Monday
October 20, 2014

Posts by drbob222


Total # Posts: 44,571

chemistry
1.06 g CaCO3 x (atomic mass Ca/molar mass CaCO3) = ? g Ca %Ca = (g Ca/mass pill)*100 = ?
October 5, 2014

Chemistry
Both of your conjectures are correct but the second one doesn't answer the question. Your first educated guess is correct; the MAX temperature of the evaporating dish MUST be 100 C because that's the boiling point of water. The evaporating dish CAN'T get hotter ...
October 5, 2014

chemistry
Zn + 2HCl ==> H2 + ZnCl2 mols Zn = grams/molar mass Using the coefficients in the balanced equation, convert mols Zn to mols ZnCl2. Now convert mols ZnCl2 to grams. g = mols x molar mass.
October 5, 2014

Chemistry Help! (Rydberg Equation)
1/wavelength = R(1/n^2 - 1/n^2) where the two n symbols are n1 for the first one and n2 for the second. So the shortest wavelength (the most energy) will come when an electron falls from the outside most energy level to the inner most energy level. Therefore, plug in n1 = 1 ...
October 5, 2014

CHEM, HELP!!
1. E = hc/wavelength. Solve for wavelength in meters and convert to nm. 2. By the orbit/shell/energy level (take your pick) in which it is located.
October 5, 2014

Chemistry
The easiest way to do 2 is to calculate the energy of each wavelength listed. For #2, wavelength = h/mv Of course you must convert 24.0 mi/h to m/s. The easy way to do that is to type in google "24.9 miles/hour to m/s" without the parentheses and hit the enter key.
October 5, 2014

chem
The equation is balanced. mols Cl2 = 360/70.9 = ? mols AlCl3 = ?mols Cl2 x (2/3) = ? I think the 1/53.96, whatever that is, is the problem.
October 5, 2014

chem
What's the 1/53.96 term?
October 5, 2014

science
http://hyperphysics.phy-astr.gsu.edu/hbase/biology/mitochondria.html
October 5, 2014

science
http://www.bio.umass.edu/biology/conn.river/calvin.html
October 5, 2014

CHEMISTRY
You do all of these with the factors to convert from any material to any other material. For example, to convert 4 mol N2H4 to mols N2O4 needed it is 4 mols N2H4 x (1 mol N2O4/2 mols N2H4) = 4*1/2 = ? 4 mols N2H4 to mols H2O produced is 4 mols N2H4 x (4 mol H2O/2 mols N2H4) = ...
October 5, 2014

Basic Chemical Engineering
Take a look at this. I don't know much about dyeing but this looks like flow diagrams.
October 5, 2014

Basic Chemical Engineering
Here are several but I didn't look at any of them. Take your pick. https://www.google.com/search?q=textile+dyeing&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:en-US:official&client=firefox-a&channel=sb
October 5, 2014

chem
The long way: 14 mols A and 14 mols B will produce 14*0.50 = 7 mols C. Then C will produce 7*0.9 = 6.3 mols D. The short way: overall yield is 0.5*0.9 = 0.45 or 45%. 14*0.45 = 6.3
October 5, 2014

Chem Help Please!
What about placing a relatively large amount of F in the same flask? That way the reverse F+D ==> C + D reaction is enabled and by Le Chatelier's Principal the decomposition of C should be minimized.
October 5, 2014

Chem Urgent Help Please!!!!
The answer to #1 depends upon how you define large scale. Chromatography has been used for prep purposes; as far as I know mg to g quantities can be prepared this way. #2. In theory you could dissolve the material in some solvent and subject both to chromatography. See if the ...
October 5, 2014

Chemistry
What in the world is 22.6 til-%? and 8.6 til=%
October 5, 2014

chemistry
What reaction? The most plausible answer for a question that leaves me with questions is dH rxn = -36.1 kJ since it is exothermic.
October 5, 2014

chemistry
basic solution. Pb + 2OH^- ==> Pb(OH)2 + 2e O2 + 4e + 2H2O ==> 2OH^- + 2OH^- Multiply equation 1 by 2 and equation 2 by 1 and add. Cancel any ions/molecules common to both sides.
October 5, 2014

