Friday
March 27, 2015

Posts by DrBob222


Total # Posts: 47,965

Chemistry
What does linear mean?
March 23, 2015

Chemistry
No. Look at the P vs V plot at that same site. It certainly is not linear. Do you know what linear means?
March 23, 2015

Chemistry
See the V vs T graph. https://www.google.com/search?q=graph+volume+gas+vs+T&ie=utf-8&oe=utf-8
March 23, 2015

Chemistry
yes
March 23, 2015

Chemistry
C20H42 + 61/2 O2 ==> 20CO2 + 21H2O dHrxn = (n*dHf CO2) + (n*dHf H2O(l)) - (n*dHf x) where x = C20H42 You're given Hf CO2 and Hf for liquid H2O and dHrxn, solve for x.
March 23, 2015

Chemistry
One of the most poorly worded questions I've seen in some time. From the description this is a limiting reagent problem in which the CuCl2 is the LR. 2AgNO3 + CuCl2 ==> 2AgCl + Cu(NO3)2 mols AgCl formed = grams/molar mass = ? mols CuCl2 initially = 1/2 mols AgCl. (CuCl2...
March 23, 2015

chemistry
I don't see how. The power stroke to me is when the small chamber of gasoline fires and the piston is driven down and drives the wheels. It appears to me that the system of gases is doing work on its surroundings.
March 23, 2015

chemistry
Look up Ka values for HCOOH, CH3COOH, HCN and convert to pKa values. Good buffers are made with pKa values close to the pH needed.
March 23, 2015

Chemistry
I think so.
March 23, 2015

Chemistry
Just as an example, O2 has a density of 32/22.4 = 1.42 g/L and N2 has 28/22.4 = 1.25 g/L. Convert that to g/mL and see if that agrees with c.
March 23, 2015

Chemistry
At this point you have a saturated solution of H2CO3. The Internet has some wide and wooly discussions about Ka for H2CO3 and molarity of a saturated solution of CO2. The (CO2) in the room temperature range is between 0.29M and 0.056M. If we use ka1 of 4.7E-7 (and there is ...
March 23, 2015

chemistry
Answered above.
March 23, 2015

Chemistry (Aspirin Synthesis- Unreacted SA
I think you meant to type in 2147. Your M is ok. However, mols = M x L (not mL) so 6.567E-5 x 0.05 = 3.284E-6 and that times molar mass SA gives grams SA in the 0.15g sample. If you subtract 0.15 - grams SA that gives you grams ASA and percent yield is (g ASA/0.15)*100 = ?
March 23, 2015

Chemistry
I would rule out a; pressure is force per unit AREA and area is not volume. If the author intended a to be the answer I think s/he erred. Answer B doesn't make sense; it decreases with decreasing T but it increases with increasing T. C makes no sense either. I think D is ...
March 23, 2015

Science
My interpretation of the question is how it impacts your daily life; I think you have answered how science may be helpful although a career in a medical field certainly would impact you. Science is around you. The plastics and metals in your car, the gasoline you use in it, ...
March 23, 2015

chemistry help
right
March 23, 2015

chemistry help
If it is 100 ppm that is 100 part is 1E6 parts or 1 part in 1E4 parts (see what I did?) or 0.1 in 1000 or 0.01 in 100 so how many would that be in 25?
March 23, 2015

Science
In general it is the series circuit. If you take any three resistors and hook them in series the total R is the sum. If you hook them in parallel total R is smaller than the lowest resistor you have in the circuit. Try it R1 = 10 ohms R1 = 20 R3 = 50 R in series is 80 ohms. R ...
March 23, 2015

Science Check Please Dr.Bob222
Yes, it does help. Remember that I'm not a biologist and I don't know all of these answers. 1 and 2 are right. I lean to a different answer for 3 although one function certainly is to support the body. I just don't know if that is the main function. 4 and 5 are ...
March 23, 2015

Chemistry
Use the Hendrson-Hasselbalch equation.
March 23, 2015

Science Check Please
Have you thought about placing an asterisk/arrow/some other notation by the choice of your choice for your answer?. When you post 12 or more question and place the answers AT THE END, we must scroll down each time, look at the answer, scroll back up to see what it said etc. It...
March 23, 2015

