Friday
August 28, 2015

Posts by DrBob222


Total # Posts: 49,817

Chemistry
Yes. Good work. Let me show you how to check that number. I almost always check my numbers some third way to see if I get the same answer. If CaO = 11.32%, then BaO must be 100-11.32 = 88.68%. So in the 4 g sample, we have g CaO = 0.1132 x 4 = 0.4528 g g BaO = 0.8868 x 4 = 3....
August 12, 2015

Chemistry
You started right; just stopped too soon. The equations are CaO + CO2 ==> CaCO3 BaO + CO2 ==> BaCO3 If x = g CaO and 4-x = g BaO, then mols CO2 reacting with CaO = x/molar mass CaO. mols CO2 reacting with BaO = (4-x)/molar mass BaO Then mols CO2 reacting with CaO + mols ...
August 12, 2015

chemistry
Is tht percent? Take 100 g of material which will give you 34.2 g Fe 65.8 g Cl. Convert to mols. 34.2/56 = about 0.6 (but get better number) 65.8/35.5 = about 2 (get better number). Now find the ratio of each with the smaller number being 1.00. The easy way to do that is to ...
August 12, 2015

Chemistry
http://chemwiki.ucdavis.edu/Physical_Chemistry/Kinetics/Rate_Laws/Reaction_Mechanisms/Reaction_Intermediates
August 12, 2015

chemistry
I don't believe this problem is workable as is. Here is why. If you use NTP, then mols in 28L is 28/24.05 = 1.164 Suppose ALL 1.164 mols are present as C2H6, then g O2 required is 1.164 x (7 mols O2/2 mols C2H6) x (32 g O2/1 mol O2) = about 130 grams O2 which comes close ...
August 12, 2015

chemistry
2Ca + O2 ==> 2CaO mols Ca = grams/atomic mass = ? Use the coefficients in the balanced equation to convert mols Ca to mols CaO. In this case mols Ca = mols CaO Then convert mols CaO to grams. g = mols CaO x molar mass CaO.
August 12, 2015

science
I'm not sure I understand the question. If you want a fill in the blank, C should dissolve 50 g NaOH NaOH in enough H2O to make 100 mL of SOLUTION.
August 12, 2015

Chemistry
Remember Cu is not soluble in HCl which means you must go around the barn to get there. Dissolve Cu metal in HNO3 and evaporate to dryness. Add water to form a solution, add Na2CO3 to ppt CuCO3. Filter, dissolve the CuCO3 in HCl and evaporate to dryness.
August 12, 2015

Chemistry
Dissolve the mixture in H2O; PbCO3 will not be soluble, filter and collect the PbCO3 as the solid. Use the filtrate, evaporate the water leaving solid Na2CO3.
August 12, 2015

Math Brain Teaser
I would buy them all for $150 @ $6 each and go home.
August 11, 2015

Chemistry
See your question under Sydney. It would be easier for us and better for you if you didn't change screen names.
August 11, 2015

Chemistry
I agree D is right but ONLY if you tell me what "approximately" in A means. Both B and C are correct. If this question has only ONE answer, then A must be true which makes D true. But I see buffer solutions on this board all the time with (Base) = 0.2(Acid) which ...
August 11, 2015

Chemistry
I think B is true. C is true. But A is not true; for example, NH3 is analogous to H2O in liquid NH3. Just as H2O + H2O ==> H3O^+ + OH^- in aqueous solution, then NH3 + NH3 ==> NH4^+ + NH2^- in liquid NH3. So I don't know about the answer. If it were D that is true ...
August 11, 2015

phyiscal science
Depends upon how much ice you have? How much does a block of ice weigh?
August 11, 2015

Chemistry
See my response above. Both B and C are correct.
August 11, 2015

Chemistry
An increase in P shifts the equilibrium to the side with fewer mols of gas; therefore, an increase in P shifts it to the left. That means you want to decrease the pressure to shift the reaction to the right.
August 11, 2015

Chemistry
See your other post.
August 11, 2015

Taxation law
I don't see a question.
August 11, 2015

Chemistry
Use the Arrhenius equation.
August 11, 2015

Chemistry
I didn't answer this the other day when you posted but I don't think your proposed answer is right. C(C6H5)3OH is a final product. Intermediate products are those between beginning and end. I agree with your net reaction.
August 10, 2015

AP chem
Why not ask yourself this question? How many pounds of metal can you get from an ore containing 50% metal? I'll bet you can do that in your head. Then look to see how you obtained that number. Then use the same process to work this problem. It's just different numbers...
August 10, 2015

