Sunday
December 4, 2016

# Posts by DrBob222

Total # Posts: 53,737

chem
What happens to the volume? If there is no volume change there is no work done. If the volume increases, then the system has done work to the outside and work is negative.
August 20, 2016

chem
Is that average velocity, root means squared velocity, other? KE = 1/2 mv^2 and Urms = sqrt (3RT/M)
August 20, 2016

chemistry
Sofie, this makes no sense. It depends upon what you want to know from G. Is it spontaneous, is it non-spontaneous, is it at equilibrium, do you want to know K or Q, etc.
August 20, 2016

chemistry
You really need to find the caps key and use it. CO, Co, co all mean something different. Na2CO3 ==> 2Na^+ + CO^3- 0.2M Na2CO3 gives 0.2M x 2 = 0.4 for (Na^+) and 0.2 x 1 = 0.2M for (CO3)2-
August 20, 2016

chemistry help!!! please!!! DrBob222 I need you!!
http://www.jiskha.com/display.cgi?id=1471635474
August 20, 2016

chemistry help!!! please!!! DrBob222 I need you!!
I answered this for you yesterday. You can go back and find my answer. Here are the instructions although my post yesterday was different than this (but the same answer). Convert 0.45 mol Al to mols C needed. Use the coefficients in the balanced equation for this. Convert mols...
August 20, 2016

chemistry help!!! please!!! DrBob222 I need you!!
A negative value for dG means it is spontaneous.
August 20, 2016

chemistry
The rate will increase by a factor of 5. Since they want a math equation I would do this. Make up a number for the rate for concns of 1 for each reactant and solve for k. That is rate = k(CHCl3)(Cl2) 25 = k(1)(1) k = 25/1 = 25 Then increase the CHCl3 by 5 but leave the Cl2 at ...
August 20, 2016

chemistry
Use the coefficients in the the balanced equation. mols C needed = 0.45 mol Al x (3 mols C/4 mols Al) = ? Then you know that 1 mol C contains 6.02E23 atoms.
August 19, 2016

Chemistry
Every compound is zero. K is 2*+1 = 2 Cr = 2*x = 2x O = 4*-2 = -8 2 + 2x + (-8) = ?
August 19, 2016

them
Water forms H bonds and has a low vapor pressure. How does that fit with B?
August 19, 2016

Chem
II is not right.The H of one molecule partially bonds with the oxygen of an adjacent molecule. Go on google and look at pictures of the H bond.
August 19, 2016

chemistry help?!
August 19, 2016

Chemistry
C is not right. The pH of strong acids is at the low(1 or less) end and pH of strong bases at the high end (13 or higher).
August 18, 2016

Chem
A gas gets hotter when it is compressed.
August 18, 2016

AP Chem help?!!!!
What do you think the answer is and why?
August 18, 2016

AP Chemistry help!!!!!
Hydrogen bonding increases the boiling point of ethanol
August 18, 2016

chemistry
I ASSUME that number is 1.2E25 atoms of oxygen. There are 9 neutrons in each atom so that will be 1.2E35 x 9 neutrons in that many atoms of O.
August 17, 2016

Chemistry
Zn + 2HCl ==> ZnCl2 + H2 mols Zn = grams/atomic mas = ? Using the coefficients in the balanced equation, convert mols Zn to mols HCl needed. You can see 1 mol Zn uses 2 mol HCl so mols Zn x 2 = mols HCl needed. Convert mols HCl needed to grams HCl by grams = mols HCl x ...
August 14, 2016

Chem 3
You have about 2 days of work here. Tell me what you know how to do, exactly what you don't understand, and post any work you have done toward this problem. I shall be glad to help you through it but I'm not inclined to do all of this work myself.
August 14, 2016

no, no, Michie--chemisrty
mass = volume x densit Therefore, density = mass/volume but you didn't substitute corrrectly. mass = 123 g volume = 17 cc So density = 123/17 = ?
August 14, 2016

Chemistry
You know (H3O^+)(OH^-) = Kw = 1E-14 and with your value of (H3O^+) that will let you calculate (OH^-).
August 14, 2016

Chemistry
mols = M x L Substitute and solve for L
August 13, 2016

Chemistry
This is a limiting reagent (LR) problem. One reagent is the LR, the other is the excess reagent (ER). I do these the long way; i.e., there are shorter ways to do them but I have trouble explaining them. Ba(OH)2 + Na2SO4 ==> BaSO4 + 2NaOH 1. mols Ba(OH)2 = M x L = ? 2. mols ...
August 13, 2016

