Saturday
November 29, 2014

Posts by drbob222


Total # Posts: 45,646

P.E. help please
I don't think A or D is correct. I'm not a biologist so perhaps you should get a second opinion; however, USUALLY when you gt an immunization, the "shot" or whatever is something to make the body make antibodies but it doesn't contain antibodies. I think ...
November 16, 2014

Chemistry
0.166 M x (5.00/250.0) = ?
November 16, 2014

Chemistry Buffers
I'll let you balance the equation and add the phases. HF and NaF. Added HCl(an acid) will react with the base (F^-) to form HF. F^- + H^+ ==> HF Why wouldn't you expect the same kind of thing with the acetate/acetic acid buffer? It should be the same. H^+ + base ==&...
November 16, 2014

Chemistry
If you will type in your work I'll find the error. Femember dGrxn = (n*dGf products) - (n*dGf reactants). Then dG = -RT*ln*K
November 16, 2014

Chemistry
Show the equation you used. I don't know the one you used. Show the work you did. I'll find the error.
November 16, 2014

Chemistry
If you will type in your work I will find the error. You should be using dGrxn = (n*dGf products) - (n*dGf reactants)
November 16, 2014

Chemistry
I think 1 is right. I don't know about 2. For 3 you want to know delta G for the reaction. You can calculate that from dG = dH - TdS. You have dH but you don't have T nor dS so I don't think you can calculate dG with two unknowns. 4. The answer isn't c. The ...
November 16, 2014

Chemistry
C. If dGrxn > 0 that means it is + some number so dGrxn for the reverse reaction will be - and a negative dG means spontaneity. D. When dG = 0 the system is at equilibrium. (because the only other possibilities are + and -; if + it goes in the reverse and if - it is ...
November 16, 2014

Chemistry
I think C and D are true; A and B are not true.
November 16, 2014

Science, Chemistry
See your post above although I think you used a different screen name. Perhaps Bob?
November 16, 2014

Science, Chemistry
acid + base ==> salt + H2O
November 16, 2014

Chemistry
I would have guessed C=O also. Try them but look up the electronegativity of each; I don't remember them that well. O is about 3.5 N about 3 C about 2.5 H about 2.1 difference is about 1 for C=O about 0.9 for NH about 0.5 for N-C I have a copy of a periodic table that ...
November 16, 2014

Chemistry
I would write it as an ionic compound with Sr^2+ and 2CN^- The dot structure for CN^- is :C:::N:-
November 16, 2014

chemistry
This is a stoichiometry problem also but in addition it is a limiting reagent problem You know it is a limiting reagent problem because amounts are given for BOTH reactants. Work this the same way as a stoichiometry problem but take each reactant separately and calculate mols ...
November 16, 2014

chemistry
The steps are exactly the same as your previous question about H2O. You would do well to remember those steps. They work for all stoichiometry problems.
November 16, 2014

chemistry
mols H2O = grams/molar mass = ? Use the coefficients to convert mols H2O to mols O2. Now convert mols O2 to grams O2. g O2 = mols O2 x molar mass O2
November 16, 2014

chemistry
mols X = 4.23E22/5.02AE23 = ? mols = grams/molar mass. You know grams and mols, solve for molar mass.
November 16, 2014

chemistry
How many mols is 4.2E23 molecules N2. One mols contains 6.02E23 molecules; therefore, mols = 4.2E23/6.02E23 = ? Use the coefficients in the balanced equation to convert mols N2 to mols NH3.
November 16, 2014

chemistry
Worked like the other one with molecules of N2.
November 16, 2014

chemistry
Look at your stoichiometry problems. This is just another stoiciometry problem.
November 16, 2014

Chemistry
heat capacity is ?J/degree C. heat gain by cool water + heat lost by warm wataer + heat gained by calorimeter = 0 [mass cool water x specific heat x (Tfinal-Tinitial)] + [mass warm water x specific heat x (Tfinal-Tinitial)] + [Ccal*(Tfinal-Tinitial)] = 0
November 16, 2014