Chemistry
6.42E22 atoms (I guess) x (1 dozen/12)= a huge number.
October 4, 2014

Chemistry
4.25% NaOH by mass means 4.25 g NaOH/100 g solution. In 2000 g of the solution we will have 4.25 x (2000/100) =
October 4, 2014

chem
Work it out. mols Cl2 = grams/molar mass = ? mols = ?mols Cl2 x (2 mols AlCl3/3 mols Cl2) = ? mols Cl2 x 2/3 = ? g AlCl3 = mols AlCl3 x molar mass AlCl3. my opinion? I think so.
October 4, 2014

chem
See your other post.
October 4, 2014

chemistry
OH is one.
October 4, 2014

Chemistry
Didn't I answer this earlier? You have 0.2M KI and it has been diluted. So the initial concn is 0.2 x [(25 mL/(25 + 48+1+1+25)] You have 0.4M Na2S2O3 so the initial concn is (before any reaction) is 0.4 x (1 mL/total ML)
October 4, 2014

chem
How many mols is 1 g NaCl? That's mols = grams/molar mass Then 1 mol contains 6.02E23 molecules.
October 4, 2014

chem
All of the stoichiometry problem are worked alike. 1. Write and balanced equation which you have. 2. Convert 30 g H2O to mols. mol = grams/molar mass 3. Using the coefficients in the balanced equation, convert mols H2O to mols or the product. 4. Now convert mols product to ...
October 4, 2014

chemistry
AgCl is very sparingly soluble in water; NaNO3 is soluble in water. Look in your text/notes for properties of solids, liquids, and gases.
October 4, 2014

chemistry
See your post above.
October 4, 2014

Chemistry
https://www.google.com/search?q=lewis+structure+CCl4&client=firefox-a&hs=fWq&rls=org.mozilla:en-US:official&channel=sb&tbm=isch&imgil=Zw725nL4iuBo8M%253A%253Bbx1IGbF8BPqTgM%253Bhttp%25253A%25252F%25252Fwww.tutor-homework.com%25252FChemistry_Help%25252FMolecular_Geometry%...
October 4, 2014

chemistry
This is a limiting reagent (LR) problem. Determine the limiting reagent. Use the coefficients in the balanced equation to convert mols of the LR to mols of the product. Then convert mols of the product to grams by = mols x molar mass.
October 4, 2014

chemistry
mols CO2 = 1.5 L x (1 mol/22.4 L) = ? Then mols O is twice that. 1 mol of anything contains 6.0E23 of that anything.
October 4, 2014

chemistry
4X + 3O2 ==> 2X2O3 mols O2 = 7.2/32 = about 0.225 mols X = 0.225 x 4/3 = about o.9 mols X = grams/molar mass. You know g and mols, solve for molar mass
October 4, 2014

chem.1
(P1V1/T1) = (P2V2/T2) Don't forget T must be in kelvin.
October 4, 2014

Chemistry
mols KI = mols I^- = M x L = ? Then (I^-) = mols/L of solution. Total L = 25 + 48 + 1 + 1 + 25
October 4, 2014

chemistry
2C2H6 + 7O2 ==> 4CO2 + 6H2O b. dHrxn = (n*dHf products) - (n*dHf reactants) c. q = dHrxn from b x (265g/2*molar mass C2H6) d.e.f. Follow a,b,c steps. Post your work if you get stuck.
October 3, 2014

chemistry
mols Br^- from HBr = M x L = ? mols Br^- from FeBr2 = M x L x 2 = ? M Br^- in solution = (total mols/total L)
October 3, 2014

chemistry
You do the math and s.f. This is a limiting reagent (LR) problem. You know that because amounts are given for BOTH of the reactants. 1.Write and balance the equation. CH4 + 2O2 ==> CO2 + 2H2O 2a. mols CH4 = grams/molar mass = ? 2b. mols O2 = grams/molar mass = ? 3a. Using ...
October 3, 2014

chemistry
mols Hg = 4.2E21/6.02E23 = ? grams Hg = mols x atomic mass = ? Since mass = volume x density that can be rearranged to volume = mass/density. Substitute mass from above and density in the problem and solve for mL as the volume and convert to L.
October 3, 2014

chemistry
You probably meant AgNO3 and (NH4)2 SO4 Ag^+ silver ion is right. NO3^- is nitrate ion. NH4^+ is the ammonium ion SO4^2- is the sulfate ion. Ag2SO4 may b formed if you have aqueous solutions that are mixed. Ag2SO4 is limited solubility so it may or may not precipitate. It all ...
October 3, 2014

chemistry
You might determine the density. You might try solubility in certain solvents. I will leave you to write how that could be done.
October 3, 2014

chemistry
This is a limiting reagent (LR) problem. 1. Write and balance the equation. You have that. 2a. mols TiO2 = grams/molar mass = ? 2b. mols Cl2 = grams/molar mass = ? 3a. Using the coefficients in the balanced equation, convert mols TiO2 to mols of the product. 3b. Do the same ...
October 3, 2014