Chemistry
CO2 + Ca(OH)2 ==> CaCO3 + H2O mols CO2 = grams/molar mass = ? Using the coefficients in the balanced equation, convert mols CO2 to mols CaCO3. You can see that 1 mol CO2 will produce 1 mol CaCO3. Now convert mols CaCO3 to grams. grams CaCO3 = mols CaCO3 x molar mass CaCO3
August 13, 2016

chemistry
?Fe^2+ + 4H^+ + [NO3]^- ==> ?Fe^3+ + 2H2O + NO You determine the number for Fe^2+ and Fe^3+ by balancing the charge on the left with the charge on the right. Hint: Try 1 and if that doesn't work try 2 and if that doesn't work try ........ etc.
August 13, 2016

Analytical Chemistry
What's the percent H2SO4 in that solution? My tables show it is 19.61% H2SO4.
August 13, 2016

Chem
A is right. B is wrong C is wrong D is worng
August 8, 2016

Chemistry
delta T = i*Kb*m Look at this logically. m = mols/kg solvent; therefore, m is constant for all of these. Kb, the boiling point constant is a constant for all of these. Therefore, the ONLY variable is i. i = 2 for A i = 1 for B i = 3 for C. i = 2 for D. i is the van't Hoff ...
August 8, 2016

Chemistry
http://www.jiskha.com/display.cgi?id=1470689042
August 8, 2016

Chemistry
1. mols C2H6 = grams/molar mass = ? 2. mols O2 = grams/molar mass = ? 3. Convert mols C2H6 to mols CO2 using the coefficients in the balanced equation. 4. Do the same with mols O2 to mols CO2. 5. In limiting regent problems, the SMALLER amount of CO2 produced is the correct ...
August 8, 2016

West Charlotte
If you want to do this by the unit factor method, do this. (0.75 lb/med loaf) x # med loaves = 3.75 lbs. The # med loaves unit cancel so lbs = lbs. Solve for # med loaves. When I was in school I never could remember which number was the numerator and which was the denominator...
August 7, 2016

chemistry assignment
I'm a little confused here. Almost everyone knows how to calculate an average. Have you done that? If not, exactly what don't understand about the question. I shall be glad to help you but I don't want to do a lot of busy work you already know how to do.
August 7, 2016

chemistry
One is HNO3, nitric acid.
August 5, 2016

Chemistry
molar mass CH4 = 16 molar mass H2 = 2 Assume any number for the mass of samples. Let's say 16 g. Then mols CH4 = 16/16 = 1 mols H2 = 16/2 = 8 mol fraction CH4 = 1/9 mol fraction H2 = 8/9 pCH4 = XCH4*Ptotal pH2 = XH2*Ptotal XH2 = 8/9
August 5, 2016

that answer is incorrect, also
That answer gives 1/9 for H2. The fraction for H2 is 8/9. See the post above http://www.jiskha.com/index.cgi? for the correct solution.
August 5, 2016

Chemistry
9% NaCl(Iassume that is mass percent) means 9 g NaCl/100 g solution. You have 250 g solution; therefore, 9 x (250/100) = ? g in 250 g solution.
August 4, 2016

Chemistry
Your post isn't quite clear. You may want percent purity of CaCO3 or you may want percentage yield of the reaction (production of CaO) but to me percentage yield of CaCO3 makes no sense because you aren't making CaCO3. Here is how to do both. CaCO3 ==> CaO + CO2 ...
August 4, 2016

Science
You want a term paper??? BOOKS have been written on this. I suggest you Google what you just posted here, read, read, read, and write your paper. Be sure and give credit for your references.
August 3, 2016

Chemistry
There are 454 g (approx) in 1 lb. Sp 5 lb x 454 g/lb = ? grams. mass = density x volume. You know mass, you know density, substitute and solve for volume, in mL, and convert to L.
August 3, 2016

chemistry
Because it has its outer shell filled with electrons.
August 3, 2016

Analytical Chemistry
That's great. Glad to help. Remember to look to see the METHOD so you will remember it.
August 3, 2016

Analytical Chemistry
pH = pK2 + log b/a 7.4 = 7.2 + log b/a log b/a = 1.58. You're right, I typed in the wrong numbers in my calculator. I typed in 7.2= 7.4 + log b/a. It helps to use the right numbers doesn't it. OK. b/a = 1.58 or b = 1.58a then a + b = 0.1 a + 1.58a = 0.1 and I suspect ...
August 3, 2016