Chemistry
Do you mean by combustion? C3H8 + 5O2 ==> 3CO2 + 4H2O mols C3H8 = grams/molar mass Convert mols C3H8 to mols CO2 using the coefficients in the balanced equation.
November 16, 2014

chemistry
I answered both question earlier. You have a lot of information that is not needed. Changing 980 % to 9.80% makes it make more sense but that number isn't needed either.
November 16, 2014

Chemistry
Note I said ABOUT 25%. I did look at the graph your post provided. IF you want to try to draw a straight line through all of those points, which actually can't be done, then try and mark off tenths between 1.0 and 2.0, you may come up with 30% or 20% or anything in between...
November 16, 2014

Chemistry
The difference is about 1.0 which I estimate is about 25% ionic character. Actually you don't need a graph to make an estimate. You know approx 1.8 or 1.9 difference is about 50%. 0 difference is 0% ionic which makes 1.0 about 25% and 0.5 about 10% or so.
November 16, 2014

Chemistry (Acid&Base)
mL1 x M1 = mL2 x M2 mL1 x 0.203 = 100 x 0.0433
November 16, 2014

chemistry Ben
Answered previously
November 16, 2014

chemistry step by step for me
1. Assuming the volumes are additive; i.e., 100 + 400 = 500 mL, then M H2SO4 = 1 M x (100/500) = ? 2. I don't know how to deal with 938% H2SO4; however, that never enters into the problem. I assume that 20.8% BaCl2 is w/v and that means 20.8 g BaCl2/100 mL. Therefore, in ...
November 16, 2014

Chemistry
dG = dH - TdS Then dG = -RTlnK Calculate K
November 16, 2014

Chemistry
Cu(NO3)2.3H2O or Cu(NO3)*3H2O or Cu(NO3)2(H2O)3
November 16, 2014

Chemistry
Fe + 2HCl ==> FeCl2 + H2 mols HCl = M x L = ? mols Fe = 1/2 that (from the coefficients in the balanced equation) g Fe = mols Fe x atomic mass Fe %Fe or %purity = (g Fe/mass sample)*100 = ? However, I don't buy your "throwaway statement" that FeCl2 solution is...
November 16, 2014

science
http://www.chemteam.info/Redox/Redox-Rules.html You need to find the caps key on your computer and use it. CO is carbon monoxide Co is cobalt co is the abbreviation for company. Mn is +2 in MnCl2. Follow those rules in the site I gave you.
November 16, 2014

Chemistry
This is a two equation problem and the two are to be solved simultaneously. These are difficult to explain by writing so I'll do it in steps. Let x = mass Na2SO4 and y = mass K2SO4 --------------------- equation 1 is x + y = 0.205 The second equation comes from the ppt of ...
November 15, 2014

Chemistry
q = [mass H2O x specific heat H2O x delta T] Then dH is q/mol Ba(OH)2 and convert to kJ.
November 15, 2014

Chemistry
If you expect to continue getting help you should show some work. Or something about how you would attack the problem. Or EXACTLY what you don't understand about the process.
November 15, 2014

Chemistry
You will have 300 mL of solution and 0.01 mol of AgCl. q = 66,000 = mass H2O x specific heat H2O x (Tfinal-Tinitial). Solve for Tf.
November 15, 2014

Chemistry
At constant volume you calculate dE. dE = [(mass H2O x specific heat H2O x (Tfinal-Tinitial)] + Ccal*(Tfinal-Tinitial) Then dE x (g C6H6/molar mass C6H6) = J/mol. Convert to kJ/mol For dH, use dE = dH + w and w can be obtained from pdV = delta n(RT) You will need to assign the...
November 15, 2014

Chemistry
How much heat is added to the calorimeter and water with the combustion of the ethanol. That's 0.0108 mol x 1365 kJ/mol = ? and convert to J. Then J heat = (mass H2O x specific heat H2O x delta T) + Ccal*delta T Solve for Ccal.
November 15, 2014

