# Posts by DrBob222

Total # Posts: 54,772

AP Chemistry
I don't think you have the right picture. Do it this way. mols WO3 = grams/molar mass = ? Use the coefficients in the balanced equation to convert mols WO3 to mols CO2. Now convert mols CO2 to grams CO2. g CO2 = mols CO2 x molar mass CO2. This gives you the grams of CO2 ...

Chemistry
You're right but I would have done it as (0.68/1.3) = 0.52 = 52%. I'm not being picky, rather, I'm pointing out that if I do it your way I'm doing two operations that are not necessary (multiplying both numerator and denominator by 1000 before dividing) and ...

Chemistry
You have 2 mols Al and 3 mols C and 9 mols O.

Chemistry
Again, I assume this is ppm w/v. Volume of 25 kg seawater is v = m/d = 5000 g/1.025 g/mL = 4878 mL. Then mg Pb/L = ? mg/L = ppm w/v

Chemistry
I assume that is ppm w/v. 5 ppm = 5 g Pb/10^6 g H2O = 5 mg Pb/10^3 g H2O = 5 mg Pb/1000 g H2O = 5 mg Pb/1L H2O if density of H2O is 1.00 g/mL (or 1000 kg/m^)

Organic Chemistry
You might think so since acetone has such as low boiling point; however, I might be worried more that the flask was heated too much in trying to get all of the solvent out. You might try dissolving the solid again in a minimum of solvent, pouring the mixture into a beaker, ...

Chemistry
The longer the chain the more intermolecular forces and the higher the boiling point (lower vapor pressure).

Chemistry
mols Fe ==> grams/molar mass = ? Convert to mols O2. That's ?mols Fe x (3 mols O2/4 mols Fe) = ? Then mols O2 x 22.4 L/mol = L O2

Chemistry
What's an IRF? 2NaOH + H2SO4 = Na2SO4 + 2H2O Convert pH of NaOH to pOH and calculate (OH^-) and (NaOH). Then mols NaOH = M x L = ? mols H2SO4 = M x L = ? Subtract to see which is in excess, calculate (H^+) or (OH^-) as it applies and convert to pH.

Chemistry
Are you sure of that formula? mols = 8.87/molar mass = ? Then M = mols/L. YOu know mols and M, solve for mL.

Chemistry
The carbon dioxide is released from the solution. At room temperature CO2 isn't very soluble in water.

chemistry
If you want to dilute the solution from 5 M to 0.5 M, you must dilute by a factor of 10. You want 100 so take 10 mL and dilute to 100. For this you will need a 10 mL pipet and a 100 mL volumetric flask. 2. Powdered Zn has MUCH MORE surface area so the reaction is faster (MUCH ...

Chemistry
We can't draw structures on this forum. I suggest you google this. Most Lewis structures on on the web.

Chemistry
P*molar mass = density*RT P must be in atm. 760 torr = 1 atm.

Chemistry
I have no idea what the domino format is.

chemistry

Chemistry
You can find the answer easily by googling scintillation counter. Wilipedia is the best sorce, I think, and you should read under "detectors".

Chemistry
I don't think it will change the position at all although your prof may be expecting an answer of D. To make it shift to the left you must add Ag+ or S2- and neither is present in (NH4)2SO4. To shift to the right you must add something that reacts with either product but (...

Chemistry
What's the problem here? Do you know the definition of Keq?

Chemistry
B is not right.

Chemistry
temperature

CHEMISTRY
The volume of H2 depends upon how much Zn you started with. You don't have that in the problem.

General
It's well and good.

Chemistry
rate O2 = 1L/37 hrs = 0.027 L/hr. rate unk = 1L/26 hrs = 0.38 L/hr. (rO2/runk)= sqrt(Munk/MO2) Substitute and solve for Munk. cheers from my boy.

