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ProPatto16
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Homework Statement
Deduce the form of the Lennard-Jones potential between two water molecules.
given/known:
molar enthalpy of evaporation of water is 4.1x104J/mol
density is 103kg/m3
Assume water molecule is surrounded by approximately ten nearest-neighbours.
Take Mr = 18
Homework Equations
from the sources i have:
V(r)=4ε[-(σ/r)6+(σ/r)12]
The Attempt at a Solution
ε is a measure of how strongly the molecules attract each other.
σ is the distance at which the intermolecular potential is zero.
r is the distance of separation between both particles.
its a bit unclear what the question means by "deduce the form" but I am assuming it means find the value r.
to find r i first find the atomic diameter d= [(Mr(X)x10-3)/(pNA)]1/3
where X is number of molecules
Mr = 18
p given at 103kg/m3
NA is avogadros constant.
and X I am unsure if it is 2 (because the question says two molecules) or if its 11 (because of the molecule plus its 10 "neighbours")
if X is 2 i get a diameter of 1.815x10-10
giving a radius of 9.07x10-11
if X is 11 i get d = 3.20x10-10
making r = 1.60x10-10
now to get the "form" i just sub an r into the potential equation??
however, i don't entirely understand the "ten nearst-neighbours" and what its used for.
i also don't use the molar enthalpy.
molar enthalpy isn't mentioned anywhere in my notes but online it says enthlpy is a measure of energy of the system.
some clarification would be much appreciated
thanks