Chemistry
dE = q+w dE = dH+w You know dH. w is pdV = delta n(RT) where work is negative since the gases are doing work against atmospheric pressure.
November 15, 2014

Chemistry
DEO?
November 15, 2014

chem
mols H2O2 = M x L = ? Convert mols H2O2 to mols H2O with the coefficients in the balanced equation. Convert mols H2O to g. g = mols x molar mass.
November 15, 2014

Chemistry
Wouldn't that be dipole-dipole?
November 15, 2014

chemistry
I don't know what the diagram in Figures 9.42 of your textbook looks like.
November 15, 2014

chemistry
Of course this could be a trick question. Since this is an exothermic transition the technical answer to the question is zero heat is absorbed. :-)
November 15, 2014

chemistry
You're method looks ok to me. I added the individual amounts and that looks ok to me. I did not check each individual calculation. I would look at two things. First, the heat is not absorbed; it is released when going from high T to lower T. And each step is a release and ...
November 15, 2014

Chemistry
Do we assume the H2O is liquid and it occupies no volume. Convert grams of each gas to mols (mols = grams/molar mass) and use PV = nRT to calculate pressure of each gas. Sum of the partial pressures will give Ptotal.
November 15, 2014

Chemistry
You made a typo on the equation. 2N2O5 ==> 4NO2 + O2 When using gases one may use the gas pressure as if it were mols. Convert atm N2O5 to atm NO2. That's 0.4 atom x (4 mols NO2/2 mols N2O5) = ? atm for NO2. 0.4 atm x (1 mol O2/2 mols N2O5) - ? atm for O2. Add the two ...
November 15, 2014

Chemistry
2KClO3 ==> 2KCl + 3O2 Use PV = nRT and calculate n for Oxygen. Using the coefficients in the balanced equation, convert mols O2 to mols KClO3. Now convert mols KClO3 to grams. g = mols x molar mass = ?
November 15, 2014

Chemistry
See your other post.
November 15, 2014

Chemistry
Each is done the same way. For CO2, X CO2 is 0.92, then pCO2 = XCO2*Ptotal
November 15, 2014

Chemistry
Calculate mols fraction each gas. For example, XN2 = (mols N2/total mols) Do the same for XO2 and XAr Then peach = Xeach*Ptotal
November 15, 2014

Chemistry
Use PV = nRT and calcualate mols in the cylinder. Use PV = nRT and calculate mols left when the cylinder is "empty". Subtract to see mols He available to fill balloons. Use PV = nRT and calculate mols needed to fill one balloon. mols He/1 balloon x # balloons = total...
November 15, 2014

Chemistry
How many mols do you have? That's mols = grams/molar mass = ? Then M = mols/L solution (which is 2.89L)
November 14, 2014

Science help
I'm torn between 1 and 3 but according to the web decaying leaf litter and decaying trees are ecosystems in themselves; i.e., lichens, mosses, etc. So I think 3 must be the correct answer; however, keep in mind I'm a chemist. I suggest you get a second opinion on 5.
November 14, 2014

Science help
I believe the first four are ok. I don't agree with 5. Aren't snails biotic?
November 14, 2014

Science
You just told me the model for Bohr and I told you about J J Thomson. If you think about it I KNOW you can go through those sentences and pick out the similarities and the differences. If I may be so bold I will suggest you just aren't thinking about it. Let me get you ...
November 14, 2014

chemistry (AP)
I'm confused by the term "immediately after the neutralization reaction has occured?" Does that mean we aren't giving the solution time to reach equilibrium temperature wise. The second thing that bothers me about this problem is that you do NOT have any H2 ...
November 14, 2014

Science Help!
OK. I'm guessing here that the part in the middle is a nucleus of an atom. The first blue ring probably is the first orbit with 2 electrons in it and the second blue ring is the second orbit with 8 electrons in it. If my guess is right that is a depiction of the atom Ne. ...
November 14, 2014