Chemistry
3G +2M ==> G3M2 mols M = 5.00/135 = approx 0.037 mols G = 0.037 x (3 mols G/2 mols M) = approx 0.0555 Then mols = g/atomic mass. You know mols G and grams G, solve for atomic mass G. I'll bet you get 36.

Chemistry
The HH equation calculates this directly.

chemistry
Great but volumes of what? What kind of formic acid solution do you have? What kind of sodium formate solution do you have.

College Chem 2
Something is amiss here. The Ksp is the Ksp. You can't have two Ksp values for Ag2CrO4.

chemistry
22 servings/box x 90 mg K/serving = ? mg K/box. Convert to g. Convert to mols. mols = grams/atomic mass = ?

chemistry
Convert 10 lb to grams. 10 lbs x (?g/lb) = ? grams sugar. Then mols sugar = grams/molar mass = ?

Chemistry
What you REALLY mean is H2SO4 (sulfuric acid) and Na2CO3 (sodium carbonate). H2SO4 + Na2CO3 ==> H2O + CO2 + Na2SO4 mols Na2CO3 = grams/molar mass = ? Using the coefficients in the balanced equation, convert mols Na2SO4 to mols H2SO4. You can see that is a 1:1 ratio. Then M ...

chem
.NH2COONH4(s) --> 2NH3(g) + CO2(g) I..................0.........0 C.................2x.........x E.................2x.........x First, remember the solid doesn't enter into Keq. Second, you know , if x = pressure, that 2x + x = 3 which makes 1 = x, which means pNH3 = 2 ...

chem
D is right BUT you have a SERIOUS error in what you wrote. Ksp expression is not what you wrote. Ksp = (Ca^2+)^3*(PO4^3-)^2. Note that you don't have that. Here is the problem. Ca3PO4 ==> 3Ca^2+ + 2PO4^3- I...........0........0 C...........3S.......2S E..........3S...

chemistry
ammonium sulfate is (NH4)2SO4 and not what you have. So if 13.2 g (NH4)2SO4 is 0.088 mols, the you get 0.099 mols SO4^2- and 2*0.099 mols NH4 for a total of ?? mols.

chemistry ksp
See my response to your post above.

chemistry
See my response to your post above.

Chemistry
Choose any convenient volume such as 100 mL. Then calculate millimols each. mmol = mL x M = ? H^+ for pH 3 = 1E-3 H^+ for pH 4 = 1E-4 H^+ for pH 5 = 1E-5 mmols pH 3 = 100 x 1E-3 mmols pH 4 = 100 x 1E-4 mmols pH 5 = 100 x 1E-5 M when mixed = total mmols/total mL. It doesn't...

Chemistry
pH = -log(H^+)

chemistry
0.50 mol/dm^3 = 0.5 M 200 cc = 0.2 L = 0.2 dm^3 mols you want Cl^- = M x L = 0.5 x 0.2 = 0.1 mol Cl^- Convert mols Cl^- to mols CaCl2. 0.1 mol Cl^- x (1 mol CaCl2/2 mols Cl^-) = 0.05 mol CaCl2. Now convert mols CaCl2 to grams. mols = grams/molar mass. You kow mols and molar ...

chemistry
Note: L is liter. K is kelvin.

Chemistry
The ion electron method OR The half reaction method.

Chemistry
2 KClO3 (s) ? 2 KCl (s) + 3 O2 (g) Use PV = nRT and solve for mols O2 at the conditions listed. Using the coefficients in the balanced equation, convert mols O2 to mols KClO3. Convert mols KClO3 to grams by g = mols x molar mass Then %KClO3 = (mass KClO3/mass sample)*100 = ?

Chemistry
Do you mean, What is the name? Strontium permanganate

Chemistry
Use PV = nRT For P use Ptotal = pH2O + pgas.