Chemistry
Take a 100 g sample which give you 40 g C 6.7 g H 100-40-6.7 = 53.3 g O Convert these g to mols. mol = g/atomic mass. 40/12 = about 3.3 mols C 6.7/1 = 6.7 mols H 53.3/16 = about 3.3 Now find the ratio of these three elements to each other. The easy way to do that is to divide ...
August 10, 2015

Chemistry
Do you want w/w or w/v %? I will assume w/v. 80% NaOH means 80g NaOH/100 mL solution. 20% KOH means 20 g KOH/100 mL solution. You don't want 100 but only 10 so 80 g x 10/100 = 8 g NaOH 20 g x 10/100 = 2 g KOH Weigh out 8 g NaOH and 2 g KOH, place in a 10 mL volumetric ...
August 10, 2015

chemistry
Le Chatelier's Principle at work. Suppose we prepare a saturated solution of CuS. The equilibrium is CuS(s) <==> Cu^2+(aq) + S^2-(aq) It will have a Ksp = (Cu^2+)(S^2-) Now if we add EITHER Cu^2+ (say from CuCl2 which is soluble) OR S^2- (say from Na2S which is ...
August 10, 2015

Chem
mols Fe2O3 in 24.6 g Fe2O3 = grams Fe2O3/molar mass Fe2O3 = 24.6/approx 160 = approx 0.15. Then mols Fe = 0.15 mols Fe2O3 x (2 mols Fe/1 mol Fe2O3) = 0.15 x 2/1 = ? You need to run through it with better accuracy than my estimates.
August 9, 2015

chemistry
Probably I would answer D also; however, although we talk about reactions going to completion(answer B), technically, that is never true. Reactions that proceed so far to the right that they are 99.99% complete falls into "essentially complete" and we call them ...
August 9, 2015

Chemistry
I agree the answers are confusing but your answer of D is correct.
August 9, 2015

Chemistry
Probably but I don't like any of them. I don't like A, C, or D but I dislike B less than the others.
August 9, 2015

math, unit price
Answer moochers do it every time.
August 9, 2015

Govt.sen.sec.school darlaghat
Is your subject Govt.sen.sec.school.d; or is it chemistry? https://www.google.com/search?q=law+thermodynamics&ie=utf-8&oe=utf-8
August 9, 2015

chemistry
OK. I see I didn't do it the same way but you can also see that my numbers are the same. That 3.92 is the absorptivity constant and the 4.056 actually was 4.0565 but I just dropped the last 5. The book method uses ratio/proportion while I tried to reason it out from the ...
August 9, 2015

chemistry
You know, of course, that I have no idea how your book explains it, poorly or otherwise. Here is how you do it but I don't know it's the same method your book uses. Personally, when I was in grad school we did it all by graphing it. Makes a lot more sense to me. You ...
August 9, 2015

Math
Is 2-3-17 a three digit number?
August 9, 2015

Kaputian central elementary school
Is that 101?
August 9, 2015

Chemistry
KHP + NaOH ==> NaKP + H2O mols KHP = mols NaOH; therefore, you can use mL KHP x M KHP = mL NaOH x M NaOH There is no way this question can be answered without the concentration of the acid.
August 9, 2015

engineering math
Do you assume H2 is an ideal gas? (V1/T1) = (V2/T2) For V1 use ANY convenient number, say 100 mL. Then for V2 you use 105. T1 is 273; T2 will be in kelvin.
August 9, 2015

org chem
I answered this question for you last night and told you what pptn was and what crystallization was. If you don't understand those definitions or those processes you should repost and explain what you don't understand about each or both. Otherwise, your problem isn'...
August 9, 2015

science
You should clarify the question. As stated I can't make sense of it. Do you want to convert frequency to wavelength? If so then C = freq x wavelength c = 3E8 m/s freq = 1E12 or 200E12 Solve for wavelength By the way a kghz (or kGHz or kilogigaherz) is a THz or teraherz.
August 8, 2015

org chem
I can give you an example of this. You may own a Honda automobile and your neighbor may own a Rolls-Royce. Both are cars (automobiles) but technically they are not the same. A second example: You may have $999,000 dollars in your pocket. In real dollars (and life) you are rich...
August 8, 2015

org chem
Because technically means we are dotting all of the "i"s and crossing all of the "t"s. That's just another way of saying we are answering the question EXACTLY. So if you are answering the question exactly and the two processes are only similar, then it ...
August 8, 2015

org chem
No. The word "technically" bothers me. I think non-technically it may be similar but technically it isn't close. Precipitation is a reaction producing a solid; crystallization is not a reaction but a material coming out of solution where it has been dissolved.
August 8, 2015

