Friday
October 24, 2014

Posts by DrBob222


Total # Posts: 44,698

Analytical CHM
This site will provide information for you. http://fclass.vaniercollege.qc.ca/~direnzom/Laboratory%20Notes%20-%20Equipment.pdf
September 5, 2014

Analytical CHM
I don't know if this will help or not. http://avogadro.chem.iastate.edu/msds/i2.htm
September 5, 2014

pharmacy math
(15g/2000)*100 =
September 5, 2014

Chemistry
1 mol CO2 has a mass (molar mass) of 44 g. right? 1 mol CO2 contains 6.02E23 molecules. right? ergo
September 4, 2014

chemistry
(200 m/21 s) x (1 km/1000 m) x (60 s/min) x (60 min/hr) = ?
September 4, 2014

physical science
density = mass/volume Substitute and solve.
September 4, 2014

chemistry
What kind of percent? volume percent, mass percent, --- If you want volume percent, then %N2 = (volume N2/total volume)*100 = ?
September 4, 2014

chemistry
http://en.wikipedia.org/wiki/D%C3%B6bereiner%27s_triads
September 4, 2014

Chemistry
mols naphthalene = grams/molar mass = ? molality = m = mols naphthalene/kg solvent Then delta T = Kf*m and solve for delta T. Subtract from the normal freezing point to arrive at the new freezing point.
September 4, 2014

chem
volume = l x w x h Substitute and calculate volume Then density = mass/volume =?
September 4, 2014

Chemistry
density = mass/volume mass = 6.8 g volume = 9.30-7.1 = ? Round the answer to two significant figures.
September 4, 2014

Bio Chem
pH = pK2 + log (base)/(acid) 9.0 = 10.33 + log b/a solve for b/a which is equation 1 but b and a will be mols and no concentration. The second equation is a + b = 0.75L x 0.100M = ? mols Solve the two equations for b and a and convert mols to grams from mols = grams/molar mass
September 4, 2014

chemistry 101
I did this for you last night before I went to bed; what's the problem? When you keep getting the wrong answer the BEST thing you can do is to show your work. That way we aren't fumbling in the dark.
September 4, 2014

chemistry
topics? The elements are Be, Mg, Ca, sr, Ba, Ra
September 4, 2014

chemistry
no equation. no rate constant. no nothing here.
September 4, 2014

biology
That means that the system is not stagnant; i.e., all of the parts of the system are changing from one form to another but the overall percentages don't change with time. Let me give you an example in chemistry (since I'm a chemist). It's similar to equilibrium. In...
September 3, 2014

Chemistry
This is a redox equation. Fe^2+ probably is oxidized to Fe^3+. C2O4^- probably is reduced to CO2. H2O2 probably is reduced to H2O Here is everything you wanted to know about redox equations. http://www.chemteam.info/Redox/Redox.html
September 3, 2014

SCIENCE:BIOLOGY>
If you will copy your post and indicate your answer NEXT TO THE QUESTION, I shall be glad to check them. 1 is done this way. 6.5 hr/day for 5 day = 32.5 hrs There are 60 minutes in an hour There are 60 seconds in a minute. Put all of that together in the form of dimensional ...
September 3, 2014

chemistry
The "type" depends upon how you want it classified. It is a double replacement (some call it double displacement) reaction. It also is a precipitation reaction since BaSO4 is insoluble. The net ionic equation is Ba^2+(aq) + SO4^2-(aq) ==> BaSO4(s) The Na and NO3 ...
September 3, 2014