Science Help!
Best for me to leave it rather than give a wrong answer
November 14, 2014

Science Help!
I can't tell from the description what you have.
November 14, 2014

chemistry
delta T = i*Kf*m Substitute into the equation and solve for delta T, then subtract from 0c to find the new freezing point. i for AgNO3 is 2. same thing for delta T = i*Kb*m but ADD delta T to normal boiling point of H2O to find the new boiling point. m = mols/kg solvent = ?
November 14, 2014

Chemistry
Oh but it is relevant and the answer is not 6. You may NEVER have more than 1 electron with the same two quantum numbers. But you may have two that differ by only one of the quantum numbers. One electron can be n = 2, l = 1, ml = -1, and ms = +1/2 I can have a second electron ...
November 14, 2014

Science Help!
Yes, the answer is isotopes.
November 14, 2014

Science Help!
So the protons are the same (at 6 each) but neutrons are not (6,7,8). What do you call atoms that have the same atomic number(number of protons at 6) but different mass numbers (12, 13, 14) which is the same thing as saying the same number of protons but different number of ...
November 14, 2014

Science Help!
If the answer is A, what bond types do you think it shows? The bond types I know about are ionic, covalent, polar covalent, etc. How would this fit in with your answer? Second question, What differences do you see in the three carbons?
November 14, 2014

Science Help!
Yes, the answer is b.
November 14, 2014

Science Help!
I don't agree with your answer. What is different about the reactants and products in C? I don't see any difference (except for a typo on C4H1 and I'm sure you meant to type in C4H10.)
November 14, 2014

chem
In one neat and tidy equation it is 1.125 g/cc x 1000 cc x (20/100) x (1 mol/40g) = ? Molar In pieces. mass of 1000 cc is 1.125 g/cc x 1000 cc = ? mass of NaOH in that 1000 cc solution is ?mass x 0.20 = ? mols NaOH in that mass NaOH is ?grams/molar mass All of that gives you ...
November 14, 2014

science Help 911!!
B and D are not right which leaves you with the only other two that must be right. It is true that Na and Cl2 WILL REACT TOGETHER to form an ionic bond but they do that by forming a Na^+ ion and a Cl^- ion. The question is what is "part" of an ionic bond; not wht ...
November 14, 2014

Science Help!
Absolutely. An endothermic reaction uses heat from the surroundings to make it go. An exothermic reaction gives off heat. Exploding fireworks, paper burning, and cellular respiration (such as humans breathing) all are examples of exothermic reactions in which heat is released ...
November 14, 2014

Science Help!
That's right. Do you think fireworks exploding is ABSORBING heat from the surroundings? Do you think paper burnins is absorbing heat from the surroundings?
November 14, 2014

Science Help!
What is an endothermic reaction?
November 14, 2014

Science Help!
I don't think C is the right answer. I don't think humans engage in photosynthesis. Plants do that. Now let me ask a question. I see you have posted more than a few science questions. Are we doing all of your homework for you in science?
November 14, 2014

Science
OK. It's obvious that if you don't know what Thomson's model is you can't very well describe the differences and similarities. You could have read about that model in your text or you could have done a Google on it. But I can do that for you here. Thomson ...
November 14, 2014

Science
Can you tell me... what is Bohr's model? What is JJ Thomson's model?
November 14, 2014

Science Help!
D is correct.
November 14, 2014

Science Help!
D is correct.
November 14, 2014

Science Help!
A is not the right answer. Look up the difference between a physical change and a chemical change.
November 14, 2014

Science Help!
I would go with b also.
November 14, 2014

science Help 911!!
I would go with A also but I don't know why B couldn't be correct too. In fact I've always more or less equated atomic theory with the atomic model.
November 14, 2014

science Help 911!!
Yes, it form a covalent bond but papers that say chemical bond should be counted right also because a covalent bond is a chemical bond.
November 14, 2014

