i need this paper to be answered all except questions 3,5 and 8 on section A.Thanks.

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i need this paper to be answered all except questions 3,5 and 8 on section A.Thanks.
	
Document Preview: This question paper consists of 
3 pages each identified by the   School of Chemistry Data & 
Code No. CHEM XXXXXXXXXXFormulae Booklet may be used

© UNIVERSITY OF LEEDS   
School of Chemistry 
May/June 2011 
CHEM121001 
ENERGY MATTERS 
Time allowed: 2 hours 
 
Candidates should attempt all questions in Section A and all questions in Section B. 
Candidates are advised to spend no longer than 45 minutes attempting questions in Section 
A (40 marks). Questions in Section B are worth 20 marks each.

Section A 
Answer all questions 
(Questions carry 5 marks each) 
  
1. Suppose the position of an electron is known to within     , where   is the Bohr 
  
radius. What is the minimum uncertainty in the speed of the electron? 
2. An electron approaches a barrier. The electron’s translational energy is 95% of the 
barrier.  Assuming that the value of the reflection coefficient is 0.65, calculate the 
value of the transmission coefficient, and comment on whether the value of the 
transmission and reflection coefficients are as you would expect on the basis of 
classical mechanics.    
3. Briefly explain the following terms: harmonic vibration and zero-point energy. 
4. Use the van der Waals equation of state to calculate the pressure exerted by 500 moles 
 
3
of CH in a volume of 0.1 m , at a temperature of 450 K. The van der Waals constants 
4
 XXXXXXXXXX
for CH are a = 2.28 dm atm mol and b = XXXXXXXXXXdm mol . 
4
2
5. Given that the collisional cross-section for O is 0.47 nm , calculate the mean free 
2
path for oxygen stored in a cylinder at 50 bar and 298 K. 
6. An inert gas is observed to effuse 2.56 times faster than Xe. What is the gas? 
7. The equilibrium constant for the isomerisation of cis-2-butene into trans-2-butene has 
the value 2.07 at 400 K.  Calculate the standard Gibbs energy change for the 
isomerisation at this temperature. 
-1 -3
8. The surface tension (?) of hexane is 18.4 mN m , and its density is 1.17 g cm .  How 
far will hexane rise up...

Robert · Accepted Answer

Solutions to Part A
Solution 
From heisenberg’s Uncertainity principle we have 
Δx*Δv = h/4πm 
Where  
Δx  = 0.5*a0 = 0.5* 5.29177 x 10 -11 meter  (5.29177 x 10 -11 meter is bhor’s radius) 
Δv = h/4πmΔx 
Δv = 6.626 x10-34 / 4 x 3.14 x 9.1 x 10-31 x 0.5* 5.29177 x 10 -11 
Δv = 0.0219 x 10-34+31+11 
Δv = 0.0219 x 108 m/s (Answer)
Solution 
Since Total energy that electron have is only .95 so the from the basic concepts of waves propagation we have 
Γ +  Τ = 0.95 
Τ = 0.95 – 0.65 
T = 0.30 (answer) 
In classical mechanics that should be equal to 1 but here its just 0.95.
Solution 
Harmonic Motion: Harmonic vibration is a periodic function which varies sinusoidally with time. 
y = A sint is an example of a harmonic vibration of amplitude A and varies sinusoidally with time. 
 Zero Point Energy: It is the lowest possible energy that a quantum mechanical system may have.
Solution 
From vanderwaal’s equation we have 
(P+n2a/V2)*(V-nb) = nRT 
Now as per the question we have 
V = 0.1m3 
T = 450K 
b = 0.0428dm3mol-1  = 0.0428 x 10-3m3mol-1 
a = 2.26 dm6atmmol-1 = 2.26 x 10-6 m6atmmol-1 
n = 500moles  
R = 8.2057m3atm/molK 
On Replacing the values in the above equation and calculating it for P we get 
(P -56.5)  = 500 x 8.2057 x 450 /(.1 – 500*0.0428 x 10-3) 
P = 23493377atm  
P = 2.34 x 1012 Pa
Solution 
Given that, 
P = 50 bar  
T = 298K 
Collisional Cross section = 0.47nm2 = 0.47 x 10-18m2 
Formula for calculating mean free path is  
λ  = kbT/√2 πd2P and kb is boltzmann constant, 
On calculating with the help of above values we get, 
λ  = 1.38x10-23 x 298 x 4 / 1.414 x 0.47 x 50 x 105 x 10-18 
λ = 48.86 x 10-10m (answer)
Solution 
From rate of effusion we know that, 
RateA/RateB= �
??????????  ????????  ????  ??
??????????  ????????  ????  ??
  
Now from the question we have, 
2.56 RateB/RateB = �
??????????  ????????  ????  ????
??????????  ????????  ????  ??????????  ??????
  
Molar mass of Xenon = 131 g/ mole from table 
Molar mass of Inert gas we get = 4.

i need this paper to be answered all except questions 3,5 and 8 on section A. Thanks. Document Preview: This question paper consists of 3 pages each identified by the School of Chemistry Data & Code...

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