Chem Help Please!!!
We can't draw diagrams (graphs or equipment set up) on this forum but here is a site that goes into this in detail. This is only one of many; if you don't find something here go to Google and type in "separation toluene and cyclohexane by distillation" ...
September 3, 2014

chem
See my response below to another post. I found values for kcal per grams glucose of 3.35 to 3.8. I have always used 4 as an average. Using 4 kcal/g you have g glucose in 2700 mL at 4g/100 mL you have infused 4 x (2700/100) = ?g glucose. Then kcal = 4 or whatever your notes/...
September 3, 2014

chemistry
rate = k(NO)^2(Br)
September 3, 2014

chemistry
I have always used 4kcal/g carbohydrate. Probably that's an average and glucose may not be "average" but based on that the answer is 3 g x (2900/100) = g glucose infused = about 87g. Then 4 kcal/g glucose x 87g glucose = ? kcal I found on the web numbers from 3.3...
September 3, 2014

math
I agree
September 3, 2014

math
He meant to measure out 60 which would have left 40 in the graduated cylinder. But he left 45 there which is 5 mL more than intended. %error =(5/60)*100 = ?
September 3, 2014

Math. HELP!
$1(#hd) + $2(#ham) = $48
September 3, 2014

math
(ab)^3/[(3a)^2*b] a^3*b*3/(9a^2*b ab^2/9
September 3, 2014

Chemistry
Read your problem and your post. I don't believe all of the information is here.
September 3, 2014

Math
To place numbers in increasing order (least to greatest), place the smallest number first followed in succession by the next highest number until the last number is in place.
September 3, 2014

Maths
I would say, "Convert to the same units and compare them".
September 3, 2014

Chemistry
First convert pints to mL. I obtained 62.9 mL but you should confirm that. 196.34 g = mass container + syrup -102.00 g = mass empty container -------------- 94.34 = mass syrup density = mass/volume = ?
September 3, 2014

Chemistry
And the question is ?
September 3, 2014

Chemistry
No it isn't the atomic number; however, I looked up the atomic mass on the periodic table and it is 63.5463 as it occurs in nature. Plug that in for z and solve.
September 3, 2014

Chemistry
I don't think you understand what I need. The ABUNDANCE of 63 is 69.170% and the ABUNDANCE of 65 is 30.83%. But you don't have the mass of anything; i.e., you don't have the mass of 63 or the mass of 65 or the mass of the isotope as it occurs in nature (the mixture...
September 3, 2014

Chemistry
I believe you also need to know the mass of the mixture occurring in nature.
September 3, 2014

Chemistry
I agree with what you have but if your prof is picky about significant figures s/he will tell you that you need another place in your answer. I believe you are allowed four s.f. so I would write that as 0.103928 which I would round to 0.1039 g.
September 3, 2014

Chemistry
let x = fractional abundance of 59Co. and 1-x = fractional abundance of 60Co. ----------------------------------------- x(58.9332) + (1-x)(59.9338) = 58.9901 Solve for x and 1-x to obtain fractional abundances for Co59 and Co60. Then 1.8276 g x fractional abundance Co60 = mass...
September 3, 2014

Analytical CHM
http://academics.wellesley.edu/Chemistry/Chem105manual/Appendices/uncertainty_volumetric.html
September 3, 2014

Analytical Chemistry
Random errors. Errors due to the weights (balance error). Most reading errors have been eliminated due to digital readout. Sloppy handling of sample.
September 3, 2014

Analytical CHM 300
You need to rephrase the question.
September 3, 2014

Sogeri high school
I assume the products are NO2 and H2O N2H4 + 3O2 ==> 2NO2 + 2H2O I will get you started but I'm having trouble understanding why you can't count bond broken and bonds formed. For bonds broken, look at N2H4. There are four N-H bonds broken plus a N-N bond broken to ...
September 3, 2014

Chemistry
q = mass fat x specific heat fat x (Tfinal-Tintial)
September 3, 2014

chemistry
density = mass/volume = 53.9/35.4 = ?
September 3, 2014

Chemistry
I answered this below lat night.
September 3, 2014

Chemistry
% mass C = (2*atomic mass C/molar mass C2H2)*100 =
September 3, 2014

Chemistry
There is a law called the Law of impenetrability which says that two objects can't occupy the same space at the same time. What this means is that the volume of the water in the graduated cylinder will rise an amount equal to the volume of the ice cube; i.e., the ice cube ...
September 3, 2014