Important question regarding chemistry
Look at the first and third pictures. The first is straight o-nitrophenol while the third one shows the H bonding. https://www.google.com/search?q=orthonitrophenol;&tbm=isch&tbo=u&source=univ&sa=X&ved=0CDQQsARqFQoTCIHhi-PomccCFYKPDQodCewOqQ&biw=1011&bih=601
August 8, 2015

Science
Here is how you do these. You can start with the topic you don't know and use as many of the steps as you need. http://www.chemteam.info/Redox/Redox.html I STRONGLY ADVISE YOU TO START BY PLACING A 2 AS A COEFFICIENT FOR HIO3 so that you are talking about electron loss/...
August 8, 2015

Chemistry
helloooo
August 7, 2015

Chemistry
I've copied this from above. And yes, in your example they are tripled and doubled because the power of each is 1. So 3^1 is 3 and 2^1 is 2. Right? So the 3^1 comes because of your tipled/doubled part and the 2^1 comes from your tripled/doubled part. And the 3 in the O3 ...
August 7, 2015

Chemistry
I made a typo in that response and that may have confused you. However, after starting that sentence with 'Now if it were a second ....." I never tripled anything. I doubled CO2 and doubled O3. i SHOULD have written, if the equation were rate = k(CO2)^2(O3)^3. Then ...
August 7, 2015

Chemistry
I think the answer to all of your questin is yes. If you double the pressure then the volume is halved and the concentration is doubled. Right? So just figures p and c are the same for this. And yes, in your example they are tripled and doubled because the power of each is 1. ...
August 7, 2015

Chemistry
For a first order reaction rate = k*(concentration)^1 k is a constant. Your question asks for the expression, not for an answer numerically. They don't give a k and they don't list a concentration. k can be determined from k = 0.693/t1/2 and you can evaluate that by ...
August 7, 2015

Chemistry
rate = k(Sr-90)
August 7, 2015

Chemistry
The problem asks for grams so I think you should make that conversion if you want to answer the question. For how you do it go back and read my response. I told you how to do it. Also you should punch those numbers into your calculator again. I didn't get that number. Also...
August 7, 2015

Chemistry
Do you mean propEne? Do you mean k = 6.22E-4 s^-1? rate = k*0.03 = mols/L*s Then mols/L*s x (60 s/min) x 10 min x 2.5 L = mols in 2.5L in 10 min. Convert to grams. mols = grams/molar mass. You know molar mass and mols, solve for grams.
August 7, 2015

Chemistry
I did this but first you know it can't be A and it can't be D. B and C are the only possibilities and I did that by ..1.0...........0......0.......0 min 0.87...........0.13...0.13.....100 min 0.74...........0.26...0.26.....200 min 0.61...........0.39...0.39.....300 min...
August 7, 2015

chemistry
I think the secret word here is "estimate". I see that the temperature is changing by 10 degrees. There is an estimate in reaction rates that a reaction doubles for every 10 degrees change. So 2 x 12 mL = ?
August 6, 2015

Math
Sorry Ms. Sue, I thought you may have called it a night.
August 6, 2015

Math
Since this is simple interest, convert 22 months to years (rate is 8.5%/yr I assume) so 22/12. I = 46945*0.085*(22/12)=? Then final value is 46,945 + I.
August 6, 2015

chemistry
mols (NH4)2SO4 = grams/molar mass = ? Then m = mols/kg solvent.
August 6, 2015

Chemistry
I hardly know what you're clarifying. The rate law, since both NO and O3 are raised to the first power should b e doubled and tripled.
August 6, 2015

Logical Reasoning
What's the question?
August 6, 2015

Opra college
2KClO3 ==> 2KCl + 3O2 mols KClO3 = grams/molar mass = ? Using the coefficients in the balanced equation, convert mols KClO3 to mols O2. Then mols O2 x 22.4L = L O2 at STP
August 6, 2015

Chemistry
I think standard conditions in this case means 25 C and 1 atm and ALL will have those conditions. What counts is dH and dS where dHrxn = (n*dHf products) = (n*dHf reactants) and dSrxn = (n*dSf products) - (n*dSf reatants) or dGrxn = (n*dGf products) - (n*dGf reactants)
August 6, 2015

