Thursday
January 19, 2017

Posts by DrBob222

Total # Posts: 53,868

Chemistry
temperature
December 10, 2016

CHEMISTRY
The volume of H2 depends upon how much Zn you started with. You don't have that in the problem.
December 10, 2016

General
It's well and good.
December 10, 2016

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.
December 10, 2016

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.
December 9, 2016

Chemistry
The HH equation calculates this directly.
December 9, 2016

chemistry
Great but volumes of what? What kind of formic acid solution do you have? What kind of sodium formate solution do you have.
December 9, 2016

College Chem 2
Something is amiss here. The Ksp is the Ksp. You can't have two Ksp values for Ag2CrO4.
December 9, 2016

chemistry
22 servings/box x 90 mg K/serving = ? mg K/box. Convert to g. Convert to mols. mols = grams/atomic mass = ?
December 9, 2016

chemistry
Convert 10 lb to grams. 10 lbs x (?g/lb) = ? grams sugar. Then mols sugar = grams/molar mass = ?
December 9, 2016

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 ...
December 8, 2016

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 ...
December 8, 2016

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...
December 8, 2016

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.
December 8, 2016

chemistry ksp
See my response to your post above.
December 8, 2016

chemistry
See my response to your post above.
December 8, 2016

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...
December 8, 2016

Chemistry
pH = -log(H^+)
December 8, 2016

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 ...
December 8, 2016

chemistry
Note: L is liter. K is kelvin.
December 8, 2016

Chemistry
The ion electron method OR The half reaction method.
December 7, 2016

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 = ?
December 7, 2016

Chemistry
Do you mean, What is the name? Strontium permanganate
December 6, 2016

Chemistry
Use PV = nRT For P use Ptotal = pH2O + pgas.
December 6, 2016

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....
December 6, 2016

chemistry chem check
I don't think so. Isn't it true that the vapor phase is enriched in the more volatile solvent?
December 5, 2016

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 = ?
December 5, 2016

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 = ?
December 5, 2016

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.
December 5, 2016

Chemistry
See your other posts.
December 5, 2016

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
December 5, 2016

Chemistry
PV = nRT R is 0.08206 T in kelvin V in liters. P in atmospheres.
December 5, 2016

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) ...
December 4, 2016

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.
December 3, 2016

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...
December 3, 2016

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 ...
December 3, 2016

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) = ?
December 3, 2016

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 = ?
December 3, 2016

chemistry
I am extremely curious about how the systematic name for NH4Br ties in with the mass of ethane.
December 3, 2016

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.
December 2, 2016

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 ...
December 1, 2016

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...
December 1, 2016

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.
December 1, 2016

chemistry
What are you using to make the HCl?
December 1, 2016

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.
December 1, 2016

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...
December 1, 2016

Chemistry
See your other post.
December 1, 2016

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...
December 1, 2016

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...
December 1, 2016

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 ...
December 1, 2016

Chemistry 30
This will do it. http://www.chemteam.info/Redox/Redox-Rules.html
December 1, 2016

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.
November 30, 2016

Chemistry
I don't see a question here.
November 30, 2016

Chemistry
1 calorie = 4.184 J
November 30, 2016

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.
November 30, 2016

Chemistry
Sorry but we aren't taking the exam.
November 30, 2016

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...
November 30, 2016

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 ...
November 30, 2016

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 ...
November 30, 2016

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.
November 29, 2016

Chemistry
You want to what? Changing 0.150 M NaOH to 0.390 M isn't exactly a dilution.
November 29, 2016

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...
November 29, 2016

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.
November 29, 2016

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...
November 29, 2016

Chemistry
A = ebc As e (molar absorptivity) increases so does A. As b (path length) decreases, so does A.
November 29, 2016

Chemistry (Dilution) Help please?
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!
November 29, 2016

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.
November 29, 2016

chemistry
See your post above.
November 29, 2016

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.
November 29, 2016

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.
November 29, 2016

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.
November 29, 2016

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
November 29, 2016

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^+).
November 29, 2016

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...
November 29, 2016

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 ...
November 29, 2016

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 ...
November 29, 2016

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 ...
November 29, 2016

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.
November 28, 2016

Chemistry
dE = hc/wavelength
November 28, 2016

Chemistry
1. There are 6.02E23 molecules in 1 mol. 2. grams PbO = mols PbO x molar mass PbO
November 28, 2016

