Posted by Peter on .
The particle wavelength of your lecturer in 3.091 on his way from the office to 10250 (200 yards, 1 yard = 0.9144 m) has been determined to be 4.045 x 10 36m. Taking his body weight to be 178 lbs (1 lb = 0.4536 kg), how long does it take him to get to his class? (answer in seconds)

chemistry 
DrBob222,
wavelength = h/mv
Solve for v. Then
distance = rate x time
Substitute and solve for time. 
chemistry 
Menes,
pls the formula :)

chemistry 
KS,
thanks bob it worked!

chemistry 
Menes,
can u help me KS

chemistry 
Hil,
Hi, Menes. I an getting a very strange answer, which is incorrect. I must be using the wrong formula. Can you assist. Thanks.

chemistry 
KS,
Okay i am going to list down all the answers i got so far, please assist me in those which i left, if you have any:
1)156.675158119
2)5
3)90.1775147929
4)3s,3p,4s,3d,5s,5p,4f
10,2,14,6
5)777
2.86e10
6)8.88
dont know what part b is
7)O2, O22
8)tetrahedral,2,1,1,no,no
9)LiF don't know the reason
10)dont know part a
6.3e4
11)BN,AlAs, C,GaAs,GaP
12)
13)1.04e3,ptype
14
15
16
17)Sn < Ge < Si
18
19) 6
20
21) B
22)1.8e6
23)0.000258
24)
25
26
27
28)A is wrong, 3320, thermoplastic no covalent bonds
29
30
31
32)0.0453
14.0453
33)4.77
10.76
1
34) hydrogen bond
Pls help me get the rest ones ASAP 
chemistry 
Hil,
Hi KS, Thanks. 6b) 3.22*10^5

chemistry 
KS,
You are welcome, thanks. I forgot to convert from KJ/mol to J/mol!
If you get anything else, pls do share on this page! 
chemistry 
Hil,
This is what I did with No. 12 Gallium Nitride.
A) I said No.
B) Wavelength = h*c/E_g = 6.626*10^34 x 3*10^8/ 3.2 x 1.602 * 10^19
= 0.388 *10^6
This is a long shot. Maybe someone can pick up on it. 
chemistry 
Hil,
28 is A and D

chemistry 
KS,
thanks for 28 it's correct, as for 12, a is yes and b is 3.88e7 I got them correct. Thanks again. feel free to brainstorm for other questions.

chemistry 
Kim,
thanks KS, 31 is A

chemistry 
Hil,
9. b) I think the answer is "Both molecules are ionic but the higher melting point has a larger cohesive energy". I ruled out some of the choices, LiF has a strong lattice energy. There are a lot of choices to choose from. This is what I think.

chemistry 
KS,
thanks kim, thanks hil, both your answers are right. Good going!

chemistry 
Hil,
Hi. KS, I have a few more to go. Only one chance left. The graphs, the one on gold, xray tube. If you can fill in what you have. 9b is correct.21. is b and both glasses are weaker. Thanks

chemistry 
KS,
Thanks man, i am telling you all i know.. don't worry, if you get more than 60 overall you will receive your certificate (like i did in bio despite failing in the final, they don't mention your score in the certificate) I don't know anything about gold or the graphs yet. rest all leads brought me nowhere, will keep you posted if I find something, we have one more day.

chemistry 
KS,
I am also telling the answers of those i myself got wrong in my previous tries. 10 a is 2.42e6 I got it wrong

chemistry 
KS,
try the stereoisomers one q27, looks pretty straightforward.

chemistry 
ZM,
Hi guys , , the answer for 6 b) is 3.22e5 .

chemistry 
KS,
Yeah hi. Hil told us that
can someone solve the lead solubility and tell us the end result please? Here are the steps:
"This is simple Stoichiometry problem
Write down PbI2 > Pb2+ + 2I
Therefore
Ksp = [Pb2+][I]^2
From the stoich you can derive that
Ksp = Cs(2Cs)^2 = 4Cs^3
Hence Cs = (Ksp/4) ^ 1/3
Then multiply the Molar Weight to get grams / Liter unit that you like
The second problem is common ion effect
First see is the added ion concentration more than or less than your Cs.
0.1 seems to be >>>> than Cs so common ion will happen
Ksp = Cs'(0.1)^2 = 0.01Cs'
Hence
Cs' = Ksp/0.01
Then just multiply by Molar weight again to convert to g/L units .
Note use the Molar Weight of PbI2 !!!!" 
chemistry 
KS,
Alright i got it
24)0.558
0.000327 
chemistry 
Zm,
Can somebody pls help me with 27 , 29 and 30 ? I'd be really grateful ,
Thankyou 
chemistry 
Zm,
The answers for question 20 are
Structure A ,
Increase ,
Decrease .
Hope it helps . . 
chemistry 
Hil,
Hi, KS and Kim. Can you help me with No. 18 electrical measurements. Metal is two orders of magnitude higher at 836 degrees than at 499 degrees C. What is the energy formation for this metal. Thanks.

chemistry 
Hil,
Hi, KS and Kim. Can you help me with No. 18 electrical measurements. Metal is two orders of magnitude higher at 836 degrees than at 499 degrees C. What is the energy formation for this metal. Thanks.
In(100)= H_v/8.314(1/772.151/1109.15) 
chemistry 
Hil,
On no. 25. I believe the highest density is Coesite. The others are tricky. Does anyone know. On 26, phases for Cu at 95wt.% I think is 2. At 15wt.% for Cu, I think is 2. For no. 29, I think linear structure has a larger molar volume. Branched structure a higher glass transition temperature. Part c is a toss up. I think it is branched because the greater amount of electrostatic interactions in the linear chain.