Analytical Chemistry
I like to do these in millimoles. That way I don't get bugged by the zeros in front. pH = pK2 + log (base)/(acid) mmols you want = 10 x 0.01 = 0.1. So equation 1 is a + b = 0.1 Equation 2 is 7.4 = 7.2 + log (b)/(a) Solve for b/a and rearrange to b = ?*a (whatever that ? ...
August 3, 2016

Chemistry
Note that the question gives three choices but the answer choices are not the same. Pressure goes down as you ascend so .......
August 3, 2016

Chemistry
Scroll down to the contents and click on preparation. https://en.wikipedia.org/wiki/Lead(II)_iodide
August 2, 2016

Chemistry
Jenny, I don't get it. I don't understand the question. Among other things, what is Mb?
August 2, 2016

Chem
LR = limiting reagent. 2Al + 6HCl ==> 3H2 + 2AlCl3 How many mols H2 produced if we had 4.5 mol Al and all of the HCl we needed. That would be 4.5 x (3 mols H2/2 mol Al) = 4.5 x 3/2 = 6.75. How many mols H2 produced if we had 11.5 mols HCl and all of the Al we needed. That&#...
August 2, 2016

Chemistry
What's the problem here. NaBr ==> Na^+ + Br^- Li3PO4 ==> 3Li^+ + PO4^3-
August 2, 2016

Phy.Chem
You need to proof your posts> Glass or gas? I suspect gas. ff? who knows? If temperature doesn't change, then volume won't change unless the pressure changes. .
August 2, 2016

Chemestry
Note the correct spelling of chemistry. CaCO3 ==> CaO + CO2 CaCO3 available = 200 x 0.25 = 50. mols CaCO3 = 50/molar mass CaCO3 = 50/100 = 0.5 So you will get 0.5 molsl CO2. Plug that into PV = nRT at NTP andf solve for volume in liters.
August 2, 2016

Chemistry
pH + pOH = pKw = 14. Solve for pOH. Then pOH = -log(OH^-). Solve for (OH^-). Call the weak base BOH. .......BOH ==> B^+ + OH^- I......0.46....0......0 C......-x......x......x E....0.46-x....x......x You know x from above. Substitute x and 0.46-x into the Kb expression and ...
August 1, 2016

analytical chemistry
See your last post. The solubility product is not 7.1. YOu must include the rest of the numbers. It is 7.1 x 10^? and without that ? I can't go anywhere.
August 1, 2016

analytical chemistry
You have made typos in your post by not including the exponent for the solubility. I can't work it as is.
August 1, 2016

chemistry
Check that post I made. I'm in a big hurry and I may have hit the wrong key on the calculator or misread an answer from the display. That is, confirm what I've written.
July 31, 2016

chemistry
Thanks you. That helps a lot. Let's call ethylamine just BNH2. BNH2 + HCl ==> BNH3^+ + Cl^- initial mols BNH2 = M x L = approx 0.01 mols HCl when adding 5 mL is M x L = 0.00175 mols. Put that on an ICE chart but I rather use millimols.. All of those zeros confuse me...
July 31, 2016

chemistry
You have a nightmare of a problem (actually 6 problems) here. It is important that you know how to do these. I don't mind helping you through it but first tell me what you know and what you don't understand. We can go from there. Please show your work.
July 31, 2016

chemistry
If the solubility at 373 is 55 g then all of it will be dissolved. At 273, it will dissolve 37 g. So 55-37 = ? will crystallize.
July 31, 2016

Chemistry
mols CaCl2 = M x L = (1.5/1000) x 0.05 = approx 7E-5 but you need a better number than that. Convert to grams CaCl2 = mols x molar mass = approx 0.008. Again, you must get a better number. Convert to grams Cl. Thats 0.008 g CaCl2 x (2*35.5/111) = approx 0.05 g Cl^-. 1 ppm = 1 ...
July 31, 2016

Chemistry
That's a new one on me. Here is what I found on google. Perhaps that will help.
July 31, 2016

Chemistry
delta T = Kf*m Find mols: mols = grams ethyl/molar mass = ? Find molality: m = molality = mols/kg solvent Plug m and Kf(1.86) into the delta T formula and solve for delta T. Then subtract that from zero to find the new freezing point.
July 30, 2016