Chemistry(Please help)
C is 1s2 2s2 2p1 2p1 and in sp3 hybrids the 1 2s orbital mixes with the 3 2p orbitals to form 4 bonds, all alike, as sp3 hybrids (hybrids as in not an s and not a p but four mixed s & p to form sp3). We write that as 1s2 sp3 sp3 sp3 sp3 with one electron in each of the 4 sp3 ...
September 2, 2014

Chemistry
No you would not do that. Mathmate's directions are to measure out 100 mL and add enough water to it to make a total volume of 600 mL. And to clarify another point, that isn't the same as adding 100 mL of the 36M stuff to 500 mL H2O BECAUSE 100 + 500 may NOT be a final...
September 2, 2014

Chemistry
Note: I am unfamiliar with how the alha amino acids dissociate so look at what follows with a skeptical eye. Here is what I think. With a concn of 0.001 the hydrochloride will consist of the fully protonated amino acid plus the chloride ion. You can assign 0.001 to (Cl^-) ...
September 2, 2014

Chemistry
How many mols CCl4 do you have? That's mols = #molecules/6.02E23 = ? Then there are 4 atoms Cl for each molecule CCl4; therefore, there are 4 x that number atoms Chlorine
September 2, 2014

chemistry
What do think the answer is and why? Oxygen is 1s2 2s2 2p4
September 2, 2014

Chemistry
pi = MRT pi in mm Hg. You know R (0.08206) and T (remember in kelvin). M = mols/L solution. where mols = grams glucose/molar mass glucose and L solution is 0.450 Solve for pi
September 2, 2014

Chem Help Please!!!
Your formulas are right. In general, ionic bonds are formed when elements from the sides of the periodic table (left side and right side) combine. Examples are LiCl, BaCl2, AlCl3 etc. In general, covalent bonds are formed when elements from the center combine with left or ...
September 2, 2014

Chemistry
12Mg is 1s2 2s2 2p6 2s2 20Ca is 1s2 2s2 2p6 3s2 3p6 3d0 4s2 The electrons in the 4s level for Ca are further removed from the nucleus than the outer electrons in the Mg atom and it takes less energy to move them to a higher level. As a result, the energy emitted when the ...
September 2, 2014

chemistry
See your other post.
September 2, 2014

chemistry
mass = volume x density density is given volume = pi*r^2*l r = 1.25/2 = ? pi = 3.14 l = 4.50m = 4500 cm
September 2, 2014

physical science
What's the density of oak? mass = volume x density volume is 12 cc density = ?
September 2, 2014

Science
area = L x W = 15.0 x 14.1 = 211.5 m^2 but the answer is not B. You can have three significant figures (because of the 15.0). I would round that 211.5 to 212 m^2.
September 2, 2014

chemistry
10 grams of what? If you had 10 g CuSO4.5H2O in 100 g H2O then you want get any back. If the 10 g is 10g solution, and the solution is saturated, then you will get 25 g x (10/100) = g CuSO4.5H2O
September 2, 2014

chemistry
Read the label for side effects. Look on the web and HOPE you can find who first manufactured it. You can look for sodium bicarbonate used for acid stomach. Look for aspirin, acetyl salicylic acid
September 2, 2014

chemistry
You asked this same question last night (actually you finished the question last night). Bob Pursely answered the question, you questioned his answer and I followed up with the same answer Damon has given you here. You may as well accept the answer because it's right; both...
September 2, 2014

Chem
26.5 L coolant is 26,500 mL/ mass = volume x density. You know volume in mL and density, solve for grams.
September 2, 2014

