Monday
September 22, 2014

Posts by drbob222


Total # Posts: 43,920

Organic CHM Lab
Look up the boiling points of n-hexane, benzene and toluene. It should be easier to separate the two with the greater boiling point difference.
September 9, 2014

Organic CHM Lab
Scroll down to flooding and read about that.
September 9, 2014

chemistry
Pethyl ether = Xethyl ether*P<aup>oethylether 380 = X*400 Solve for X
September 9, 2014

chemistry
You must not have copied all of the problem. How far is the jet going?
September 9, 2014

chemistry
How many mols Al(NO3)2 do you have? That's 5.6g/molar mass Al(NO3)3 = ? Then there are 9 mols O (not O2) for every 1 mol Al(NO3)3; therefore, mols Al(NO3)3 x 9 = mols O (not O2). Finally mols O x 16 = grams O.
September 9, 2014

science
mass = volume x density
September 9, 2014

I dont understand this
A. Does the dog have brown fur or does the bone have brown fur?
September 9, 2014

Chemistry, HELP!!
zinc(S) + hydrochloric acid(aq) ==> zinc chloride(aq) + hydrogen(g) Zn(s) + HCl(aq) ==> ZnCl2(aq) + H2(g) Then balance. Zn(s) + 2HCl(aq) ==> ZnCl2(aq) + H2(g)
September 9, 2014

math problem solving
Is it 16?
September 9, 2014

Hard math 7th grade
42 – 2(3 • 5 + 1) = 42 - 2(16) = 42-32 = ?
September 9, 2014

Physical Science
I found this on the net. https://answers.yahoo.com/question/index?qid=20080817023758AAmRgMo
September 9, 2014

chem
CH3COOH + NaOH ==> CH3COONa + H2O mols KOH = M x L = ? mols CH3COOH = mol KOH from the coefficients in the balanced equation. M CH3COOH = mols CH3COOH/L CH3COOH
September 9, 2014

chemistry
You're looking for what we called in much earlier days the chemical factor. It is taught less and less theses days but is very useful. 2Mg/Mg2P2O7 3UO2/U3O6 (NOTE: I assume U3O6 is a made up part of the problem. I would have written it as UO2 but then there is no ...
September 9, 2014

chemistry
BaCl2 + 2KIO3 ==> Ba(IO3)2 + 2KCl millimols BaCl2 = M x mL = 1.4 mmols KIO3 = 3 The is a limiting regent (LR) and solubility product problem rolled into one. First, what is the LR? 1.4 mmols BaCl2 will form 1.4 mmols Ba(IO3)2 if we have all of the KIO3 needed. 3 mmols KIO3 ...
September 9, 2014

chemistry
KBrO3 is a salt soluble in water that ionizes 100%; ie., ..........KBrO3==> K^+ + BrO3 I.........0.01.....0......0 C........-0.01....0.01....0.01 E..........0......0.01....0.01 .........AgBrO3 --> Ag^+ + BrO3^- I........solid......0......0.01 C........solid......x..........
September 9, 2014

biology - - -chemistry
This is chemistry?
September 9, 2014

chemistry
MgCO3(s) → MgO(s) + CO2(g) So the loss in mass is due to the evolved CO2. mass CO2 = 21.8603 - 18.7358 = ? Convert mass CO2 into mass MgCO3 this way. mass MgCO3 = mass CO2 x (molar mass MgCO3/molar mass CO2) = ?
September 9, 2014

Chemistry
a. mols KMnO4 = M x L = about 0.00054 but you need to do that more accurately. Thjat's just an estimate. b. 5Fe^2+ + MnO4^- ==> 5Fe^3+ + Mn^2+ Note that I balanced only the redox part to save a little time but that's all we really need to balance. So mols Fe^2+ must...
September 8, 2014