Chem
Reason it out. Use the equation. That tells you that 1 mol Mg (that's 24.3 grams Mg) evolves 466.85 kJ. So what will 5.00 g Mg evolve? You can set up a ratio/proportion or use 466.85 kJ x (5.00 g/24.3g) = ? kJ. The ratio/proportion looks like this. (5.00/24.3) = (x kJ/466....

chemistry chem check
I don't think so. Isn't it true that the vapor phase is enriched in the more volatile solvent?

Chemistry
hbl, I think you jumped the gun. mols CaCO3 = 1/2 mols HCl as Bob P wrote. He assumed you would be able to convert mols to grams. Then mass CaCO3 = mols CaCO3 x molar mass CaCO3 = ?

Chemistry
Fe2O3 + 2Al = Al2O3 + 2Fe mols Fe2O3 ==> grams/molar mass = ? Using the coefficients in the balanced equation, convert mols Fe2O3 to mols Al2O3. Now convert mols Al2O3 to grams Al2O3. g = mols x molar mass = ?

Chemistry
mols Al2O3 = ? Convert mols Al2O3 to mols Al Convert mols Al to grams Al. See your post above if you need refreshing. Same process. All of these stoichiometry problems are done the same way.

Chemistry

chemistry
1/wavelength = RZ^2(1/1^2 - 1/infinity) R is Rydberg constant. You can look that up in (in meters) The term of 1/infinity will be zero. This will give you wavelength and you can convert to energy with E = hc/wavelength. Z is the atomic number of Be

Chemistry
PV = nRT R is 0.08206 T in kelvin V in liters. P in atmospheres.

Chemistry (equlibrium direction) urgent
You're right. There are 2 mols gas on the left and 2 mols gas on the right; therefore, pressure has no effect. You're right again on the catalyst. A catalyst will change the speed of a rxn but not the equilibrium point (that is, the rxn will get to equilibrium faster) ...

chemistry
The simple thing to do is to ignore it. It's a spectator ion. The rxn is between the chromate ion and the ferrous (FeII) ion.

chemistry
The procedure for working stoichiometry problems. 1. Write and balance the equation. You have that. 2. Convert whatinformation you have (you want 50 g Na3PO4) into mols. mols = grams/molar mass = ? 3. Using the coefficients in the balanced equation, convert mols Na3PO4 to mols...

chemistry
The following procedure will work these stoichiometry problems. 1. Write and balance the equation. You have that. 2. Convert What you have (C2H6) to mols. mols = grams/molar mass = ? 3. Using the coefficients in the balanced equation, convert mols what you have (C2H6) to mols ...

chemistry
When dealing with gases we can use a shortcut and use L as if it were mols. 900 L NO2 x (1 mol NO/3 mols NO2) = ?

Chemistry
CH4 + 2O2 ==> CO2 + 2H2O mols CH4 = grams/molar mass = ? Using the coefficients in the balanced equation, convert mols CH4 to mols CO2. Now convert mols CO2 to grams CO2. g = mols x molar mass = ?

chemistry
I am extremely curious about how the systematic name for NH4Br ties in with the mass of ethane.

University
Your post isn't clear to me at all. It appears you want to know the concn of the H2SO4 but the word "matter" in there makes no sense at all. Try rephrasing the question and this time proof what you've written. Thanks.

Chemistry
A buffer is a combination of a weak acid and the salt of its salt (acetic acid and sodium acetate) or a weak base and its salt (NH3 and NH4Cl). Buffers resist a change in pH. Here is how an acid buffer works. Say it is HAc and Ac^-. If a strong acid, such as HCl is added, the ...

chemistry chem check
I don't think so. When Raoult's Law tells you that the vapor pressure of a pure solvent is lowered when a non-volatile solvent is added. mols solute = 0.4 mols solvent = 0.8 total mols 1.2 Xsolvent = 0.8/1.2 = ? Then pmixture = Xsolvent*Po solvent. So it must be either...

chem
You don't have enough info posted to answer this question. If you know grams CO2 or mols CO2, use PV = nRT and solve for V.

chemistry
What are you using to make the HCl?