Chemistry
See your post above.
October 3, 2014

Chemistry
How much of this do you know how to do? Surely you aren't looking for someone to do your entire prelab workup.
October 3, 2014

Chemistry
What have you come up with so far. I don't want to duplicate any of them.
October 3, 2014

oops--Chemistry
Sorry but I made an error above in the conversions and the 5:1:3 IS right after all. mols CO2 = g/molar mass = 2.2/44 = 0.05. I convert to grams C which isn't right. mols C is the same as mols CO2; therefore, we have mols C = 0.05 mols N = 0.01 mols O = 0.03 and the ratio ...
October 3, 2014

Chemistry
2g CO2 x (atomic mass C/molarmass CO2) = approx 0.6 mols C 6.02E21/6.02E23 = 0.01 mols N 0.03 mols O but that isn't 5:1:3 but more like 60:1:3
October 3, 2014

Chemistry
You are right. 1/8 + 1 is not 1/9.
October 3, 2014

Chemistry
1/8 + 1 = 1/9? I don't think so. 1/8 + 1 = 1/8 + 8/8 = 9/8 :-0
October 3, 2014

chemistry
an acid base indicator is ONE substance; universal indicators are a mixture.
October 3, 2014

6TH GRADE MATH
How much did Tony save? That's 2.50/hr x 18.2 hrs = $45.50 The games cost 35.75 each 35.75/game x # games = 45.50 # games = 45.50/35.75 = 1.27 games so Tony can buy one (1) game and have some money left over.
October 2, 2014

Chemistry
How much of this do you already know how to do. I don't need to work those parts you know. If you want to post your work I'll look at it up to the point you don't know how to proceed.
October 2, 2014

chemistry
Note that what I said to type into Google won't do it because I typed in cm/sec to mph and you want feet/hr. Do all of them by dimensional analysis. I don't know all of the conversion factor but I can get there from what I know. Sometimes it just takes a while. You ca ...
October 2, 2014

chemistry
The easy way to do it is to type into Google the following: 3E10 cm/sec to mph and hit the enter button.
October 2, 2014

Science
Gravity makes a huge difference in calculating weight; however, the mass doesn't change. As for turning corners and stopping etc: Momentum is m*v. the m did not change so momentum still rules.
October 2, 2014

Chemistry
4Al + 3O2 ==> 2Al2O3 kilomols Al2O3 = kg/molar mass = kmols needed at 100%. Call that ? kmol needed at 89.4% = ?.0.894 Convert kmols Al2O3 to kmols Al using the coefficients in the balanced equation. Now convert kmols to grams. kmols x atomic mass = kg Al.
October 2, 2014

chemistry
Do you intend 2.6 Mg to mean 2.6 mg (meaning milligrams)? mols Mg = grams/molar mass Using the coefficients in the balanced equation, convert mols Al to mols Na3AlF6. Then mass cryolite = mols x molar mass = ? Here is how you do the mols conversion. ?mols Al x (2 mols Al2O3/4 ...
October 2, 2014

Chemistry
This is a limiting regent (LR) problem. You know that when amounts are given for BOTH reactants. mols AgNO3 = M x L = ? mols K2C4O4 = M x L = ? Using the coefficients in the balanced equation convert mols AgNO3 to mols Ag2CrO4 Do the same for mols K2CrO4 to mols Ag2CrO4 It is ...
October 2, 2014

Chemistry
I agree
October 2, 2014

Chemistry
mols CCl4 = grams/molar mass = ? mols SbF3 = grams/molar mass = ? Convert mols CCl4 to mols SbF3. If the SbF3 mols is greater than CCl4 is the limiting reagent. If not SbF3 is the LR. Post your work if you get stuck.
October 2, 2014

Chemistry
[mass ice x heat fusion]+[mass melted ice x specific heat ice x (Tfinal-Tinitial)] + [mass warm water x specific heat H2O x (Tfinal-Tinitial)] = 0 Substitute the numbers and solve for Tf.
October 2, 2014

chemistry
I've ignored the numbers since they seem to be in stoichiometric quantities and no excess of either reagent is left. magnesium metal plus hydrochloric acid yields magnesium chloride + hydrogen. Mg + HCl ==> MgCl2 + H2 Mg + 2HCl ==> MgCl2 + H2 Mg + 2HCl ==> H2 + MgCl2
October 2, 2014

Chemistry
C3H8 is propane, right. C3H6O is not acetone propane. What I drew for you is propene-1-ol
October 2, 2014