Chemistry
Ca(OH)2 + SO2 ----> CaSO3 + H2O mols SO2 = 1000/molar mass SO2 = approx 15.6 but you need to confirm that as well as all of the other numbers I do becuase I estimate some of them. Convert to mols Ca(OH)2 and 15.6 mols SO2 x (1 mol Ca(OH)2/1 mol SO2) = 15.7. Grams Ca(OH)2 = ...
September 8, 2014

science
distance = rate x time 30 m = rate x 20 min Solve for rate = 30 m/20 min = 1.5 m/min Now redo d = rt and plug in 1.5 for rate and 60 min for time and solve for d. You can do it with ratio/proportion, also (30 m/20 min) = (x m/60 m) x = ?
September 8, 2014

chemistry
q = mass x specific heat x (Tfinal-Tinitial) Substitute into the equation and solve for Tfinal.
September 8, 2014

Science
http://www.answers.com/Q/Can_one_organism_be_a_consumer_an_omnivore_a_predator_and_prey
September 8, 2014

math
If 5/7 are girls then 2/7 must be boys. Therefore, ......
September 8, 2014

Chemistry help
What trouble are you having doing these? or show your work and I'll check them.
September 8, 2014

please help
Then how are we to tell you which equation is correct?
September 8, 2014

Math - Urgent
5/6 = 15/18 2/9 = ?
September 8, 2014

algebra
4y^2 + 2y -(7y^2 - 3y) ----------- When subtracting, change the sign of the subtrahend and add algebraically. Therefore, this becomes 4y^2 + 2y -7y^2 + 3y ----------- -3y^2 + 5y
September 8, 2014

MATH
Reread your question and tell me what numbers you're talking about.
September 8, 2014

Science
It rotates on its axis once per day (that makes day and night). The earth rotates around the sun once in a year.
September 8, 2014

Physical Science 8th grade
Less dense objects float on more dense objects. For example, a piece of wood floats on water because the water is more dense than wood. Likewise, a balloon filled with He will float in air because air is more dense than He.
September 8, 2014

SCIENCE
You must first find the volume of the flask. Do that with the water. 121.6 g = mass flask + water - 46.8 g = mass flask empty ---------- 74.8 = mass water. density of water is 1.00 g/mL; therefore, m = volume x density 74.8 = volume x 1.00 g/mL volume = 74.8 mL. Then find mass...
September 8, 2014

Science!
I think you're right with D. Suspension, bed load and material in solution are part of stream load. I think D has nothing to do with stream load.
September 8, 2014

chemistry
A radius of 215 pm = diameter of 430 pm and that is 430E-12m. The distance to be covered is 4.47mm or 4.47E-3m. So 430E-12m x #atoms = 4.47E-3 m Solve for # atoms.
September 8, 2014

Chemistry
I would do this. ln (k2/k1) = Ea/RT You know k2 is 1E6k1 and you know Ea for A, solve for Ea for B in which k1 is the rate constant for reaction A and k2 is the constant for reaction B. If products are more stable than reactants then reactions A and B are exothermic and Ea ...
September 8, 2014

Chemistry
dG = -RTlnK
September 8, 2014

science
I can't help with a fourth scenario until I know what the first three are.
September 8, 2014

chemistry
PV = nRT You have P, n, R and T (change to kelvin). Solve for V in liters.
September 8, 2014

Chemistry
physical and physical Adding water to salt and gravel just dissolves the salt. However, the salt is still salt and the gravel still gravel so no reaction took place. Same thing with CO2. Water freezes at zero C and boils at 100 C BUT whether it is in the form of solid ice, ...
September 8, 2014

Chemistry 2
If you start with 0.762M NOBr then NO will be 0.762 x 0.651 = about 0.496M and Br will be 1/2 that. The un-dissociated NOBr will be 0.762 x 0.349 = ? Substitute those values into the Kc expression and solve.
September 8, 2014

