Wednesday
November 26, 2014

Posts by DrBob222


Total # Posts: 45,630

Chemistry (Equilibrium)
You went wrong on the C step and E step. (HBr) = mols/L = 0.5/1 L = 0.5M which you hvave correctly. ..............2HBr <==> H2 + Br2 I..............0.5.......0....0 C..............-2x.......x....x E............0.5-2x......x....x The problem states that (Br2) is 0.0855 (...
November 13, 2014

chemistry
I don't get it. rastor? I assume molar mass is 46. You don't list grams water. Is that density of 1.86? 1.86 WHAT units? That isn't the density of ethanol. What about just reposting the question.
November 13, 2014

Equilibrium
Yes and no. 3.9 is the correct answer and I would not round up to 4 since you are allowed two s.f. in the answer. But you choose 4.0 as the answer since that's the closest of the choices.
November 13, 2014

Equilibrium
Looks like the second set up is correct but you punched in the wrong numbers on your calculator. I get about 4 or close to that.
November 13, 2014

Chemistry
It makes it easier if you don't change screen names. Use the HH equation as in in the formic acid/sodium formate buffer There is one difference. In the formic/formate buffer you have the components separated. In this one you must combine the acid and base, calculate how ...
November 13, 2014

Chemistry
Use the Henderson-Hasselbalch equation. Convert Ka to pKa. 10.0 mL x 1.0 M sodium format is 10 millimols base. 20.0 mL x 1.00 M formic acid is 20 mmols of the acid. Plug and chug.
November 13, 2014

sixth grade math
12/15 is a fraction already. Both 12 and 15 are divisible by 3 to make it 4/5. As a decimal divide 4 by 5 to obtain 0.80 and multiply that by 100 to obtain 80%.
November 12, 2014

Chemistry (Equilibrium)
I have removed the (g) designation in order to get all of this on one line. ..........H20 + CO <==> H2 + CO2 I.........5.0...4.0.....0.....0 C.........-x.....-x.....x.....x. E.......................2......... If 2.0 mols H2 are present at equilbrium then x must be 2.0 ...
November 12, 2014

chemistry
mols solute = M x L = ? Calculate each and the highest wins.
November 12, 2014

chemistry
It was 0.1 in the V1 (whatever volume that is) and you diluted it to 250 sothe new concn is It's 0.1 x (V1/250) = ? I don't know why you wrote it was placed in a V2.0 volumetric flask. If it were brought to 250.0 mL I would assume it was placed in a 250 mL flask.
November 12, 2014

chemistry
You just do the reverse of the previous problem. How many mols do you need? That's M x L = ? Then mols = grams/molar mass. You have mols and molar mass, calculate grams.
November 12, 2014

chemistry
mols CaCl2 = grams/molar mass M CaCl2 solution = mols CaCl2/L solution.
November 12, 2014

Chemistry 11
I'm glad you asked that question. All of the work you have done is exactly right BUT you haven't worked the problem. You worked a similar problem but not the one stated. % Na FROM THE DATA IN THE PROBLEM is (g Na/total g)*100 = (13.45/24.34)*100 = 55.26% Then % Cl = ...
November 12, 2014

Chemistry
That's right. You start with 2.0 (intial), take away -2x (the change) and end up with 2-2x (equilibrium).
November 12, 2014

Chemistry
To do the equilibrium sign you simply use the < the > and == like this <==>. Most of use just use a straight arrow, either --> or ==> and let it go. (HI) = mols/L = 4.0/2.00 = 2.00M Set up an ICE chart as below: ........2HI ==> H2 + I2 I.......2.0M.....0...
November 12, 2014

Chemistry
Cl2(g) + 2NaBr(aq) ==> Br2(l) + 2NaCl The second part of the question. You "bubble in" (I guess it means mark in) E which is Br2 and D which is NaCl.
November 12, 2014

chemistry
Three equations work almost all of these. In general here they are. Fit them to your problem. WITHIN a phase (all liquid, all steam, all ice) use q = mass of the phase x specific heat of the phase x (Tfinal-Tinital) At a phase change (example melting point) use q = mass of the...
November 12, 2014

chemistry
mass = volume x density. You will need to look up the density. You can look it up on Google. I'm not sure I remember it right but I think it is 0.789 g/mL.
November 12, 2014