Chemistry
Calcium acetate is Ca(C2H3O2)2 which I abbreviate as Ca(Ac)2. Remember the definition. M = mols/L solution. mols given in the problem as 62.1 volume given as 585.1 mL which is 0.5851 L. Then 62.1 mols/0.5851 L = 106.136 M for Ca(Ac)2. There are two Ac^- ions in each molecule ...
September 1, 2014

chemistry
Sr(OH)2 + 2HNO3 ==> Sr(NO3)2 + 2H2O 1. Write and balance the equation as above. 2. How many mols do you have to neutralize? That's mols Sr(OH)2 = M x L = ? 3. Using the coefficients in the balanced equation, convert mols Sr(OH)2 to mols of the other reagent. In this ...
September 1, 2014

Chemistry
Show your work and I'll tell you what is wrong with your factors.
September 1, 2014

Chemistry
How many hours in a week. (24 hrs/day) x (7 days/week) = 168 hrs/week. So (12 donu/36 hrs) x (168 hrs/week) = ? 56 doughnuts/week?
September 1, 2014

chem
Hey, volume is volume. The volume is the same and each will displace a volume of water equal to its own volume, no matter what it's identity.
September 1, 2014

chemistry
SA = salicylic acid ASA = aspirin mols SA = grams/molar mass = ? mols ASA produced = mols SA grams ASA = mols ASA x molar mass ASA. This is the theoretical yield (TY) Actual yield (AY) either 1.15 or 0.15 depending upon how you read the question. % yield = (AY/TY)*100 = ?
September 1, 2014

chemistry
How many moles do you want? That's M x L = ? mols. Then mols = grams/molar mass, You know mols from above and molar mass, solve for grams.
September 1, 2014

Chem Help Please!!! DrBob222
Simple distillation at atmospheric pressure. These differ little from diagram to diagram but the parts are labeled. https://www.google.com/search?q=image+simple+distillation&client=firefox-a&hs=YcY&rls=org.mozilla:en-US:official&channel=sb&tbm=isch&tbo=u&source=univ&sa=X&ei=...
September 1, 2014

chemistry
First, determine the molarity of the solution of HCl and Second, use the dilution formula. 1.20 g/mL x 1000 mL x 0.40 x (1 mol/36.5g) = 13.15 which I would round to 13.2 M Then c1v1 = c2v2 13.2*v1 = 0.2M x 500 mL Solve for v1. You can do the M of the initial HCl solution ...
September 1, 2014

Chemistry
Yes, 1s2 2s1 2p3 would be 2s up, 2p up 2p up 2 up BUT then the four hybridize to form four sp3 hybrid bonds.
September 1, 2014

Chemistry
When bonding in organic molecules in which the C atom shares the four electrons, what happens is that the ground state of 1s2 2s2 2p2 and one of the two 2s2 electrons gets promoted to the 2p and the configuration becomes 1s2 2s1 2p3. Then the 2s1 and 2p3 hybridize to form an ...
September 1, 2014

chemistry
See your other post.
August 31, 2014

chemistry
Are you new to chemistry. Two things to keep in mind. 1. Start sentences with a capital letter and put in periods. Otherwise it makes it difficult to know the question. 2. Find the caps key and use it. Co, CO, and co means something different. 3. Note correct spelling of ...
August 31, 2014

Chemistry
You want to convert rate to time. 7.5m/hr x ?hr = 10,000m Solve for ?hr and convert to minutes. OR, use the distance formula that is distance = rate x time. 10,000 = 7.5 m/hr x ?hr. Solve for ?hr and convert to minutes.
August 31, 2014

chemistry
mass = volume x density or volume = mass/density. mass = 4100 g density 1.11 Substitute and solve for volume (in mL) and convert to L.
August 31, 2014

