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Posts by DrBob222

Total # Posts: 54,759

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.

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.

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

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

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

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 = ?

chemistry
https://en.wikipedia.org/wiki/Solubility_table

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

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^-?

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^-?

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

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

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 ...

chemistry
Substitute into PV = nRT and solve.

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.

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.

Chemistry
Do you have a list or you want the one of millions of compounds known?

Chemistry (ap)
And CV stands for what?

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.

Chemistry
mL1 x M1 = mL2 x M2 mL1 x 12.1M = etc

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

chemistry
Look in your text/notes about how to solve limiting reagent problems.

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.

@ 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.

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

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

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.

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.

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

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 ...

Chemistry
M = mols solute/L solution. mols solute = grams/molar mass = ? L solution = 0.2 L

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

@ 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...

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

chemistry
multiple proportions.

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 = ?

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.

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.

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 ...

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.

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

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 = ?

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 = ?

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...

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...

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

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 ...

chemistry
See your post above.

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

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.

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. ...

chemistry
Bromothymol blue is yellow in acid and blue in basic solution.

Chemistry
Don't you usually neutralize acid solutions?

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

Chemistry
See your post below. mol = M x L

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.

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.

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

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.

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

@ 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.

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.

Chemistry
I answered this for you last night. Look for your other post below.

Chemistry
mol HCl initially = 1.38 mol NaOH initially = 2.90 mol NaOH after reacting = 2.90 - 1.38 = ? mols.

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

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!

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

chemistry (ap)
You don't have enough information listed.

CHEMISTRY
See your post above.

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) = ?

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

chemistry
I don't see a question here.

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

Chemistry
https://www.youtube.com/watch?v=1ZlnzyHahvo

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 ...

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

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 (...

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 ...

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.

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

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

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.

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 = ?

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

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

Chemistry
See your post above.

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.

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.

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 ...

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)

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

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 = ?

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.

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

chemistry
See above

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.

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 = ?

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...

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...

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.

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