Posts by drbob222

Total # Posts: 54,970

Science

chemistry
M = molarity = mols/L How many mols? That's mols = grams/molar mass L = 0.250

College Chemistry!!
I believe you've made a typo with Ka. Call phenol just HP. HP ==> H^+ + P^- Ka = (H^+)(P^-)/(HP) Convert pH to (H^+) and substitute that along with Ka value and solve for the ratio of HP/P

chemistry
You've made a typo. Do you mean Radium or Radon? I'll assume Rn-222. k = 0.693/t1/2 Then ln(No/N) = kt. Substitute and solve for N

Science
Two equations in two unknowns and you solve them simultaneously. 2CuO ==> 2Cu + O2 2Cu2O ==> 4Cu + O2 ----------------- Let x =g CuO and y = g Cu2O ---------------- eqn 1 is x + y = 1g eqn 2. This converts Cu from CuO and Cu from Cu2O to grams Cu that you end up with of ...

@ MeGaTrOn---chemistry
You're not willing to do ANY of this work? I've posted a hint at your duplicate post above. You're right, mols are given BUT you know grams and you can calculate mols.

chemistry
To what? The ocean? under the h house? in the drinking water?

chemistry
No but that's my mistake. I didn't write all of the equation. It should be (P1V1/T1) - P2V2/T2) Substitute and solve for V2.

chemistry
I thought that would be the next question. :-) Use P1V1 = P2V2. That will give you the volume at STP if you plug in values for STP of 273 K and 101.325 kPa.

chemistry
Remember Dalton's Law of Partial Pressures; i.e., the total pressure of a system is the sum of the partial pressures of each gas. So Total P = pH2O vapor + pH2(dry) gas. You know total pressure--that's air pressure of 95.97 kPa. You are given the pH2O at that ...

chemistry---kenson r
heat lost by water + heat gained by Al = 0 [mass H2O x specific heat H2O x (Tfinal - Tinitial)] + [mass Al x specific heat Al x (Final-Tinitial)] = 0 Substitute and solve for Tf.

science
Your post is hard to decipher because you didn't use punctuation (like commas) but I think you have a mixture of these three substances and you treat them SEPARATELY with NaHCO3, HCl and NaOH. I can't do flow charts on this forum and that's too much for me to do ...

CHEMISTRY.
This is a common ion problem. The ionization of HF, a weak acid, is reduced (suppressed somewhat) by the addition of the F^- from the NaF. The F^- is the common ion. ......HF --> H^+ + F^- I...0.15.....0.....0 C.....-x.....x.....x E...0.15-x...x.....x The NaF is 100% ...

Thermodynamics
q = mcdT 800 = 120g x 1 cal/g x delta T Solve for delta T.

Thermodynamics

Chemistry
It has 4 lone pairs. https://www.google.com/search?q=lewis+structure+chloride+ion&tbm=isch&tbo=u&source=univ&sa=X&ved=0ahUKEwiE2ZeA4uXTAhUH2WMKHUBiCXwQsAQINg&biw=998&bih=600

Chemistry
light, ppt, gas, color. Read here. http://www.ric.edu/faculty/ptiskus/reactions/

science
Go to Google and type in..... define:troposphere define:stratosphere

Chemistry
I'm not inclined to help when you change screen names but here is site. http://www.chemteam.info/Redox/Redox.html

chemistry
heat to convert solid Tl to liquid Tl at 304 C. q1 = mass Tl x heat fusion = approx 4300 J; therefore, there is not enough heat to melt all of the Tl. How much can we melt? That's 476 J = mass Tl x 21 J/g mass Tl = 476/21 = about 23 g

science
......pbCl2 ==> Pb^2+ + 2Cl^- I.....solid.....0........0 C.....solid.....x........2x E.....solid.....x........2x Qsp = (Pb^2+)(Cl^-)^2 (Pb^2+) = 0.005 mols/L (Cl^-) = 2x from the PbCl2 if it ppts and 0.035 from the KCl so We can ignore the 2x. Qsp = (0.0050)(0.035)^2 = ...

Science
Isn't 3 true also? For every + pole there is a - pole and the problem says "different:.