Chemistry
Frankly, I think there is insufficient information for all of them. You need delta G. In a general sense exothermic reactions (delta H is -) often are spontaneous unless delta S screws things up and endothermic reactions (delta H is +) unless delta S screws things up. ...
August 6, 2015

DPS sub: science ( chemistry)
S won't do it since it isn't soluble in water. (C and Si are not soluble either). The answer is sodium. 2Na + 2H2O ==> H2 + 2NaOH and NaOH is a strong base which will turn phenolphthalein pink.
August 6, 2015

chemistry
HBr + NaOH ==> NaBr + H2O Since HBr is a strong acid and NaOH is a strong base, the material at the end is just a salt in water. The pH of the water will be 7 (at least that's the simple answer and it neglects ionic strength and the Debye-Hueckel theory).
August 6, 2015

Chemistry
What is glacial acid. Do you mean glacial acetic acid.
August 6, 2015

chemistry
You can easily pick up cellulose (paper) fibers from the filter paper and that contaminates the material before you take the melting point.
August 6, 2015

Chemistry
I don't know what your instructions are. One answer is all that you have given; i.e., T, dH and dS because you can calculate dG from those three. If I had a choice I would choose dG.
August 5, 2015

Chemistry
You need dG. If you don't have that, you can calculate it from dG = dH - TdS
August 5, 2015

Chemistry(Titration)
Back titration with what? Probably because MO indicator changes color approximately 4 while phenolphthalein changes color approximately 8.3. If you are titrating CO3^2- with acid, using phenolphthalein the end point is not as sharp AND it titrates only 1 H^+ while the MO is a ...
August 5, 2015

Enthalpy Change Calculations
Yes but I don't understand why you did all of that work. dH = (n*dHf products) - (n*dHf reactants) dH = (1*-242 kJ) - (1*-286 kJ) dH = -242-(-286) = 44 kJ. Since dH is +, the reaction is endothermic. I looked up the Hof in a set of tables.
August 5, 2015

Logical Reasoning
D. It COULD be locked to the post but why couldn't it be in the garage also so I don't think D is correct? What about E? Since ALL of the bikes in the shed are red, (and Lynn's bike is green) aren't you quite certain it isn't in the shed?
August 5, 2015

Algebra
Rodney is 1 mi/1 hr = 1 mph Patrick is 1 mi/1.5 hr = 0.67 mph 1-0.67 = 0.33 mph faster
August 5, 2015

college. physics and chemistry and mathematics
a = 4r/(2)^1/2 a = 4*200/1.414 = ?
August 5, 2015

chemistry
A. pH = pKa + log (base)/(acid) Convert 26.56 g NaAc to mols, convert to M, plug into the above equation and solve for pH. B. I like to work these by millimols (mmol) and not M. mmols HAc = 250 x 1.56 = about 400 but you need a more accurate number. mmols NaAc = 26.56/82 x ...
August 5, 2015

Chemistry
Yes and no. I have copied the problem below and added my comments in bold. Balance the equation CuSO4 + Pb(NO3)2 → PbSO4 + Cu(NO3)2 Find the number of moles for CuSO4 c=n/v n=c × v n=0.2 × 0.01 n=0.002 mol Since it is a 1:1 ratio, the number of moles for Pb(...
August 5, 2015

Chemistry
I assume principle means that there may be intermediate reactions but what is shown is the overall reaction. I agree with you that delta S probably is negative and for the reason you cite. You don't mention the water but that is a liquid and S is lower for liquids than ...
August 4, 2015

college chemistry
Enrique is correct but just for the record this is how I did it. 7600 ft^3 x (1,728 in^3/ft^3) x (2.54 cm/in)^3 x (1 L/1000 cc) = ? 1,728 and 2.54 and 1000cc to 1L are just three of those conversion factors I memorized back in the days before calculators, computers, and such ...
August 4, 2015

college chemistry
Sara, sam, et al. Why not use the same screen name? volume room is 950 ft^2 x 8 ft = ? cubic feet. Convert to L. You have 53 atoms Rn222/L so 53 atoms/L x #L = # Rn222 atoms in the basement. B. Convert # atoms Rn to mols Rn and use PV = nRT to solve for P.
August 4, 2015

college chemistry
It is easier to help you if you use the same screen name. You don't list the half life but step 1 is to determine k. That is k = 0.693/t1/2 Then ln(No/N) - kt No = 100 N = 64.3 k from above Solve for t I used 100 and 64.3; you can use ANY number for No, then N is No*0.643
August 4, 2015