Chemistry
It's tough to do this on the internet but follow these instructions. K^+ and PO4^3- will be K3PO4 Write the ions together like this. KPO4. I like to put parentheses around those that are polyatomic ions like PO4^3-. So K(PO4) above the K write its charge of 1 and above the...
July 30, 2016

Foundation Chem
I don't know because I don't know what experiment you're talking about.
July 29, 2016

Chm
What reaction? Increase from what to what?
July 29, 2016

Chemistry
96,485 C will deposit 63.54/2g Cu: therefore, how many C will deposit 1 g Cu? That's 96,485 x 2/63.54 = ? Then 96,485 will deposit 160/2 g Br2. How man g will ? from above deposit. That's (160/2) x ? from above = ?g Br2. You should confirm all of the calculations AND ...
July 29, 2016

Chemistry
One allotrope is graphite and another is diamond. You can google carbon and I suggest you use the Wikipedia link, and find other allotropes as well as the physical and chemical properties of each.
July 29, 2016

@ Ms Sue---Chemistry
Sarah does that. Any time you see Sarah's name you can find a plethora of posts under other names. She/he makes it difficult to help her/him. You would think he/she/it would want to make it easy for us but apparently that isn't the case.
July 29, 2016

Chemistry
This forum does not lend itself to drawing molecules; therefore, polarity is tough to explain. I suggest you google "polarity" and read and look at the examples Wikipedia gives. That site goes a good job of explaining it. I suspect you want to know how you know by ...
July 29, 2016

Chemistry Theory
You know it can't be linear because it is a polar molecule and has a dipole moment associated with it.
July 29, 2016

chemistry
What's your problem here? Just look up the Keq for each half and multiply them together.
July 29, 2016

Chemistry
Call AgC2H3O2 as AgAc. .........AgAc ==> Ag^+ + Ac^- I.......solid.....0.......0 C.......solid.....x.......x E.......solid.....x.......x Ksp = (Ag^+)(Ac^-+ Ksp = (x)(x) You are given the value of x, substitute that value and solve for Ksp.
July 29, 2016

Chemistry
You work this one in reverse from your post on determining the Ksp for AgAc. mols AgC2H3O2 = 14.1 molar mass AgC2H3O2 = approx 0.08 M AgAc = 0.08 AgAc/1.7L = approx 0.05 mols/L. ........AgAc ==> Ag^+ + Ac^- I.......solid....0.......0 C.......solid....x.......x E.......solid...
July 29, 2016

Chemistry
Could you type in the example problem of PbI2 and the answer they gave for that example. If so perhaps I can help. Don't make a new post out of it; use this post for that.
July 29, 2016

Chemistry
millimols H2PO4- = mL x M = approx 10 millimols HCl added = 6 ......H2PO4^- + H^+ ==> H3PO4 I......10.......0........0 add............6................ C......-6......-6........6 E......4........0.........6 Substitute the E line into the HH buffer equation and solve for pH...
July 29, 2016

Chemistry
This is multifaceted problem. Please explain fully what you don't understand about each.
July 29, 2016

chemistry
Co^2+ ==> Co^3+ + e HO2^- + 2e + H2O ==> 3OH^- Multiply eqn 1 by 2 and add. Cancel the 2e on each side. ------------------------ 2Co^2+ +HO2^- +H2O=> 3OH^- +2Co^3+ You can add in the Cl^- here as 2CoCl2 + HO2^- + H2O ->2Co^3+ + 3OH^- + 4Cl...
July 28, 2016

chemisty
See your other problem below but note you have made a typo on H2PO4. You mean H3PO4 or NaH2PO4 or H2PO4^-.
July 28, 2016

chemisty
Mg + 2HCl ==> MgCl2 + H2 mols HCl = M x L = ? Convert mols HCl to mols H2. That will be mols H2 = 1/2 mols HCl. Then convert mols H2 to L at STP knowing that 1 mol H2 will occupy 22.4 L at STP, then convert that to mL.
July 28, 2016

Chemistry
........C2D3 ==> 2C^3+ + 3D^2+ I.......solid.....0.......0 C.......solid.....2x......3x E.......solid.....2x......3x Ksp = (C^3+)^2(D^2+)^3 9.14E-9 = (2x)^2(3x)^3 Solve for x for solubility of C2D3. Units: Technically the unit is "activity" since Ksp is a ...
July 28, 2016