General Chemistry
Convert 245 lb to grams. (83.5g/g ore)*10^6 = ? ppm
March 23, 2015

CHEMISTRY
Choose any convenient volume size, say 1 L. rate A = 1L/10 sec rate B = 1L/20 sec (rate1/rate2) = sqrt(M2/M1) Substitute and solve for M2.
March 23, 2015

chemistry
I always revert to half reactions when I have trouble. Most students forget to compare apples with applies; i.e., you should make that 2Br^ on the right to sstart. But let's do try this way. Cr is +3 on the left and +6 on the right so a gain of 3e. Br is zero on the left ...
March 22, 2015

Chemistry help
See your duplicate post below. By the way, if you put in some screen name, even something as simple as spam or nyet, it would allow us to check back later and find if you have follow up questions. As it is, anonymous isn't very definitive.
March 22, 2015

Chemistry help
I'm sorry but my crystal ball is not working very well tonight. What reaction. What experiment? What goes in the reaction beaker?
March 22, 2015

Chemistry
I have deleted my answer to your earlier post.That answer I gave was partially right but not 100% right. Here is how the answer comes up to be 0.0376 BUT I'm not ready to buy into the solution. This is just to show you how the author came up with that answer. 1.22 g/mL x ...
March 22, 2015

science
3CaCl2 + 2Na3PO4 ==> Ca3(PO4)2 + 6NaCl It would have been nice to given us the molar masses you found; otherwise the ratio may be slightly different if you are using one molar mass and we use another. molar mass CaCl2 = approx 111 molar mass Na3PO4 = approx 259 So 111*3 g ...
March 22, 2015

Chemistry
Is that ferrous phosphate; aka, iron(II) phosphate? mols Fe3(PO4)2 = grams/molar mass = ? # molecules = mols x 6.02E23 = ?
March 22, 2015

chemistry
..........2NO2(g) ⇌ 2NO(g) + O2(g) I..........3..........0.......0 C.........-2x........ 2x......x E.........3-2x....... 2x......x OK?
March 22, 2015

To Krishna--Chemistry
DON'T post piggy back on another post as an answer. Go to the top of the page and click on "post a new question".
March 22, 2015

To Jane--Chemistry
I don't understand what you're having trouble with. Will you please clarify?
March 22, 2015

general chemistry
How many mols do you need? That's M x L = mols. Then grams = mols/molar mass. You know molar mass and mols, solve for grams.
March 22, 2015

chemistry
You had H2CaO2 written ok; it just isn't the usual way we see it. You can see that's the same thing as Ca(OH)2.
March 22, 2015

Chemistry
So this gas has a mass of 0.24g and a volume at NTP of 45 mL. What is the mass of H2 at NTP of 45 mL. n of H2 = 0.045L/molar volume @ NTP = ? Solve for n of H2. Then n x molar mass H2 = grams. v.d. = mass unknown gas/g H2 for that volume.
March 22, 2015

CHEMISTRY
Do you want to know if your answer of 365 is correct? It is. Do you want to know how to work it? P1V1 = P2V2
March 22, 2015

CHEMISTRY
PV = nRT n = grams/molar mass If you use R as 0.08206 L*atm/mol*K, volume must be changed to L. 1 cubic meter = 1E6 cc and 1000 cc = 1L
March 22, 2015

CHEMISTRY
Another way. My suspicion is that your chem prof wanted you to get practice on mole fractions. Assume any number of mols; i.e., 1 is a good number but any number will work. n CO = 1 n N2 = 1 Total mols = 2 XCO = mols fraction = n CO/total mols = 1/2 XN2 = n N2/total mols = 1/2...
March 22, 2015

Chemistry
I assume you made that entry by error and put me as the author since the IP address for your original question and that answer attributed to me is the same. If my answer still needs clarification I can help but let's not have any funny business.
March 22, 2015

Chemistry
H2A + OH^- ==> HA^- + H2O k1 = 0.0126 HA^- + OH^- ==> A^2- + H2O k2 = 2E-7 Convert pKa values to k1 and k2 as above. pk1 = 1.9; pk2 = 6.7 You start with 20 mL of 0.1M H2A and you titrate it half way with 10 mL of the NaOH; i.e., starting with 20 mL of 0.1M H2A you have ...
March 22, 2015

