Monday
September 22, 2014

Posts by DrBob222


Total # Posts: 43,913

Chem
number of protons. Look at the atomic number. The atomic number is the number of protons in the nucleus of the atom. For example, Na will have 11. What about electrons. The number of electrons in the neutral atom is the same as the number of protons in the nucleus. Therefore, ...
September 5, 2014

chemistry
You must have meant PV/nR = T PV = nRT is that P = 36 atm or some other unit. is that V = 8.6L or some other unit? So n = PV/RT = 36*8.6/(0.08*200).
September 5, 2014

chemistry
I don't know how to write the lamda symbol;I will call it L. Then if hvL = mv2, then L = mv2/hv = mv/h
September 5, 2014

chemistry
74.0 g = mass dish+mass salt+mass water -52.5 g = mass dish + mass salt -----------------========== 21.5 g = mass water Note that if you subtract equation 2 from equation 1 the number is 21.5 g and the mass dish + mass salt cancel leaving mass water.
September 5, 2014

chemistry
Maybe forever because I don't know how you get the temperature to 156 C because all of the fluid would boil away at just over 100 C. But we'll not worry about that; I assume this is just a made up problem and the author of the problem didn't think about that. So ...
September 5, 2014

6th grade math
I don't understand the problem. 26, 17, 15, 6, -19, -20. Yes, -19 is a larger number than -20.
September 5, 2014

chemistry
You have the problem spelled out so well, why not just use d = m/v or v = m/d = 550 g/1.10 mL = ? mL.
September 5, 2014

CHEM 1A
On the right track but not quite right. You may have just mislabeled your numbers. 51,800 g O2 is what you want. mols O2 = 51,800/32 = 1618.7 MOLES O2 (not grams) needed. Convert that to mols KNO3 by multiplying by 4/5 = 1295 mols KNO3 and you have that labeled right. Then ...
September 5, 2014

chemistry
I would do this. pH = 5 means (H^+) - 1E-5 M. mols (H^+) in flask A = M x L = 1E-5*0.1 = 1E-6. So to make a pH = 7 we must exactly neutralize the acid to give pure H2O which has a pH of 7.00. So we need exactly 1E-6 mols OH^- in flask B and that in 100 mL (0.1L) is (OH^-) = 1E...
September 5, 2014

Chem
Your post is confusing? Are you calling buttermilk and butterfat the same? You drank 3L milk x 0.0236 = 0.0708 L buttermilk in that 3L. For the second part, grams = volume x density volume buttermilk you drank is 3L = 3000 mL and it is 2.36% buttermilk, then in 3L you drank ...
September 5, 2014

physical chemistry
I don't know what a concentration quotient is. What does it say in your text/notes? If you are talking about the formation constant for FeSCN, look through the experiment and note those areas where an measurement error may have occurred.
September 5, 2014

Chemistry
Doesn't this depend upon how these are broken down? H2O + CO2 <--> H2CO3 <-->H^+ + HCO3^- <--> H^+ + CO3^2- How many reactions is that? Is it one or three or six? Not a very good question in my mind; i.e., the question isn't very well defined. And we ...
September 5, 2014

Chemistry
I assume 872 nM is 872 nanomolar which would make it 872-9M or 8.72E-7M. The problem states that OH is ADDED UNTIL the OH^- is 8.72E-7M. Now, since (H^+)(OH^-) = 1E-14 Plug in OH and solve for H. I get 1.15E-8 M and convert that to pH.
September 5, 2014

Chemistry
No. What you have drawn is not an isomer of C2H2 for it doesn't have the formula of C2H2 but C4H8.
September 5, 2014

CHEM
A valence electron is an electron in the outside shell. Br has 7, S has 6, Na has 1. Look at the group of the periodic table in which the electron is found. That often tells you the number of valence electrons. I don't know how your are supposed to handle a "...
September 5, 2014

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

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