Saturday
February 25, 2017

Posts by DrBob222

Total # Posts: 54,062

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

Chemistry
See this link. Read down the right side table to solubility. It gives solubility at three temperatures and shows an increase. https://en.wikipedia.org/wiki/Calcium_iodate
February 6, 2017

chemistry
Use the dilution formula. %1*mL1 = %2*mL2 10*mL1 = 0.5*50 Solve for mL1 of the 10% stock solution, pipet that quantity into a 50 mL volumetric flask, add DI H2O to the mark, mix thoroughly, stopper and viola!
February 6, 2017

Chemistry
ln(Ao/A) = kt If you use k as listed than t is 5 min x (60 s/min) = 300 s. Solve for A
February 6, 2017

chemistry (ap)
You don't have enough information listed.
February 6, 2017

CHEMISTRY
See your post above.
February 6, 2017

Chemistry
mols HCl = grams/molar mass = approx 0.3 but that's an estimate. Then M HCl = approx 0.3/5L = about 0.06 pH = -log (HCl) = ?
February 6, 2017

chemistry
dE = 2.180E-18[1/(n1)^2 - (1/(n2)^2] n1 = 1 and 1^2 = 1 n2 = 5 and 5^2 = 25
February 6, 2017

chemistry
I don't see a question here.
February 5, 2017

Chemistry
Use the De Broglie equation but first convert the mass to kg and the wavelength to m.
February 5, 2017

Chemistry
https://www.youtube.com/watch?v=1ZlnzyHahvo
February 5, 2017

Chemistry
One thing you could have done is to provide the possible answers. An aliquot is the way to go. Without knowing the details I can only generalize. What you want to do is to take an aliquot of the sample. Apparently you are titrating into a 10 mL graduated cylinder, or at least ...
February 5, 2017

Chemistry
And you haven't come close to providing enough information for us to know what the problem is.
February 5, 2017

BIOCHEMISTRY
You need two equations to solve simultaneously. Equation 1 is the Henderson-Hasselbalch equation. pH = pKa + log (base)/(acid) 5 = pKa + log (base/acid) Substitute and solve for ratio (base)/(acid). Equation 2 is (acid) + (base) = 0.2 M Solve the two equations for (base) and (...
February 5, 2017

Chemistry
If you assume this is an ideal solution. Take 100 g solution. mass acetone = 5g mols acetone = 5/molar mass = ? mass H2O = 95 g mols H2O = 95/molar mass H2O = ? total mols = mols acetone = mols H2O = ? Xacetone = mols fraction acetone = nacetone/total mols xH2O = nH2O/total ...
February 5, 2017

Chemistry
rate1 = 0.33/s for T1 = 29C (302 K) rate2 = 0.27/s for T2 = 23 (296 K) rate1 = k1(A) rate2 = k2(A) Calculate k1/k1 knowing rate1 and rate2. (A) is constant. ln(k2/k1) = Ea(1/T1-1/T2)/R Substitute and solve for Ea.
February 5, 2017

Chemistry
At what T? Ne is a gas at room T and quite a bit below room T.
February 5, 2017

@coolest
I responded to your question above. Please don't post questions piggy back. Most of that type never gets and answer.
February 5, 2017

Chemistry
Fe + S ==> FeS mols S = grams/atomic mass S = ? Convert mols S to mols FeS. Look at the equation. See that 1 mol S forms 1 mols FeS. Then grams FeS = mols FeS x molar mass FeS.
February 5, 2017

Chemistry
mols O2 = grams/molar mass O2 = ? Using the balanced equation, convert mols O2 to mols H2O. You can seee that 1 mol O2 requires 2 mols H2O. Then convert mols H2O to grams H2O. grams H2O = mols x molar mass = ?
February 4, 2017

CHEM 114
Sure, why not. You have two reactants, each can be first order, which makes the total reaction second order.
February 4, 2017

Chemistry
0.01m/s x (39 in/m) x (1 ft/12 in) x #sec = 8 ft Solve for # sec.
February 4, 2017

Chemistry
See your post above.
February 4, 2017

Chemistry
Note the correct spelling of Celsius. delta T = i*Kf*m i for urea = 1 Kf for H2O = 1.52 You know delta T = 4. Solve for m = molality Then m = grams/kg solvent You know kg solvent and m, solve for grams.
February 4, 2017

chemistry
This is at least an hour's worth of explaining. Surely you know how to to portions of this. How what you know how to do, explain what you don't understand, and I can help you through with the rest of it.
February 3, 2017