Chemistry
I have no clue how to start this any help would be appreciated!
March 22, 2015

Chemistry
The critical points on the curve are given by a,b,c. How much of this do you know how to do. Explain the parts you don't know how to do. I don't want to do a lot of work on what you already understand.
March 22, 2015

Chemistry
Write and balance the equation. H3AsO4 + KOH ==> KH2AsO4 + H2O mols H3AsO4 = M x L = ? Now use the coefficients in the balanced equation to convert mols H3AsO4 to mols KOH. That's 1:1 so mols H3AsO4 = mols KOH. Then M KOH = mols KOH/L KOH. You have mols KOH and M KOH, ...
March 22, 2015

Chemistry
You are right. When working with gases, one may use the volumes as if they were mols. That isn't exactly right but the math works out that way. So use volumes and convert with the coefficients in the balanced equation to convert volume CH4 to mols O2 for the first one and ...
March 22, 2015

Science
I agree with some of what you have but not all of it. Here is your work. .1g/100= .001g gold I agree with 1E-3g Au .001 g gold/ml * .5 ml = .00005 g gold 0.001 x 0.5 = 5E-4--you have 5E-5. The rest of this I don't get. It appears to me that all of the Au you have at this ...
March 22, 2015

Chemistry
But note that I get 11.86 mL which I would round to 11.9 mL to three significant figures.
March 22, 2015

Chemistry
What's 11.8 M NiCl2? The problem says M NiCl2 is 0.258. You must mean 11.8 mL. mols Na2CO3 = M x L = 0.153 x 0.020 = ? mols NiCO3 formed = same since there is 1 mol NiCO3 for 1 mol Na2CO3. grams NiCO3 = mols NiCO3 x molar mass NiCO3.
March 22, 2015

chemistry
I don't see a question here.
March 22, 2015

Chemistry
yes. http://antoine.frostburg.edu/chem/senese/101/acidbase/faq/negative-pH.shtml
March 22, 2015

chemistry
I think you converted the wrong way. 28,000 gallons x (3.785 L/gallon) = 1E5 ESTIMATED. You need a better answer than that. How many mols do you need? That's M x L = approx 1E5 mol HCl. M HCl = mols HCl/L HCl. You know M and mols, solve for L. That really looks like a ...
March 21, 2015

chemistry
I have no idea what griest is? Can you help. Is it a liquid, solid, gas? What's the specific heat?
March 21, 2015

Chemistry
......PCl5 ==> PCl3 + Cl2 I.....1.46......0......0 C.....-p........p......p E.....1.46-p....p......p Substitute into the Kp expression and solve for p, then evaluate 1.46-p.
March 21, 2015

Chemistry 2
Or tell me in detail what it is you don't understand. You can't leave us dangling like that. Help us help you.
March 21, 2015

Chemistry 2
Then show me what you've done with those instructions I gave you.
March 21, 2015

chemistry
......HA ==> H^+ + A^- I.....0.5....0......0 C.....-x.....x......x E...0.5-x....x......x Enter the E line into Ka expression and solve for Ka. The problem tells you the pH which will give you the (H^+) and (A^-). Then convert to pKa.
March 21, 2015

chemistry
right. The definition will always tell you.
March 21, 2015

chemistry
What you picked is a very good buffer. Do you know what a buffer is. Acid buffers are WEAK acids and their salts. Base buffers are WEAK bases and their salts. You chose CH3COOH which is acetic acid and that is a weak acid. NaCH3CO2 is the salt of acetic acid so that makes a ...
March 21, 2015

chemistry
No but I would go with 9.87 I don't know what you're supposed to do with the error unit of 0.1.
March 21, 2015

chemistry
Not quite. Thanks for showing your work. 0.00150/40 = mols KOH and that's right. But that's divided by L (0.500) and not 500. That give you about 7.4E-5 and that is the (KOH) in the solution. Take the -log of that to give pOH and subtract from 14 to obtain the pH.
March 21, 2015

chemistry
DON'T USE all lower case for chemical symbols. CO is carbon monoxide. Co is cobalt. co is the abbreviation for company. It doesn't tell us a thing. And I don't like Fe2 either. I assume you were in such a hurry you omitted the rest of the formula of Fe2O3. Finally...
March 21, 2015

chemistry
Why are you posting this again. I thought we took care of this below. Your 4.47 was/is correct.
March 21, 2015