Chemistry
Would that be CH3CH=CHOH? 1 double 6 single no lone pairs. Check that.
October 2, 2014

chemistry, biotechnology
If molar extinction coefficient is 1.4 A units/mg then wouldn't c come out in mg?. But that confuses me too. The usual unit is M which is mols/L and this unit you quote is just mg. Yes you should make a correction for dilution. So whatever c is the original solution will ...
October 2, 2014

chemistry
A is right. C is right. I don't agree with B. If dE = q + w and q is zero as you answered in C and work is done as you answered in A, how can dE be zero as you answered in B.
October 2, 2014

Chemistry
gain of heat on melting ice + gain of heat on raising T from 0C to Tfinal + heat lost by 120 g H2O at 70.5C to Tfinal = 0 Each [ ] gives the three processes above. [mass ice x heat fusin] + [mass melted ice x specific heat H2O x (Tfinal-Tinitial)] + [mass warm water x specific...
October 2, 2014

Math - Please Check My Answer - Probably Last One!
D is correct.
October 2, 2014

chemistry
1. It would help if we knew what you were recrystallizing. 2. This question makes no sense at all. First they don't melt then they do.
October 2, 2014

chemistry
A = ebc 0.427 = 6130*1*c c in the 10 mL flask = ? M. c in c in 5.00 mL flask = 10x that = ? mols 5.00 flask = M x L g 5.00 flask = mols x molar mass = ? mass% in sample = (g in 5.00 flask/mass sample)*100 =? mass% =
October 2, 2014

chemistry
What's your problem here Mathew? You calculate mols H^+ and mols OH and see where you stand.
October 2, 2014

ph
pH = -log(H^+) BUT I don't see that this has anything to do with your post.
October 2, 2014

chemistry
No it isn't. Go back and look at that work I did for you last night. You have smatterings right but you've incorrectly interpreted what I wrote in several places. mols HCl = 53/36.5 = ? mols NaOH = same as mols HCl because of the 1:1 ratio. g NaOH = mols NaOH x molar ...
October 2, 2014

chemistry
10% HCl means 10g HCl/100 mL so you spilled 10 x 530/100 = 53 g mols HCl = grams/molar mass = approx 1,5 but you need a more accurate answer than that. NaOH + HCl ==> NaCl + H2O You have approx 1.5 mols HCl so you ned approx 1.5 mols NaOH. mols NaOH = gram/molar mass. You ...
October 2, 2014

Chemistry 104
Mg^2+ + NH3 + 7H2O + PO4^3- ==> MgNH4PO4.6H2O + OH^- mols PO4^3- = M x L = 1.0 x 0.010 = 0.010 mols MgNH4PO4.6H2O = 0.010 g MgNH4PO4.6H2O = mols x molar mass = 0.010 x 245.41 = ? This is the theoretical yield. %yield = (2.2034/?)*100 = ???
October 2, 2014

chem
No. As far as I know the Lewis Structure must be drawn. I would look at IO3^- as the culprit.
October 2, 2014

Chenistry
For this problem you do not need pKa1.(Note that pK1 has H3PO4 in it and that isn't one of the ingredients.) I obtained the same answer and I did it with mols ONLY (which doesn't involve dilution and I like that way) but I also did it with molarity and took into ...
October 2, 2014

Chemistry 30
And your problem is?? For a). HNO2(aq) + H2O(l) ↔ H3O^+(aq) + NO2^-(aq) Now you look at thwich has more H and which has fewer. HNO2 is the acid NO2^- on the right is the conjugate base. H2O on the left is the base. H3O^+ on the right is the conjugate acid.
October 2, 2014

Chemistry 30
2NaOH + H2SO4 ==> Na2SO4 + 2H2O mols NaOH = M x L = approx 0.01 mols H2SO4 = 1/2 that from the coefficients in the balanced equation. M H2SO4 = mols H2SO4/L H2SO4 = ?
October 2, 2014

Chem 400
.........I2 + Cl2 ==> IxCly + xs Cl2 .....0.678g..0.851g....0..........x 2Na + Cl2 --> 2NaCl You know NaCl weighed 0.450. Convert that to grams Cl2 and that is the excess amount. Subtract that from the 0.851 g there initially. Now you have 0.678 g I2 and I obtained 0.578...
October 1, 2014

chemistry
CuO + H2SO4 ==> CuSO4 + H2O You want 0.025 mols CuSO4 so you must have start with 0.025 mols H2SO4 (from the coefficients in the balanced equation). Then M H2SO4 = mols H2SO4/L H2SO4. You know M and mols, solve for L and convert to mL. I have no idea what "allowing for...
October 1, 2014

chem
I can't help here but I hope you received my correction last night on the 2-ethylhexene becoming 2-methylheptane.
October 1, 2014

