40.0 mL of a 0.65 M solution of HF is titrated with 0.100 M NaOH. After 0.400 L of the NaOH solution has been added, the resultant solution is:

The solution is basic and after the equivalence point

Explanation:

HF reacts with NaOH as follows:

HF + NaOH → H₂O + NaF

1 mole of acid reacts per mole of base.

The solution of HF contains:

40.0mL = 0.0400L × (0.65mol / L) = 0.026 moles of HF,

The titration will reach equivalence point when you add 0.026 moles of NaOH. If more NaOH is added the solution will be basic because NaOH (A base) is in excess doing the solution basic.

Moles added of NaOH are:

0.400L × (0.100 mol / L) = 0.0400 moles of NaOH

As the addition of NaOH is > 0.026 moles,

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.