Chemistry 2
You really need to find the arrow key and use it. .....2HI ==> H2 + I2 I.................... C.................... E......y......x....0.351 So if I2 is 0.351 that means H2 is 0.351 (and that does NOT means HI is 0.351). Write the Kc expression, substitute for H2 and I2 and ...
March 21, 2015

chemistry
HCl + KOH ==> KCl + H2O mols HCl = M x L = 0.015 mols KOH = the same since 1 mol HCl reacts with 1 mol KOH = 0.015 Then M KOH = mols KOH/ L KOH. You know M and mols, solve for L. 1.00 = 0.015/L and L = 0.015/1.00 = 0.015L. Convert that to mL for 15 mL.
March 21, 2015

chemistry
To add a little clarification to the answer already posted. The correct answer to 3 s.f. is 100. and the period at the end is necessary and it not the end of the sentence. That sometimes leads to confusion and another way to do it to write 1.00E2 and that way a period is not ...
March 21, 2015

chemistry
Steve is right. CCl3COOH is not it.
March 21, 2015

Analytical Chemistry
I assume the half cell for the Pt/O2 couple is 4H^+ + 4e + O2 ==> 2H2O E = 1.229 v as a reduction. Add that to the H2 couple of H2 ==> 2H^+ + 2e E = 0 as an oxidation. The cell reaction then is 2H2 + 4H^+ + 4e + O2 ==> 2H2O + 4H^+ 4e The 4e cancel. I've arranged ...
March 21, 2015

science
I agree
March 21, 2015

chemistry
I would choose RbOH and CH3COO^- RbOH is a strong base, CH3COO^- is the base part of acetic acid.
March 21, 2015

chemistry
OH groups in inorganic chemistry are basic. I see two of them. NH3 is a base, also, but it is a weak one.
March 21, 2015

chemistry
D is right.
March 21, 2015

chemistry
B isn't right and you should know not to pick that. pH of 7.51 is basic and this is an acid. If you will show your work I will find where you went wrong.
March 21, 2015

chemistry
Can you write and balance the molecular equation? If so, do that, convert to complete ionic equation, then cancel materials common to both sides and you have the net ionic equation. Go as far as you can and I can help you finish.
March 21, 2015

English
Well, EXCUSE ME P/m; I learn something new every day. From the way those posts have read and the problems encountered by Writeacher, Reed, and Ms Sue over the last two or three days, I assumed we were trying to deal with someone not doing well with their ESL and I was trying ...
March 21, 2015

English
I know I'm butting in where I don't belong but I think a vital point is missing here and/or not being considered. It appears to me that m has trouble with the English language. Students that don't speak/write English very well can't fix what they don't ...
March 21, 2015

Science
Yes, 1 and 2 are right.
March 21, 2015

Science
You have far too many questions for one post. Here is the information for the first one. pH < 7 = acid pH > 7 = base pH = 7 = neutral.
March 21, 2015

Chemistry
To raise to the 1/4 power I use 0.25 etc. That parenthesis thing gets confusing to me.
March 21, 2015

Chemistry
Your button just isn't called the y^x button but you see you raised 12.5 to the 1/3 power. I don't do that. I plug in 12.5 and raise it to the 0.3333 power and that way I don't worry about the parentheses.
March 21, 2015

Chemistry
.........N2 + 3H2 ==> 2NH3 E........1.2....x......0.015 Kp = p^2NH3/pN2*p^3H2 Your set up is right; you're not doing the algebra right. To take the cube root you don't divide by 1/3; you hit the y^x button and use 0.3333 for the x. That gives you 2.3 atm. Try these ...
March 21, 2015

Chemistry
I2 + 6H2O ==> 2IO3^- + 10e + 12H^+ OCl^- + 2e + 2H^+ ==> Cl^- + H2O Multiply equation 1 by 1 and equation 2 by 5 and add, then cancel any common materials on both sides (like H2O) I think your error was in not comparing apples with apples; ie. I2 can't go to IO3^-. ...
March 21, 2015