Chemistry
If I work this out I find that the water of crystallization(s) are not whole numbers. There are compounds where the hydration number is not a whole number. Do you have any indication that this is the case for this problem.

Chemistry
1. Working in millimols. mmols NaoH added = 55 x 1.1 = 60.5 ......HAc + OH^- ==> Ac^- + H2O I.....400...0.........400 add........60.5............... C..-60.5..-60.5.......+60.5 E...339.5...0........460.5 Convert the E line (in mmols) to M with M = mmols/total mL. Total mL...

Chemistry

Chemistry
a. 2NH3 + 3CuO ==> N2 + 3Cu + 3H2O First this is a limiting reagent (LR) problem. You know that because amounts are given for BOTH reactants. b. mols NH3 = grams/molar mass = ? mols CuO = grams/molar mass = ? Using the coefficients in the balanced equation, convert mols NH3...

chemistry
You didn't copy all of the H-H equation but you meant pH = pKa + log (b/a) For an acid, HA, it is HA ==> H^+ + A^- Ka = (H^+)(A^-)/(HA) Solve for (H^+). (H^+) = Ka*(HA)/(A^-) but that is (H^+) = Ka*(acid)/(base) or (H^+) = Ka*(a/b) Multiply by -1 -(H^+) = -Ka*(a/b) then...

chemistry
Use the H-H equation I just derived for you. Next, decide how much want to prepare. Make it easy to prepare 1 L. 3.79 = pKa + log (b/a) Solve for b/a. Assume you want to a to be 1M, the solve for b = ?*a. That gives b. Knowing you want a to be 1M and you want 1 L, calculate ...

Chemistry 30
This will do it. http://www.chemteam.info/Redox/Redox-Rules.html

chemistry
% w/w = [(mass solute)/(total mass soln)]*100 = ? mass soln is mass solute + mass solvent. If the total is 100 g and mass solute is 9.25 g, what is mass solvent.

Chemistry
I don't see a question here.

Chemistry
1 calorie = 4.184 J

Chemistry
K = (SO3)^2/(SO2)^2(O2) You are given the concentrations of each (I assume that m stands for M). Just substitute and you get K. What happens to the equilibrium constant if SO2 is added or O2 removed? Nothing happens. The CONCENTRATIONS will change but the K will not.

Chemistry
Sorry but we aren't taking the exam.

Chemistry 1
I was stumped, also, but after thinking long and hard I believe the answer is C. Choices a, b, and d are cases in which the solute is completely soluble in the solvent. Methanol and hexane are not miscible so there is an equilibrium set up between the two for the solubility of...

Chemistry 1
2Mg + O2 ==> 2MgO 3Mg + N2 ==> Mg3N2 mols Mg3N2 = grams/molar mass = approx 0.0016 but you need a more accurate answer than that estimate. Convert mols Mg3N2 to mols Mg used. That's 0.0016 x (3 mols Mg/1 mol Mg3N2) = approx 0.0045. Convert that to g Mg = mols Mg x ...

Chemistry
2KClO3 ==> 2KCl + 3O2 mols KClO3 = grams/molar mass = ? Using the coefficients in the balanced equation, convert mols KClO3 to mols O2 produced. Now convert mols O2 to grams O2. g O2 = mols O2 x molar mass O2 = ? This is the theoretical yield (TY). The actual yield (AY) is ...

chemistry
Please re-read your post and define "therapy". Perhaps you meant enthalpy or some other word. Perhaps you want heat of neutralization. That's the most likely, I think. Enthalpy of neutralization is the same thing.

Chemistry
You want to what? Changing 0.150 M NaOH to 0.390 M isn't exactly a dilution.

CHEMISTRY
Confused? That makes two of us. And I don't go with Fluffy's explanation either. It all depends upon the color of the solution you are measuring. Also, "lighter colored" doesn't mean anything either. That's a relative term. I understand the difference...

Chemistry
See your post above. It makes it a lot easier to answer your questions if you use the same screen name. Sammy and Marlene are not the same in my book.

