? delta T = Kf*m You know delta T. m = mols/kg solvent; mols naph = 1.28/molar mass naphthalene kg solvent = ? g benzene/1000 Solve for Kf
February 8, 2017

Chemistry
heat lost by Zn + heat gained by water = 0 [mass Zn x specific heat Zn x (Tfinal-Tinitial)] + [mass H2O x specific heat H2O x (Tfinal-Tinitial)] = 0 You have Tfinal as the only unknown. Solve for it.
February 7, 2017

Chemistry
The first paragraph gives you the answer. https://www.google.com/search?q=colligative+properties&ie=utf-8&oe=utf-8
February 7, 2017

@ Scott
Not quite. The reaction is SO2 + H2O ==> H2SO3 which is sulfurous acid. It is true, however, that the SO2 gets blown into the higher atmosphere where it may react with O2 to form SO3 and that reacts, as you show, to form sulfuric acid.
February 7, 2017

Chemistry
I'm sorry but I don't see the problem. I tried to decipher the problem from your work but I don't know where you started. It would help if you posted the original problem, then showed what you did.
February 7, 2017

Chemistry
I answered this for you last night. Look for your other post below.
February 7, 2017

Chemistry
mol HCl initially = 1.38 mol NaOH initially = 2.90 mol NaOH after reacting = 2.90 - 1.38 = ? mols.
February 7, 2017

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