Organic Chemistry
Here is a table that lists the pKa for organic and inorganic compounds. http://www.cup.uni-muenchen.de/oc/trauner/files/evans_pKa_table.pdf For example, H2O is 15.7 and HF is 3.17. That means HF is a stronger acid than H2O. I couldn't find NH3 in that list but it is 9.25. ...
September 8, 2014

Biochemistry
I suppose the problem is asking for the anion. If HB is the acid, then the base is B^- and that hydrolyzes in water solution this way. .............B^- + HOH ==> HB + OH^- I..........0.1M............0....0 C...........-x.............x....x E.........0.1-x............x....x ...
September 8, 2014

science
These look ok to me.
September 8, 2014

chemistry
pi = MRT Substitute and solve for M. Then M = mols/L. You know M and L, solve for mols. Then mols = grams/molar mass. You know mols and grams, solve for molar mass.
September 8, 2014

chemistry1411
Use the Clausius-Clapeyron equation. P1 is 630mm Hg and T1 is the unknown. P2 is 760 mm Hg and T2 is 100 C. Remember T must be used in kelvin.
September 8, 2014

chem
1.39 um^3 x (1 mm/1000 um)^3
September 8, 2014

CHEMISTRY
(A) in mols/L or M rate in change in M/s k then is s^-1
September 8, 2014

CHEMISTRY
See your other post.
September 8, 2014

chemistry
rate D is 1/2*d(D)/dT which is 1/2*change in (D)/time. rate E is 1/2*d(E)/dT rate F is d(F)/dT etc. rate = -d(D)/2*dT = -1/2*(0.3) = -0.15 M/s = rate rate = d(H)/dT = 0.15 M/s
September 8, 2014

chemistry
k = 0.693/t1/2 Then substitute k in the following: ln(No/N) = kt No = 100 (I assume this arbitrarily and calculate N based on what I chose for N.) N = 12.8 k from above t = solve for t in years. Note the correct spelling of isotope.
September 8, 2014

chemistry
For mole fraction, X CsBr. mols CsBr = from the problem mols H2O from the problem = grams/molar mass Then X CsBr = mols CsBr/total mols. mass % CsBr is grams CsBr/100 g solution.
September 8, 2014

chemistry
m = mols solute/kg solvent You know m and kg solvent; solve for mols solute. Then mols solute = grams/molar mass You know mols solute and molar mass, solve for grams.
September 8, 2014

chemistry
mass % is grams solute/100 g solution. 12.8% w/w is 12.8g NH3/100 g solution. mass = density x volume. You know 100 g solution and density of the solution; solve for volume of the solution. Convert g NH3 to mols NH3. g/molar mass = mols. Then M = mols/L solution. m = mols ...
September 8, 2014

Biology Help
Enzymes speed up the rate of conversion from reactants to products by lowering the activation energy needed for the reaction to occur.
September 8, 2014

chemistry
There are 453.6 g in 1 lb and 1000 g in 1 kg. There are 12 inches in 1 foot There are 2.54 cm in an inch. There are 100 cm in a m.
September 7, 2014

Chemistry
volume of water = 58.5 mL volume cubes = 2.0 x 2.0 x 2.0 = 8 cc = 8 mL. new volume in BOTH graduated cylinders is 58.5 + 8 = ? No, I didn't err. Both Pb and Al have the same volume so the water levels will be the same when both are submerged.
September 7, 2014

Science
Usually that is applied to a statement when facts are enough to back up the explanation but it makes sense with the information we have. Then we stay that is a tentative explanation because in the future we may find we need to tweak the explanation.
September 7, 2014

science
A hypothesis becomes a theory if the experimental details fit. Then theories become laws with time (sometimes the theory must be tweaked to make it fit new data)
September 7, 2014

chemistry
Most of your questions are about conversions. What is your main problem with these? You need to learn how to do them yourself. If you will explain in detail perhaps we can set you on the right track.
September 7, 2014

chemistry
See your other post.
September 7, 2014

chemistry
1A = 1E-8 cm
September 7, 2014

Chemisty 132
Didn't I do this earlier? (or at least one just like it)
September 7, 2014

chemistry
E = hc/wavelength
September 7, 2014

chemistry
You don't need us to do this for you. Punch in the numbers and that's it.
September 7, 2014