Chemistry
Volume = mass/density volume Fe = 52.3/7.87 = ? New volume water is the sum of initial volume + volume Fe. Note that two objects can't occupy the same volume at the same time; therefore, the Fe must displace the water by the iron's volume.
November 12, 2014

chemistry
You can do a ratio/proportion like this: (g/atoms) = (g/atoms) (28.09g/6.02E23atoms) = (x g/1.06E25 atom) and solve for x. OR you can remember that 1 mol of atoms contains 6.02E23 atoms so how many mols do you have? That's 1.06E25/6.02E23 = ? 1 mol has a mass of 28.09 g so...
November 12, 2014

Chemistry
See your post above.
November 12, 2014

chemistry
2NaOH + H2SO4 ==>Na2SO4 + 2H2O 1. The NaOH is the titrant; H2SO4 is the analyte. 2. mols NaOH = M x L mols H2SO4 = 1/2 mols NaOH (Look at the coefficients in the balanced equation.) 3. M H2SO4 = mols H2SO4/L H2SO4 4. g H2SO4 = mols H2SO4 x molar mass H2SO4 5. mass S = mass ...
November 12, 2014

chemistry
2K + 2H2O ==> 2KOH + H2
November 12, 2014

chemistry
See your post above.
November 12, 2014

Chemistry
Zn(OH)42-
November 11, 2014

Chemistry
Ag is 2 Cd is 4 (en) is 2 + 2Br = 4.
November 11, 2014

AP Chem
OK. We'll take your number of 0.116M for the solubility of KBr in a saturated solution. I don't know what value you used for Ksp but I used one from the web and ended up with 0.0118M so the answers are pretty close. You probably used a value for Ksp close to what I ...
November 11, 2014

Chemistry
Use PV = nRT T will have units of kelvin
November 11, 2014

chemistry
ln(k2/k1) = A*Ea*(1/T1 - /T2)/RT Substitute and solve for k2. Remember to convert kJ to J.
November 11, 2014

chemistry
This is a limiting reagent (LR) problem and you know that because amounts are given for BOTH reactants. Pb(NO3)2 + 2KIO3 ==> Pb(IO3)2 + 2KNO3 mols Pb(NO3)2 = M x L = ? mols KIO3 = M x L = ? Using the coefficients in the balanced equation, convert mols Pb(NO3)2 to mols Pb(...
November 11, 2014

Chem
Yes. n, l, and mL are the same BECAUSE one of the electrons is ms = +1/2 and the other one is ms = -1/2.
November 11, 2014

Ochem
How would you like for us to help you with this assignment?
November 11, 2014

Chemistry
See your original post.
November 11, 2014

Chemistry
Since can't draw diagrams on this forum here is the best I can do. Below are the electrons changes; you can draw the lines/arrows and whatever else you need to do but this is the heart of the problem. C2H5OH. Both carbons are -4 total. CH3COOH. Both carbons are zero each(...
November 11, 2014

chemistry
The pressure inside the container will be 100 mm Hg when equilibrium is reached. Use PV = nRT and solve for n, then n = grams/molar mass to solve for grams. Compare grams in the vapor with grams of the liquid to know if all will have evaporated.
November 11, 2014

chemistry
You didn't give the specific heat of the metal but see this post and response. http://www.jiskha.com/display.cgi?id=1415735118
November 11, 2014

chem
This is a limiting reagent (LR) problem and you know that because amounts are given for BOTH reactants. mols Ba(NO3)2 = M x L = ? mols Na2SO4 = M x L = ? Using the coefficients in the balanced equation, convert mols Ba(NO3)2 to mols BaSO4. Do the same for mols Na2SO4 to mols ...
November 11, 2014