chemistry 
Tania,
9a is LiF

chemistry 
Zm,
pls help me with 27, 29 and 30 .

chemistry 
Tania,
¹14 is 1.42e9,
2.36e10
¹15 is 7.23e11,
2.48e11
¹16 is 6.89
¹20 is structure A, decrease, increase
Zm is wrong
¹29 is
branched structure,
branched structure,
Linear, because the branches can become more entangled than the linear chain. 
chemistry 
Hil,
Thanks Tania. I was making calculation errors and unsure of what they were looking for on the gold problem. I am having he same problem with no 18. I know the formula but getting the wrong answer. Temp = 836 C and 499 C
In(100)=H_v/8.314(1/772.151/1109.15)
Thanks. 
chemistry 
Anonymous,
Is the answer in number 29 correct? Linear is less viscous? isn't it suppose to be that branched be less viscous?

chemistry 
ss01,
anyone up for 16?

chemistry 
Anonymous,
Estimate the fraction of copperrich phase at 900 C and an overall composition of 80 wt. % Cu. Have anyone solve that?

chemistry 
Hil,
No.29 is correct. No. 18 can you check my math.
ln(100)=H_v/8.314*(1/772.151/1109.15)
ln(100)= H_v/8.314*0.000393
H_v= ln(100)*8.314/0.000393
H_v=ln(100)*21155.2163)
H_v=97423.37 joules
H_v=97.42337 kilo joules
Thanks. 
chemistry 
Anonymous,
^ seems to be correct make sure that your queestion says double magnitude and those values for temperature are all Kelvin

chemistry 
Costas,
The answer for 18 is 92.8892497896....
Any help for No.30(K SURFACE ENERGY)? 
chemistry 
Anonymous,
I get that why linear is less viscous than Branched, i forgot that this question is about polymers and not short chain hydrocarbons...
Has anyone have answers for the Stereoisomer thing. I am very confused with it cause of the wording "number of possible stereoisomers"
Cause if that was the question then i would just use the formula 2^n where n is the number of chiral centers!!! For this the answer is 2^2 = 4
But then again if it was really asking number of possible optically different stereoisomers than the answer is only 3 since the other one is only similar to the other due to the plane of symmetry, i bet it was called a meso compound back in the tartaric acid lecture !!! 
chemistry 
Anonymous,
for K Surface Energy just do the following steps
Potassium is BBC hence 2 atom per lattice
Use Atomization Enthalphy from periodic table  Divide this by avogadros  to get per atom  then remember that in BBC u have 8 surrounding atoms,  so divide that value again by 8
That now will be energy / bond !!!
Then now calculate the area of the plane (110)
Just get lattice constant (a) using (2*Molar Volume / Avogadros) ^ 1/3
Theen solve the area using = a*sqrt(a)
Then now use your energy in Joules / bond and divide it by the area your calculated. 
chemistry 
Anonymous,
Alright i tried my theory and my understand about the meso compound situation is correct!!!
So if you see an axis of symmetry remove 1 from the 2^n formula
:) 
chemistry 
Hil,
No. 25 This is my answer: lowest density: cristobalite;
next lowest: tridymite; next lowest: beta quartz; next lowest: alpha quartz; highest density: coesite.
Please verify. 
chemistry 
Karpov,
25) tridymite,crystobalite, betaquartz, alphaquartz,coesite.
cristobalite and liquid have approximately the same density 
chemistry 
Anonymous,
guys how about this question?
What is the minumum acceleration potential (V) that must be applied to a beam of free electrons for diffraction to occur in a crystal of niobium (Nb)? Express your answer in volts.
I've answered it by both 2663V and 2.7x10^3 it says im wrong. What is the ryt answer?
My Solution was Nb is BBC so i find highest plane (110) that gives max wavelength. since h+k+l = even.
Also lambda max = 2d
d = a/sqrt(h^2 + k^2 + l^2)
h = 1, k = 1, l =0 from (110)
a = (2 * Molar Volume / Avogadros )^2
Then substitute lamda max to
Volts = h*c/(e*lambda max) = 2667 Volts
I tried 2.7 x 10^3 volts i am still wrong :( any suggestions? 
chemistry 
Anonymous,
For above my a
Sorry Typo
a = (2 * Molar Volume / Avogadros)^ (1/3) 
chemistry 
KS,
for Nb correct answer is 6.89 Volts.
Thanks alot ZM for posting the wrong answer. Next time please double check before sharing your results.
I tried the steps anonymous posted for K surface energy from bananas but its giving me the wrong result. Anyone else can give a try? 
chemistry 
Zm,
Im extremelyy sorry KM and others, i just checked. I was a mistake , I had no such intension . Just wannad to help.
The correct ans. for stereoisomers is
3 , 4 , 4 . I got it wrong .
Apologies. . :(
Thank you . 
chemistry 
KS,
its alright your intentions were good i can see that so your apology is accepted. sorry for being harsh when all you did was trying to help. i met up with someone who got 94 in the finals and he was kind enouigh to give me some answers
26)1, 3, 0.57; 27 (successively)
27)3,4,4
30)9.3e6
Thanks to all that helped! couldn't have made it this far without your help. Hope we can assist each other another time :) 
chemistry 
Zm,
:) , , agreed with KS , thanks alot everyone for the assistance ! God bless you all . .
Good Luck :) . .
Regards. 
chemistry 
chemi,
I had 2 wrong attempts of 18 can someone help me with this
Please
On the basis of electrical measurements, it is concluded that the equilibrium vacancy concentration in a given metal is two orders of magnitude higher at 849oC than at 492oC. What is the energy of vacancy formation (ΔHv in kJ/mol) for this metal?