Chemistry
232 amu x (1 g/6.022E23 amu) = ? For d there are 1E-8 cm = 1 A and 1E-9 nm = 1 m
September 7, 2014

chemistry
See your post above.
September 7, 2014

chemistry
volume = (2.04 cm)^3 density = mass/volume
September 7, 2014

questions- - -a level chemistry
1. Is the 0.78 atm the partial pressure to start or after equilibrium is established? 2. What's the new Kp (or Kc) at 350K? I suggest you repost the question at the top of the page and include the information in answer to the questions 1 and 2.
September 7, 2014

Chemistry
q1 = energy released on vapor cooling from 93 C to 78.3 C q1 = mass ethanol x specific heat ethanol vapor x (Tfinal - Tinitial) note: Tf is 78.3 and Ti is 93.0. q2 = energy released on changing from vapor at 78.3 to liquid at 78.3 q2 = mass ethanol x heat vaporization q3 = ...
September 7, 2014

Young Harris College
You do this in steps. q1 = energy needed to heat solid ice from -30 C to solid ice at 0 C. q1 = mass ice x specific heat ice x (Tfinal-Tinitial) where Tf is 0 and Ti is -30 C. q2 = heat needed to change the phase at zero C from solid ice to liquid water. q2 = mass ice x heat ...
September 7, 2014

Chemistry
$155 x (1 kWh/0.129) x (1 J/2.78E-7 kWh) = ?
September 7, 2014

chemistry
I would look at B as the incorrect one.
September 7, 2014

Chemisty 132
So this in steps. Within a phase the formula is q = mass x specific heat x (Tfinal-Tinitial). For example, to heat liquid H2O from zero C to 100 C use q = mass x specific heat x (100-0) = ? At a phase change (from ice to liquid at the melting point or from liquid to steam at ...
September 7, 2014

CHM
I have spent a lot of time looking for a site to which I could refer you to for this question but to no avail. So here is my best educated guess and the reasoning. I think volumetric pipets are #1 in accuracy. They require only one measurement reading (when the pipet is full...
September 7, 2014

Chemistry
mols CO2 = 0.0489. Using the coefficients in the balanced equation, convert mols CO2 to mols NaHCO3. Then convert g NaHCO3 to mols; as g = mols x molar mass
September 7, 2014

Chemistry
1.60M x (59.9/208) x [134/(134+111)] = ?
September 7, 2014

Physical Science
What's the density?
September 7, 2014

Chemistry- urgent!
You need to know the rules for significant figures. Here is a good site. Study it carefully. http://www.chemteam.info/SigFigs/SigFigs.html For 15: All multiplication and division. The s.f. rule is the final answer can have as many s.f. as the LOWEST number involved. All of ...
September 7, 2014

analytical chm
I don't know to which methods you refer. You weigh it once, heat, weigh again, and repeat until constant weight.
September 7, 2014

Chemistry (concentrations)
I think Mr. Pursley hit a 6 instead of a 5 and meant 2*12.6 = 25.2 ppt Cl^-.
September 7, 2014

chemistry
2KBr ==> 2K + Br2
September 7, 2014

Organic chemistry
I assume NaCl does not ionize when dissolved in glucose. mols NaCl = grams/molar mass. Subsittute and solv for mols NaCl. Then m = molality NaCl = mols/kg solvent Substitute mols from above and kg solvent is 0.200 kg, and solve for m. Then delta T = Kf*m You have Kf for ...
September 7, 2014

chemistry
I think I would look at B is the incorrect one.
September 7, 2014

chemistry
Is that an all gaseous reaction? If so change in volume will have no effect on the equilibrium.
September 7, 2014

chemistry
I really don't know how to answer this because the answers are confusing. A is not true for certain. B. The electron configuration is 1s2 2s2 2p4 and that 2p4 would make it a true statement; however, I don't think that is the answer wanted. Oxygen has 6 electrons in n...
September 6, 2014