Chemistry
dGo rxn = (n*dGo products) - (n*dGo reactants) Then dGo = -RTln*Kc

Chemistry
The hint is supposed to tell you what to do. Since HSO4^- is the stronger acid, it will be the donor and the other will be the acceptor. HSO4^- + HPO4^2- ==>SO4^2- + H2PO4^-

Chemistry
Use dG = dGo + RTlnQ where Q=(pHI)^2/pH2*pI2

Chemistry
I don't see a question here.

chemistryy
pH = -log(H3O^+) Substitute and solve for H.

Chemistry
c. You have 0.05M x 50 mL = 2.5 mmols of the amino acid. When you have titrated with 25 mL of 0.1 M NaOH, you have neutralized all of the COOH part but none of the amine part and you have the zwitter ion. That is the first equivalence point (or the isoelectric point and pH = (...

Chemistry
I will assume that the reaction is as follows and that the concn of NO2 initially is 10 mol/1L = 10 M and 8.8 mols/L or 8.8 M at the end. ......2xNO2 + O2 ==> NO + O3 I.....10....6......0.....0 C.....-x....-x.....x.....x E....10-x..6-x.....x.....x Therefore, x must be 10-8....

Chemistry
Determine Kc for which reaction?

Chemistry ASAP
I agree. Protons are 2 ups and 1 down. Neutrons are two downs and 1 up.

Environmental Science
Just to add fuel the fire I will add my two cents worth. When I first read the post and the response (but before MSE took the quiz) I started to make a comment that a should not be included because just costing money is not the issue. I intended to give an example of a project...

Chemistry

Chemistry
mmols U at finish = 270 mmols Pb at finish = 110 mmol U at start = 380 ln(380/270) = kt Solve for t You need k and k = 0.693/t1/2 = ?

oops????
We can NOT draw diagrams on this forum.

????
I'm sorry but we can draw diagrams on this forum.

Chemistry
You want 222 Kg U so you will need 222 x (atomic mass U/molar mass UF4) = ? to start. Then a 10% excess of that will be ? + 0.1*? = ??

chemistry
a. decreases activation energy. b. reaction mechanism changes (because intermediates are formed). c. enthalpy doesn't change. d.increases rate of fwd rxn. e. increases rate of reverse rxn.

Chemistry
I'm writing this after reading your first post. 10% w/w means you want 10g solute/100 g solution; therefore, to make only 50 g total you will need just half that or 5 g.

Chemistry
0.1 x 50 = ?

Chemistry

Chemistry
They don't. Look up Graham's Law. The rate of effusion is inverse;u proportional to the square root of the molar mass.

Chemistry
But does each gas effuse at the same rate?

Chemistry
yes. Write out eqn 1 and add it to the reverse of eqn 2 and see if it give you the reaction you want.

Chemistry
To get equation 1 you want to add equn 1 to rhe reverse of equn 2. reversing eqn 2 makes it a minus dH2. Look to me like c is not right

Chemistry
Sorry I didn't get back sooner. It is not. My half cell is correct. The Cl should be 2e + Cl2 ==> 2Cl^- Multiply my eqn by 1 and the Cl by 3 to end up with I^- + 3H2O + 3Cl2 ==> IO3^- + 6H^+ + 6Cl^- Check it. 1 I on each side 3O on each side 6H on each side -1 charge...

Chemistry
Here is the I^- ==> IO3^- 1. oxidation number of I is -1 on the left; +5 on the right. 2. Add electrons to the appropriate side. That is I^- ==> IO3^-+ 6e 3. Add up the charges and add H^+ to balanced the charge. I see -1 on the left side and -7 on the right. I- ==> ...

Chemistry
Ca(OH)2 ==> Ca^2+ + 2OH^- SO, if [Ca(OH)2] = 0.0027 M then (OH^-) must be twice that. Right?

Chemistry
pH = -log (H3O^+) and since HCl is a strong acid and ionizes 100%, then pH = -log(HCl). In very weak acid solutions it is necessary to take into account the H^+ contribution of the H^+ in water but I don't think that will be necessary in this concentration.

Chemistry
Set up Kp expression. You know Kp and pCS2. Solve for pS2 at equilibrium. Remember not to include C(s) in the expression. Kp = 5.6 - pCS2/pS2

Chemistry
Go to this site and read the assumptions. https://en.wikipedia.org/wiki/Kinetic_theory_of_gases

chemistry
I need to know the solubility of KNO3 at 50 C and 40 C. You must have a table or a graph that gives you this information.

