Pure hexane has negligible ultraviolet absorbance above a wavelength of 200 nm. a solution prepared by dissolving 25.8 mg of benzene (c6h6, fm 78.11) in hexane and diluting to 250.0 ml had an absorption peak at 256 nm with an absorbance of 0.266 in a 1.000-cm cell. find the molar absorptivity of benzene at this wavelength.

ε = 201.5

Explanation:

Given data-

mass of benzene = 25.8 mg

= 25.8×10^-3 kg

Atomic  mass of benzene= 78.11 amu

volume of hexane = 250.00 ml = 0.2500 L

Absorbance =  0.266

Length of the cell = 1.00 cm

Hence concentration =

solving we get

= 0.00132 M

Formula:

A= εcl

A= absorbance

c= concentration and l=  length of cell

now substituting values in the above formula

0.266= ε×0.00132×1.000

⇒ε =

⇒ε = 201.5

the electronic configuration of an atom with eight electrons is 1s²2s²2p⁴. the orbital diagrams are shown in the figure.

as per the hunds rule:

1. electrons tend to avoid being in the same orbital as per as practicable.

2. electrons in different orbitals of the same energy will have their spin parallel.

this can be illustrated from the multiplicity of the orbitals of the atom. as there are four electrons in the p orbital and p orbital has 3 sub-shells. the electrons can be fed in different ways as shown in the figure but the correct orbital diagram will be as per the hunds rule.