Chem 130
Look at the limiting reagent problem you posted just above. This is worked the same way. Your equation looks ok.
November 11, 2014

Chemistry
Frankly I don't know how to answer this question. I don't know if it is a trick question or not. Here is my problem. The equivalence point is the theoretical point at which the acid just neutralizes the base. The end point (different from the equivalence point) is the ...
November 11, 2014

Chemistry
Tell me your problem here. Do you know how to write the Keq expression? It tells you in the problem what Keq is.
November 11, 2014

Chemistry
Are those the equilibrium concentrations? I assume they are. Writ the Keq expression, substitute those numbers and solve for Keq. Post your work if you get stuck.
November 11, 2014

Chemistry
Note the correct spelling of celsius. You have half of it but not the other half. The metal is heated to 95 C then placed in the water. Then heat lost by the metal + heat gained by the water = 0 heat lost by metal is q = mass metal x specific heat metal x (Tfinal-Tinitial) ...
November 11, 2014

Science-Chemistry
I suggest you look in your text or notes and if that is not an option look for the tables on Google.
November 11, 2014

Chem 2 help
http://en.wikipedia.org/wiki/Half-life See the above for q 1 and 2. For q 3, depending upon the age, the method may be used. Here is another link that describes the other "dating" methods starting with paragraph 3 then see the table just below that with a list of the...
November 11, 2014

science
Do you know the proportions (average I guess) of each in the human body.
November 10, 2014

science
q = 1673 J = mass H2O x specific heat H2O x delta T. You will need to look up the specific heat of liquid water. Delta T is 2.0 C and mass will come out i grams if specific heat is substituted in joules/g*C.
November 10, 2014

incomplete--chemistry
You didn't post a question AND you didn't post the total amount of solution for each nor the amount of each solution.
November 10, 2014

science
q = mass graphite x specific heat graphite x (Tfinal-Tinitial) q = 350 J mass graphite is 33.0 g You will need to look up the specific heat graphite. delta T is Tfinal-Tinitial and you are to solve for delta T.
November 10, 2014

science
q = mass H2O x specific heat H2O x (Tfinal-Tinitial)
November 10, 2014

History (1 word)
Jane, I apologize but the devil made me do it. I think the word you're looking for is "nullify". Here are a couple of links to read. http://en.wikipedia.org/wiki/Nullification_%28U.S._Constitution%29 http://www.cato.org/publications/commentary/yes-states-can-...
November 10, 2014

History (1 word)
stupid?
November 10, 2014

Chemistry
35.0 what of NaCl? What is the total volume. If you don't know that then what is the density of the solution. Why? Because NaCl + 125 mL H2O is MORE than 125 mL volume.
November 10, 2014

Chemistry
M = mols/L. 12.0 M = mols/10.5L Solve for mols.
November 10, 2014

Intro to Chemistry
mols CaCO3 = grams/molar mass = ? mols HCl = grams/molar mass = ? Using the coefficients in the balanced equation, convert mols CaCO3 to mols CaCl2. Do the same to convert mols HCl to mols CaCl2. It is likely that the two values will not agree which means one of them is not ...
November 10, 2014

Intro to Chemistry
This is a limiting reagent (LR) problem; you know that because amounts are given for BOTH reactants. mols H2O2 = grams/molar mass = ? mols N2H4 = grams/molar mass = ? Using the coefficients in the balanced equation, convert mols H2O2 to mols N2. Do the same to convert mols ...
November 10, 2014

chemistry
The molecular weight of the compound would be some kind of a weighted average between the compound and the air that was left.
November 10, 2014

Science
https://www.google.com/search?q=define+ecosystem&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:en-US:official&client=firefox-a&channel=sb
November 10, 2014

Quotes
http://www.brainyquote.com/quotes/keywords/find.html
November 10, 2014

Chemistry
(P1V1/T1) = (P2V2/T2) Remember T must be in kelvin.
November 10, 2014

no statements--science

November 10, 2014

statistics help needed--Dine

November 10, 2014

Science
high, low, diffusion
November 10, 2014

Science
http://www.sciencelearn.org.nz/Science-Stories/Earthworms/Characteristics-of-living-things
November 10, 2014

