In Impedance track algorithm, How is resistance is related to soc(state of charge)?
The impedance represent the internal serial resistance of the battery.

It is important to know this, because the state of charge greatly depends on it.

Basically, a part of the energy you will input (or draw) on the battery will be lost due to the internal serial resistance.

In other words, the state of charge is somewhat equal to the energy you input, minus the losses of the impedance.

Hence, to know the state of charge of the battery, you also need to know how much energy is being lost because of its impedance.

It also depends a lot on how much current you are injecting or drawing from the battery, as higher current you will have higher losses, as the loss is equal to the square of the current. Ploss = Rser * I ^ 2.



EDIT

You can have a look at this article it contains valuable information and even refers to an IC able to evaluate this for you, if you are using Li-Ion.