Algebra
The boat travels downstream at the rate of r+3.5 and r-3.5 upstream. distance down stream = r*time = (r+3.5)*5 and upstream is (r-3.5)*12. Since the distance downstream is the same as distance upstream, these two are equal to each other. (r+3.5)*5 = (r-3.5)*12 Solve for rate ...
August 31, 2014

science
All information that follows is based on FOOD calories (which really are kilocalories). CH2O contains 4 cal/gram protein contains 4 cal/gram fat contains 9 cal/gram so (100*4)+(20*4)+(20*9) = ? %CH2O = [(100*4)/total]*100 = ? same format for protein and fat.
August 31, 2014

science
See your other post.
August 31, 2014

Chemistry
Rf value short wavelength = (distance moved by shortest/distance moved by solvent). Rf value for long wavelength = (distance moved by longest/distance moved by solvent)
August 31, 2014

summer math hw
A1 = pi*5^2 = ? = 25pi A2 = pi*10^2 = ? = 100pi Looks like 4 times.
August 31, 2014

Science(density)
density = mass/volume. You have mass and volume in the problem. Substitute and solve for d.
August 31, 2014

chemistry
Is that millijoules? Multiply by 1E6. Is that megajoules? Divide by 1000.
August 31, 2014

Chemistry
I agree with John.
August 31, 2014

Chemistry
You seem to have the right idea.
August 31, 2014

Chemistry
Your solution assumes that 2-nitrophenol is a strong acid and dissociates completely (100%). But I found a pKa on the web listed as 7.2 which means Ka = 6.3E-8. If we call this compound HP, then ...........HP ==> H^+ + P^- I.......0.0353....0......0 C.........-x......x........
August 31, 2014

chemistry calculations
See your other post below on solving for Kc. This is just a substitution problem. Substitute partial pressures and solve for Kp.
August 30, 2014

chemistry calculations
mols N2O4 = 4/molar mass = 4/92 = about 0.0435M M N2O4 = 0.0435/2 = about 0.0217M ..........N2O4 ==> 2NO2 I.........0.0217.....0 C.........-x........2x E.......0.0217-x....2x Substitute the E line into Kc expression and solve for x and 0.0217-x b and c are done the same way...
August 30, 2014

chemistry calculations
What's your problem here? You substitute the concn listed into the Kc expression and solve for Kc.
August 30, 2014

algebra 2
19.49 x 0.7 = ?
August 30, 2014

algebra 2
550 mi to Texasl 2*550 = 1100 mi for the round trip. 1100 miles x (1 gallon/25 miles) = ? gallons. ?gallons x (1 tank/15 miles) = ? tanks and round to whole number.
August 30, 2014

Chem Help Please!!!
You don't have a manual that gives you this information? Do you have any idea of what you might need? I'll be glad to critique your thoughts.
August 30, 2014

Chemistry
First, balance the equation. C3H8 + 5O2 -> 3CO2 +4H2O. Use the coefficients to convert mols propane to mols O2 this way. 1.75 mols C3H8 x (5 mols O2/1 mol C3H8) = 1.75 x 5/1 = ?
August 30, 2014

chemistry
Convert F to C. That's (F-32)*5/9 = C I came up with 77F = 25C Then C + 273.15 = K I came up with 298.15 K.
August 30, 2014

Algebra 1
let s = side of triangle let q = side of square ----------------- s+4 = 2q (equation 1) perimeters equal so s+s+s+s = q+q+q+q or 4s = 4q (equation 2) Solve the two equations simultaneously for s and q.
August 30, 2014

science
density = mass/volume Substitute and sovle.
August 30, 2014

Chemistry Science
2C8H18 + 25O2 --> 16CO2 + 18H2O 80L gasoline. mass = volume x density = 80,000 mL x 0.703 g/mL = ? mols octane = grams/molar mass octane = ? Using the coefficients in the balanced equation, convert mols octane to mols CO2. Now convert mols CO2 to mass. grams CO2 = mols CO2 ...
August 30, 2014

Physical Science
If the block of wood is homogeneous throughout, yes.
August 30, 2014

chemistry
Lower the temperature. Can you figure from there?
August 30, 2014

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