Chemistry
If you want to do this exactly, you will need to know the masses of the isotopes; i.e., they are not exactly 25, 26, and 24. The problem is done this way. Let x = abundance 25 Then 1.00-0.79-x =0. 21-x = abundance 26. (0.79*24) + (x*25) + (0.21-x)*26 = 24.3 You will need to ...
February 3, 2017

Chemistry
I assume you have aqueous solutions of both. molecular equation: Sr(NO3)2(aq) + Na2CO3(aq) ==> SrCO3(s) + 2NaNO3(aq) Net ionic equation: Sr^2+(aq) + CO3^2-(aq) ==> SrCO3(s)
February 2, 2017

chemistry
NH4NO3 ==> N2O + 2H2O The problem tells you it is a decomposition reaction.
February 1, 2017

chemistry
mols K2CrO4 = M x L = ? Using the coefficients in the balanced equation, convert mols K2CrO4 to mols PbCrO4(hint: 1 mol K2CrO4 = 1 mol PbCrO4) Then convert mols PbCrO4 formed to grams by g = mols x molar mass = ?
February 1, 2017

chemistry
If done in detail this will take 10-15 pages of explanation. Surely you know how to do parts of this. I can help you through the parts you don't understand but show what you can do first.
January 31, 2017

chemistry
2Na + Cl2 ==> 2NaCl 2 mols Na x (1 mol Cl2/2 mols Na) = 2*1/2 = ?
January 31, 2017

chemistry
See above
January 30, 2017

Chemsity
http://www.cod.edu/people/faculty/jarman/richenda/1551_hons_materials/Activity%20series.htm The METAL will oxidize any ION below it in the activity series.
January 30, 2017

chem
...AgCl(s) ==> Ag^+(aq) + Cl^-(aq) I..solid.......0...........0 E..solid.....1.35E-5.....1.35E-5 Ksp = (Ag^+)(Cl^-) = (1.35E-5)^2 = ?
January 30, 2017

chemistry
grams HCl in 1000 mL is 1.18 g/mL x 1000 mL x 0.37 = approx 437 g but that's just an estimate. Then mols in that 1 L = grams/molar mass = approx 437/36.5 = about 12 M, another estimate. Since that is mols/L that is M. b. g HCl = mols HCl x molar mass HCl so g HCl = 0.315 x...
January 30, 2017

oops---Chemistry
I think this question should be reviewed and/or rethought. a. mL x N x milliequivalent weight = grams. 500 x 4 x (98/3000) = about 65 g. b. 8N is right c. There is a typo here. 600*20 = 12,000 mL or 12 L. d. mols = M x L = 6 x 0.3 = 1.8 mols. Then grams = mols x molar mass = 1...
January 30, 2017

Chemistry
C6H12O6 + 6O2 ==> 6CO2 + 6H2O + 15.7 kJ dHfrxn = (n*dHf products) - (n*dHf reactants) 15.7 kJ/mol = [(6*dH CO2)+(6*dH H2O)] - (0 + dH glucose). Solve for dH glucose.
January 30, 2017

chemistry
I agree with the response by v. Here is another way of saying the same thing. Li has +3 charge in nucleus and 2e in the first energy level; therefore, the outside electron "sees" +1 charge. Na has 11+ charge in nucleus and the outside electrons "sees" 1&...
January 30, 2017

chemistry
HCl + NH3 ==> NH4Cl millimols HCl = mL x M = 25 x 0.1 = 2.5 mmols NH3 = 2.5 so volume must be 25.0 mL. Total volume - 50 mL. M NH3 = mmols/mL = 2.5/50 = 0.05 M. The pH at equivalence point is determined by the hydrolysis of the NH4Cl. .......NH4^+ + H2O ==> NH3 + H3O^+ I...
January 29, 2017

Chrmisty
HF + NaOH ==> NaF + H2O millimols HF initially = mL x M = 25 x 3 = 75 mmols NaOH added = 25 x 0.3 = 7.5 mmols HF left un-neutralized = 75-7.5 = 67.5 volume of new solution = 26 mL + 25 mL = 50 mL. M HF left = mmol/mL = 67.5/50 = 1.35 M. ......HF ==> H^+ + F^- I....1.35...
January 29, 2017

Chemistry 112
A little tough on this site but it would be easier to do if you posted the data.
January 29, 2017

Chemistry
4 g He will occupy 22.4L at STP. So 1g will occupy .......?
January 29, 2017

Chemistry 112
yes
January 29, 2017

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