Forces between atoms can be considered to be spring-like forces. Itmeans that th

Question

Forces between atoms can be considered to be spring-like forces. Itmeans that the force along the line connecting the atoms can begiven as F =-k(r-r0),where r0is the equilibrium separation of theatoms, k is the force constant of the molecule.
The force constant of the HF molecule: k=900 N/m. Let'sstretch the molecule by 50 pm, (its total length is about 100 pm,or in a non SI unit: 1 Angtrom). Calculate the work done bystretching! This work is enough to break up a single HF moleculeinto separate atoms of H and F. Calculate the energy (work)necessary to break up 1 mol HF!

Explanation / Answer

stretching the molecule by 50 pm means r-r0 = 50 pm W=0.5k(r-r0)2 W=0.5*900(50*10-12)2 W=1.125*10-18J 1 mole = 6.02*1023 molecules, so the work needed tobreak up 1 mole = 6.02*1023*Wone molecule =6.02*1023*1.125*10-18 J = 677.25 kJ

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