Chemistry
HCl + NaOH ==> NaCl + H2O mols HCl = M x L = ? Look at the coefficients in the balanced equation. mols HCl = mols NaOH. Then g NaOH = mols NaOH x molar mass NaOH = ? This is the theoretical yield. %yield = (mass NaOH/mass sample)*100 = ?
November 14, 2014

Chemistry
mols H2 = grams/molar mass = ? Using the coefficients in the balanced equation, convert mols H2 to mols H2SO4. Then M H2SO4 = mols H2SO4/L H2SO4. You know mols and M, solve for L.
November 14, 2014

Organic Chem
This is a limiting reagent (LR) problem. You know that because amounts are given for BOTH reactants. Using the coefficients in the balancaed equation, convert 12 mols KO2 to mols O2. Do the same to convert mols CO2 to mols O2. It is likely the two values will not be the same ...
November 14, 2014

chemistry
We can't draw these on this forum and I can find an OF^- on Google. Follow this AND the added instructions. Hope it makes sense. :O:F:. Add .. top of O, top of F, bottom of O, bottom of F and add -1 charge to the ion and you'll have it.
November 14, 2014

chemistry
Did you make up this problem or have it handed to you? However it was done you should recognize that H2S is a gas and isn't about to stand around in a titration vessel and wait to be titrated. Anyway, in the spirit of the problem here is how it is solved. H2S + Sr(OH)2 ==&...
November 14, 2014

chemistry
The problem says 22.11 and not 21.11 (and I made the same typo in my response) and atomic mass Zn is 65.38 and not 65.28.
November 13, 2014

chemistry
Did you make a typo? From your work I assume Ti is 15 and not 1 as you posted. Your q calculation is almost correct. It should be 100 mL x 4.18 x (21.11-Ti) = q in Joules. Note it's the water you're heating and although the Zn absorbs a little heat you're ignoring ...
November 13, 2014

sixth grade math
1 yes 2 no 3 yes
November 13, 2014

Chem
wavelength in m = h/mv mass is 9.1E-31 kg. Solve for wavelength and convert to nm.
November 13, 2014

Chemistry
OK. Let's look at the two 1s electrons. Remember those configurations give you n and l. So for 1s2 n must be 1 and s electrons have ell = 0 and the two electrons of 1s2 can have +1/2 and other one -1/2 Therefore, one electron has n = 1, l = 0 mL = 0 (see the rules;; i.e., ...
November 13, 2014

Chemistry
16S = 1s2 2s2 2p6 3s2 3p4 What is it about this that you don't understand? Here are the rules. n can be any whole number starting with 1. l can be any whole number less than n-1. ml can be -ell to +ell including 0. ms can be either +1/2 or -1/2.
November 13, 2014

chemistry
54.3 g/formula unit mass = ?
November 13, 2014

CHEM
0.254 what? mm, atm, kPa? and you want the total pressure where? in the flask? I don't know what you mean by total pressure.
November 13, 2014

O-Chem
We can't draw diagrams on this forum. Sorry about that. I suggest you try Google. Many of the sites show the mechanism.
November 13, 2014

chemistry
Two ways. If you have the grams NaCl, mols = grams/molar mass = ? If you have a solution (M) of NaCl, mols = M x L = ? Of if the solution is in molality(m), mols = m x kg solvent = ?
November 13, 2014

Chemistry
1. 2H2O2 ==> 2H2O + O2 mols H2O2 = grams/molar mass = 10/34 = 0.294/ Using the coefficients in the balanced equation, convert mols H2O2 to mols O2. That's 0.294 mols H2O2 x (1 mol O2/2 mols H2O2) = 0.294 mols H2O2 x 1/2 = 0.147 mols O2. Now convert mols O2 to grams. g ...
November 13, 2014

Chemistry
You must scroll down and find the original post. Here is a link. http://www.jiskha.com/display.cgi?id=1415924736
November 13, 2014

Chemistry
Bob Pursley answered your first post. It's below.
November 13, 2014

Chemistry
I've tried to help at your other post.
November 13, 2014

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