Chemistry
If HCl is in excess, calculate how much excess in mols, divide by the TOTAL volume at that point to obtain (HCl) in mols/L; ie., M, then pH = -log(HCl) since HCl is a strong acid and ionizes 100%.
March 21, 2015

chemistry
You have the pKa values wrong. pK1 = 2.15; pK2 = 7.2 (which you have right) and pK3 = 12.1. Use the Henderson-Hasselbalch equation. pH = pk2 + log (base)/(acid) 7.5 = 7.2 + log (base)/(acid) or 7.5 = 7.2 + log b/a H3PO4 + NaOH ==> NaH2PO4 + H2O NaH2PO4 + NaOH ==> Na2HPO4...
March 21, 2015

Chemistry
I assume that Kzny is Kf for ZnEDTA = 3E16. millimols Zn = 50 x 0.2 = 1.00. millimols EDTA = 20 x 0.05 = 1.00 .......Zn^2+ + EDTA ==> ZnEDTA I......1.00....1.00......0 C.....-1.00...-1.00......1.00 E......0........0........1.00 With such a large Kf of 3E16, it is reasonable...
March 21, 2015

chemistry
dG = dH - TdS dG is the total; dS is just a part. dS contributes its part but clearly it must be added into dH before one knows the total energy of the system.
March 21, 2015

chemistry
Why did you change screen names from Muli to Joseph? dG = -RTlnKp Substitute and solve for Kp. By the way, remember dG goes in the equation as J/mol.
March 21, 2015

Chemistry
PV = nRT and solve for n = number of mols. Then n = grams/molar mass. You know molar mass and n, solve for grams.
March 20, 2015

Science
The switch and the lamp are connected in series.
March 20, 2015

chemistry
mols SO3 = grams/molar mass = ? mols H2O = grams/molar mass = ? Using the coefficients in the balanced equation, convert mols SO3 to mols H2SO4. Do the same and convert mols H2O to mols H2SO4. In limiting reagent problems the SMALLER amount of product formed is ALWAYS the ...
March 20, 2015

Science!
I don't agree with 5,6,9. The others are right except for 10. See my note below about 10. I don't see the right answers to 10. Evaporating the WATER (OR SOLVENT) I would buy but you can't evaporate the mixture. Using a filter will not do it nor will using a magnet ...
March 20, 2015

chemistry
Probably dipole-dipole.
March 20, 2015

Science
In parallel, each switch controls each lamp. In series any switch controls all of the lamps.
March 20, 2015

chem
mols SbCl5 = grams/molar mass = ? M = mols/5.0L = approx 0.007 but that's an estimate. ............SbCl5 ==> SbCl3 + Cl2 I...........0.007.......0......0 C............-x.........x......x E..........0.007-x......x......x Substitute the E line into the Keq expresson and ...
March 20, 2015

Chemistry
NaOH + HOOCCH3 ==> NaOOCCH3 + H2O millimols CH3COOH = mL x M = ? millimols NaOH = mL x M = ? Can you take it from here. If not please explain in detail what you don't undrstand.
March 20, 2015

Chemistry
Sample size in the titrated sample (25 mL) is 0.5 x 25/100 = ? mols EDTA = M x L = ? mols Zn = mols EDTA grams Zn = mols Zn x atomic mass Zn %Zn = (mass Zn/mass sample in 25 mL)*100 = ?
March 20, 2015

Chemistry
I need some help. What do you not understand about these questions? Both are bases and Mg(OH)2 does not form complex ions.
March 20, 2015

Chemistry
g = mols x molar mass = ?
March 20, 2015

Chemistry
use the dilution formula. mL1 x M1 = mL2 x M2 3*4 = 50*x solve for x
March 20, 2015

Chemistry
mols ethanol = grams/molar mass = ? Then M = mols/L or mols/0.250 = ?
March 20, 2015

chemistry
138 pm = 138E-12 m wavelength = h/mv
March 20, 2015

Chemistry
%MgSO4 in MgSO4.7H2O = [(molar mass MgSO4/molar mass MgSO4.7H2O)]*100 = ? Then 2.4g x (%MgSO4/100) = ?
March 20, 2015

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