Science
Generally enzymes are the catalysts for specific reactions in a living organism. More specifically they lower the activation energy for a chemical reaction.
November 10, 2014

chemistry
Here is one form of the dilution equation. mL1 x M1 = mL2 x M2 ?mL1 x 5.50M = 350.0 x 0.500M ?mL1 = ?
November 10, 2014

chemistry
That doesn't help. What you posted is your answer. What I need is your WORK. I need to see your work to find your error; however, I think I see what you did (with a little help from my crystal ball). You followed half of my instructions and quit. You need to look at the ...
November 10, 2014

chemistry
I can't guess what you've done. Post your work and I'll find the error. My first guess is that you didn't convert 750 mL to 0.750 L.
November 10, 2014

chemistry
How many mols do you want? That's mols = M x L = ? Then mols = grams/molar mass. You know molar mass and mols, solve for grams.
November 10, 2014

chemistry
A good conversion factor to remember when dealing with ppm and ppb is 1 ppm = 1 mg/L so if you have 355 ug/L that is 0.355 mg/L = 0.355 ppm.
November 10, 2014

chemistry
q = mass H2O x specific heat H2O x (Tfinal-Tinitial)
November 10, 2014

Science
https://answers.yahoo.com/question/index?qid=20090422184611AAnbEvc http://www.youtube.com/watch?v=cIfpKL0brwQ
November 10, 2014

Science
what kind of impacts?
November 10, 2014

Science
Without you writing everything in section 8.1 we don't have any idea what the central theme is.
November 10, 2014

Science
The only statement you've posted is false.
November 10, 2014

no statements---Science

November 10, 2014

chemistry
mL1 x M1 = mL2 x M2 ? mL1 x 4.50 = 400 mL x 0.500 ? mL1 = ?
November 10, 2014

chemistry
How many mols do you want? That's M x L = ? Then mols = grams/molar mass. You know mols and molar mass, solve for grams.
November 10, 2014

chemistry
mols = M x L = ?
November 10, 2014

Science
2HgO ==> 2Hg + O2 mols HgO = grams/molar mass = ? Using the coefficients in the balanced equation, convert mols HgO to mols O2. Now convert mols O2 to whatever unit you want. The post doesn't say. If grams, then grams O2 = mols O2 x molar mass O2. If volume at STP, then...
November 10, 2014

Chemistry
Increased pressure, decreased volume; more moles of the gas, decreased T
November 10, 2014

Chemistry
dGo = -RTlnK 8600 J = -8.314*298*K Solve for K, then K = pH2O This gives pH2O in atmospheres; that x 760 converts to mm Hg. I get about 24 mm or so but that's approximate.
November 10, 2014

Science
Because no more KNO3 will dissolve in a saturated solution and when a small amount of the solvent available evaporates the excess KNO3 must come out of solution; i.e., it crystallizes into a solid.
November 10, 2014

chemisrty
Take 100 g sample which gives you 7.252 g Na 75.084 g U 17.664 g O ------------ Convert to mols by mols = g/atomic mass. mols Na = 7.252/23 = approx 0.315 mols U = 75.084/238.02 = approx 0.315 mols O = 17.664/16 = approx 1.104 Now convert these numbers into ratio to each ...
November 10, 2014

Chemistry
Frankly I don't see that the kind of bond N2 makes is relevant. dHrxn = (n*dHformation products) - (n*dHf reactants) Look up the dH formation for products and reactants and solve for dHrxn. Hint in solving: dHformation H2 and dH formation N2 are zero by definition.
November 10, 2014

Chemistry
Remember this. Bond strength is a function of electronegativity as one goes from the left to the right in the periodic table. So CO2, NH3, HF is stronger from left to right. Bond strength decreases as we go DOWN the table because of size. So HF is stronger than HCl > HBr etc.
November 10, 2014