Lccn
You're typing gibberish. Make sense out of this or quit wasting our time. Type your question if you have one.
August 4, 2015

Lccn
I have no idea what RMNO4 is.
August 4, 2015

Lccn shool
mg means nothing. I assume you mean Mg. Mg + 2H2O ==> H2 + Mg(OH)2
August 4, 2015

Lccn shool
What do you want. products are KCl and H2O BUT that is assuming you mean HCl and KOH. Use your caps key correctly. Proof what you write before posting.
August 4, 2015

Chemistry
I don't believe you have posted the entire question; however, what you have is correct so far. Personally, I would have used 4.184 for the specific heat. Most of these questions ask for the heat/mol; you have calculated the heat of the reaction as shown.
August 4, 2015

URGENT CHEMISTRY
Why do I want to do all of your home work? What don't you understand about this? It's products divided by reactants with coefficients for each material becoming the exponent for that material. For example, f is K = (SO3)^2/(SO2)^2(O2)
August 4, 2015

Chemistry
Your two equations are not balanced and we can't do anything with them until they are. For example, #1. You have 2A on the left and 2A on the right. You have 2/3 C2 which is 4/3 C on the left but 3 on the right. Are you sure that isn't 2A + 3/2 C2 = A2C3? And #2 would ...
August 4, 2015

Chemistry
I don't think you read my response. Re-read. mols C = grams/atomic mass C.
August 3, 2015

Chemistry
If that is all that's confusing you the easiest way to take care of it is that you don't start with 5.00 kg but 5.00 kg x 0.962 = ? kg and I would change that to grams. mols C = grams/atomic mass C = ? Then 395 kJ/mol x # mols = ? kJ released. Personally I don't ...
August 3, 2015

chemistry
See your earlier post below.
August 3, 2015

Chemistry
q = mass H2O x heat fusion You know mass H2O in grams, look up the heat fusion in J/g and solve for q in joules. The problem actually is not complete because it doesn't tell you the temperature of the water being sprayed. I think it assumes you will assume the temperature ...
August 3, 2015

chemistry
I have looked under reactions of azomethine, reaction of 4-aminotoluene and vanillin, reaction or p-aminotoluen and vanillin, and other variations and came up with nothing. You might have better luck trying some variation of those on Google. Sorry about that. I did find these ...
August 3, 2015

chemistry
You want me to write up your experiment. No thanks.
August 3, 2015

Chemistry
You may be overwhelmed with information that is not needed. You don't care what it's being used for nor even what it is. All you need to do is to convert kJ to calories. There are 4.184 J in 1 calorie and 1000 J in 1 kJ. So 1367 kJ x (1000 J/1 kJ) x (4.184 J/cal) = ? ...
August 3, 2015

Urgent chemistry
Something is missing here. You saw that answer from Sarah and I explained that part. What do you not understand about this? All you need to do is reason out the law. In fact I answered what P will do (both increase and decrease). I explained about adding NH3. Why won't the...
August 3, 2015

Chemistry
2 is C for sure. #1 is not that easy I don't think. The question asks about total energy but provides only the fact it is endothermic. Endothermic tells you that the reaction absorbs heat from the surroundings in order to occur. It doesn't say anything about the total ...
August 3, 2015

Chemistry
If you are having a problem balancing these you need to tell us what the problem is. All appear to be balanced to me.
August 3, 2015

Chemistry
That's right. Increasing P shifts to the side with fewer mols OF GAS. There are 4 mols on the left and 2 on the right so increasing P shifts to the right; decreasing P shifts it to the left.
August 3, 2015

Chemistry
In common words, Le Chatelier's Principle tells us that when a system in equilibrium is subjected to a stress, it will shift to undo what we did to it. So look at the equation. 3 H2(g) + N2(g) <- -> 2NH3(g) + heat Adding NH3. So the reaction will try to use up NH3 to...
August 3, 2015

Chemistry
See your other post.
August 3, 2015

Equilibrium
In the problem, yes. In real day to day work, you must know the temperature for which the K is given because K is different at some other temperature.
August 3, 2015

Equilibrium
You work this EXACTLY as you did for the previous problem. The 852 never enters into it EXCEPT that the Keq you calculate will be good ONLY for that temperature.
August 3, 2015

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