The energy required to break one mole of Cl - Cl bond is #"242 kJ/mol"#. What is the longest wavelength of light capable of breaking a single Cl - Cl bond? (take #c = 3 xx 10^8# #"m/s"# and #N = 6.022 xx 10^23# #"mol"^(-1)#)

Question

86230 views around the world

You can reuse this answer
Creative Commons License

Answer 1 · 2017-05-07T16:51:50

#sf(495color(white)(x)nm)#

#sf(Cl_2rarr2Cl*)#

#sf(DeltaH=+242color(white)(x)"kJ/mol")#

I will work out the energy required to dissociate #1# molecule of #sf(Cl_2)#:

#sf(E=(242xx10^(3))/(6.022xx10^(23))=4.0186xx10^(-19)color(white)(x)J)#

Now I use the Planck Expression:

#sf(E=hf=(hc)/lambda)#

#:.##sf(lambda=(hc)/E)#

#sf(lambda=(6.63xx10^(-34)xx3xx10^(8))/(4.0186xx10^(-19))color(white)(x)m)#

#sf(lambda=4.949xx10^(-7)color(white)(x)m)#

#sf(lambda=495color(white)(x)nm)#