Chemistry
6 g 12C = how many mols? That's 6g/12 = 0.5 mols C. 0.5 x 6 = 3 mols neutrons. 3 x 6.02E23 = 18.1E23 neutrons. Now to 14N which really is 14N2. 18.1E23 neurons/6.02E23 = 3 mols neutrons. N2 contains 7 p + 7 n = 14 total for N or 14 n for N2. 3 mols neutrons x 1 mol N2/14 ...
July 28, 2016

Chemistry
Complete reaction of nitromethane with what?
July 28, 2016

Chemistry
pH = 5.50 pH = -log(H^+) (H^+) = approx 3.2E-6 but you need a more accurate answer than that. .........HA ==> H^+ + A^- I.........y.....0......0 C........-x.....x......x E........y-x....x......x Ka = (H^+)(A^-)/(HA) 5.7E-10 = (x)(x)/(y-x) You know x, substitute and solve ...
July 28, 2016

........PbI2 ==> Pb^2+ + 2I^- I.......solid....0.......0 C.......solid....x.......2x E.......solid....x.......2x Ksp = (Pb^2+)(I^-)^2 Ksp = (x)(2x)^2 You know x = 2.4E-3 M, substitute and solve for Ksp.
July 28, 2016

Chemistry
Note the correct spelling of celsius. You don't have enough information in your post. What limiting reagent? What is the experiment? What are you washing?
July 28, 2016

Organic Chemistry
He is a noble gas but placing that under "organic chemistry" is a sin.
July 27, 2016

........AgCN ==> Ag^+ + CN^- I......solid.....0.......0 C......solid.....x.......x E......solid.....x.......x Ksp = (Ag^+)(CN^-) Ksp = (x)(x) The problem tells you x = 1.4E-6. Calculate Ksp.
July 27, 2016

chemistry
I did that last night for you.
July 27, 2016

Chemistry
Note the correct spelling of celsius. Use PV = nRT and solve for n, then n = grams/molar mass.
July 27, 2016

chemistry
mL1 x M1 = mL2 x M2 mL1 x 0.5M = 2000 mL x 0.4 Solve for mL1.
July 27, 2016

chemistry
1 ppm = 1 mg/kg and 1 ppb = 1 mg/1000 kg. 15 mg/kg = ? ppb is 1000 more mg.
July 27, 2016

Chemistry
You didn't list any values. The salt will have a pH less than 7; most likely it will be about 4 to 5 that isn't a rule.
July 26, 2016

Che
What are you calling fundamental particles? Do you want electrons, protons, neutrons, or do you want electrons, up quarks and down quarks?
July 26, 2016

Army school math
I don't know how the army does this. Trig? formula. The formula using straight algebra is A = sqrt(p(p-a)(p-b)(p-c) where p is 1/2 the perimeter and a,b,c are the sides. The perimeter is 26 and the base is 6 which makes the other two sides 26-6 = 20 and since it is an ...
July 26, 2016

Chemistry
If you are using M for mols, that won't get it. M stands for molarity. I will assume you meant mols. You have four limiting reagent (LR) problems here. I'll do the first two for you; you follow the plan to do the other two. Zn + 2HCl ==> ZnCl2 + H2 a. 1. mols HCl = ...
July 26, 2016

Organic Chemistry
Two comments: 1. How in the world did this get named as a question in organic chemistry. Helium is about as un-organic as you can get. 2. With regard to Yang's answer. That's a great answer EXCEPT that "all noble gases have the maximum number of electrons possible...
July 25, 2016

Chemistry
I'll do the first one; you do the second. CH4 + 2O2 --> CO2 + 2H2O dHrxn = (n*dHf products) - (n*dHf reactants) If dHrxn is -, rxn is exothermic. If dHrxn is +, rxn is endothermic.
July 24, 2016

chemistry
This is a condensation polymer. I googled "condensation polymer" and this is what I got. Let me be clear that this is copied word for word from the web. I suspect it is found this way in Wikipedia. "Condensation polymers are any kind of polymers formed through a...
July 24, 2016

Analytical Chemistry
No. You have no concn for that so how would you put that on the graph? You look at the A value on the graph, read the concn in mg Fe from the curve, and use that in the final % w/w calculation.
July 22, 2016

Analytical Chemistry
You can do this mathematically but it is easier, I think, to draw a graph for the calibration curve. On the Y axis you place the absorbance which I assume is the "signal" in your post. If not, it might be %T; whatever it is plot it (Absorbance or whatever) on the Y ...
July 22, 2016

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