Chemistry
Fe + 2HCl ==> FeCl2 + H2 mols Fe = grams/molar mass = approx 0,06 but you need a better answer than that. Convert to mols HCl which will be twice mols Fe and you get that from the coefficients in the balanced equation. Then M HCl = mols HCl/L HCl. You have M and mols, solve...
October 1, 2014

Chemimstry
So you have approx 0.018 mols Br2. That means twice that for mols XBr so 0.036. Since mol = g/molar mass then molar mass = g/mol = 5.20/0.036 = approx 144. Subtract atomic mass Br from that to find the atomic mass of X and identify from the periodic table. I would look in the ...
October 1, 2014

Chem
g CO2 = 3.626 g H2O = 0.9897 Plan. 1. Convert g CO2 to g C. 2. Convert g H2O to g H. 3. Find g O in the C,H,O compound from 3.297g total - g C - g H = g O. mols CO2 = g/molar mass = 0.0842 and that x 12 = 0.9889 g C g H = 0.9897*2/18 = 0.1099 g O = 2.198 Convert g each to mols...
October 1, 2014

Chemistry
How much hexane was burned? How much O2 was used?
October 1, 2014

chemistry
0.88 what? g/mL; lb/cubic foot; kg/L; tons/gallon? I'll assume you mean 0.88 g/mL. 0.75 lb x 453.6 g/lb = z grams Then 0.88 g/mL x ?mL = z grams from above. Solve for ?mL.
October 1, 2014

Chemistry/Math
It would be great if you would write the entire problem and let us help. Your 0.01403 g doesn't tell us what? Is that the mass CaCO3 or the mass of the sample. And somehow H2O got into the problem. Do you want ppm CaCO3 dissolved in the water?
October 1, 2014

Chemistry/Math
Anyone pick a number and be right.
October 1, 2014

Science
If you mean a changing definition of a CHEMICAL element I must say I didn't know it had changed. I've been using the same definition for the last 70 or more years. I assume you do not mean element as in an element of story or a heating element or something like that.
October 1, 2014

chemistry
Dissolve in water, filter, the AgNO3 is in the aqueous layer, the AgCl is on the filter paper, evaporate the solvent to recover the AgNO3.
October 1, 2014

matter and energy
You didn't provide what you used for the melting point or the heat fusion or the specific heat so I don't know it that is right or not. Using 327.5 for m.p. and 22.4 J/g for heat fusion and 0.16 J/g*C, I obtained 350 Joules.
October 1, 2014

matter and energy
Note the correct spelling of celsius. The melting point of Pb is 327.5 C. q added to raise temperature from 30 C to 327.5C is q1 = mass Pb x specific heat Pb x delta T. You will need to look up the specific heat Pb. delta T is 327.5-30. q2 = heat needed to melt Pb at 327.5 C ...
October 1, 2014

chemistry
mols KCl = grams/molar mass = approx 0.32 g but you need a more exact number for this and all of the estimates that follow. M KCl = 0.32/0.5L = about 0.64 Then mL x M = mL x M 27.3 x 0.64 = 45.0 x M AgNO3 Solve for M AgNO3. The mL x M = mL x M works because the equation is 1:1...
October 1, 2014

CHM 300
pKa = -log Ka
October 1, 2014

chemistry
I don't see a question here.
October 1, 2014

Science
True, the nitride ion is N^3-. False, the Stock system shows the charge on the positive ion.
October 1, 2014

Chem (general)
Your value of 2.19 g Ag2S appears to be right. If you can calculate mols Ag2S why not use the same reasoning to calculate mols H2S used. 2AgNO3 + H2S ==> Ag2S + 2HNO3 mols AgNO3 = 3.00/170 = approx 0.00833 Convert mols AgNO3 used to mols H2S used the same way. 0.00833 mols ...
October 1, 2014

Chemistry
See your later post above.
October 1, 2014

chemistry
HNO3 + xBOH ==> xH2O + B(NO3)x millimols HNO3 = 12 mL x 0.150M = 1.8 millimols base = 30 x 0.03 = 0.9. The titration step shows us that we take twice as much HNO3 as the base; therefore, the base must contain two OH groups; therefore, I would look at Mg(OH)2, Ba(OH)2, Sr(OH...
October 1, 2014

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