Chemistry
We can't place bars over anything. #2 has no zeros but I guess you could rewrite it as 42ssss and all of the zeros (represented by s) are non-significant zeros. I would rewrite 1 as 8.04sE3 where s stands for the non-significant zero. #3 can be written as 0.00000470 or s....
September 6, 2014

chem help plz
Convert 125 km to miles. I get about 77.7 miles but you should confirm that. 77.7 mi/day x 7 days/week = about 544 miles but that's approx. You should redo all of the math before and after this sentence. 544 miles x (1 gal/22.0mi) approx 24.7 gallons. 24.7 gallons x (1 L/0...
September 6, 2014

Chemistry
Here are two good sites. The first one tells you how to do s.f. and the other is the definition of decimal place. http://www.chemteam.info/SigFigs/SigFigs.html https://www.google.com/search?q=what+is+a+decimal+place&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:en-US:official&client=...
September 6, 2014

ANALYTICAL CHM
Align the eye EXACTLY in line with the bottom of the meniscus (to avoid parallax) and read the bottom of the meniscus. I use my finger placed just below the meniscus on the outside of the buret so that my finger image is reflected off the bottom of the meniscus. That allows me...
September 6, 2014

ANALYTICAL CHM
http://chemed.chem.purdue.edu/genchem/lab/equipment/pipet/error.html http://chemed.chem.purdue.edu/genchem/lab/equipment/buret/error.html
September 6, 2014

CHEM 1A
This is a limiting reagent (LR) problem and I work these the long way and probably not at all like your prof does. But here goes. mols Ca = 6.87/atomic mass Ca = approx 0.171 which you have. mols O2 = 4.58/32 = approx 0.143 ( you used the atomic mass of O and not the molar ...
September 6, 2014

chemistry
For the impure Cu the rxn is Cu ==> Cu^2+ + 2e. anode At the pure Cu the rxn is Cu^2+ + 2e ==> Cu(s) cathode
September 6, 2014

chemistry
a. At the anode you have 2Cl^- ==> Cl2 + 2e. b. What do you think the Cl2 will react with?
September 6, 2014

Chemistry
It isn't right and your gut should tell you that. How can you have an acid solution with a pH greater than 7. Remember 7 is neutral so a pH of 7.70 means your acid solution is basic and that can't be. Where are you in chemistry? If it is not beginning chemistry there ...
September 6, 2014

Chemistry
Convert 1.25 lb Hg to grams. That's 1.25 lb Hg x (453.6 g/lb) = ? grams Hg. Then mass = volume x density. You know mass and volume, solve for density.
September 6, 2014

Chemistry
Pb(NO3)2 + 2HCl ==> PbCl2 + 2HNO3 mols Pb(NO3)2 = grams/molar mass = ? Then convert mols Pb(NO3)2 to mols PbCl2. That's a 1:1 conversion. Then mols PbCl2 x (6.02E23 molecules/mol) = ?
September 6, 2014

Chemistry
Because they are soluble in water.
September 6, 2014

Chemistry
Specific gravity of Pb is 11.34 but I didn't get that from the problem.
September 6, 2014

Chemistry
You will need the density of Au, then volume = mass/density Substitute mass from the problem and density you have to find volume. Then volume Au + 10.10 mL = new volume of the ethanol in the graduated cylinder.
September 6, 2014

Chemistry
volume of Au cube is 3 x 3 x 3 = 27 cc New volume reading for water level will be 27 + 5.75 = ?
September 6, 2014

chemistery
Surely, if you tell us what you don't understand about them. Most of us, however, aren't prepared to write a chapter or two or three.
September 6, 2014

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