Chemistry
Use PV = nRT and solve for n in the flask initially. Then mols N2 added = 2 grams/molar mass N2. Add to find total n (no of mols), and substitute into a new PV = nRT along with the new conditions and solve for the new pressure. Don't forget that T must be in kelvin.
November 28, 2016

Biochemistry
Use Henderson-Hasselbalch equation and solve for (base)/(acid) ratio. That is equation 1. Use pKa2. Then set up (base) + (acid) = 0.2 for equation 2. Solve those simultaneously for (acid) and (base) Convert (acid) to grams NaH2PO4 Convert (base) to grams Na2HPO4. Remember this...
November 28, 2016

@ muhammad--Chemistry
The short answer is that I beg to differ with you but I thank you for your comments; however, if you will read the question again, along with my response, you will see I stated it will not react AND I stated WHY there is no reaction. I see we agree on that. But those four ...
November 28, 2016

Chemistry
no reaction. Rxn occur for only a few reasons. 1. A ppt is formed. none here. 2. A gas is formed. none here. 3. A weak electrolyte is formed. none here. 4. redox rxn. none here.
November 28, 2016

Chemistry
Something tells me you haven't posted all of the problem. You can't get NaOH with an NH3 solution.
November 28, 2016

chemistry
You made a typo. You meant HNO3 and you omitted H2O as one of the products. Cu + HNO3-Cu(NO3)2 + NO + H2O Cu on left has oxidation number 0; on right is +2. N on left is +5 and on right is +2 (in NO) and for the moment ignore the NO3 ion in Cu(NO3)2. So multiply the Cu change ...
November 26, 2016

Chemistry
Adam, I can't begin to decipher your post. No caps, no arrow, no differentiation between reactants and products, no question.
November 25, 2016

Chemisty
Use the coefficients. 18 L CO2 x (7 mols O2/4 mols CO2) = 18 x 7/4 = ? The answer is NOT 22.909.
November 23, 2016

Analytical chemistry
mols B6 = grams B6/molar mass B6 =? Then M B6 = mols B6/L soln = mols B6/0.1L = ? Do same for caffeine. Note: I assume you want concn in molarity; however, not that you could do it in g/L, M, m, N, etc.
November 23, 2016

Chemistry
M HI = mols/L = 4.00/2.00 = 2.00 .......2HI ==> H2 + I2 I ......2.......0....0 C.......-2x.....x....x E.....2-2x......x....x Substitute the E line into Keq expression. You know x = (H2) = 0.4,calculate concns and Keq from that.
November 23, 2016

chemistry
Technically you can't do this without knowing the reaction. But USUALLY, when the reaction isn't know, one assume that one takes the molarity and multiplies by the total positive or negative charge. mols Na2CO3 = grams/molar mass. M = mols/L N = M x 2.
November 23, 2016

chemistry
hydrated
November 23, 2016

Chemistry
Six problems in here. What do you know about any of these?
November 22, 2016

chemistry
Actually, this can't be answered because you didn't identify the numbers; however, I have assumed the first number is n, the second is l and the third and fourth are ms. If that isn't correct ignore the following. i no. Can't have two ms of 1/2 ii no, Can't...
November 22, 2016

AP Chem
This is a limiting reagent (LR) problem and you know that because amounts are given for BOTH reactants. CaCl2 + 2AgNO3 ==> Ca(NO3)2 + 2AgCl mols CaCl2 = M x L = ? = approx 0.001 but you need to confirm. mol AgNO3 = M x L = approx 0.001 x 1 = 0.001. You see the mols AgCl are...
November 21, 2016

Chemistry
I would use specific heat water as 1 cal/g*C and not do the Joule to calories conversion. q = cal = mass H2O x specific heat H2O x (Tfinal-Tinitial). If you want to use 4.182 J/g*C, the do that and convert to cal by 1 cal = 4.182 J.
November 21, 2016

Chemistry
15 mg/mL x # mL = 12 mg Solve for # mL.
November 21, 2016

chemistry
mass = volume x density You have the mass and density, substitute and solve for volume.
November 21, 2016

Chemistry
I think you just made a a couple of typos. You left no space between Sn+2Ag and you omitted the 2Ag on the right. Sn + 2Ag ==> An^2+ + 2Ag
November 20, 2016

chemistry
If you intended KClO2 (and not KClO3), here is he scoop. K is +1. It's ALWAYS +1 because it's in group I of the periodic table. Cl is +3 on the left (remember all compounds are 0 so K + Cl + 2O = 0; therefore, 1 + ? + 2*-2 = 0. That makes Cl +3) and O is -2 for EACH ...
November 20, 2016

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