Since the rate must have the following units: mol/(L*s), the suitable units for k, considering that the term [D] [X] leads to mol^2/(L^2) (it means a second order kinetic law), are L/(mol*s), nevertheless, that answer isn't in the given options.
Colloid consist of the particles having size between 1 - 1000 nm i.e, 0.001- 1μm.
The particles in colloid can not be seen through naked eye.
It is homogeneous.
We can not separate the colloidal through the filtration. The pore size of filter paper is 2μm. However it can be separated through the ultra filtration. In ultra filtration the pore size is reduced by soaking the filter paper in gelatin and then in formaldehyde. This is only in case of when solid colloidal is present, if colloid is liquid , there is no solid particles present and ultra filtration can not be used in this case.
Suspension:
The particle size in suspension is greater than 1000 nm.
These particles can seen through naked eye.
It is heterogeneous.
The particles in suspension can be separated through the filtration.