Chemistry
mols K3PO4 = grams/molar mass = ? mols H3PO4 used in the reaction is 1 mol H3PO4 used for every 1 mol K3PO4 produced (look at the coefficients). grams H3PO4 to start = trams used + grams remaining

Chemistry

Chemistry
You can figures these out if you remember that a beta particle has a -1 charge and a mass number of 0 and you think about it. In radioactive reactions the subscripts must add up and the superscripts must add up. Here is an example. It's difficult to write subscripts and ...

chemistry
The problem states that the 100 g C is an excess; therefore, this is not a limiting reagent problem, assuming that statement is correct. Therefore, it's worked as a simple stoichiometry problem.

Chemistry
All look true to me except for C.

Chemistry
Zn ==> Zn^2+ + 2e is the strongest reducing agent (easiest to oxidize). 2H2O ==> O2 + 4e + 4H^+ is the weakest reducing agent, hardest to oxidize.

Chemistry
I don't see a reaction.

Chemistry
See my first line. Not only did I tell you that you needed coulombs but I told you how to calculate it. coulombs = A x seconds. amperes in the problem = 2.00 A. time in the problem = 19.0 min or 19.0 x (60 seconds/min) = ? seconds so coulombs = 2.00 x 19.0 x 60 = >

Chemistry
coulombs - A x seconds = ? 096,485 coulombs will deposit 63.55/2 g Cu = approx 32 but you need a better number than that. Then 32? x coulombs/96,485 = g Cu deposited.

Chemistry
coulomhs = A x seconds = about 7,200. 96,485 coulombs will plate out, in grams, atomic mass Gd/#e = 157.25 g/#e. grams Gd plated = 0.025 x 157.25 = about 3.93 grams. atomic mass Gd/#e x 7,200/96,485 = 3.93 Solve for #e and I would round to the nearest whole number. My guess, ...

Chemistry
coulombs = A x secnds = ? Cr probably in the +3 state so 96,500 coulombs will deposit atomic mass/3 g Cr (about 52/3 = 17). Then 17 x (coulombs,96,500) = ? g Cr.

Chemistry
I didn't check the math on the calculator but the process and the numbers are correct.

Science
Organic chemist, pharmacy to develop new drugs, certainly forensics, med tech in hospital or similar setting, teaching, water analysis for organic pollutants, and a host of others. I know a number of MDs who didn't like the "beside manner" requirements and they ...

Chemistry
right

Chemistry
See my response under your other post where you used the Cee name. If I know it, and I usually do, I am starting a new "me" by not answering questions posted by ad nauseam number of screen names.

chemistry
First off, please don't change screen names. It confuses us and you don't get answers as fast as you may wish. CHEMICAL properties are those which take place with a chemical reaction. If something different (a different substance) is formed, that is a chemical property...

Chemistry
Please don't change screen names. Lucy, John Butch, etc won't cut it. We can help better if we can keep one name. For the Bi half, Bi on the left has an oxidation number of +3 and on the right is 0 so that is a gain of 3e and the 3e goes on the right. That's how ...

chemistry

This info isn't made obvious in most chem classes and isn't prominent in texts so here is a tid bit of info that may prove useful to you. permanganate (MnO4)^- goes to manganate (MnO4)^2-in basic solution, to MnO2 is neutral or near neutral solution and to Mn^2+ in ...

Chem
Adam, please see the responses to Lucy, John Butch, etc. Your mistake here is that you are balancing the reaction in acidic solution. MnO4^- goes to MnO4^2- in basic solution. You seem to be OK with these so I'll leave that with you but if you have trouble, please re-post ...

Chem
It's on the reactant side but it isn't 4. If you'll post your half cell reactions I'll find the error.

Chemistry
mols Fe(NO3)3 = M x L = ? Use the coefficients in the balanced equation to convert mols Fe(NO3)3 to mols K2C2O4. Then M K2C2O4 = mols K2C2O4/L K2C2O4. You know mols and M, solve for L and convert to mL if needed. Post your work if you get stuck.

Chemistry
First, your rationale is OK about energy and wavelength. You KNOW the answer can't be c or d because the atom ABSORBS energy to do that. Atoms EMIT energy only when they go from a higher level to a lower level. So that leaves a or b as the only possibilities so you can ...