Chemistry (Molarity) Help
What's the total volume? That's 0.50 + 2.50 + 2.00 mL = 5.00 mL. How many mols FeSCN^2+ do you have? That's mols = M x L = 1.25E-4 x 0.0005 = ? (You're assuming here that the formation constant for FeSCN^2+ is so large that the reaction goes so far to the right...

Chemistry
A = ebc As e (molar absorptivity) increases so does A. As b (path length) decreases, so does A.

Don't know why. 1.25E-4M x 100 mL = 0.0025M*mL Solve for mL of the 0.0025 M solution, add that to a 100 mL volumetric flask, dilute to the mark, mix thoroughly, stopper, voila!

chemistry
CaCO3 ==> CaO + CO2 mols CaCO3 = grams/molar mass = ? You see 1 mol CaCO3 produces 1 mol CO2 Then use PV = nRT, solve for V in L.

chemistry

Chemistry
V1/T1 = V2/T2. For A, it is 600/400 = 800/T2. Solve for T2 Do the same for the 800 to 1200(that's B). Compare T2 values.

chemistry
An electron in an excited atom is at a higher orbit in the H atom. When it falls to a lower orbit, the energy is emitted as a specific energy and that has a specific wavelength.

Chemistry
The 0.01 M HCl has been diluted to 0.01 x (1 mL/1001 mL) = 9.99E-6 M ....H2O ==> H^+ + OH^- I.........9.99E-6..0 C...........x......x E.......9.99E-6+x..x Kw = (H^)(OH^-) 1E-14 = (9.99E-6+x)(x) Solve the quadratic, add x to 9.99E-6 to find total H^+, then convert to pH.

Chemistry
[mass cool H2O x specific heat H2O x (Tfinal-Tinitial)] + [mass warm H2O x specific heat H2O x (Tfinal-Tinitial)] = 0 mass cool H2O = x look up specific heat H2O Tf cool H2O = 40 Ti cool H2O = 10 mass warm H2O = 300 g Tfinal warm water = 40 Tinitial warm water = 80 Solve for x

Chemistry
First calculate M. 1000 mL x 1.0 g/mL x 0.36 x (1/molar mass HCl) = ? M. Then convert M to pH using pH = -log(H^+).

Chemistry
mols NH4NO3 = grams/molar mass = ? This is approx 180 but that's just an estimate. You need a more accurate answer. Then mols N2 formed = 180 x (2 mols N2/2 mols NH4NO3) = approx 180. mols O2 formed = 180 x (1 mol O2/2 mols NH4NO3) = approx 180/2 = approx 90 mols H2O (gas...

Chemistry
I assume you want the molarity of the Na^+. Also, I assume the temerature of the water is such that the density is 1.00 g/mL. How many mols H2O do we have? That's 256 molecule x (1 mol/6.02E23) = ? How many grams is that? That's ?mols H2O x (18 g/mol) = ? How many mL ...

chemistry
Here are the definitions. Loss of electrons is oxidation. Gain of electrons is reduction. The material oxidized is the reducing agent. The material reduced is the oxidizing agent. 2Fe3+ + Sn ==> 2Fe2+ + Sn2+ You can see that 2Fe^3+ goes from 6+ to 4+ so that is a gain of ...

chemistry
I ASSUME the temperature of the liquid ether is at its boiling point of 34.6 C because you didn't list that; however, in problems of this type, especially since you gave the specific heat of the liquid, that the initial T is less than 34.6 C. q needed to convert liquid ...

Chemistry
dT = Kb*molality You know Kb and dT, solve for m. m = mols sugar/kg solvent You know m and you don't know kg H2O. Can't go further. If you hae that info, then substitute and solve for mols sugar.

Chemistry
dE = hc/wavelength

Chemistry
1. There are 6.02E23 molecules in 1 mol. 2. grams PbO = mols PbO x molar mass PbO

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