1. What is the relation between the force of friction and speed?
… is inversely proportional to speed.
(B) … is independent of speed.
(C) … is proportional to speed.

2. What is the relation between the force of friction and speed?
… in inversely proportional to speed.
(B) … is independent of speed.
(C) … is proportional to speed.

3. What do you think is the typical size that needs to be taken into account in applying the Stokes law to ion mobility?
Roughly the van-der-Waals size of the ion.
Roughly the size of the “ion atmosphere” according to Debye-Hückel theory.
Roughly the size of the first solvation shell of the ion.

4. What do you think is the typical size that needs to be taken into account in applying the Stokes law to ion mobility?
Roughly the van-der-Waals size of the ion.
Roughly the size of the “ion atmosphere” according to Debye-Hückel theory.
Roughly the size of the first solvation shell of the ion.
Note that this is a rough estimate only. The hydrodynamic radius can be smaller than that, and ion-ion interaction can also contribute to the “effective viscosity” of the solution.

5. Is the thermodynamic force a real force acting on the molecules in solution?
Yes.
No.

6. Is the thermodynamic force a real force acting on the molecules in solution?
Yes.
No.
FTD is not a real force, rather a tendency for molecules to move in a particular direction (e.g. due to a concentration gradient).
It can be understood as an “effective force”.
Dimensions of FTD: force per amount of substance [FTD] = N·mol-1
FTD is a molar quantity!