Chemistry
Lattice energy generally decreases as we go down the periodic table and with charge. So mark off all of the group I oxides since they have +1 charge and that leaves just two from which to choose; i.e., SrO and BeO. BeO is more covalent bond whereas SrO is ionic. I think I ...
November 10, 2014

Physical Science
It takes 80 calories to melt 1 g of ice. So you have 400,000 calories. 400,000/80 = 5,000. So 5,000 grams of ice will melt and you should end up with 5000 g liquid water and 9,000 g un-melted ice all at zero C.
November 10, 2014

Physical Science
See your other post. Same process.
November 10, 2014

pharmacy math
Let x = amount of the 0.025% (and it's easier if we just leave it in percent). Then 180-x = amount of the 0.1%. 0.025x + (180-x)*0.1 = 180*0.05 Solve for x and 180-x I've estimated this will be 120 of the 0.025% and 60 of the 0.1% to give 180 of 0.05% but you should ...
November 10, 2014

chemistry
Fe2O3 + 3CO ==> 3CO2 + 2Fe mols Fe2O3 = grams/molar mass = ? Using the coefficients in the balanced equation, convert mols Fe2O3 to mols CO Now convert mols CO to grams CO. gCO = mols CO x molar mass CO
November 9, 2014

Chemistry 2
You made a typo in your post. Aniline is C6H5NH2 Let's call aniline a simple ANH2. ........ANH2 + HOH ==> ANH3^+ + OH^- I.......0.13............0........0 C........-x.............x........x E.......0.13-x..........x........x Substitute the E line into the Kb expression ...
November 9, 2014

Chem
.........2SO2(g) + O2(g)=> 2SO3(g) I.........0.51.....0.51......0 C..........-2x......-x......2x E.......0.51-2x...0.51-x....2x Substitute the E line into Kp expression and solve for x, then evaluate the other numbers.
November 9, 2014

chemistry
This is a limiting reagent (LR) problem; you know that because amounts are given for BOTH reactants. C2H5OH + 3O2 ==> 2CO2 + 3H2O grams ethanol = volume x density = approx 40 but that's an estimate as are all of the other calculations here. mols ethanol = grams/molar ...
November 9, 2014

Chemisty
2CH3OH + 3O2 ==> 2CO2 + 4H2O mols methanol = grams/molar mass = ? Using the coefficients in the balanced equation, convert mols methanol to mols CO2. The convert mols CO2 to grams. g = mols x molar mass.
November 9, 2014

chemistry
I wonder if you really meant CuNO3. I'll assume you did. mols CuNO3 = grams/molar mass = ? The M = mols/L solution. You know M and you know mols, solve for L solution.
November 9, 2014

Chemistry
I'm sure someone could help if we just knew what you wanted? "What happens" paints with such a broad brush. It could be color, volume, temperature, delta S, delta H, delta G, and so on into the night. Give us a hint what you are looking for.
November 9, 2014

chemistry
C6H6Br + Mg ==> C6H6MgBr which is the phenylmagnesium bromide. C6H6MgBr + C10H13O ==> C16H19OMgBr C16H19OMgBr + H2O(H^+) ==> C16H19OH + MgOHBr. I can't draw the structures. I think I've counted the C, H, O etc but you should check it out. The follows this ...
November 9, 2014

Chemistry
Cu3+------Cu2+-----Cu+-----Cuo ...........|...0.15.|..0.52..| |......1.28.........| I hope the spacing comes out well enough that you can make it out. The idea here is that you have the total of voltage from 3+ to 1+ and you have the single leg of Cu2+ to Cu+. What you need to...
November 9, 2014

chemistry
Note the correct spelling of celsius. n x = 0.5 mol TaCl5 = grams/molar mass Xx = nx/total mols XTaCl5 = nTaCl5/total mols. pTaCl5 = Xx*PoTaCl5
November 9, 2014

chemistry
Use PV = nRT and solve for n = number of mols. Then n = grams/molar mass. You have mols and grams, solve for molar mass.
November 9, 2014

Pages: <<Prev | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | Next>>

Search
Members