Chemistry
95% by mass ethanol means 95 g ethanol in 100 g total. 100 g total-5g ethanol = 95 g H2O. mols ethanol = grams/molar mass = ? mols H2O = grams/molar mass total mols = mols ethanol + mols H2O Xethanol = mol ethanol/total mols. Post your work if you get stuck.

Chemistry
No. Oxidation is the loss of electrons; reduction is the gain of electrons. Your equation is not right to begin with. It shows a reduction half but NOT an exidation half. I suspect you intended to write CO2(s) + H2(g) ==> CO(g) + H2O(g) Start by assigning oxidations numbers...

Chemistry
The question asks for the NET ionic equation. What you have written (correctly) is the MOLECULAR equation. To turn the molecular equation into the net ionic equation you cancel ions common to both sides. That means 2Na^+ and 2HCO3^- cancel leaving Pb^2+(aq) + S^2-(aq) ==> ...

Chemistry
Use the coefficients to convert mols of what you have to mols of what you want. 2 mols O3 x (1 mol NO2/1 mol O3) = 2 x 1/1 = 2 mols NO2. Now convert mols NO2 to grams. Grams = mols NO2 x molar mass NO2 = ?

Chemistry
You're right

Chemistry
That is exactly right. That problem set a trap and you fell for it. The GRAMS of H in a 20 g sample will be different than the grams in a 10 g sample but the % stays the same.

Chemistry
No. The answer isn't 1/2 of 11.19 either. Your guessing. If you have 5g apples and 5g oranges (10 g total), percent apples is ?. If you have 100g apples and 100g oranges (200 g total), percent apples is ? If you have 25g apples and 25g oranges(50 g total), percent apples ...

Chemistry
No. The answer is NOT twice 11.19.

Chemistry
OK but because Li is smaller size.

Chemistry
For M2S3, that means S is -2 and M is +3. Hint: O is in the same column as oxygen.

CHM
dE - q _ w w = -340 J dE = 8450 J Solve for q. q = mass gas x specific heat x (Tfinal-Tinitial) Substitute and solve for specific heat.

Chemistry
The way I see it is that HI doesn't share an electron between H 1s and I 5p. Rather, HI is a strong acid, it ionizes completely and I look at it as an ionic compound in which the 1s electron from H is transferred to the 5p5 (to make 5p6 and that with the 5s2 makes 8 ...

physical science
Not through a vacuum but any solid, liquid, gas.

Chemistry
CS2 + 3Cl2 => CCl4 + S2Cl2. mols Cl2 = grams/molar mass = ? Convert mols Cl2 to mols CS2 using the coefficients in the balanced equation. Then grams CS2 = mols CS2 x molar mass CS2. Post your work if you get stuck.

Chemistry
If a is the edge length of the cell, then 4r = 1.414*a Solve for a, then volume = a^3.

Chemistry
right. It is not.

Chemistry 212
#1 is that I think you are using the wrong equation. Although you didn't define your symbols, I think the equation should be t = ln(No/Nt)/k where No is what we start with (100) and Nt is what we end up with (100-61.7 - 38.3) and k is 0.004278 using your formula (which is ...

Chimie, Sciences,Effets inductifs
I presume this is organic chemistry. You can best read about inductive effects by searching on google. The inductive effect is caused largely by highly electronegative atoms such as F and Cl.

chemistry
Interesting student. I don't aee a question. Try to post your questions without theatrics please. The line AUTOMATICALLY moves to the next line. You need not hit the enter button after every one or two.

chemistry
Your method of posting makes it difficult to read. Also, you don't ask a question but if you want to know how much is the final volume use the dilution formula. mL1 x M1 - mL2 x M2 55 x 2.80 = mL2 x 2.00

chemistry
I looked for, but could not find, anything on Google that gave an answer to your question. I did find this site that gives some info on how to set up MO bonds. Perhaps it will help you get started. https://www.chem.fsu.edu/chemlab/chm1046course/motheory.html

science
First, what experiment have you done? Second, are you looking for someone to write your paper for you. We're not inclined to do that.

word problem
C = # children A = # adults ---------------- A + C = 312 9.00A + 3.50C = 1884 Solve these two equations simultaneously for A and C. Post your work if you get stuck.

Chemistry
Check your work. I found 9.52. I used 9.26 for pKa. 14-4.74 = 9.26

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